Circalittoral rock (and other hard substrata)
Circalittoral rock is present all around the coast of the United Kingdom, and is characterised by animal dominated communities (a departure from the algae dominated communities in the infralittoral zone). The circalittoral zone can itself be split into two sub-zones; upper circalittoral (foliose red algae present) and lower circalittoral (foliose red algae absent). The depth at which the circalittoral zone begins is directly dependent on the intensity of light reaching the seabed; in highly turbid conditions, the circalittoral zone may begin just below water level at mean low water springs (MLWS). The biotopes identified in the field can be broadly assigned to one of three energy level categories: high, moderate and low energy circalittoral rock (used to define the habitat complex level). The character of the fauna varies enormously and is affected mainly by wave action, tidal stream strength, salinity, turbidity, the degree of scouring and rock topography. It is typical for the community not to be dominated by single species, as is common in shore and infralittoral habitats, but rather comprise a mosaic of species. This, coupled with the range of influencing factors, makes circalittoral rock a difficult area to satisfactorily classify; particular care should therefore be taken in matching species and habitat data to the classification.
Circalittoral rock features include circalittoral fouling communities (CR.FCR.FouFa) and circalittoral caves and overhangs (CR.FCR.Cv). These features are present throughout the circalittoral zone in a variety of wave exposures and tidal streams.
Caves and overhanging rock in the circalittoral zone, away from significant influence of strong wave action (compare FIR.SG). This habitat may be colonised by a wide variety of species, with sponges such as Dercitus bucklandi, anemones Parazoanthus spp. and the cup corals Caryophyllia inornatus, Hoplangia durotrix and others particularly characteristic.
Sponges, cup corals and anthozoans on shaded or overhanging circalittoral rock
This biotope occurs on shaded and overhanging rock, such as on cave walls and ceilings although there are very few records of caves in conditions not subject to wave surge (i.e. deeper circalittoral habitats) and almost all are different in species composition. There are also a few examples of similar communities on very deep (70-100 m+) upward-facing rock (in Loch Hourn) and more may be found through the use of ROVs. These often species-rich habitats are almost invariably adjacent to well-mixed turbulent water. Characteristic species include the sponges Stryphnus ponderosus, Dercitus bucklandi, Chelonaplysilla noevus, Pseudosuberites sp. and Spongosorites sp., the anemones Parazoanthus spp., the cup corals Leptopsammia pruvoti, Hoplangia durotrix, Caryophyllia inornatus and the soft coral Parerythropodium coralloides. Thymosia guernei is sometimes present. This biotope is likely to need further splitting with further data and analysis.
Circalittoral fouling faunal communities
This biotope complex contains two biotopes which, although have different physical habitat characteristics, share the fact that they colonise new areas of artificial substrata relatively quickly. The Ascidiella aspersa fouling biotope (Aasp) is found on wave-sheltered artificial substrata such as discarded fishing nets/mooring lines. A separate fouling biotope (AdigMsen) is described for open coast wrecks. This biotope has a characteristic faunal community of Alcyonium digitatum and the anemone Metridium senile. Other species recorded in this complex (primarily under the AdigMsen biotope) include the hydroid Nemertesia antennina, the anemones Actinothoe sphyrodeta and Sagartia elegans, the cup coral Caryophyllia smithii, the bryozoans Flustra foliacea and Bugula plumosa, the crabs Necora puber, Cancer pagurus and Maja squinado and the lobster Homarus gammarus.
Ascidiella aspersa on circalittoral artificial substrata
Sheltered artificial substrata (such as discarded fishing nets or scrap metal on muddy sediment plains), sometimes subject to variable salinity, with high numbers of the ascidian Ascidiella aspersa which is capable of rapidly colonising hard substrata. Other species that are quickly able to take advantage of such substrata include the dahlia anemone Urticina felina and the plumose anemone Metridium senile. The edible crab Cancer pagurus, the velvet swimming crab Necora puber and the shore crab Carcinus maenas may occasionally be found hiding under the discarded nets, lobster pots or anchor chains.
Alcyonium digitatum and Metridium senile on moderately wave-exposed circalittoral steel wrecks
This biotope is found on moderately wave-exposed circalittoral steel wrecks that are subject to moderately strong to weak tidal streams. The vertical and upward facing sides of the wreck stand proud of the seabed, and may be colonised by dense aggregations of Alcyonium digitatum, Metridium senile and Actinothoe sphyrodeta. Caryophyllia smithii and Corynactis viridis are also recorded with varying abundance. A mixed faunal turf may also be present on the vertical sides, with Nemertesia antennina, Flustra foliacea and Bugula plumosa. Where tidal stream strength is elevated, for example if the wreck is situated in a straight or sound, the hydroid Tubularia indivisa may prevail. Crustaceans such as the crabs Necora puber, Maja squinado and Cancer pagurus, the lobster Homarus gammarus and barnacles are all recorded. The top shell Calliostoma zizyphinum is also recorded.
This habitat complex occurs on extremely wave-exposed to exposed circalittoral bedrock and boulders subject to tidal streams ranging from strong to very strong. Typically found in tidal straits and narrows. The high energy levels found within this habitat complex are reflected in the fauna recorded. Sponges such as Pachymatisma johnstonia, Halichondria panicea, Esperiopsis fucorum and Myxilla incrustans may all be recorded. Characteristic of this habitat complex is the dense 'carpet' of the hydroid Tubularia indivisa. The barnacle Balanus crenatus is recorded in high abundance on the rocky substrata. On rocky outcrops, Alcyonium digitatum is often present.
This biotope complex typically occurs on deep (commonly below 30m depth), wave-exposed circalittoral rock subject to negligible tidal streams. The sponge component of this biotope is the most striking feature, with similar species to the bryozoan and erect sponge biotope complex (BrErSp) although in this case, the sponges Phakellia ventilabrum, Axinella infundibuliformis, Axinella dissimilis and Stelligera stuposa dominate. Other sponge species frequently found on exposed rocky coasts are also present in low to moderate abundance. These include Cliona celata, Polymastia boletiformis, Haliclona viscosa, Pachymatisma johnstonia, Dysidea fragilis, Suberites carnosus, Stelligera rigida, Hemimycale columella and Tethya aurantium. The cup coral Caryophyllia smithii and the anemone Corynactis virdis may be locally abundant in some areas, along with the holothurian Holothuria forskali. The soft corals Alcyonium digitatum and Alcyonium glomeratum are frequently observed. The bryozoans Pentapora foliacea and Porella compressa are also more frequently found in this deep-water biotope complex. Bryozoan crusts such as Parasmittina trispinosa are also occasionally recorded. Isolated clumps of large hydroids such as Nemertesia antennina, Nemertesia ramosa and Sertularella gayi may be seen on the tops of boulders and rocky outcrops. Large echinoderms such as Echinus esculentus, Luidia ciliaris, Marthasterias glacialis, Strichastrella rosea, Henricia oculata and Aslia lefevrei may also be present. The sea fan Eunicella verucosa may be locally common but to a lesser extent than in ByErSp.Eun. The top shell Calliostoma zizyphinum is often recorded as present.
Phakellia ventilabrum and Axinellid sponges on deep, wave-exposed circalittoral rock
This biotope typically occurs on the upper faces of deep (commonly below 30m depth), wave-exposed circalittoral rock subject to negligible tidal streams. Although it occurs in exposed and very exposed conditions, at such depth, the turbulent wave action appears to have a much-attenuated effect on the fauna compared with shallower depths. As the majority of records are from depths between 30-50+ m, slightly deeper than the depths of most surveys, it is possible that this biotope is more widespread than the available dataset indicates. The sponge component of this biotope is the most striking feature, with similar species to the bryozoan and erect sponge biotope complex (BrErSp) although in this case, the sponges Phakellia ventilabrum, Axinella infundibuliformis, Axinella dissimilis and Stelligera stuposa dominate. Other sponge species frequently found on exposed rocky coasts are also present in low to moderate abundance. These include Cliona celata, Polymastia boletiformis, Haliclona viscosa, Pachymatisma johnstonia, Dysidea fragilis, Suberites carnosus, Stelligera rigida, Hemimycale columella and Tethya aurantium. The cup coral Caryophyllia smithii and the anemone Corynactis virdis may be locally abundant in some areas, along with the holothurian Holothuria forskali. The soft corals Alcyonium digitatum and Alcyonium glomeratum are frequently observed. The bryozoans Pentapora foliacea and Porella compressa are also more frequently found in this deep-water biotope. Bryozoan crusts such as Parasmittina trispinosa are also occasionally recorded. Isolated clumps of large hydroids such as Nemertesia antennina, Nemertesia ramosa and Sertularella gayi may be seen on the tops of boulders and rocky outcrops. Large echinoderms such as Echinus esculentus, Luidia ciliaris, Marthasterias glacialis, Strichastrella rosea, Henricia oculata and Aslia lefevrei may also be present. The seafan Eunicella verucosa may be locally common but to a lesser extent than in ByErSp.Eun. The top shell Calliostoma zizyphinum is often recorded as present.
This biotope complex occurs in wave-exposed, tide-swept narrows and straits on circalittoral bedrock and boulders. The biotopes within this complex are characterised by a high abundance of the robust hydroid Tubularia indivisa. The barnacle Balanus crenatus is characteristic of BalTub, the cushion sponges Halichondria panicea and Myxilla incrustans are characteristic of CTub.CuSp and Alcyonium digitatum is characteristic of CTub.Adig. The anemones Sagartia elegans, Actinothoe sphyrodeta, Urticina felina, Corynactis viridis and Metridium senile are all found within this complex. Other species present in this high-energy complex are the sponges Esperiopsis fucorum and Pachymatisma johnstonia, the bryozoans Alcyonidium diaphanum and Flustra foliacea, Cancer pagurus, Sertularia argentea and Asterias rubens. Within this complex, two biotopes have been identified: BalTub and CTub.
Balanus crenatus and Tubularia indivisa on extremely tide-swept circalittoral rock
This biotope typically occurs on upward-facing, extremely tide-swept, circalittoral bedrock, boulders and cobbles found in a broad spectrum of wave-exposures. It is characterised by a few species that are capable of maintaining a foothold in strong tides. These species either form a flat, adherent crust in the case of the barnacle Balanus crenatus, or have strong attachment points and are flexible, bending with the tide, such as the turf of the hydroid Tubularia indivisa. Other species able to tolerate these very strong tides, or just situated slightly out of the main force of the current, include the sponge Halichondria panicea, the robust hydroid Sertularia argentea and current-tolerant anemones such as Sagartia elegans, Urticina felina and Metridium senile. Mobile species such as the starfish Asterias rubens, the crab Cancer pagurus and the whelk Nucella lapillus may also be present.
Tubularia indivisa on tide-swept circalittoral rock
This biotope is typically found on the vertical and upper faces of strongly tide-swept, wave-exposed circalittoral bedrock and boulders. It is characterised by a dense carpet of the robust hydroid Tubularia indivisa. The barnacle Balanus crenatus, where present, is recorded as common. The accompanying species in the community are determined by tidal stream strength. On the more sheltered sides of headlands, where tidal streams are accelerated, sponges such as Pachymatisma johnstonia, Esperiopsis fucorum, Myxilla incrustans and Halichondria panicea proliferate forming the CTub.CuSp sub-biotope. There may also be a scattered bryozoan turf, formed by criisid bryozoans. However, where tidal streams are slightly reduced, but on more wave-exposed coasts, anthozoans such as Alcyonium digitatum become more prominent forming the CTub.Adig biotope. Other species recorded in this biotope include the anemones Sagartia elegans, Actinothoe sphyrodeta, Corynactis virdis and Urticina felina. There may be scattered clumps of hydroids such as Sertularia argentea and Nemertesia antennina. Where `relative shelter' is afforded by the topography of the seabed, the bryozoans Flustra foliacea, Alcyonidium diaphanum and the crab Cancer pagurus may be found. More ubiqutous species such as Asterias rubens and Calliostoma zizyphinum may also be present.
Alcyonium digitatum with dense Tubularia indivisa and anemones on strongly tide-swept circalittoral rock
This variant is typically found on exposed circalittoral bedrock and boulders in sounds, narrows and around tide-swept promontories in accelerated tidal streams. It is dominated by aggregations of dead man's fingers Alcyonium digitatum, and dense clumps or continuous cover of the robust hydroid Tubularia indivisa, particularly on prominent ledges and ridges. Anemones such as Sagartia elegans, Urticina felina, Metridium senile, Actinothoe sphyrodeta and Corynactis virdis form a prominent component of the community. Occasionally, massive sponges such as Pachymatisma johnstonia and Esperiopsis fucorum may be present. Encrusting species such as the polychaete Pomatoceros triqueter and the barnacle Balanus crenatus may be dotted around the rocks, and the top shell Calliostoma zizyphinum may also be observed. Clumps of the bryozoan Flustra foliacea are occasionally seen. The starfish Asterias rubens may be seen amongst a patchy turf of Crisia denticulata and the bryozoan Alcyonidium diaphanum. This variant may also be found on tideswept wrecks and other artificial sustratum.
Tubularia indivisa and cushion sponges on tide-swept turbid circalittoral bedrock
This variant is typically found on the vertical and upper faces of strongly tide-swept, exposed circalittoral bedrock and boulders. It is commonly associated with areas where turbidity levels are high for much of the year, for example, around Anglesey and the Lleyn Penisula. From afar, this variant appears as a dense carpet of Tubularia indivisa covering tide-swept gully walls, floors and boulders. T. indivisa is frequently observed growing through sheets of sponges such as Myxilla incrustans and Halichondria panicea as well as through dense patches of the barnacle Balanus crenatus and tubes of the amphipod Jassa spp. Several other species of sponge appear to be tolerant of the high turbidity in areas where this variant occurs, many of which are common in other biotopes. These include Esperiopsis fucorum, Pachymatisma johnstonia, Hemimycale columella, Dysidea fragilis and Clathrina coriacea. Robust hydroids (other than T. indivisa) such as Nemertesia antennina and Sertularia argentea occur in patches. The anemones Urticina felina, Actinothoe sphyrodeta and Sagartia elegans are typically common. A short bryozoan turf consisting of crisiid bryozoans, Alcyonidium diaphanum, Bicellariella ciliata, Bugula turbinata and Bugula flabellata may be present. Alcyonium digitatum may occasionally be seen although it doesn't tend to be as dominant as in CTub.Adig. Individual Corynactis viridis may be seen scattered across the gully walls and boulders. The starfish Henricia oculata may be seen on boulders and gully floors whilst typical under-boulder fauna includes the crab Cancer pagurus.
This biotope complex occurs on wave-exposed circalittoral bedrock and boulders, subject to tidal streams ranging from strong to moderately strong. This complex is characterised by its diverse range of hydroids (Halecium halecinum, Nemertesia antennina and Nemertesia ramosa), bryozoans (Alcyonidium diaphanum, Flustra foliacea, Bugula flabellata and Bugula plumosa) and sponges (Scypha ciliata, Pachymatisma johnstonia, Cliona celeta, Raspailia ramosa, Esperiopsis fucorum, Hemimycale columella and Dysidea fragilis) forming an often dense, mixed faunal turf. Other species found within this complex are Alcyonium digitatum, Urticina felina, Sagartia elegans, Actinothoe sphyrodeta, Caryophyllia smithii, Pomatoceros triqueter, Balanus crenatus, Cancer pagurus, Necora puber, Asterias rubens, Echinus esculentus and Clavelina lepadiformis. Nine biotopes have been identified within this complex: ByErSp, FluCoAs, FluHocu, CvirCri, SwiLgAs, Mol, SubCriTf, SpNemAdia and SpAnVt.
Bryozoan turf and erect sponges on tide-swept circalittoral rock
This biotope is typically found on wave-exposed circalittoral bedrock or boulders subject to tidal streams ranging from moderately strong to strong. It often has a thin layer of silt covering the seabed, and is characterised by a bryozoan/hydroid turf with erect sponges. Typical bryozoans to be found include crisiids, Alcyonidium diaphanum, Flustra foliacea, Pentapora foliacea, Bugula plumosa and Bugula flabellata, while typical hydroids include Nemertesia antennina, Nemertesia ramosa and Halecium halecinum. The soft coral Alcyonium digitatum is frequently recorded on the tops of boulders and rocky outcrops. Characteristic erect sponges include Raspailia ramosa, Stelligera stuposa and Stelligera rigida; other sponges present include Cliona celata, Dysidea fragilis, Pachymatisma johnstonia, Polymastia boletiformis, Hemimycale columella, Esperiopsis fucorum, Polymastia mamillaris and Tethya aurantium. Other species present include Caryophylia smithii, Actinothoe sphyrodeta, Corynactis viridis, Urticina felina, Balanus crenatus, Asterias rubens, Marthasterias glacialis, Henricia oculata, Echinus esculentus, Clavelina lepadiformis, Calliostoma zizyphinum and Necora puber. Three variants of this biotope have been described, but all are characterised by a bryozoan turf with erect sponges. ByErSp.Eun is found primarily on circalittoral bedrock and is dominated by the seafan Eunicella verrucosa. ByErSp.DysAct is found under slightly stronger tide-swept conditions, and is characterised particularly by the sponge D. fragilis and the anemone A. sphyrodeta. Finally ByErSp.Sag is characterised by the anemone Sagartia elegans.
Mixed turf of bryozoans and erect sponges with Dysidea fragilis and Actinothoe sphyrodeta on tide-swept wave-exposed circalittoral rock
This variant typically occurs on exposed and moderately wave-exposed bedrock and boulders subject to a variety of tidal regimes (from strong through to weak). It is found mainly in the 10-20m depth range and does not usually occur deeper than 30 m. It therefore often straddles the upper circalittoral and lower infralittoral. It often has a light covering of silt and sand may be in the vicinity. Sponges form a dominant part of this variant, although cover usually appears patchy, with no single species dominating. Species present include Dysidea fragilis, Pachymatisma johnstonia, Esperiopsis fucorum, Hemimycale columella, Cliona celata, Stelligera rigida, Polymastia boletiformis, Stelligera stuposa, Raspailia ramosa, Tethya aurantium, Polymastia mamillaris and Axinella dissimilis. Tufts of large hydroids such as Nemertesia antennina, frequently recorded on the tops of outcrops and boulders, stand out more clearly than the understorey of finer hydroid and bryozoan turf such as Aglaophenia pluma, Bugula flabellata, Bugula plumosa, crisiids, Cellaria sinuosa and Bugula turbinata. Other bryozoans such as Alcyonidium diaphanum and Flustra foliacea are also frequently recorded. Other more widespread species present include Asterias rubens, Actinothoe sphyrodeta, Balanus crenatus, Caryophyllia smithii, Corynactis viridis, Necora puber and Clavelina lepadiformis. This variant has been recorded off the south east coast of Ireland, the welsh coast and Lundy Island.
Eunicella verrucosa and Pentapora foliacea on wave-exposed circalittoral rock
This variant typically occurs on wave-exposed, steep, circalittoral bedrock, boulder slopes and outcrops, subject to varying tidal streams. This silty variant contains a diverse faunal community, dominated by the seafan Eunicella verrucosa, the bryozoan Pentapora foliacea and the cup coral Caryophyllia smithii. There are frequently numerous Alcyonium digitatum, and these may become locally abundant under more tide-swept conditions. Alcyonium glomeratum may also be present. A diverse sponge community is usually present, including numerous erect sponges; species present include Cliona celata, Raspailia ramosa, Raspailia hispida, Axinella dissimilis, Stelligera stuposa, Dysidea fragilis and Polymastia boletiformis. Homaxinella subdola may be present in the south west. A hydroid/bryozoan turf may develop in the understorey of this rich sponge assemblage, with species such as Nemertesia antennina, Nemertesia ramosa, crisiids, Alcyonidium diaphanum and Bugula plumosa. The sea cucumber Holothuria forskali may be locally abundant, feeding on the silty deposits on the rock surface. Other echinoderms encountered include the starfish Marthasterias glacialis and the urchin Echinus esculentus. Other fauna includes aggregations of colonial ascidians Clavelina lepadiformis and Stolonica socialis. Anemones such as Actinothoe sphyrodeta and Parazoanthus axinellae may be seen dotted across the rock surface. This biotope is present in south west England and Wales.
Mixed turf of bryozoans and erect sponges with Sagartia elegans on tide-swept ciraclittoral rock
This variant is typically found on wave-exposed circalittoral bedrock and boulders, on steep slopes and upper faces in moderate tidal streams. This species-rich biotope is characterised by a dense sponge, hydroid and bryozoan turf and frequent Alcyonium digitatum. There are frequently large growths of Cliona celata and Pachymatisma johnstonia. Other species present in this diverse sponge community include Polymastia boletiformis, Haliclona viscosa, Polymastia mamilliaris, Scypha ciliata, Hemimycale columella and Dysidea fragilis. Axinellid sponges such as Stelligera stuposa and Raspailia ramosa may be present in low abundance, and are usually more abundant in deeper water. A dense hydroid turf forms a significant part of this biotope, with tufts of large hydroids such as Nemertesia antennina and Nemertesia ramosa frequently recorded. Other hydroid turf component species include Halecium halecinum, Aglaophenia tubulifera and Abietinaria abietina. Anemones are also well represented, with species such as Urticina felina, Sagartia elegans and Metridium senile recorded. The cup coral Caryophyllia smithii and the anemone Corynactis viridis are also frequently seen. The bryozoan turf is composed predominantly of Alcyonidium diaphanum and Flustra foliacea, whilst crustose species such as Parasmittina trispinosa contribute to a lesser extent. The delicate Bugula plumosa may also be present. There is a significant echinoderm component in this biotope. Species such as the starfish Asterias rubens, Henricia oculata, Marthasterias glacialis and Luidia ciliaris, the sea urchin Echinus esculentus and the crinoid Antedon bifida are all regularly recorded. Other species which may be observed include the top shell Calliostoma zizyphinium, the colonial ascidian Clavelina lepadiformis and the barnacle Balanus crenatus. The crab Cancer pagurus is typically found under boulders. This variant has been recorded from from various sites including Pembrokeshire, the Calf of Man and the west coast of Ireland.
Corynactis viridis and a mixed turf of crisiids, Bugula, Scrupocellaria, and Cellaria on moderately tide-swept exposed circalittoral rock
This biotope typically occurs on wave-exposed, vertical or steep, circalittoral bedrock or large boulders, usually subject to moderate or strong tidal streams. It is characterised by dense aggregations of the anemone Corynactis viridis and the cup coral Caryophyllia smithii intermixed with a short bryozoan turf of one or more Crisia spp., Scrupocellaria spp., Bugula spp. and Cellaria spp. Occasionally, this turf obscures the underlying C. virdis and C. smithii. Cushion and encrusting sponges, particularly Pachymatisma johnstonia, Cliona celata, Esperiopsis fucorum and Dysidea fragilis, are present in moderate amounts at many sites. The axinellid sponges Stelligera spp. and Raspailia spp. are less frequently recorded. Clumps of large hydroids such as Nemertesia antennina and Nemertesia ramosa as well as the soft coral Alcyonium digitatum and the bryozoan Alcyonidium diaphanum may be found covering the hard substratum. The anemones Actinothoe sphyrodeta and Sagartia elegans are typically present in low numbers, while the hard `coral' Pentapora foliacea is also occasionally observed. The most frequently recorded echinoderms are Marthasterias glacialis and Asterias rubens, although other species such as Echinus esculentus may also be seen. The rocky substratum may have a patchy covering of encrusting red seaweeds/algae. The crabs Necora puber and Cancer pagurus may be seen in crevices or under overhangs. This biotope is regularly recorded around south west England and Wales, often on vertical rock faces.
Flustra foliacea and colonial ascidians on tide-swept moderately wave-exposed circalittoral rock
This biotope typically occurs on the upper faces of moderately tide-swept, moderately wave-exposed circalittoral bedrock or boulders (although a variant is found on mixed substrata). It most frequently occurs between 10-20m water depth. The biotope is exposed to varying amounts of scour (due to nearby patches of sediment) and, as a consequence, is characteristically dominated by dense Flustra folicaea, a range of colonial ascidians and a variety of other scour/silt-tolerant species. In addition to F. foliacea, other bryozoans present in this biotope include Alcyonidium diaphanum, Bugula flabellata and Bugula plumosa. Varying amounts of the soft coral Alcyonium digitatum may be recorded, depending on the amount of scouring which may vary locally. Where scour is a major factor, species such as the scour-tolerant Urticina felina are frequently observed. Hydroids present in this biotope include Nemertesia antennina, Halecium halecium, Tubularia indivisa and Hydrallmania falcata. Other species present include silt-tolerant sponges such as Scypha ciliata, Cliona celata, Leucosolenia botryoides, and the ascidians Clavelina lepadiformis and Botryllus schlosseri. Balanus crenatus may be recorded occasionally on the boulder/rock surface, and the crab Cancer pagurus may be observed finding refuge in crevices and under boulders. More ubiquitous species present include Asterias rubens, Crossaster papposus, Ophiothrix fragilis and Pagurus bernhardus. Three variants of this biotope have been defined. FluCoAs.SmAs tends to have a high abundance of barnacles, which populate the rocky seabed. The second variant (FluCoAs.Paur) is characterised by abundant Polyclinum aurantium in addition to F. foliacea, which often incorporates sand grains into itself, giving the crustose appearance of sandy rock nodules. Finally, FluCoAs.X is found on mixed substrata and is characterised by a dense hydroid turf growing alongside F. foliacea and other scour-tolerant species.
Polyclinum aurantium and Flustra foliacea on sand-scoured tide-swept moderately wave-exposed circalittoral rock
This variant is typically found on the upper face of moderately exposed, moderately tide-swept, circalittoral bedrock or boulders. Sand and silt are periodically re-suspended in the water column, resulting in scour-tolerant species being characteristic of these areas. There is a dense covering of the scour-resistant bryozoan Flustra foliacea attached to the bedrock plains and boulders. The colonial ascidian Polyclinum aurantium commonly covers the rock surface at most locations within this biotope - itself incorporating sand grains into its surface to give it the appearance of sandy rock nodules. Other ascidians that may occur in this crust are the flat, encrusting colonial Botrylloides leachi, Botryllus schlosseri and the colonial ascidian Clavelina lepadiformis, although in varying quantities at each location. A short turf of other bryozoans such as Alcyonidium diaphanum, Bugula plumosa and Bugula flabellata occur amongst the ascidians. Other species found in this biotope are the sponges Cliona celata, Leucosolenia botryoides and Scypha ciliata, the hydroids Tubularia indivisa, Nemertesia antennina, Halecium halecinum and the anthozoans Alcyonium digitatum and Urticina felina. Echinoderms which may be present include the starfish Asterias rubens, Crossaster papposus and the brittlestar Ophiothrix fragilis. Crustaceans such as the crab Cancer pagurus, the hermit crab Pagurus bernhardus and the lobster Homarus gammarus may be observed in crevices and under boulders. The palps of the polychaete Polydora spp. may be observed whilst the nudibranch Janolus cristatus may be seen preying on the hydroid/bryozoan turf. This variant is commonly found on the Northumberland coast, Flamborough Head and the Lleyn Peninsula.
Flustra foliacea, small solitary and colonial ascidians on tide-swept circalittoral bedrock or boulders
This sub-biotope is typically found on the upper faces of exposed to moderately exposed, tide-swept, scoured, circalittoral bedrock or boulders. It most frequently occurs between 10-20m water depth. The biotope is characteristically dominated by dense Flustra foliacea with a variety of slightly scour/silt-tolerant species forming a dense turf. This turf is primarily composed of bryozoans (Alcyonidium diaphanum, Bugula flabellata, Bugula plumosa, Bicellariella ciliata) and hydroids (Tubularia indivisa, Nemertesia antennina, Sertularia argentea, Hydrallmania falcata, Abietinaria abietina). Where space permits, barnacles such as Balanus crenatus may be found encrusting on the rock surface. There may also be occasional crusts formed by the polychaete Sabellaria spinulosa, especially where the rock is most influenced by sand. Anthozoans which may be observed include Urticina felina, Sagartia elegans, whilst the soft coral Alcyonium digitatum may be recorded on the tops of boulders and bedrock ridges. A range of small solitary and colonial ascidians may be seen, including Polycarpa scuba, Dendrodoa grossularia, Molgula manhattensis, Botryllus schlosseri, Clavelina lepadiformis and polyclinids. Sponges found include Scypha ciliata, Cliona celata, Esperiopsis fucorum and Dysidea fragilis. Echinoderms such as Asterias rubens, Henricia oculata and Crossaster papposus may be seen on the rock surface. Other species found include the top shell Calliostoma zizyphinum, the crabs Cancer pagurus and Necora puber.
Flustra foliacea and colonial ascidians on tide-swept exposed circalittoral mixed substrata
This variant is typically found on very exposed to moderately exposed, circalittoral mixed substrata subject to moderately strong tidal streams. It most frequently occurs between 10m and 20m water depth. This variant is characterised by a dense hydroid and Flustra foliacea turf, along with other scour-tolerant species, growing on the more stable boulders and cobbles which overlie coarse muddy sand and gravel. Although Nemertesia antennina is the dominant species within the hydroid turf, other species such as Halecium halecinum, Nemertesia ramosa and Hydrallmania falcata may also be present. Other bryozoans found amongst the hydroid and Flustra turf include Cellepora pumicosa, Bugula flabellata, Bugula turbinata, and a crisiid turf. Encrusting red algae, the polychaete Pomatoceros triqueter and barnacles such as Balanus crenatus may be found on the smaller cobbles and pebbles, which may become mobile during extreme storms. Echinoderms such as Asterias rubens and Ophiothrix fragilis may be present on the boulders, or the coarse sediment in between. On the larger, more stable boulders, isolated sponge communities may develop, with species such as Scypha ciliata, Dysidea fragilis, Hemimycale columella, Esperiopsis fucorum and Stelligera rigida. In addition, small Alcyonium digitatum, various ascidians (Clavelina lepadiformis, Botryllus schlosseri), Pododesmus patelliformis and top shells (Calliostoma zizyphinum, Gibbula cineraria) may colonise the upper faces and vertical sides of larger boulders. At some shallower sites, the foliose red algae Hypoglossum hypoglossoides may be found on the tops of larger boulders. Within the coarse sediment underlying these boulders and cobbles, anemones such as Cerianthus lloydii and Urticina felina may be recorded. Under-boulder fauna typically consists of terebellid worms, and crabs such as Pisidia longicornis and Cancer pagurus.
Flustra foliacea and Haliclona oculata with a rich faunal turf on tide-swept circalittoral mixed substrata
This biotope is typically found on exposed slopes of silty cobble and pebble subject to strong to moderate tidal streams. From afar, large 'finger' growths of the sponge Haliclona oculata occur amongst a rich faunal turf of hydroids and bryozoans with Flustra foliacea prominent. The dense faunal turf growing on the cobbles is composed of the bryozoans F. foliacea, Alcyonidium diaphanum and Crisia eburnea and sporadic occurrences of the hydroids Nemertesia antennina, Hydrallmania falcata, Tubularia larynx, Rhizocaulus verticillatus and Halecium halecinum. Caprellid shrimps may be observed within this faunal turf. The hard substratum frequently has a dense covering of the sponge H. oculata and occasionally Esperiopsis fucorum, while the softer gravely/sand between the cobbles provides a habitat for anemones such as Urticina felina and Cerianthus lloydii. The nudibranch Janolus cristatus may be seen preying on the faunal turf and the fan worm Sabella pavonia is occasionally seen amongst the cobbles. The soft coral Alcyonium digitatum is often attached to the upper faces of more stable cobbles and rocks, while in the crevices between cobbles, the anemone Sagartia elegans, the crab Cancer pagurus, the prawn Pandalus montagui and the amphipod Dyopedos porrectus may be observed. Under-cobble fauna includes terebellid worms and Harmothoe spp. This biotope has been recorded from the Menai Strait, Milford Haven and Morecambe Bay.
Molgula manhattensis with a hydroid and bryozoan turf on tide-swept moderately wave-exposed circalittoral rock
This biotope is typically found on slightly sand-scoured, tide-swept, moderately exposed circalittoral bedrock and cobbles. It is commonly recorded from the shallower reaches of the circalittoral around depths from 5m to 15m BCD, as it occurs mostly in very turbid waters. From afar, the physical characteristics are usually silted bedrock reefs and cobble, interspersed with patches of clean sand, causing a scour effect on the rock. Dense aggregations of the ascidian Molgula manhattensis form a silty mat on the rock and there is a sparse hydroid and bryozoan turf. A hydroid turf, composed of Nemertesia antennina, Halecium beanii, Hydrallmania falcata, Sertularella gaudichaudi, Tubularia indivisa and Alcyonium digitatum, in varying amounts, occurs at most sites on the tops of boulders and ridges. A bryozoan turf is also present, but not usually dense and includes Flustra foliacea, Alcyonidium diaphanum, Electra pilosa and the crust-forming bryozoan Conopeum reticulum. The polychaete Lanice conchilega thrives in the sandy patches which often occur between the rock ridges. The scour effect tends to reduce the diversity of sponges present with only Halichondria panicea occasionally present. Isolated clumps of the polychaete Sabellaria spinulosa may be present but they do not occur in dense aggregations as in the Sspi.ByB biotope. The anemones Urticina felina and Sagartia troglodytes may occur in cracks between cobbles or on stones buried in the sandy substratum. The anemone Sagartia elegans is more commonly found attached to crevices in the bedrock. Other species such as the hermit crab Pagurus bernhardus, the barnacle Balanus crenatus, the polychaete Sabella pavonia and Pomatoceros triqueter may all be present whilst the crab Pisidia longicornis may be found under cobbles and stones. Records of this biotope are distributed along the south coast of England and the north Wales coast as well as Pembrokeshire near the entrance to Milford Haven.
Sponges and anemones on vertical circalittoral bedrock
This biotope is found on exposed to moderately wave exposed , vertical and overhanging, circalittoral bedrock, subject to strong through to weak tidal streams. This biotope is characterised by a mixed faunal turf of hydroids (Nemertesis antennina, Tubularia indivisa and Halecium halecium) and bryozoans (Alcyonidium diaphanum and crisiid turf). There is frequently a diverse range of sponges recorded, including Cliona celata, Pachymatisma johnstonia, Dysidea fragilis and Hemimycale columella. There may be dense aggregation of dead mans fingers Alcyonium digitatum along with clumps of the cup coral Caryophyllia smithii, and the anthozoans Corynactis viridis, Actinothoe sphyrodeta, Sagartia elegans and Metridium senile. Other species present include the echinoderms Echinus esculentus, Asterias rubens, Marthasterias glacialis, Henricia oculata, Holothuria forskali and Antedon bifida, clumps of the lightbulb tunicate Clavelina lepadiformis and the top shell Calliostoma zizyphinum. Three regional variations of this biotope have been recorded. The first variant is characterised by a Bugula turf along with the pink sea fan Eunicella verrucosa, and has been recorded from around southwest England and Wales. The second variant, characterised by a dense 'carpet' of Corynactis viridis and Metridium senile has been recorded predominantly from the west coast of Ireland. The final variant is characterised by a very diverse, dense faunal turf of hydroids, bryozoans and ascidians and has been recorded from the coasts around Northern Ireland.
Sparse sponges, Nemertesia spp. and Alcyonidium diaphanum on circalittoral mixed substrata
This biotope is found on moderately wave-exposed sand-scoured, circalittoral boulders, cobbles and pebbles that are subject to moderately strong tidal streams (referred to as lag-cobbles locally). It is characterised by sparse sponges and a diverse bryozoan and hydroid turf. The sparse sponge community is primarily composed of Dysidea fragilis and Scypha ciliata. The mixed faunal turf is composed of Nemertesia antennina, Nemertesia ramosa, Halecium halecinum, Sertularia argentea, Alcyonium digitatum, Bugula flabellata, Bugula turbinata, Bugula plumosa, Flustra foliacea, Cellepora pumicosa, Alcyonidium diaphanum, Cellaria fistulosa and crisiid bryozoans. The anemones Epizoanthus couchii, Sagartia elegans and Cerianthus lloydii may also be recorded. Echinoderms such as the starfish Asterias rubens, Crossaster papposus, Henricia oculata and the crinoid Antedon bifida. Other species present include the colonial ascidian Clavelina lepadiformis, the barnacle Balanus crenatus, the top shell Gibbula cineraria, the polychaete Pomatoceros triqueter, the ascidian Morchellium argus, Prosthecareus vittatus and the crab Cancer pagurus. It is distributed off Pen Llyn and over considerable areas of the Irish Sea.
Suberites spp. with a mixed turf of crisiids and Bugula spp. on heavily silted moderately wave-exposed shallow circalittoral rock
This biotope is found on heavily silted, moderately wave-exposed circalittoral bedrock and boulders (often limestone) that are subject to moderately strong tidal streams. A very high silt loading in the water column means that this 'circalittoral' biotope occurs at unusually shallow depths (1 - 10 m BCD). It is characterised by a mixed faunal turf and `massive' examples of the sponges Suberites ficus, Suberites carnosus and Hymeniacidon perleve. Other sponges recorded in this biotope are Cliona celata, Halichondria panicea, Esperiopsis fucorum, Raspailia ramosa, Polymastia mamillaris, Dysidea fragilis, Scypha ciliata, Stelligera rigida and Haliclona oculata. Also characteristic of this biotope is a dense bryozoan turf with one or more crisiid species, Flustra foliacea and Bugula plumosa. The polychaete Polydora spp. and the rock-boring bivalve Hiatella arctica are able to bore into the relatively soft limestone. There is an ascidian component to the biotope, with Morchellium argus and Clavelina lepadiformis among the most abundant. There may be scattered clumps of the hydroids Abietinaria abietina and Hydrallmania falcata. Other species present include the anemones Metridium senile, Sagartia elegans and Urticina felina, the starfish Asterias rubens, the crab Necora puber, the nudibranch Janolus cristatus and the soft coral Alcyonium digitatum. This biotope has currently only been recorded off the east coast of Anglesey, Wales.
Mixed turf of hydroids and large ascidians with Swiftia pallida and Caryophyllia smithii on weakly tide-swept circalittoral rock
This biotope typically occurs from exposed through to sheltered circalittoral bedrock or boulders subject to moderately strong to weak tidal streams. It is found in water depths ranging from 4m to 37m. This biotope is distinguished by frequently occurring Swiftia pallida, abundant Caryophilia smithii and a diverse range of ascidians including Clavelina lepadiformis, Ascidia mentula, Polycarpa pomaria, Diazona violacea and Corella parallelogramma. A sparse, yet diverse hydroid turf is often apparent, with species such as Aglaophenia tubulifera, Nemertesia antennina, Polyplumaria frutescens, Halecium halecinum, Abietinaria abietina, Nemertesia ramosa and Halopteris catharina often recorded. Spaces amongst the turf are usually colonised by the polychaete Pomatoceros triqueter and encrusting red algae. Crinoids such as Antedon petasus, Antedon bifida and Leptometra celtica may be seen filter feeding on the tops of outcrops and boulders, along with the soft coral Alcyonium digitatum. Other echinoderms such as Echinus esculentus, Crossaster papposus and Asterias rubens may also be recorded. There may also be a bryozoan component to the sparse faunal turf. Species such as Securiflustra securifrons and Eucratea loricata as well as the crustose Parasmittina trispinosa are all usually present. There may be a few isolated growths of sponge, such as Iophonopsis nigricans, Axinella infundibuliformis and Haliclona urceolus. Other species that may be present include the brachiopod Terebratulina retusa and the top shell Calliostoma zizyphinum. The crustacean Munida rugosa may be visible in crevices. All records are from the west coast of Scotland (east coast of Lewis /Outer Hebrides).
This habitat complex occurs on wave-sheltered circalittoral bedrock and boulders subject to mainly weak/very weak tidal streams. The biotopes identified within this habitat complex are often dominated by encrusting red algae, brachiopods (Neocrania anomala) and ascidians (Ciona intestinalis and Ascidia mentula). Two fouling biotopes have also been identified: Aasp has been recorded from disused fishing nets and other artificial substrata, and is characterised by aggregations of Ascidiella aspersa whilst AdigMsen has been recorded from steel wrecks, and is characterised by dense aggregations of Alcyonium digitatum and Metridium senile. The LgAsSp biotope is characteristic of the wave-sheltered conditions found in the Kenmare River on the west coast of Ireland.
This biotope complex occurs on the wave-sheltered, circalittoral bedrock and boulders subject to weak tidal streams. The biotopes within this complex are typically found in the Scottish sealochs (with the exception of LgAsSp, recorded off Ireland) and are characterised by brachipod and ascidian communities. Ascidians often recorded in this complex are Ciona intestinalis, Ascidia mentula, Ascidia virginea and Clavelina lepadiformis. The brachiopod Neocrania anomala is also characteristic of the biotopes within this complex recorded in Scottish sealochs. The polychaete Pomatoceros triqueter, the saddle oyster Pododesmus patelliformis, the cup coral Caryophyllia smithii and encrusting red algae are frequently recorded on the rocky substrata. Echinoderms such as the brittlestars Ophiothrix fraglis, Ophiocomina nigra and Ophiura albida, the starfish Asterias rubens, Crossaster papposus and Henricia oculata, the crinoid Antedon bifida and the urchin Echinus esculentus are all found in this complex. Other species present include the squat lobster Munida rugosa, the hermit crab Pagurus bernhardus, Alcyonium digitatum, the anemone Protanthea simplex and the hydroid Kirchenpaueria pinnata. Within this biotope complex, four biotopes have been identified: AmenCio, LgAsSp, AntAsH and NeoPro.
Solitary ascidians, including Ascidia mentula and Ciona intestinalis, on wave-sheltered circalittoral rock
This biotope predominantly occurs on the upper faces of wave-sheltered (often sealochs) circalittoral bedrock, boulder and cobble slopes with little tidal flow. Apart from the solitary ascidians Ciona intestinalis and Ascidia mentula, this biotope has a rather barren, pink appearance (due to the encrusting red algae), possibly due to grazing pressure from the sea urchin Echinus esculentus. Other organisms found encrusting the rocky surface include the polychaete Pomatoceros triqueter and the cup coral Caryophyllia smithii. Other species occasionally encountered include Alcyonium digitatum, Asterias rubens, Pagurus berhardus, Crossaster papposus, Antedon bifida and Metridium senile. Crustaceans such as Munida rugosa and Cancer pagurus may be recorded in crevices. Two variants of this biotope exist: AmenCio.Ant and AmenCio.Bri. AmenCio.Bri occurs where is a dense carpet of brittlestars which sometimes completely cover the rocky substratum. Species present include Ophiothrix fragilis, Ophiocomina nigra and Ophiura albida.
Solitary ascidians, including Ascidia mentula and Ciona intestinalis, with Antedon spp. on wave-sheltered circalittoral rock
This variant occurs on circalittoral bedrock or boulder slopes in generally wave-sheltered conditions (often in sea lochs) with little tidal flow. It is frequently found on vertical or steeply-sloping rock. Apart from the large ascidians, Ascidia mentula and Ciona intestinalis, the rock surface usually has a rather sparse appearance. Scyphistomae larvae are often present on any vertical surfaces. Grazing by the sea urchin Echinus esculentus leaves only encrusting red algae (giving the bedrock/boulder substratum a pink appearance), cup corals Caryophyllia smithii and the keelworm Pomatoceros triqueter. There may be a few hydroid species present, such as Nemertesia spp. and Kirchenpaueria pinnata, occasional Alcyonium digitatum and occasional Metridium senile. Barnacles Balanus spp. and the colonial ascidian Clavelina lepadiformis also occasionally occur. At some sites, echinoderms such as the crinoid Antedon spp., the starfish Crossaster papposus and Asterias rubens and the brittlestar Ophiothrix fragilis (in low densities) may be found. The squat lobster Munida rugosa is likely to be found in crevices, under boulders, and the hermit crab Pagurus bernhardus may be observed moving around the rock surface. The brachiopod Neocrania anomala is frequently observed (especially where this biotope occurs shallower than NeoPro for example). The saddle oyster Pododesmus patelliformis may occasionally be seen attached to the rock/boulder face.
Dense brittlestars with sparse Ascidia mentula and Ciona intestinalis on sheltered circalittoral mixed substrata
This biotope is typically found on wave-sheltered sites (although it may be found in wave-exposed through to extremely wave-sheltered conditions), on circalittoral mixed substrata (Bedrock, boulders, cobbles, pebbles and gravel), subject to moderately strong to weak tidal streams. This biotope often has a silty appearance in parallel with AmenCio.Ant but is characterised by a dense carpet of brittlestars (Ophiothrix fragilis, Ophiocomina nigra and to a lesser extent Ophiura albida) which virtually cover the seabed. Where the underlying substratum is visible, pink coralline crusts and the white calcareous tubes of the keelworm Pomatoceros triqueter are often observed. Hydroids and bryozoans are scarce, perhaps partly due to the smothering effect of the brittlestars and possibly due to the grazing pressure of the sea urchin Echinus esculentus which is occasionally recorded. Other echinoderms present include Asterias rubens and Crossaster papposus. The solitary ascidian Ciona intestinalis may be seen attached to isolated rocks and boulders, whilst on the tops and sides of larger boulders, dead man's fingers Alcyonium digitatum may be recorded. The hermit crab Pagurus bernhardus is often recorded, whilst under boulders and in crevices the claws belonging to the long-clawed squat lobster Munida rugosa may be seen.
Antedon spp., solitary ascidians and fine hydroids on sheltered circalittoral rock
This biotope is typically found on silty boulder or rock slopes, in the sheltered parts of sealochs, subject to weak or very weak tidal currents. The seabed consists of smooth, silty bedrock or boulders, often as outcrops on mixed muddy sediment. There are often small vertical faces on the sides of rock ridges, and at few sites, there may be more extensive steep or vertical bedrock. In sharp contrast to the barren, grazed appearance of AmenCio.Ant, the species composition of AntAsH is quite diverse, although no one phyla dominates. A wide range of encrusting species may be found, including the brachiopod Neocrania anomala, the saddle oyster Pododesmus patelliformis, encrusting red algae and polychaetes (Pomatoceros triqueter and Protula tubularia). Other conspicuous species include crinoids on the tops of boulders (Antedon bifida, commoner in shallower water and Antedon petasus, commoner in deeper water), scattered solitary and colonial ascidians (Ascidia mentula, Ascidia virginea, Corella parallelogramma, Clavelina lepadiformis and Ciona intestinalis) and tufts of fine hydroids (Kirchenpaueria pinnata, Nemertesia antennina, Obelia dichotoma and Halceum halecinum). The cup coral Caryophyllia smithii and the crustose bryozoan Parasmittina trispinosa are all typically present, as are a wide range of echinoderms, including the sea urchin Echinus esculentus, the starfish Asterias rubens and Crossaster papposus, and the brittlestars Ophiothrix fragilis and Ophiura albida. Other species recorded are the squat lobster Munida rugosa, the hermit crab Pagurus bernhardus and the chiton Tonicella marmorea.
Large solitary ascidians and erect sponges on wave-sheltered circalittoral rock
This biotope is typically found on silty circalittoral bedrock and boulders in wave-sheltered channels subject to varying amounts of tidal flow. These fully marine inlets and channels have steep, often vertical sides with small terraces or ledges. This biotope, characterised by erect sponges and large solitary ascidians, appears to be biologically diverse. A diverse ascidian fauna is generally present, including Ascidia mentula, Aplidium punctum, Corella parallelogramma, Ascidia virginea, Botryllus schlosseri, Clavelina lepadiformis and Ciona intestinalis. An equally diverse sponge fauna, with massive erect sponges particularly noticeable, compliments these species. Dominant species include Esperiopsis fucorum, Dysidea fragilis, Tethya aurantium, Polymastia boletiformis, Raspailia ramosa, Stelligera stuposa, Polymastia mamilliaris and Pachymatisma johnstonia. Other sponges present are Suberites carnosus, Haliclona fistulosa, Stelligera rigida, Mycale rotalis, Haliclona simulans, Iophon hyndmani and Hemimycale columella. Various sponge crusts may also be present but in most cases in lower abundances. Other significant components of the community include the cup coral Caryophyllia smithii and various echinoderms, including the sea urchin Echinus esculentus and the starfish Henricia oculata and Marthasterias glacialis. Small isolated clumps of Nemertesia antennina and individual Alcyonium digitatum may be seen, whilst the top shell Calliostoma zizyphinum may also be present. At present, there are relatively few records in this biotope, as it is only reported from around the south-western coast of Ireland, where sponge diversity is very high.
Neocrania anomala and Protanthea simplex on sheltered circalittoral rock
This biotope typically occurs in full to variable salinity conditions on very wave-sheltered circalittoral bedrock and boulder slopes subject to negligible tidal streams (this tends to be in the landward, very sheltered basins of fjordic sealochs). This biotope is characterised by often dense populations of the anemone Protanthea simplex, growing on the silty bedrock. The underlying rock surfaces are usually covered by encrusting red algae, the polychaete Pomatoceros triqueter, the brachiopods Neocrania anomala and Terebratulina retusa, the saddle oyster Pododesmus patelliformis and the polychaete Sabella pavonina. Scattered colonies of Alcyonium digitatum and the hydroid Bougainvillia ramosa may occasionally be recorded. A diverse range of ascidians including Ciona intestinalis, Ascidia mentula, Corella parallelogramma, Ascidia virginea, Polycarpa pomaria and Dendrodoa grossularia are also occasionally recorded. Echinoderms such as the common brittlestar Ophiothrix fragilis are frequently reported with their arms protruding from crevices in the rock, whilst the starfish Asterias rubens, Henricia oculata, and the sea urchin Echinus esculentus and Psammechinus miliaris are occasionally found on the boulder/rock surface. The whelk Buccinum undatum is often present but in very low numbers. The squat lobster Munida rugosa may be seen hiding in crevices. The hermit crab Pagurus bernhardus may also be recorded.
Neocrania anomala and Protanthea simplex on very wave-sheltered circalittoral rock
This variant typically occurs on deep, lower circalittoral bedrock or boulder slopes (often-vertical walls) in the landward, very sheltered basins of fjordic sealochs. In these very sheltered conditions, there are frequently dense populations of the anemone Protanthea simplex growing on the silty boulder or rock slope, and on the tubes of the parchment worm Chaetopterus variopedatus. The underlying rock surfaces are usually covered with encrusting red algae, the polychaete Pomatoceros triqueter, the brachiopod Neocrania anomala, the saddle oyster Pododesmus patelliformis and the conspicuous fan worm Sabella pavonina. Scattered colonies of Alcyonium digitatum are occasionally present along with the hydroid Bougainvillia ramosa. The barnacle Balanus balanus and the hermit crab Pagurus bernhardus is occasionally seen on boulder or rock surface, whilst underneath in crevices, the squat lobster Munida rugosa may be present. A diverse range of solitary ascidians, typically found in sheltered conditions, are often present including Ciona intestinalis, Corella parallelogramma, Polycarpa pomaria, Ascidia mentula and Ascidia virginea. Echinoderms such as brittlestars Ophiothrix fragilis are frequently seen with their arms protruding from crevices in the rock, whilst the starfish Asterias rubens, the sea urchin Echinus esculentus and Psammechinus miliaris are occasionally found on the boulder or rock surface. The whelk Buccinum undatum is often present but in very low numbers.
Neocrania anomala, Dendrodoa grossularia and Sarcodictyon roseum on variable salinity circalittoral rock
This variant typically occurs on lower circalittoral silty, bedrock or boulder cliffs and ridges in very wave-sheltered fjordic sealochs subjected to variable salinity regimes (such as Loch Etive). In these sheltered conditions, there are frequently dense populations of the ascidian Dendrodoa grossularia, the brachiopod Neocrania anomala and to a lesser extent, the brachiopod Terebratulina retusa, which are able to tolerate the variable salinity. Other solitary ascidians that may be present include Ciona intestinalis, Corella parallelogramma, Ascidiella scabra, Ascidia mentula, Ascidia virginea and Polycarpa pomaria. The anemone Protanthea simplex is occasionally seen, although to a lesser extent than in NeoPro, possibly due to the variable salinity. The hydroids Bougainvillia ramosa and Lafoea dumosa, the cup-coral Caryophilia smithii and Sarcodictyon roseum are occasionally present. The tubes formed by the polychaete Sabella pavonina may be observed standing erect from the rock surface. The rest of the rock surface is usually covered by encrusting red algae and the polychaete Pomatoceros triqueter and Protula tubularia. The sea cucumber Psolus phantapus may be found on the underside of boulders. Other species such as the hermit crab Pagurus bernhardus and the spider crab Hyas araneus may be found amongst the rock/boulders. The starfish Asterias rubens, Crossaster papposus, and Henricia spp. and the sea urchin Psammechinus miliaris are also recorded within this variant. The relatively bare, silty rock supports low numbers of a relatively few species. Although barren rock grazed by the sea urchin Echinus esculentus is found in other sea loch biotopes (see FaAlCr.Pom and FaAlCr.Car), E.esculentus is virtually absent within NeoPro.VS.
This habitat complex mainly occurs on exposed to moderately wave-exposed circalittoral bedrock and boulders, subject to moderately strong and weal tidal streams. A few biotopes (FluCoAs.X, FluHocu) also occur on more mixed substrata featuring cobble and sand. This habitat complex contains a broad range of biotope complexes, from mixed faunal turf (XFa) to Sabellaria reefs (CSab) and circalittoral mussel beds (CMus).
Circalittoral faunal communities in variable salinity
This biotope complex occurs on wave-sheltered, variable salinity bedrock and cobbles, subject to moderately strong to weak tidal streams. This complex contains a suite of sponges able to tolerate the variable salinity conditions like Hymeniacidon perleve, Suberites ficus, Halichondria panicea, Halichondria bowerbanki, Cliona celata and Leucosolenia botryoides. The barnacle Balanus crenatus is frequently recorded in this complex. A sparse hydroid/bryozoan turf composed primarily of Nemertesia antennina, Nemerteis ramosa, Plumularia setacea, Alcyonidium diaphanum and Bugula plumosa is often recorded. Other species recorded are the ascidians Clavelina lepadiformis, Morchellium argus and Dendrodoa grossularia, the anemones Metridium senile and Sagartia troglodytes, the starfish Asterias rubens and the crab Carcinus maenas. Two biotopes have been identified within this complex: CuSpH (cushion sponges with hydroids) and HbowEud.
Cushion sponges and hydroids on turbid tide-swept sheltered circalittoral rock
This biotope is found in variable salinity environments and tends to occur on the upper faces of circalittoral bedrock and boulders, in sheltered sites subject to moderately strong tidal streams. This biotope is characterised by aggregations of cushion sponges such as Hymeniacidon perleve, Halichondria panicea, Halichondria bowerbanki and Cliona celata, other sponges (Leucosolenia botryoides and Suberites ficus) along with occasional hydroid tufts of Nemertesia antennina, Nemertesia ramosa and Plumularia setacea. Other species that may be present include the colonial ascidians Clavelina lepadiformis and Morchellium argus, Dendrodoa grossularia, the anemones Metridium senile and Sagartia troglodytes, the barnacle Balanus crenatus, Asterias rubens, Carcinus maenas and Bugula plumosa. Two variants of this biotope have been recorded: CuSpH.VS and CuSpH.As.
Cushion sponges, hydroids and ascidians on turbid tide-swept sheltered circalittoral rock
This sub-biotope typically occurs in a mixture of turbid, full and variable salinity water, on wave-sheltered and moderately exposed bedrock or boulders. Tidal streams are typically moderately strong but may vary considerably. This sub-biotope occurs in relatively shallow water (typically 5m to 11m water depth) and is dominated by cushion sponges, hydroids and ascidians. On the silty, rocky substrata, large growths of sponge are usually associated with this biotope (Suberites ficus, Hymeniacidon perleve, Cliona celata, Halichondria panicea, Raspailia ramosa). The tasselled form of Esperiopsis fucorum is also notably present. Other epifauna present includes silty hydroids such as Nemertesia antennina, Nemertesia ramosa, Plumularia setacea, Hydrallmania falcata and Halecium halecinum. Individual colonies of dead mans fingers Alcyonium digitatum and plumose anemones Metridium senile may be seen attached to the tops of boulders and ridges. At some sites, whole sides of rocks may be colonised by the anemones Sagartia elegans, Sagartia troglodytes and Actinothoe sphyrodeta. Within crevices in the rocky substratum and at the base of boulders Urticina felina and Cereus pedunculatus may be found. Ascidians such as Clavelina lepadiformis, Morchellium argus, Dendrodoa grossularia, Diplosoma listerianum and Distomus variolosus may all be observed. Other ubiquitous species which may be recorded include Polydora, terebellid worms, Balanus crenatus, Alcyonidium diaphanum and Asterias rubens.
Cushion sponges and hydroids on turbid tide-swept variable salinity sheltered circalittoral rock
This sub-biotope typically occurs in turbid, variable salinity water, on wave-sheltered bedrock in estuaries subject to strong tidal regimes where circalittoral communities occur in relatively shallow water (typically 5m to 8m water depth). Cushion sponges, hydroids and ascidians dominate the biotope. Large growths (often up to 50cm across) of the sponges Halichondria panicea mixed with Halichondria bowerbanki almost entirely cover the bedrock, appearing in places like a continuous cushion. Haliclona oculata, Suberites ficus, Leucosolenia botryoides, various hydroids such as Plumularia setacea, Nemertesia antennina, Nemertesia ramosa and various bryozoans such as Bugula plumosa, Bugula turbinata and Bowerbankia pustulosa protude through the Halichondria spp. sponge growth. Colonial ascidians such as the lightbulb ascidian Clavelina lepadiformis and Morchellium argus may also be observed. Other more ubiquitous species include Balanus crenatus, Carcinus maenas, Asterias rubens, Metridium senile, Sagartia elegans and Ophiothrix fragilis.
Halichondria bowerbanki, Eudendrium arbusculum and Eucratea loricata on reduced salinity tide-swept circalittoral mixed substrata
This biotope typically occurs on circalittoral mixed substrata (bedrock, boulders, cobbles, pebbles and gravel) in the moderately strong, tide-swept narrows near the entrance of Loch Etive, although not in the extremely tide-swept Falls of Lora. This sea loch is unique in having a substantial freshwater input from the surrounding moorland, yielding the most brackish, large sea loch in Scotland. Large growths of the brackish-tolerant sponge Halichondria bowerbanki cover the cobble and boulder seabed, interspersed with Mycale lobata, the hydroid Eudendrium arbusculum and the bryozoan Alcyonidium diaphanum which are particularly characteristic of these conditions. Tufts of the bryozoan Eucratea loricata are occasional in most areas. Other species recorded include Carcinus maenas, Asterias rubens, Crossaster papposus, Buccinum undatum, Pagurus berhardus, Henricia spp., Onchidoris bilamellata and Palio dubia, tolerant of the low salinity, are found in the circalittoral throughout this area. Ascidians such as Ascidiella scabra and Corella parallelogramma may also be present. A very impoverished low salinity version is present in the upper basin of Loch Etive. The biotope CuSpH is similar in several respects to this biotope and will develop in less brackish situations where species-richness is generally greater.
This biotope complex occurs on moderately wave-exposed upper circalittoral bedrock subject to strong or moderately strong tidal streams. This complex is characterised by dense aggregations of the mussels Mytilus edulis or Musculus discors carpeting the underlying substrata. Sponges that may be recorded in this complex are Scypha ciliata, Tethya aurantium, Pachymatisma johnstonia, Dysidea fragilis and Cliona celata. A sparse hydroid/bryozoan turf composed primarily of Nemertesia antennina, Alcyonidium diaphanum and Flustra foliacea is often recorded. Anemones present are Urticina felina and Sagartia elegans. Other species recorded are the crabs Cancer pagurus, Carcinus maenas and Necora puber, the starfish Crossaster papposus and Asterias rubens, and Alcyonium digitatum. In this upper circalittoral complex, algae species such as Dictyota dichotoma, Cryptopleura ramosa and Plocamium cartilagineum. Two biotopes have been identified: CMyt (M. edulis dominated) and Mdis (M. discors dominated).
Mytilus edulis beds with hydroids and ascidians on tide-swept exposed to moderately wave-exposed circalittoral rock
This biotope typically occurs on the upper faces of tide-swept circalittoral bedrock, boulders and mixed substrata exposed to varying amounts of wave action. The mussel Mytilus edulis forms dense beds, to the exclusion of other species. The starfish Asterias rubens is frequently recorded, and it predates heavily on the mussels. Occasionally, the anemone Urticina felina may be seen within crevices in the rock or on gravel patches. Crabs such as Necora puber and Carcinus maenas may be seen on the rock or mussels whilst fauna observed in crevices typically consists of the lobster Homarus gammarus and the crab Cancer pagurus. The anemone Sargatia elegans can be seen attached to bedrock and cobbles, whereas the barnacle Balanus crenatus may be seen attached to the mussels themselves.
Musculus discors beds on moderately exposed circalittoral rock
This biotope typically occurs on the upper faces of moderately exposed, moderately tide-swept bedrock, boulders and cobbles in slightly silty conditions. The mussel Musculus discors occurs in dense mats and occasionally completely coats all available surfaces. There is also often a layer of pseudofaeces, forming a thick, silty matrix. A relatively diverse fauna of cushion and branching sponges is often present on rocky outcrops and other hard substratum that is free of mussels. These include Tethya aurantium, Scypha ciliata, Pachymatisma johnstonia, Dysidea fragilis, Cliona celata and Stelligera stuposa. There may be isolated clumps of silt-tolerant bryozoans such as Flustra foliacea and Bugula plumosa. Various species may be observed on top of the mussels, including Asterias rubens, Crossaster papposus and the brittlestar Ophiura albida. Occasional Alcyonium digitatum and clumps of the hydroid Nemertesia antennina are found attached to rocky outcrops and boulders whilst the anemone Urticina felina may be seen in crevices in the rock or on gravely patches between boulders. Colonial ascidians such as Clavelina lepadiformis and didemnids may occasionally be present. A wide range of seaweeds may be present, including Dictyota dichotoma, Plocamium cartliagineum, Dictyopteris membranacea, Cryptopleura ramosa and Heterosiphonia plumosa. The crab Cancer pagurus may be observed in crevices. The majority of the records for this biotope are from the Lleyn Peninsula.
Circalittoral Sabellaria reefs (on rock)
This biotope complex occurs on moderately wave-exposed, circalittoral bedrock, boulders and cobbles subject to moderately strong tidal streams. It is characterised by dense crusts of the polychaete Sabellaria spinulosa covering the substratum. Other fauna present in many cases reflects the biotopes found on nearby rock, so to a certain extent, is quite variable. Species typically present include the bryozoans Flustra foliacea, Alcyonidium diaphanum and Pentapora foliacea, the hydroid Nemertesia antennina, the sponges Tethya aurantium and Phorbas fictitius, the anemones Urticina felina and Sagartia elegans, and the ascidians Distomus variolosus, Polycarpa pomaria and Polycarpa scuba. The barnacle Balanus crenatus, the polychetes Pomatoceros triqueter and Salmacina dysteri, the starfish Crossaster papposus, and Alcyonium digitatum may also be recorded. Two variants of the Sspi biotope have been identified: Sspi.ByB and Sspi.As (characterised by didemnid ascidians).
Sabellaria spinulosa encrusted circalittoral rock
This biotope is typically found encrusting the upper faces of wave-exposed and moderately wave-exposed circalittoral bedrock, boulders and cobbles subject to strong/moderately strong tidal streams in areas with high turbidity. The crusts formed by the sandy tubes of the polychaete worm Sabellaria spinulosa may even completely cover the rock, binding the substratum together to form a crust. A diverse fauna may be found attached to, and sometimes obscuring the crust, often reflecting the character of surrounding biotopes. Bryozoans such as Flustra foliacea, Pentapora foliacea and Alcyonidium diaphanum, anemones such as Urticina felina and Sagartia elegans, the polychaete Pomatoceros triqueter, Alcyonium digitatum, the hydroid Nemertesia antennina and echinoderms such as Asterias rubens and Crossaster papposus may all be recorded within this biotope. There are two variants. The first (Sspi.ByB) contains significant cover of barnacles (Balanus crenatus) and bryozoans. The second (Sspi.As) has a dense turf of didemnid ascidians as well as scour-tolerant bryozoans such as F. foliacea, sponges such as Tethya aurantium and Phorbas fictitius, colonies of the serpulid worm Salmacina dysteri and patchy occurrences of the ascidians Distomus variolosus, Polycarpa pomaria and Polycarpa scuba. This biotope has been recorded from the Lleyn Peninsula, Lundy Island (including the wreck of the MV Robert) and the north-east and south coast of England.
Sabellaria spinulosa, didemnids and other small ascidians on tide-swept moderately wave-exposed circalittoral rock
This variant is typically found on tide-swept, moderately wave-exposed circalittoral bedrock, boulders and cobbles subject to slight sand-scour. It occurs predominantly in the lower circalittoral. This variant normally appears as a bedrock/boulder outcrop or reef with a dense crust of the polychaete Sabellaria spinulosa and a dense turf of didemnid ascidians and scour-tolerant bryozoans such as Flustra foliacea, Pentapora foliacea and Cellaria species. There may be discreet clumps of Alcyonium digitatum and sparse sponges such as Tethya aurantium and Phorbas fictitius. Patchy occurrences of the small ascidians Polycarpa scuba, Polycarpa pomaria and Distomus variolosus may be present on the tops of rocks and boulders whilst in crevices between, the anemone Urticina felina may be found. Species such as Asterias rubens, Crossaster papposus, the serpulid worm Salmacina dysteri and the anemone Sagartia elegans are occasionally seen on the rock surface. This variant has been recorded from the Lleyn Peninsula, the Skerries and around Pembrokeshire in Wales.
Sabellaria spinulosa with a bryozoan turf and barnacles on silty turbid circalittoral rock
This variant is typically found encrusting the upper faces of exposed and moderately exposed circalittoral rock and mixed substrata, subject to strong and moderately strong currents and high turbidity levels. The crusts formed by the sandy tubes of the polychaete worm Sabellaria spinulosa may completely cover the rock, binding gravel and pebbles together. A diverse fauna may be found attached to this crust, and in many cases reflects the character of nearby biotopes. There is normally considerable variation in the associated fauna encountered. There may be a sparse bryozoan turf (Flustra foliacea, Alcyonidium diaphanum, Bicellariella ciliata, Bugula plumosa and Vesicularia spinosa) attached to the Sabellaria crust and available rocky substrata. Other scour-tolerant species such as Urticina felina are occasionally observed. Clumps of robust hydroids such as Tubularia indivisa, Nemertesia antennina, Hydrallmania falcata and Halecium halecinum may also be observed. Other species which may be present include the polychaete Pomatoceros triqueter, Balanus crenatus, Asterias rubens, Pagurus bernhardus and Gibbula cineraria. Occasionally, sponges such as Haliclona oculata and Halichondria panicea, and ascidians such as Dendrodoa grossularia may also be observed.
This biotope complex occurs on wave-exposed, moderately strong to weakly tide-swept, circalittoral bedrock and boulders. Echinoderms, faunal (Parasmittina trispinosa) and algal crusts (red encrusting algae) dominate this biotope, giving a sparse appearance. Typical echinoderms present are the starfish Asterias rubens, the brittlestar Ophiothrix fragilis and the sea urchin Echinus esculentus. There may be isolated clumps of the hydroids Nemertesia antennina and Abietinaria abietina, Alcyonium digitatum, the anemone Urticina felina and the cup coral Caryophyllia smithii. Other species present may include the polychaete Pomatoceros triqueter and the top shell Calliostoma zizphinum. Five biotopes have been identified within this biotope complex: CarSwi, CarSp, FaAlCr, UrtScr and AdigVT.
Alcyonium digitatum and faunal crust communities on vertical circalittoral bedrock
This biotope typically occurs on the vertical faces and overhangs of exposed to moderately exposed lower infralittoral and upper circalittoral bedrock subject to moderately strong to weak tidal streams. Due to the large numbers of the urchin Echinus esculentus often recorded, this biotope tends to have a grazed appearance, and the bedrock is often encrusted with pink coralline algae, encrusting bryozoans such as Parasmittina trispinosa and the calcareous tubeworm Pomatoceros triqueter. Dense aggregations of dead mans fingers Alcyonium digitatum may be present along with the cup coral Caryophyllia smithii. Other species present include the echinoderms Asterias rubens, Ophiothrix fragilis and Antedon bifida, the ascidians Clavelina lepadiformis, Ciona intestinalis and Ascidia mentula, the anthozoans Urticina feline, Cortynactis viridis, Metridium senile and Sagartia elegans, the gastropod Calliostoma zizyphinum and the crustacean Cancer pagurus. Three regional variations of this biotope have been recorded. One variant found typically off the north-east coast of Scotland and around the Northern Isles, has a very impoverished appearance dominated by anthozoans. A second variant occurs along the west coast of Scotland, extending to Rockall in the west, and the Northern Isles in the north-east, and has a more fauna, characterised by hydroids, sponges, anthozoans and echinoderms. A third variant occurs along the north-east coast of England (Northumberland) up to the Northern Isles and is dominated by Alcyonium digitatum, brittlestars and Echinus esculentus.
Caryophyllia smithii, sponges and crustose communities on wave-exposed circalittoral rock
This biotope typically occurs on the upper and vertical faces of wave-exposed, moderately strong to weakly tide-swept, circalittoral bedrock or boulders, with a water depth range of 20-30m. This often silty biotope has a typically sparse fauna, appearing grazed, and is characterised by common cup corals Caryophyllia smithii, frequent Alcyonium digitatum and occasional urchins Echinus esculentus. There may be occasional large growths of the sponge Cliona celata, Haliclona viscosa, Pachymatisma johnstonia and the axinellid sponge Stelligera stuposa. Echinoderms form a prominent feature of the fauna within this biotope, with species such as Marthasterias glacialis, Asterias rubens, Luidia ciliaris, Henricia oculata, Holothuria forskali, Antedon bifida and Aslia lefevrei present. Bryozoan crusts such as Parasmittina trispinosa and encrusting red algae cover the rock/boulder surface. The bryozoan Porella compressa may also be recorded occasionally. Isolated clumps of hydroids feature species such as Nemertesia antennina, Nemertesia ramosa, Abietinaria abietina, Halecium halecinum and Sertularella gayi. Other species observed include the anemone Corynactis viridis, Urticina felina, Sagartia elegans, Calliostoma zizyphinum, Balanus crenatus and Pomatoceros triqueter. Two variants within this biotope have been distinguished: CarSp.PenPcom and CarSp.Bri. While CarSp.PenPcom tends to have the bryozoans Pentapora foliacea and P. compressa, while CarSp.Bri features a dynamic community of brittlestars covering the seabed in a dense mat. Ophiothrix fragilis is usually the dominant species in shallow water but tends to be replaced by Ophiocomina nigra in deeper water.
Brittlestars overlying coralline crusts, Parasmittina trispinosa and Caryophyllia smithii on wave-exposed circalittoral rock
This variant is typically found on the upper faces of wave-exposed circalittoral bedrock or boulders subject to moderately strong to weak tidal streams, on open coasts. However, the depth at which the variant occurs means that wave action is not so severe on the seabed as to displace the dense mat of brittlestars that covers the seabed. Ophiothrix fragilis is usually the most dominant species in shallow water, with Ophiocomina nigra usually found amongst them, but sometimes becoming the dominant species in deeper water. Although brittlestar biotopes are typically species-poor, the underlying fauna in this variant is relatively diverse and resembles that of CarSp.PenPcom. Species such as the anemone Urticina felina, the cup coral Caryophyllia smithii, and the anemone Corynactis viridis may occasionally be present. There may also be sparse clumps of various hydroids including Halecium halecinum, Nemertesia antennina, Nemertesia ramosa, Sertularella gayi and Abietinaria abietina. Soft coral Alcyonium digitatum is occasionally present and there may be sparse specimens of the sponges Cliona celata and Polymastia boletiformis. In addition, various echinoderms such as Asterias rubens, Antedon bifida, Echinus esculentus, Henricia oculata, Marthasterias glacialis and Luidia ciliaris may be observed. The barnacle Balanus crenatus and the polychaete Pomatoceros triqueter may be seen attached to any available space on the bedrock and boulders not smothered by brittlestars. Bryozoan crusts such as Parasmittina trispinosa may also be present.
Caryophyllia smithii and sponges with Pentapora foliacea, Porella compressa and crustose communities on wave-exposed circalittoral rock
This variant is typically found on the upper faces and vertical sides of wave-exposed bedrock or boulders subject to moderately strong to weak tidal streams. The fauna is often sparse with the frequently observed Echinus esculentus giving it a grazed appearance, but the community may also be affected by violent storm action working into deep water during winter storms. Despite this spartan appearance, the community is relatively diverse and contains a wide range of sponges, hydroids, bryozoans and echinoderms. This variant is found on open coasts or offshore, and is characterised by the cup-coral Caryophyllia smithii, Alcyonium digitatum, the sea urchin Echinus esculentus, large specimens of the sponge Cliona celata, encrusting bryozoans and encrusting red algae. Although this variant tends to occur in deep water (depth range of 20-30m), a high degree of water clarity allows some red algae to grow at these depths. Other species recorded include large specimens of Haliclona viscosa, the bryozoans Parasmittina trispinosa, Porella compressa and Pentapora foliacea, the sea cucumbers Holothuria forskali and Aslia lefevrei and sparse hydroids such as Abietinaria abietina, Nemertesia antennina, Nemertesia ramosa and Halecium halecinum. Anemones such as Corynactis viridis, Sagartia elegans and Urticina felina are also frequently seen. Various other species characteristic of wave-exposed rock include the sponges Pachymatisma johnstonia, Stelligera stuposa, the starfish Luidia ciliaris, Marthasterias glacialis, Asterias rubens, Henricia oculata, the crinoid Antedon bifida, the barnacle Balanus crenatus, the top shell Calliostoma zizyphinum and the polychaete Pomatoceros triqueter. The majority of the records within this variant originate from the west coast of Ireland.
Caryophyllia smithii and Swiftia pallida on circalittoral rock
This biotope is typically found on the upper and vertical faces of very exposed through to wave-sheltered circalittoral bedrock and boulders, which are typically subject to weak tidal streams. It is characterised by dense aggregations of the cup coral Caryophyllia smithii and the sea fan Swiftia pallida on the silty substratum. Under the silt, bryozoan crusts such as Parasmittina trispinosa and encrusting red algae may be seen. This biotope may have a grazed appearance, perhaps attributable to the frequently occurring Echinus esculentus. There may be a sparse hydroid turf present, with species such as Nemertesia antennina, Nemertesia ramosa and Halecium halecinum present. The soft corals Alcyonium glomeratum and Alcyonium digitatum may be present on the tops of boulders along with the crinoids Antedon petasus and Antedon bifida. Other echinoderms occasionally observed include the starfish Marthasterias glacialis, Asterias rubens and Luidia ciliaris. Sponges feature only occasionally in this biotope, including species such as Cliona celata. The bryozoan Porella compressa may also be recorded. Ascidians occasionally present include Ascidia mentula, Clavelina lepadiformis and Ciona intestinalis. Under-boulder fauna typically consists of the crustacean Munida rugosa. The polychaete Pomatoceros triqueter may be seen encrusting the rocky surface. Two variants of this biotope have been identified; CarSwi.Aglo and CarSwi.LgAs. CarSwi.Aglo is a heavily silted biotope characterised by the sea fan S. pallida, the cup coral C. smithii and the soft coral A. glomeratum and is only present in Irish waters. CarSwi.LgAs has been recorded off the west coast of Scotland, and is characterised by large solitary ascidians and the cup coral C. smithii.
Caryophyllia smithii, Swiftia pallida and Alcyonium glomeratum on wave-sheltered circalittoral rock
This variant typically occurs on sheltered, ridged, circalittoral bedrock or boulders subject to only weak tidal streams, but may be found in somewhat more exposed conditions. It is found in water depths ranging from 15m to 32m. Commonly occurring Swiftia pallida characterises this heavily silted biotope along with Caryophyllia smithii and frequent Alcyonium glomeratum. Under the silt, bryozoan crusts such as Parasmittina trispinosa may be found. There is a strong echinoderm component to the community, with the tentacles of Aslia lefevrei frequently seen protruding from crevices in the ridged bedrock. Holothuria forskali is often seen on the upper faces of boulders and bedrock. Marthasterias glacialis, Asterias rubens, Echinus esculentus, Henricia oculata and Luidia ciliaris may also be present. A sparse hydroid turf may also be present, with species such as Polyplumaria frutescens, Halecium halecinum and Nemertesia antennina. In addition, there may be anthozoans such as Isozoanthus sulcatus and Corynactis viridis. The sponge Suberites carnosus is typically associated with a heavily silted habitat. Other sponges present include Cliona celata, Stelligera stuposa and Polymastia boletiformis. The only records are from the west coast of Ireland.
Caryophyllia smithii, Swiftia pallida and large solitary ascidians on exposed or moderately exposed circalittoral rock
This variant typically occurs on exposed to moderately wave-exposed, circalittoral bedrock and boulders rock subject to mainly weak tidal streams and has a thin layer of silt present. It is found predominantly from 10-30m water depth. From afar, this biotope is mostly distinguished by the frequently occurring seafan Swiftia pallida, encrusting red algae and the abundant cup coral Caryophyllia smithii. This biotope has quite an impoverished appearance, compared with SwiLgAs which has a strong sponge component. Other species present are typically in low abundance. Echinoderms such as Echinus esculentus, Antedon bifida, Antedon petasus, Leptometra celtica, Marthasterias glacialis, Luidia ciliaris and Asterias rubens may be recorded. Large hydroids such as Nemertesia antennina and Nemertesia ramosa may occasionally be seen in isolated clumps on the tops of boulders and rocky outcrops. The anthozoan Parazoanthus anguicomus may be recorded. Bryozoans such as Parasmittina trispinosa and Porella compressa are occasionally observed. The polychaete Pomatoceros triqueter may be observed encrusting the sides of rocks and boulders while occasional Alcyonium digitatum may also be seen. A small suite of large ascidians may be present, including Ascidia mentula, Clavelina lepadiformis, Ciona intestinalis, Diazona violacea and Ascidia virginea. Sponges are typically absent from this biotope, although Cliona celata may be recorded occasionally. The top shell Gibbula cineraria is usually present. Under boulders and overhangs, the squat lobster Munida rugosa can usually be seen hiding. All these records are from the west coast of Scotland (East coast of Lewis /Outer Hebrides).
Faunal and algal crusts on exposed to moderately wave-exposed circalittoral rock
This biotope typically occurs on the vertical and upper faces of wave-exposed and moderately wave-exposed circalittoral bedrock or boulders subject to mostly moderate to weak tidal streams (a variant of this biotope containing brittlestar is found on bedrock, boulders and cobbles). The biotope is dominated by faunal (e.g. Parasmittina trispinosa) and algal (Corallinaceae) crusts, and tends to have a grazed appearance; this may be partially attributable to the abundance of Echinus esculentus found in this biotope. Occasionally, the rock may appear pink from a distance, due to the expanses of encrusting red algae on the rock surface. Alcyonium digitatum is one of the few species to stand erect from the encrusted rock surface and are frequently encountered, on the tops of rocky outcrops and boulders. Hydroids do not form a prominent feature of this biotope, with only robust species such as Abietinaria abietina frequently recorded. Sponges and Caryophyllia smithii are rarely present while erect bryozoans and ascidians are scarce (although there are exceptions, see variants). The E. esculentus grazed substratum may be interspersed with other encrusting species such as the polychaete Pomatoceros triqueter and the saddle oyster Pododesmus patelliformis. Other species present include Asterias rubens, Ophiothrix fragilis, Urticina felina, Ophiocomina nigra, Pagurus bernhardus, Flustra foliacea, Gibbula cineraria, Calliostoma zizyphinum, Ophiura albida, Ciona intestinalis and Antedon bifida. Six variants of this biotope have been recorded. FaAlCr.Flu is dominated by the silt and scour tolerant bryozoan F. foliacea. FaAlCr.Adig is dominated by A. digitatum. FaAlCr.Sec is dominated by Securiflustra securifrons. FaAlCr.Pom looks extremely impoverished (even for a grazed community). FaAlCr.Bri has a dense covering of brittlestars while FaAlCr.Car is only found under weak/very weak tides and is dominated by C. smithii.
Alcyonium digitatum, Pomatoceros triqueter, algal and bryozoan crusts on wave-exposed circalittoral rock
This variant is typically found on the vertical, steep and upper faces of wave-exposed circalittoral bedrock or boulders subject to varying amounts of current. The variant has a very grazed, sparse appearance, dominated only by the presence of Alcyonium digitatum and large expanses of encrusting red alage and bryozoan crusts particularly (Parasmittina trispinosa). The sparse appearance can be attributed to the frequently observed sea urchin Echinus esculentus. The polychaete Pomatoceros triqueter can be locally abundant, and may in some cases cover far more rock surface than A. digitatum, especially on vertical faces. Clumps of robust hydroids such as Abietinaria abietina occur occasionally. Other species present include the echinoderms Asterias rubens, Henricia sanguinolenta, Ophiothrix fragilis, the anemone Urticina felina, Calliostoma zizyphinum and Cancer pagurus.
Brittlestars on faunal and algal encrusted exposed to moderately wave-exposed circalittoral rock
This variant is typically found on the upper faces of exposed and moderately wave-exposed circalittoral bedrock, boulders and cobbles subject to moderately strong to weak tidal streams. It is characterised by high densities of brittlestars (predominantly Ophiothrix fragilis, Ophiocomina nigra and Ophiura albida). In fact, they may form such dense beds that the seabed underneath may not be visible. The rocky substratum is usually colonised by species such as encrusting red algae and the white, calcareous tubes of the polychaete Pomatoceros triqueter. Only robust hydroids such as Abietinaria abietina, Alcyonium digitatum and bryozoan crusts such as Parasmittina trispinosa are able to tolerate the significant smothering effect from the dense mat of brittlestars. Other species typically seen include Echinus esculentus, Asterias rubens, Pagurus bernhardus, Anapagurus hyndmanni, Gibbula cineraria, Urticina felina, Pododesmus patelliformis and Ciona intestinalis.
Caryophyllia smithii with faunal and algal crusts on moderately wave-exposed circalittoral rock
This variant is typically found on the upper and vertical faces of exposed and moderately wave-exposed circalittoral rock, subject to very little water movement. Where this variant is found on slightly more wave-exposed sites, it tends to be found towards the bottom of its depth range. The rocky substratum has a grazed appearance, with encrusting red algae. Diversity of species is very low, possibly due to grazing pressure from the sea urchin Echinus esculentus. From afar, there is little evident epifauna attached to the rocks apart from the white, calcareous tubes of the polychaete Pomatoceros triqueter and the cup-coral Caryophyllia smithii. In addition, bryozoan crusts such as Parasmittina trispinosa are frequently seen. Under closer inspection, a few more species become apparent but few are typically characterising of this particular variant. The echinoderms Antedon bifida, Asterias rubens, Ophiothrix fragilis, Marthasterias glacialis, Ophiocomina nigra and Crossaster papposus are occasionally present. Sparse clumps of hydroids such as Halecium halecinum, Kirchenpaueria pinnata and Nemertesia antennina may be found attached to rocky outcrops or boulders. Small specimens of Alcyonium digitatum may be present. The ascidians Ciona intestinalis, Clavelina lepadiformis and Ascidia mentula also occur in this variant but are found in greater numbers in other biotopes. The top shells Calliostoma zizyphinum, Gibbula cineraria, and the saddle oyster Pododesmus patelliformis may be seen on the rock surface whilst the crab Cancer pagurus may be seen under boulders and in crevices. The anemone Metridium senile may be found under rocky overhangs and on the sides of boulders.
Flustra foliacea on slightly scoured silty circalittoral rock
This variant is typically found on the upper faces of moderately wave-exposed circalittoral bedrock or boulders subjected to moderately strong tidal streams. These rocky patches may be interspersed with gravelly sand patches, causing a scouring effect. From afar, the variant appears dominated by the bryozoan Flustra foliacea. Alcyonium digitatum may also be seen attached to the rocky substratum. Under closer inspection, the white tubes of the polychaete Pomatoceros triqueter may be observed on the rock and boulders, especially on vertical faces. There may be sandy/gravelly patches in between the boulders colonised by the anemone Urticina felina. The regular occurrence of large numbers of the sea urchin Echinus esculentus in this biotope may be responsible for grazing the faunal and algal turf, thus keeping species richness relatively low. Other echinoderms that may be seen include the ubiquitous starfish Asterias rubens and the common brittlestar Ophiothrix fragilis. Sparse clumps of the hydroids Thuiaria thuja, Abietinaria abietina, Nemertesia antennina and Tubularia indivisa are occasionally seen attached to the rocky substratum. The hermit crab Pagurus bernhardus, the polychaete Sabella pavonina and sparse bryozoan crusts may also be present. This biotope is characteristic of the bedrock terraces along the Northumberland coast that are generally species impoverished compared to similar F. foliacea biotopes on the west coasts of the UK, which have a more diverse range of sponges, hydroids and bryozoans. As the turbidity levels increase in this fairly silty biotope, so the species diversity is reduced.
Faunal and algal crusts with Pomatoceros triqueter and sparse Alcyonium digitatum on exposed to moderately wave-exposed circalittoral rock
This variant is typically found on the upper faces of exposed and moderately exposed circalittoral bedrock or boulders subjected to moderately strong to weak tidal streams. From afar, the seabed has a rather sparse, grazed appearance, reminiscent of a brittlestar bed after the brittlestars have moved elsewhere. The rocky substratum is generally covered with encrusting red algae and the white, calcareous tubes of the polychaete Pomatoceros triqueter, dotted with the abundant urchin Echinus esculentus. Under closer inspection, Alcyonium digitatum are usually seen attached to the rocky surface underneath rock overhangs and large boulders. Although they may be recorded as abundant or common in some areas, their relatively small size means that their biomass is generally lower than in other biotopes. Sparse clumps of robust hydroids such as Abietinaria abietina are frequently observed, and bryozoan crusts such as Parasmittina trispinosa are occasionally seen. Echinoderms such as the brittlestars Ophiothrix fragilis and Ophiocomina nigra, and the crab Cancer pagurus may be seen within crevices in the boulders/rock whilst the starfish Asterias rubens may be seen on the rock surface. Muddy-gravel patches between boulders (especially within Scottish sealochs) provide a suitable habitat for the anemone Urticina felina. The top shell Gibbula cineraria is occasionally seen grazing on the rock surface. Within this biotope, there is some regional variation. The robust hydroid A. abietina is typically found in higher abundances in northern (Scottish) regions, especially around the Isle of May.
Alcyonium digitatum with Securiflustra securifrons on tide-swept moderately wave-exposed circalittoral rock
This variant is typically found on the upper and vertical faces of moderately wave-exposed circalittoral bedrock subject to moderately strong to weak tidal streams. The rock surface is dominated by Alcyonium digitatum and the bryozoan Securiflustra securifrons. The rock between these species appears fairly sparse and grazed, with expanses of encrusting red algae. The sea urchin Echinus esculentus is frequently seen, and in collaboration with the light attenuating effects of depth, is probably the principal reason for the lack of algal turf. Other species found include the hydroids Abietinaria abietina, Nemertesia antennina, Thuiaria thuja, the bryozoans Cellepora pumicosa, Parasmittina trispinosa, Flustra foliacea, Alcyonidium diaphanum and other bryozoan crusts. Encrusting species such as the polychaete Pomatoceros triqueter and the barnacle Balanus balanus are frequently observed. Other species present include Asterias rubens, Antedon bifida, Ophiura albida, Ophiothrix fragilis, Caryophyllia smithii, Urticina felina, Clavelina lepadiformis, Calliostoma zizphinium and Pandalus montagui.
Urticina felina and sand-tolerant fauna on sand-scoured or covered circalittoral rock
This biotope typically occurs on tide-swept circalittoral bedrock, rock adjacent to mobile sand/gravel in gullies, and cobbles on gravel and sand, characterised by scour-tolerant robust species. Although many of these species are found on subtidal rock, they tend to occur in larger numbers in these highly sand-influenced conditions. The dominant species by far is the anemone Urticina felina which commonly occurs on rocks at the sand-rock interface, where the scour levels are at a maximum and few species can tolerate this abrasion. The sponge Ciocalypta penicillus is also very characteristic of shifting sand-covered rock. This biotope is only occasionally recorded as a separate entity, because its extent is typically restricted to a very narrow band of rock at the sediment interface. Only occasionally does it cover a large extent of rock (e.g. where the wave action is strong enough to cause sand abrasion well up the rock face or where the rock is low-lying). More often, this scoured zone is recorded as part of whatever biotope occurs on the nearby hard substrata. Other species (which are able to survive, and benefit from the reduced competition) include Balanus crenatus, Pomatoceros triqueter, Cellepora pumicosa, Alcyonidium diaphanum, Cliona celata, encrusting red algae and Asterias rubens.
This biotope complex occurs on moderately wave-exposed, circalittoral soft bedrock subject to moderately strong tidal streams. As this complex is found in highly turbid water conditions, the circalittoral zone may begin at the low water mark, due to poor light penetration. This complex is dominated by the piddock Pholas dactylus. Other species typical of this complex include the polychaete Polydora and Bispira volutacornis, the sponges Cliona celata and Suberites ficus, the bryozoan Flustra foliacea, Alcyonium digitatum, the starfish Asterias rubens, the mussel Mytilus edulis and the crab Necora puber and Cancer pagurus. Foliose red algae may also be present. Three biotopes have been identified within this complex: Pid, Pol and Hia. Please note: in areas subject to very high turbidity, biotopes within this biotope complex may occur in the infralittoral and even the littoral zone.
Hiatella-bored vertical sublittoral limestone rock
Moderately exposed vertical and overhanging soft rock (typically chalk), subject to moderately strong to weak tidal streams, bored by the rock-boring mollusc Hiatella arctica. As with other biotopes in the soft rock complex, it is found in areas of high turbidity, where there is poor light penetration. There may be isolated clumps of the hydroid Nemertesia antennina and a sparse bryozoan turf formed by various crisiids, Bugula plumosa and Bugula flabellate (often being grazed on by the nudibranch Janolus cristatus), Alcyonidium diaphanum, Flustra foliacea and Cellapora pumicosa. A patchy 'carpet' of the brittlestar Ophiothrix fragilis is often recorded along with other echinoderms such as Asterias rubens and Henricia sanguinolenta. Other species present include the colonial ascidians Polyclinum aurantium, Botrylloides leachi, Clavelina lepadiformis, Aplidium punctatum and Botryllus schlosseri, dead mans fingers Alcyonium digitatum and the crab Cancer pagurus. Sponges present include the boring sponge Cliona celata, Halichondria panicea, Myxilla incrustans, Leucosolenia botryoidesand Dysidea fragilis. Occasionally, the foliose red seaweed Delessaria sanguinea may be recorded.
Piddocks with a sparse associated fauna in sublittoral very soft chalk or clay
This biotope occurs on circalittoral soft rock, such as soft chalk or clay, most often in moderately exposed tide-swept conditions. As soft chalk and firm clay are often too soft for sessile filter-feeding animals to attach and thrive in large numbers, an extremely impoverished epifauna results on upward-facing surfaces, although vertical faces may be somewhat richer. The rock is sufficiently soft to be bored by bivalves. Species vary with location, but Pholas dactylus is the most widespread borer and may be abundant. Other species present may include the sponges Dysidea fragilis and Suberites carnosus and the polychaete Bispira volutacornis. Foliose red algae may be present on the harder, more stable areas of rock. Mobile fauna often include the crabs Necora puber and Cancer pagurus.
Polydora sp. tubes on moderately exposed sublittoral soft rock
Large patches of chalk and soft limestone are occasionally covered entirely by Polydora sp. tubes to the exclusion of almost all other species. This tends to occur in highly turbid conditions and spans the infralittoral and circalittoral in limestone areas such as the Great and Little Ormes (North Wales) and Gower (South Wales). It is even present on the lower shore in the Severn estuary. The boring form of the sponge Cliona celata often riddles the surface layer of the stone. Other sponges present include Halichondria panicea, Haliclona oculata and Hymeniacidon perleve. Polydora sp. also frequently occurs in small patches as part of other biotopes (e.g. FluCoAs). Other species present include Alcyonium digitatum, Sarcodictyon roseum, the hydroids Halecium halecinum, Abietinaria abietina and Tubularia indivisa, the ascidians Clavelina lepadiformis, Botryllus schlosseri and Morchellium argus, the anemones Urticina felina, Metridium senile and Sagartia elegans and the bryozoans Flustra foliacea and a crisiid turf. The starfish Asterias rubens, the crabs Inachus phalangium and Carcinus maenas, the polychaete Pomatoceros triqueter, the barnacle Balanus crenatus and the brittlestar Ophiothrix fragilis may also be seen. Please note: this biotope may extend into the infralittoral and littoral zone in areas where water turbidity is sufficiently high.
Infralittoral rock (and other hard substrata)
Infralittoral rock includes habitats of bedrock, boulders and cobbles which occur in the shallow subtidal zone and typically support seaweed communities. The upper limit is marked by the top of the kelp zone whilst the lower limit is marked by the lower limit of kelp growth or the lower limit of dense seaweed growth. Infralittoral rock typically has an upper zone of dense kelp (forest) and a lower zone of sparse kelp (park), both with an understorey of erect seaweeds. In exposed conditions the kelp is Laminaria hyperborea whilst in more sheltered habitats it is usually Laminaria saccharina; other kelp species may dominate under certain conditions. On the extreme lower shore and in the very shallow subtidal (sublittoral fringe) there is usually a narrow band of dabberlocks Alaria esculenta (exposed coasts) or the kelps Laminaria digitata (moderately exposed) or L. saccharina (very sheltered). Areas of mixed ground, lacking stable rock, may lack kelps but support seaweed communities. In estuaries and other turbid-water areas the shallow subtidal may be dominated by animal communities, with only poorly developed seaweed communities.
Only one biotope complex is currently found within the infralittoral rock features habitat complex: Surge Gulleys (SG). Surge Gulleys features are found throughout the infralittoral rock zone, and usually consist of vertical bedrock walls, occasionally with overhanging faces, and support communities, which reflect the degree of wave surge they are subject to and any scour from mobile substrata on the cave/gully floors. The larger cave and gully systems, such as found in Shetland, Orkney, the Western Isles and St Kilda, typically show a marked zonation from the entrance to the rear of the gully/cave as wave surge increases and light reduces.
Infralittoral fouling seaweed communities
Moderately exposed to wave-sheltered artificial substrata (such as steel wrecks/concrete pilings/cable debris etc) subject to moderately strong to weak tidal streams in the infralittoral zone. This biotope complex is characterised by a dense covering of filamentous and foliose algae on vertical as well as the upper faces of the substrata. Although there are no biotopes currently defined under this biotope, due to the low number of records, it is suspected that this has been highly 'under-recorded', and that additional records will be added in the near future, leading to the definition of biotopes.
Infralittoral rocky habitats subject to strong wave surge conditions, as found in surge gullies and shallow caves, and typically colonised by faunal communities of encrusting or cushion sponges, colonial ascidians, short turf-forming bryozoans, anthozoans, barnacles and, where there is sufficient light, red seaweeds. These features usually consist of vertical bedrock walls, occasionally with overhanging faces, and support communities which reflect the degree of wave surge they are subject to, and any scour from mobile substrata on the cave/gully floors. The larger cave and gully systems, such as found in Shetland, Orkney, the Western Isles and St Kilda, typically show a marked zonation from the entrance to the rear of the gully/cave as wave surge increases and light reduces. This is reflected in communities of anthozoans, ascidians, bryozoans and red seaweeds near the entrance, leading to sponge crust-dominated communities and finally barnacle and spirorbid worm communities in the most severe surge conditions. Gully/cave floors usually have mobile boulders, cobbles, pebbles or coarse sediment. The mobile nature of the gully/cave floors leads to communities of encrusting species, tolerant of scour and abrasion or fast summer-growing ephemeral species. The lower zone of the gully side walls are also often scoured, and typically colonised by coralline crusts and barnacles.
Coralline crusts in surge gullies and scoured infralittoral rock
Scoured rock in wave-surged caves, tunnels or gullies often looks rather bare, and may be characterised by a limited scour-tolerant fauna of Balanus crenatus and/or Pomatoceros triqueter with spirorbid polychaetes. In areas where sufficient light is available and scour is severe, encrusting coralline algae and non-calcareous crusts cover the rock surface, giving a pink appearance. This biotope most commonly occurs at the bottom of walls in caves and gullies, where abrasion by cobbles and stones is severe, especially during winter. In some gullies, extreme scouring and abrasion produces a narrow band of bare coralline algal crust at the very bottom of the walls, with a band of P. triqueter and/or B. crenatus immediately above. Other scour-tolerant species, such as encrusting bryozoans may also be common. Crevices and cracks in the rock provide a refuge for sponge crusts such as Halichondria panicea and occasional anemones Urticina felina and Sagartia elegans. More mobile fauna is usually restricted to the echinoderms Asterias rubens and Echinus esculentus as well as the crab Cancer pagurus. Two variants have been identified: Wave-surged bedrock with coralline crust, B. crenatus and P. triqueter (CC.BalPom) and coralline crusts on mobile boulders in severely scoured caves (CC.Mo).
Balanus crenatus and/or Pomatoceros triqueter with spirorbid worms and coralline crusts on severely-scoured vertical infralittoral rock
Severely scoured bedrock in wave-surged caves, tunnels or gullies often looks rather bare, and may be characterised by a limited scour-tolerant fauna of Balanus crenatus and/or Pomatoceros triqueter with spirorbid polychaetes. In areas where sufficient light is available, encrusting coralline algae and non-calcareous crusts cover the rock surface, giving a pink appearance. This biotope most commonly occurs at the bottom of walls in caves and gullies, where abrasion by cobbles and stones is severe, especially during winter. In some gullies, extreme scouring and abrasion produces a narrow band of bare coralline algal crust at the very bottom of the walls, with a band of P. triqueter and or B. crenatus immediately above. In some caves extreme wave surge at the back of the cave leads to a zone of this biotope which may also be dominated solely by sprorbids or by the barnacle Verruca stroemia. Other scour-tolerant species, such as encrusting bryozoans may also be common. Crevices and cracks in the rock provide a refuge for sponge crusts, small Mytilus edulis and occasional Actinia equina, Urticina felina and Sagartia elegans. More mobile fauna is usually restricted to the echinoderm Asterias rubens and the crab Cancer pagurus. During periods of relative stability in the summer, small quantities of foliose red seaweeds and opportunistic kelps may occur where sufficient light is available; the seaweeds however do not dominate (compare with FoSwCC).
Coralline crusts and crustaceans on mobile boulders or cobbles in surge gullies
Highly mobile and scoured boulders and cobbles found on cave and gully floors and which often appear bare. Where there is sufficient light and stability, however, the boulders are encrusted by coralline algal crusts. Barnacles Balanus crenatus and keelworms Pomatoceros triqueter may survive in areas protected from severe abrasion. Crabs such as Cancer pagurus and Carcinus maenas may occur, often beneath and between the rocks, along with the gastropod Calliostoma zizyphinum. The anemone Actinia equina may be present in low numbers.
Crustose sponges on extremely wave-surged infralittoral cave or gully walls
Walls, or massive boulders, in caves or gullies that are subject to severe wave-surge and characterised by extensive thin crusts of the sponge Halichondria panicea with smaller patches of other sponges such as Esperiopsis fucorum or Clathrina coriacea. Small turfs of robust hydroids, such as Diphasia rosacea and Ventromma halecioides, and patches of the barnacle Balanus crenatus, coralline crusts and tube-building spirorbid polychaetes may be present. The starfish Henricia spp., the brittlestar Ophiopholis aculeata and the crabs Cancer pagurus and Necora puber can be present. The anemones Sagartia elegans, Urticina felina and Actinia equina can be found in cracks and crevices or under boulders. The mussel Mytilus edulis may be present in low densities.
Anemones, including Corynactis viridis, crustose sponges and colonial ascidians on very exposed or wave surged vertical infralittoral rock
Vertical very exposed and exposed bedrock gullies, tunnels and cave entrances subject to wave-surge dominated by sponge crusts such as Clathrina coriacea, Myxilla incrustans, Pachymatisma johnstonia and Halichondria panicea and anthozoans such as Sagartia elegans, Urticina felina, Alcyonium digitatum, Corynactis viridis and dwarf Metridium senile generally dominate the area; the anthozoans often appearing to protrude through the sponge layer. There may be dense aggregations of the hydroid Tubularia indivisa, the cup coral Caryophyllia smithii and the colonial ascidians Botrylloides leachi and Polyclinum aurantium. There may be a short crisiid turf, interspersed with Scrupocellaria reptans. Encrusting coralline algae may occur on well-illuminated rock faces. The echinoderms Asterias rubens, Marthasterias glacialis, Echinus esculentus, Antedon bifida and Ophiothrix fragilis, the topshell Calliostona zizphinum and the calcareous tubeworm Pomatoceros triqueter may also be present on the rock face. The crabs Cancer pagurus and Necora puber may also be recorded. Due to the wave-surged nature and vertical orientation of these biotopes, kelps are rare and certainly never dominate.
Crustose sponges and colonial ascidians with Dendrodoa grossularia or barnacles on wave-surged infralittoral rock
Vertical and overhanging, exposed to moderately exposed bedrock gullies, tunnels and cave entrances subject to wave surge, and dominated by the crustose sponges Halichondria panicea, Myxilla incrustans, Clathrina coriacea, Leucosolenia botryoides, Esperiopsis fucorum and Grantia compressa. There may also be dense aggregations of the anthozoan Sagartia elegans, dwarf Metridium senile, Alcyonium digitatum, and Urticina felina, and a dense covering of the barnacle Balanus crenatus on the bare rock face. Dense aggregations of the robust hydroid Tubularia indivisa may be recorded, growing through the sponge crust. Colonial ascidians such as Polyclinum aurantium, Botryllus schlosseri, Botrylloides leachi, Aplidium nordmanni and the solitary ascidian Dendrodoa grossularia may all be recorded. The echinoderms Asterias rubens, Echinus esculentus, Henricia sp., the crab Cancer pagurus and the calcareous tubeworm Pomatoceros triqueter may also be present on the rock face, along with encrusting coralline algae.
Dendrodoa grossularia and Clathrina coriacea on wave-surged vertical infralittoral rock
Vertical or overhanging infralittoral rock subject to considerable wave-surge, especially in the middle or back of caves but also in gullies and tunnels, and dominated by dense sheets of the ascidian Dendrodoa grossularia, together with variable quantities of the sponge Clathrina coriacea. At some sites D. grossularia forms continuous sheets, with few other species present. Other sponges such as Esperiopsis fucorum, Pachymatisma johnstonia, Leucosolenia botryoides, Scypha ciliata and Halichondria panicea regularly occur in this biotope, though generally at low abundance. Other ascidians, especially Polyclinum aurantium, Diplosoma spp. and other didemnids may also occur, though only P. aurantium is ever as abundant as D. grossularia. Being characteristically found in the middle or towards the backs of the caves mean that there is generally insufficient light to support any foliose seaweeds, although encrusting coralline algae are not uncommon. More scoured areas may also contain the anemone Urticina felina, whilst Sagartia elegans is often present in low numbers. Mobile fauna are often limited to the starfish Asterias rubens and Henricia spp., the brittlestar Ophiopholis aculeata and crabs Cancer pagurus and Necora puber. The barnacle Balanus crenatus can occur, usually in low densities.
Foliose seaweeds and coralline crusts in surge gully entrances
This biotope is found on steep wave-surged entrances to gullies and caves and on unstable boulders in the entrance to caves and gullies. The rock may be abraded by the movement of the boulders and cobbles in heavy surge and tends to be dominated by dense foliose seaweeds that grow rapidly in the calmer summer months. Beneath the foliose seaweeds the rock surface is typically covered with coralline crusts, which are longer-lived, and tolerant of abrasion. The flora of this biotope is relatively varied, depending upon the amount of light and degree of abrasion or rock mobility with red seaweeds such as Cryptopleura ramosa, Plocamium cartilagineum, Odonthalia dentata, Callophyllis laciniata, Phycodrys rubens, Hypoglossum hypoglossoides, Phyllophora crispa and Corallina officinalis. The brown seaweed Dictyota dichotoma also occurs in these conditions, since it is tolerant of some sand scour. During the summer months small fast-growing kelp plants can arise in this biotope, although the mobility of the substratum prevents the kelp from forming a kelp forest. Dense swathes of very young kelp such as Laminaria hyperborea are, however, not uncommon. The faunal community consist of the anemone Urticina felina, the sponge Halichondria panicea and the ascidian Dendrodoa grossularia. More mobile fauna include the echinoderms Asterias rubens and Echinus esculentus, the top shell Gibbula cineraria and the crab Cancer pagurus.
Rocky habitats in the infralittoral zone subject to exposed to extremely exposed wave action or strong tidal streams. Typically the rock supports a community of kelp Laminaria hyperborea with foliose seaweeds and animals, the latter tending to become more prominent in areas of strongest water movement. The depth to which the kelp extends varies according to water clarity, exceptionally (e.g. St Kilda) reaching 45 m. The sublittoral fringe is characterised by dabberlocks Alaria esculenta. Surge gullies and caves typically lack kelp, and in reduced light conditions lack red seaweeds and are dominated by communities of sponges, ascidians, bryozoans, mussels and barnacles.
Kelp with cushion fauna and/or foliose red seaweeds
Rocky habitats in the infralittoral zone subject to exposed to extremely exposed wave action or strong tidal streams. Typically the rock supports a community of kelp Laminaria hyperborea with foliose seaweeds and animals, the latter tending to become more prominent in areas of strongest water movement (LhypFa, LhypR and LhypR.Pk). The depth to which the kelp extends varies according to water clarity, exceptionally (e.g. St Kilda) reaching 45 m. In some areas, there may be a band of dense foliose seaweeds (reds or browns) below the main kelp zone (FoR). The sublitttoral fringe is characterised by dabberlocks Alaria esculenta (Ala biotopes). In very strong wave action the sublittoral fringe A. esculenta zone extends to 5 to 10 m depth, whilst at Rockall A. esculenta replaces L. hyperborea as the dominant kelp in the infralittoral zone (AlaAnCrSp).
Alaria esculenta on exposed sublittoral fringe bedrock
Exposed sublittoral fringe bedrock with an Alaria esculenta forest and an encrusting fauna of the mussel Mytilus edulis and barnacles such as Semibalanus balanoides. The kelp Laminaria digitata can be part of the canopy. Underneath the canopy are red seaweeds such as Mastocarpus stellatus and Palmaria palmata, while encrusting coralline red algae such as Lithothamnion graciale covers the rock surface. The limpet Patella vulgata can be found grazing the rock surface, while the whelk Nucella lapillus is preying on the limpets, barnacles and mussels. Two variants of this biotope are described. In more wave exposed conditions Laminaria digitata is absent and the rock surface is often characterised by dense patches of mussels (Ala.Myt). In slightly less exposed sites the A. esculenta is mixed with L. digitata (Ala.Ldig).
Alaria esculenta and Laminaria digitata on exposed sublittoral fringe bedrock
Exposed sublittoral fringe bedrock characterised by a mixture of the kelps Laminaria digitata and Alaria esculenta with an understorey of red seaweeds including Palmaria palmata and Corallina officinalis with encrusting coralline algal on the rock surface. Anthozoans such as Halichondria panicea, the mussel Mytilus edulis and the barnacle Semibalanus balanoides can be found attached in cracks and crevices. The limpets Patella vulgata or on southern shores Patella ulyssiponensis can be found in their characteristic "scars" grazing the biofilm/algal crusts on the rock surface, while the limpet Helcion pellucidum is restricted to grazing the kelp fronds. Colonies of the bryozoan Electra pilosa can cover the red seaweeds Mastocarpus stellatus and Chondrus crispus or the rock surface.
Alaria esculenta, Mytilus edulis and coralline crusts on very exposed sublittoral fringe bedrock
Very exposed sublittoral fringe bedrock characterised by the kelp Alaria esculenta and dense patches of small individuals of the mussel Mytilus edulis, both of which grow over a dense cover of encrusting coralline algae. Foliose red seaweeds may also be present, but the species composition and their abundance vary between sites. Species such as Corallina officinalis occur widely. The kelp Laminaria digitata is usually absent, although stunted plants may be present at a few sites. The limpet Patella vulgata and the barnacle Semibalanus balanoides are often common. Patches of anthozoans and the hydroid Tubularia spp. occur in more wave-surged areas. In extremely exposed areas the A. esculenta zone can extend as deep as 15 m, where it has less S. balanoides, M. edulis and greater densities of Tubularia spp. (e.g. Barra and shallow areas of Rockall).
Alaria esculenta forest with dense anemones and crustose sponges on extremely exposed infralittoral bedrock
This biotope has only been recorded from Rockall, where Alaria esculenta appears to replace Laminaria hyperborea as the dominant kelp forest species on the extremely wave-exposed steep and vertical rock, a zone that extends from 14 m down to 35 m. Beneath the A. esculenta canopy, the rock surface is covered by a dense turf of anthozoans such as Sagartia elegans, Phellia gausapata and Corynactis viridis, encrusting sponges and coralline algae. The gastropod Margarites helicinus can be found grazing on the kelp fronds, whereas the crab Cancer pagurus can be found among the kelp stipes. The bryozoan Tubularia indivisa also occur, but it does not form such a dense turf as in more shallow waters, while the ascidian Botryllus leachi is found encrusting the large brown seaweeds. Cryptopleura ramosa is the dominant red seaweed on horizontal surfaces. The kelp Laminaria digitata is reported to occur mixed with A. esculenta on the nearby Helen's reef.
Foliose red seaweeds on exposed lower infralittoral rock
A dense turf of foliose red seaweeds on exposed or moderately exposed lower infralittoral rock, generally, at or below the lower limit of the kelp. Most of the red seaweeds are common to the kelp zone above, while the faunal component of the biotope is made up of species that are found either in the kelp zone or the animal-dominated upper circalittoral below. Foliose species commonly present include Dilsea carnosa, Hypoglossum hypoglossoides, Schottera nicaeensis, Cryptopleura ramosa and Delesseria sanguinea. The red seaweed species composition varies considerably; at some sites a single species may dominate (particularly Plocamium cartilagineum). Small filamentous red seaweeds can be found here as well. These include species such as Heterosiphonia plumosa, Brongniartella byssoides. As well as a varied red seaweed component, this biotope may also contain occasional kelp plants and patches of the brown foliose seaweed Dictyota dichotoma. Coralline crusts covers the bedrock beneath the seaweeds. The fauna generally comprises low-encrusting forms such as the tubeworms Pomatoceros spp., anthozoans including Alcyonium digitatum, Urticina felina and Caryophyllia smithii) and occasional sponge crusts such as Cliona celata, Esperiopsis fucorum, Scypha ciliata and Dysidea fragilis. More mobile fauna include the gastropod Calliostoma zizyphinum, the echinoderms Echinus esculentus as well as the starfish Asterias rubens and Marthasterias glacialis and lastly, the crab Cancer pagurus. Bryozoan crusts such as Electra pilosa can be found fronds on the foliose red seaweeds while scattered hydroids such as Nemertesia antennina form colonies on shells, cobbles and available rock. At some sites erect bryozoans Crisia spp. and Bugula spp. are present. Ascidians such as Clavelina lepadiformis and Clavelina lepadiformis may also be common. In the north the foliose red seaweed Callophyllis laciniata may occur.
Foliose red seaweeds with dense Dictyota dichotoma and/or Dictyopteris membranacea on exposed lower infralittoral rock
A dense turf of foliose red seaweeds mixed with a dense turf of the foliose brown seaweeds Dictyota dichotoma and/or Dictyopteris membranacea on exposed and moderately exposed lower infralittoral rock, generally at or below the lower limit of the kelp zone. In some areas the lower infralittoral is subject to a moderate amount of scour from nearby sand. D. dichotoma is relatively tolerant of such scour and in such areas a zone forms with other sand-tolerant seaweeds. D. membranacea is confined to south-western coasts. Typically brown seaweeds dominate the seabed or are at least in equal abundance to the red seaweeds, some of which may also form dense stands such as Plocamium cartilagineum, Calliblepharis ciliata, Cryptopleura ramosa, Bonnemaisonia asparagoides, Heterosiphonia plumosa, Delesseria sanguinea and Brongniartella byssoides. The urchin Echinus esculentus can be found grazing the rock surface which can be covered in coralline algae. The anthozoans Caryophyllia smithii and Alcyonium digitatum are usually present in this biotope along with the tube-building worm Pomatoceros sp. which is more common in sand-scoured areas. The starfish Asterias rubens and Henricia sp. and sponge crusts including Cliona celata can also be found here. D. dichotoma also occurs in the kelp park, and records should only be assigned to this biotope where kelp such as Laminaria hyperborea is sparse or absent and a relatively high density of D. dichotoma and/or D. membranacea is present.
Laminaria hyperborea forest with a faunal cushion (sponges and polyclinids) and foliose red seaweeds on very exposed upper infralittoral rock
Very exposed and exposed, but wave-surged, upper infralittoral bedrock and massive boulders characterised by a dense forest of the kelp Laminaria hyperborea with a high diversity of seaweeds and invertebrates. The shallowest kelp plants are often short or stunted, while deeper plants are taller with heavily epiphytised stipes with foliose red seaweeds such as Delesseria sanguinea, Cryptopleura ramosa or Plocamium cartilagineum or even the brown seaweed Dictyota dichotoma. Also found on the stipes or on the rock below the canopy are red seaweeds including Phycodrys rubens, Kallymenia reniformis, Callophyllis laciniata, Caryophyllia smithii, and Corallina officinalis, while encrusting coralline algae can cover any bare patches of rock. At some sites the red seaweeds can be virtually mono-specific, while at other sites show considerable variation containing a dense mixed turf of a large variety of species. The red seaweed Odonthalia dentata can be present in the north. The faunal and floral under-storey is generally rich in species due, in part, to the relatively low urchin-grazing pressure in such shallow exposed conditions. The faunal composition of this biotope varies markedly between sites, but commonly occurring are the soft coral Alcyonium digitatum and the anthozoans Sagartia elegans and Corynactis viridis. Sponges form a prominent part of the community with variable amounts of the sponges Halichondria panicea and Pachymatisma johnstonia and several other species. The crab Cancer pagurus and the starfish Asterias rubens are normally present in small numbers foraging beneath the canopy, while the sea urchins Echinus esculentus and Urticina felina graze on the seaweeds. The hydroid Obelia geniculata, the ascidian Botryllus schlosseri and the bryozoan Membranipora membranacea compete for space on the kelp, whereas the bryozoan Electra pilosa also can be found on foliose red seaweeds.
Sparse Laminaria hyperborea and dense Paracentrotus lividus on exposed infralittoral limestone
This biotope is known from only one location, the Aran Islands, Co. Galway. Here, a limestone platform between 3 m and 6 m of depth is dominated by a dense population of the urchin Paracentrotus lividus, which heavily graze and burrow into the soft limestone. So intense is the grazing pressure that the rock appears completely bare, except for a coralline algal crust and occasional Laminaria hyperborea and Saccorhiza polyschides. The anthozoans Sagartia elegans and Corynactis viridis are also present, though at low abundance. The grazed kelp also extends deeper to 20 to 25 m further offshore. (Only one CB record within this biotope).
Laminaria hyperborea with dense foliose red seaweeds on exposed infralittoral rock
Very exposed to exposed infralittoral bedrock or large boulders characterised by the kelp Laminaria hyperborea, beneath which is a dense turf of foliose red seaweeds. Three variations of this biotope are described: the upper infralittoral kelp forest (LhypR.Ft), the kelp park below (LhypR.Pk) and a third type of kelp forest, confined to southern England, that is characterised by a mixture of L. hyperborea and Laminaria ochroleuca (LhypR.Loch). The fauna of these biotopes is markedly less abundant than kelp forests in areas of greater wave surge (LhypFa); sponges, anthozoans and polyclinid ascidians may be present, though never at high abundance. Beneath the under-storey of red seaweeds, the rock surface is generally covered with encrusting coralline algae.
Laminaria hyperborea forest with dense foliose red seaweeds on exposed upper infralittoral rock
Very exposed to exposed upper infralittoral bedrock or large boulders characterised by a dense forest of the kelp Laminaria hyperborea. On the rock surface beneath the kelp canopy is a dense turf of red foliose seaweeds including Cryptopleura ramosa, Plocamium cartilagineum, Phycodrys rubens and Callophyllis laciniata as well as encrusting coralline algae and the foliose brown seaweed Dictyota dichotoma. The red algal turf can be virtually mono-specific, dominated by stands of P. cartilagineum, C. ramosa or Heterosiphonia plumosa, Kallymenia reniformis or in the north, Odonthalia dentata. Other sites may contain a dense mixed turf of these and other species. The dense turf is due, in part, to the relatively low grazing pressure from the urchin Echinus esculentus in such shallow exposed conditions. The shallowest kelp plants are often short or stunted, while deeper plants are taller and the stipes are heavily epiphytised by red seaweeds such as Delesseria sanguinea and Membranoptera alata. The bryozoan Electra pilosa can form colonies on the foliose red seaweeds, while the bryozoan Membranipora membranacea more often can be found on the L. hyperborea fronds along with the ascidian Botryllus schlosseri and the hydroid Obelia geniculata. The gastropods Gibbula cineraria and Calliostoma zizyphinum are found grazing among the kelp holdfasts, while a few individuals of the barnacle Balanus crenatus can present along with the white calcareous tubes of the polychaete Pomatoceros triqueter, where substratum is available. The starfish Asterias rubens can be found predating on polychaetes, mussels and small crustaceans. The soft coral Alcyonium digitatum can be present covering the rock surface as well as the anthozoan Urticina felina.
Mixed Laminaria hyperborea and Laminaria ochroleuca forest on exposed infralittoral rock
Mixed Laminaria hyperborea and Laminaria ochroleuca forests on upper infralittoral exposed rock with a dense community of foliose red seaweeds such as Cryptopleura ramosa, and Plocamium cartilagineum as well as small filamentous red seaweeds including Bonnemaisonia asparagoides, Heterosiphonia plumosa, Pterosiphonia parasitica and Brongniartella byssoides. L. hyperborea has a rough stipe which allow dense assemblages of epiphytic red seaweeds to form including the foliose Callophyllis laciniata, Delesseria sanguinea and Hypoglossum hypoglossoides. Unlike L. hyperborea, however, L. ochroleuca has a smooth stipe and so it lacks dense assemblages of epiphytic seaweeds L. ochroleuca has a smooth stipe. Encrusting coralline algae often cover much of the rock surface along with a few brown seaweeds including Dictyota dichotoma, Dictyopteris polypodioides and Desmarestia aculeata present as well. In mixed kelp forest L. ochroleuca may predominate with L. hyperborea more common at shallower depths. Whilst foliose red seaweeds dominate the upward-facing rock beneath the kelp canopy, much of the fauna is restricted to crevices or vertical faces, possibly due to grazing pressure. Echinoderms are often common in this biotope, in particular the sea urchin Echinus esculentus and the starfish Asterias rubens and Marthasterias glacialis. Verticals are colonised by anthozoans including the anthozoans Corynactis viridis, Caryophyllia smithii, Actinothoe sphyrodeta and Alcyonium digitatum, while the bryozoan Membranipora membranacea colonise the Laminaria sp. fronds. This biotope is restricted to the coast of Cornwall and the Isles of Scilly. L. ochroleuca occurs at low abundance in other kelp biotopes (sheltered through to exposed) from Dorset to Lundy Island. In such cases, records should be treated as regional variations of these biotopes. Records should only be assigned to the LhypR.Loch biotope when the canopy is dominated by L. ochroleuca alone, or (more usually) by a mixture of both L. hyperborea and L. ochroleuca (at similar abundance). Both this biotope and Lhyp.Loch are common on the Brittany and Normandy coasts.
Laminaria hyperborea park with dense foliose red seaweeds on exposed lower infralittoral rock
Very exposed to exposed lower infralittoral bedrock or large boulders characterised by a kelp park of Laminaria hyperborea with a dense turf of foliose red seaweeds and encrusting coralline algae. These red seaweeds dominate kelp stipes and bedrock in a similar abundance and composition to the upper infralittoral kelp forest, the most commonly occurring species being Callophyllis laciniata, Cryptopleura ramosa, Plocamium cartilagineum, Kallymenia reniformis, Delesseria sanguinea, Phycodrys rubens, Hypoglossum hypoglossoides, Heterosiphonia plumosa and Bonnemaisonia asparagoides. In addition, moderate to high abundance of foliose brown seaweeds, such as Dictyota dichotoma are more common than in the kelp forest above. More upper circalittoral fauna occur in the park than in the kelp forest, such as the cup-coral Caryophyllia smithii. Some species more often present in the kelp park than the forest include the anthozoan Alcyonium digitatum and the featherstar Antedon bifida. The urchin Echinus esculentus, the gastropods Gibbula cineraria and Calliostoma zizyphinum and the starfish Asterias rubens are normally present underneath the canopy along with the anthozoans Urticina felina and Corynactis viridis. The sponge Cliona celata is also present often found boring into shells or soft rock where available. The bryozoan Membranipora membranacea can be found on the L. hyperborea fronds along with the hydroid Obelia geniculata and the ascidian Botryllus schlosseri. The polychaete Pomatoceros sp. is present on the rock surface.
Laminaria hyperborea and red seaweeds on exposed vertical rock
On exposed coasts with moderately strong to weak tidal currents generally at depths of 0-10m, vertical rock communities dominated by frequent Laminaria hyperborea and its commonly associated red seaweeds Delesseria sanguinea, Cryptopleura ramosa and Plocamium cartilagineum can be found. Within this biotope the jewel anemone Corynactis viridis is frequently found in dense aggregations attached to the vertical rock surface. This biotope contains 5 sub-biotopes, distinguished by their biogeography. On the west coast of Scotland, the Northern Isles and the Isle of Man on extremely exposed coasts a variant of this biotope characterised by frequent Metridium senile and occasional Sagartia elegans can be found. Further south on the west coast of Ireland, southern Scotland, Wales, and south west England a second variant characterised by frequent Alcyonium digitatum and occasional Cliona celata can be distinguished. A third variant has been recorded from Northern Ireland characterised by the red seaweeds Lithophyllum and Ptilota gunneri, the sea squirt Dendrodoa grossularia and the bryozoan Membranipora membranacea. South from the Isle of Man, on the Welsh Coast, and on the south west and southern English coasts a fourth variant of this biotope is found, which is characterised by the barnacle Balanus crenatus, which may be more frequent in this sub-biotope, and the rarity of Alcyonium digitatum, a species which is more frequent in other variants. This variant has mainly been recorded in shallow water (0-5m). The final biogeographic variant of this biotope is, as with the previous variant, found on the coasts of Wales and south west England. It can be distinguished from the previous variant by the frequent Diplosoma listerianum and occasional Lissoclinum perforatum, although these species are not always present.
Sediment-affected or disturbed kelp and seaweed communities
Infralittoral rock habitats, subject to disturbance through mobility of the substratum (boulders or cobbles) or abrasion/covering by nearby coarse sediments or suspended particulate matter (sand). The associated communities can be quite variable in character, depending on the particular conditions, which prevail. The typical Laminaria hyperborea and red seaweed communities of stable open coast rocky habitats (IR.MIR.KR) are replaced by those, which include more ephemeral species or those tolerant of sand and gravel abrasion. As such Laminaria saccharina, Saccorhiza polyschides or Halidrys siliquosa may be prominant components of the community.
Dense Desmarestia spp. with filamentous red seaweeds on exposed infralittoral cobbles, pebbles and bedrock
Wave-exposed seasonally mobile substrata (pebbles, cobbles) dominated by dense stands of the brown seaweed Desmarestia aculeata and/or Desmarestia ligulata. Infralittoral pebbles and cobbles that are scoured through mobility during storms, but become stable in the summer allowing the growth of such algae as Desmarestia spp. Filamentous red seaweeds such as Bonnemaisonia asparagoides and Brongniartella byssoides are usually present. Stunted individuals of the kelp such as Laminaria hyperborea and Laminaria saccharina may be present where bedrock is available. A variety of foliose red seaweeds such as Cryptopleura ramosa, Chondrus crispus, Plocamium cartilagineum, Hypoglossum hypoglossoides and Nitophyllum punctatum may on occasion be present underneath the kelp canopy. Other red algae including Corallina officinalis, Rhodomela confervoides and coralline crusts including Lithothamnion spp. may be present as well as well as the foliose brown seaweed Dictyota dichotoma and the green Enteromorpha intestinalis. Due to the nature of this biotope the faunal component is very impoverished though the gastropod Gibbula cineraria can be found among the cobbles.
Laminaria saccharina, Chorda filum and dense red seaweeds on shallow unstable infralittoral boulders or cobbles
Seasonally disturbed unstable boulders and cobbles in very shallow water dominated by the fast-growing brown seaweed Chorda filum together with the kelp Laminaria saccharina. The brown seaweed Desmarestia aculeata is also typical of this disturbed environment as well encrusting coralline algae and brown crusts. Beneath the prolific growth of C. filum, red and brown seaweeds densely cover many of the boulders, cobbles and pebbles. Other sediment-tolerant seaweeds such as species from the Ectocarpales (brown filamentous seaweeds) and the red seaweeds Chondrus crispus, Phyllophora pseudoceranoides, Dilsea carnosa and Corallina officinalis is normally present. Other red seaweeds which can be found here include Chondria dasyphylla, Brongniartella byssoides, Polysiphonia elongata, Ceramium nodolosum, Cystoclonium purpureum, Heterosiphonia plumosa, Rhodomela confervoides and Plocamium cartilagineum. The brown seaweeds Punctaria sp. and Cladostephus spongiosus are generally present. The faunal component of this biotope is typically sparse - the starfish Asterias rubens and the crabs Pagurus bernhardus and Necora puber are amongst the most conspicuous animals. The bryozoan crust Electra pilosa colonise many of the algae along with the ascidian Botryllus schlosseri. Occasional the polychaete Lanice conchilega may occur in the sand between pebbles, and the anthozoan Urticina felina may be found amongst pockets of gravel along with the gastropod Gibbula cineraria. At some sites the rock beneath the algae can be occupied by the tube-building polychaete Pomatoceros triqueter. This biotope is also present at other open coast sites around the UK where suitable shallow, seasonally stable boulders, cobbles and pebbles occur. Typical examples of this biotope occur on the shallowest areas of the Sarns in Cardigan Bay, Wales, where reef crests are formed by embedded and mobile boulders, together with cobbles and pebbles in between (typically at 2-3m depth).
Laminaria saccharina and/or Saccorhiza polyschides on exposed infralittoral rock
A forest or park of the fast-growing, opportunistic kelps Laminaria saccharina and/or Saccorhiza polyschides often occurs on seasonally unstable boulders or sand/pebble scoured infralittoral rock. The substratum varies from large boulders in exposed areas to smaller boulders and cobbles in areas of moderate wave exposure or nearby bedrock. In these cases, movement of the substratum during winter storms prevents a longer-lived forest of Laminaria hyperborea from becoming established. This biotope also develops on bedrock where it is affected by its close proximity to unstable substrata. Other fast-growing brown seaweeds such as Desmarestia viridis, Desmarestia aculeata, Cutleria multifida and Dictyota dichotoma are often present. Some L. hyperborea plants may occur in this biotope, but they are typically small since the plants do not survive many years. The kelp stipes are usually epiphytised by red seaweeds such as Delesseria sanguinea and Phycodrys rubens. Other red seaweeds present beneath the kelp canopy include Plocamium cartilagineum, Nitophyllum punctatum, Callophyllis laciniata and Cryptopleura ramosa. Encrusting algae often form a prominent cover on the rock surfaces, including red, brown and coralline crusts. Faunal richness and diversity is generally low compared to the more stable L. hyperborea kelp forest and park communities (LhypR). Where some protection is afforded the anthozoan Alcyonium digitata can occur in addition to the more robust species such as the tube-building worm Pomatoceros triqueter. Mobile species include the to shell Gibbula cineraria and Calliostoma zizyphinum and the sea urchin Echinus esculentus. The hydroid Obelia geniculata and the bryozoan Membranipora membranacea can often be found colonising the kelp fronds.
Polyides rotundus, Ahnfeltia plicata and Chondrus crispus on sand-covered infralittoral rock
Low-lying rock surrounded by mobile sand and often subject to burying by the sand, with a turf of resilient red seaweeds Chondrus crispus, Polyides rotundus and Ahnfeltia plicata typically protruding through the sand on the upper surfaces of the rock. Other scour-tolerant seaweeds include Rhodomela confervoides, Phyllophora pseudoceranoides, Phyllophora crispa, Furcellaria lumbricalis, Gracilaria gracilis, Ceramium rubrum, Plocamium cartilagineum, Heterosiphonia plumosa, Cryptopleura ramosa and Dilsea carnosa. Coralline crusts typically cover the rock, while scattered individuals of the brown seaweeds Halidrys siliquosa, Cladostephus spongiosus, Dictyota dichotoma and Laminaria saccharina can be present. The large anthozoan Urticina felina can occur in this biotope but there are few other conspicuous animals.
Saccorhiza polyschides and other opportunistic kelps on disturbed sublittoral fringe rock
Exposed low-lying reefs in the sublittoral fringe or upper infralittoral (generally above 5m depth), mainly in the southwest and west, dominated by the kelp Saccorhiza polyschides. This opportunistic coloniser replaces Laminaria digitata or Laminaria hyperborea as the dominant kelp, following 'disturbance' of the canopy. This may be the result of storms, when loose sediment and even cobbles or boulders are mobilised, scouring most seaweeds and animals from the surrounding rock. As S. polyschides is essentially a summer annual (occasionally it lasts into a second year), it is also particularly common close to rock/sand interfaces which become too scoured during winter months to prevent the longer-living kelps from surviving. As a result of the transient nature of this biotope, its composition is varied; it may contain several other kelp species, including L. digitata, Laminaria saccharina and Alaria esculenta, at varying abundances. Laminaria spp. sporelings can also be a prominent feature of the site. Beneath the kelp, (scour-tolerant) red seaweeds including Corallina officinalis, Kallymenia reniformis, Plocamium cartilagineum, Chondrus crispus, Dilsea carnosa and encrusting coralline algae are often present. Foliose red seaweeds such as Callophyllis laciniata, Cryptopleura ramosa and Palmaria palmata also occur in this biotope. P. palmata and Delesseria sanguinea often occur as epiphytes on the stipes of L. hyperborea, when it is present. The foliose green seaweed Ulva spp. is fast to colonise newly cleared areas of rock and is often present along with the foliose brown seaweed Dictyota dichotoma. Due to the disturbed nature of this biotope, fauna are generally sparse, being confined to encrusting bryozoans and/or sponges, such as Halichondria panicea and the gastropod Gibbula cineraria.
Halidrys siliquosa and mixed kelps on tide-swept infralittoral rock with coarse sediment
Tide-swept boulders and cobbles, often with a mobile component to the substrata (pebbles, gravel and sand), characterised by dense stands of the brown seaweed Halidrys siliquosa. It is can be mixed with the foliose brown seaweed Dictyota dichotoma and kelp such as Laminaria saccharina and Laminaria hyperborea. Below the canopy is an undergrowth of red seaweeds that are tolerant of sand-scour such as Phyllophora crispa, Phyllophora pseudoceranoides, Rhodomela confervoides, Corallina officinalis and Chondrus crispus. Other red seaweeds such as Plocamium cartilagineum, Calliblepharis ciliata, Cryptopleura ramosa, Delesseria sanguinea, Heterosiphonia plumosa, Dilsea carnosa, Hypoglossum hypoglossoides and Brongniartella byssoides may be locally abundant, particularly in the summer months. There may be a rich epibiota on H. siliquosa, including the hydroid Aglaophenia pluma, ascidians such as Botryllus schlosseri. There is generally a sparse faunal component colonising the boulders and cobbles, comprising the tube-building polychaete Pomatoceros triqueter, the crab Cancer pagurus, the starfish Asterias rubens, the gastropod Gibbula cineraria and the sea anthozoan Urticina felina. The bryozoan Electra pilosa can form colonies on the kelp.
Mixed kelps with scour-tolerant and opportunistic foliose red seaweeds on scoured or sand-covered infralittoral rock
Bedrock and boulders, often in tide-swept areas, that are subject to scouring or periodic burial by sand, characterised by a canopy of mixed kelps such as Laminaria saccharina, Laminaria hyperborea and Saccorhiza polyschides and the brown seaweed Desmarestia aculeata; there may also be an understorey of foliose seaweeds that can withstand scour such as Plocamium cartilagineum, Chondrus crispus, Dilsea carnosa, Callophyllis laciniata as well as the filamentous Heterosiphonia plumosa and the foliose brown seaweed Dictyota dichotoma. The perennial red seaweed Brongniartella byssoides re-grows in the summer months. The L. hyperborea stipes often support a growth of epiphytes, such as Delesseria sanguinea, Phycodrys rubens and Cryptopleura ramosa. The scour can reduce the rock surface to bare coralline crusts at times; sponge crusts and the colonial ascidian Botryllus schlosseri can also grow on the stipes and holdfasts. The faunal diversity on the rock is usually low and restricted to robust, low-profile animals such as the tube-building polychaete Pomatoceros triqueter, the barnacle Balanus crenatus, encrusting bryozoans such as Membranipora membranacea, the anthozoan Urticina felina, the starfish Asterias rubens and the urchin Echinus esculentus. Deeper sites support more hydroids and bryozoans, particularly Bugula spp. Where this biotope occurs in very shallow water Laminaria digitata may be found in combination with the other kelp species. Other species present only in shallow water include the red algae Corallina officinalis and the sand-binding alga Rhodothamniella floridula.
Infralittoral rock in wave and tide-sheltered conditions, supporting silty communities with Laminaria hyperborea and/or Laminaria saccharina (K). Associated seaweeds are typically silt-tolerant and include a high proportion of delicate filamentous types. In turbid-water estuarine areas, the kelp and seaweeds (KVS) may be replaced by animal-dominated communities (FaVS) whilst stable hard substrata in lagoons support distinctive communities (Lag).
Faunal communities on variable or reduced salinity infralittoral rock
Shallow subtidal rocky habitats which support faunal-dominated communities, with seaweed communities only poorly developed or absent. In some sealochs dense mussel Mytilus edulis beds (MytRS) develop in tide-swept channels, whilst upper estuarine rocky habitats in the south-west coast rias may support particular brackish-water tolerant faunas (CcasEle; HarCon).
Cordylophora caspia and Electra crustulenta on reduced salinity infralittoral rock
Shallow sublittoral rock in the upper estuary of one of the south-west inlets (Tamar) with very high turbidity and therefore no seaweeds. The brackish-water hydroid Cordylophora caspia and small colonies of the encrusting bryozoan Electra crustulenta and a few Balanus crenatus characterise this biotope. More information required to validate this description.
Hartlaubella gelatinosa and Conopeum reticulum on low salinity infralittoral mixed substrata
Upper estuarine mixed hard substrata colonised by very sparse communities of animals with low species richness and with a few seaweeds in very shallow water. In the Tamar estuary the hydroid Hartlaubella gelatinosa and bryozoan Conopeum reticulum are found on stones. In the River Dart the bryozoan Bowerbankia imbricata is most abundant. The mussel Mytilus edulis, the crab Carcinus maenas and the hydroid Obelia dichotoma can be present. A similar brackish-water rocky biotope is recorded from the Bann Estuary, Northern Ireland. There are considerable differences in species composition between sites, but all occur in brackish turbid-water conditions. More information required to validate this description.
Mytilus edulis beds on reduced salinity infralittoral rock
This biotope occur in shallow, often tide-swept, reduced salinity conditions. Dense beds of the mussel Mytilus edulis with the occasional barnacle Balanus crenatus. A wide variety of epifaunal colonisers on the mussel valves, including seaweeds, hydroids and bryozoans can be present. Predatory starfish Asterias rubens can be very common in this biotope. This biotope generally appears to lack large kelp plants, although transitional examples containing mussels and kelps plants may also occur. More information needed to validate this description.
Silted kelp communities (sheltered infralittoral rock)
Infralittoral rock in wave and tide-sheltered conditions, supporting silty communities with Laminaria hyperborea and/or Laminaria saccharina. Associated seaweeds are typically silt-tolerant and include a high proportion of delicate filamentous types. Some areas, particularly in the lower infralittoral zone, are subject to intense grazing by urchins and chitons and may have poorly developed seaweed communities.
Silted cape-form Laminaria hyperborea on very sheltered infralittoral rock
Cape-form of the kelp Laminaria hyperborea on very silted rock, particularly in extremely sheltered sealochs of western Scotland. Below the huge kelp fronds (which often trail onto the seabed) foliose seaweeds form a silted understorey on the rock including Phycodrys rubens, Delesseria sanguinea, Cryptopleura ramosa and Plocamium cartilagineum as well as coralline crusts. At some sites the filamentous red seaweed Bonnemaisonia hamifera, Heterosiphonia plumosa and Brongniartella byssoides may carpet the seabed. Ascidians, particularly Ascidiella aspersa, Ascidia mentula, Ciona intestinalis and Clavelina lepadiformis thrive well in these conditions. The echinoderms Antedon bifida, Echinus esculentus and Asterias rubens are often present along with the gastropod Gibbula cineraria. An abundant growth of the hydroid Obelia geniculata can cover the silted kelp fronds along with the bryozoan Membranipora membranacea. The anthozoan Caryophyllia smithii can be present among the kelp holdfasts. The tube-building polychaete Pomatoceros triqueter can be present on the rock surface along with the crab Necora puber. This biotope generally occurs on shallow bedrock or boulder slopes or isolated rocks protruding through muddy sediment.
Mixed Laminaria hyperborea and Laminaria ochroleuca forest on moderately exposed or sheltered infralittoral rock
Mixed Laminaria hyperborea and Laminaria ochroleuca forest on upper infralittoral moderately exposed or sheltered rock is restricted to the coast of Cornwall and the Isles of Scilly. Unlike L. hyperborea, however, L. ochroleuca has a smooth stipe and it lacks the epiphytic growth of seaweeds. The bryozoan Membranipora membranacea may encrust the very lower part of the stipe but the rest of the stipe is characteristically bare. The fronds too are generally free of encrusting hydroids, bryozoans and grazing gastropods as compared to L. hyperborea. L. ochroleuca holdfasts, however, are often encrusted with sponges and colonial ascidians. A large variety of foliose and filamentous red seaweeds are often present underneath the canopy. These include Callophyllis laciniata, Plocamium cartilagineum, Cryptopleura ramosa, Delesseria sanguinea, Dilsea carnosa Bonnemaisonia asparagoides, Erythroglossum laciniatum, Sphaerococcus coronopifolius, Polyneura bonnemaisonii and Corallina officinalis. The foliose brown seaweed Dictyota dichotoma is frequently found in this biotope along with the occasional kelp such as Saccorhiza polyschides and Laminaria saccharina. The faunal composition of the biotope as a whole is often sparse. The anthozoans Corynactis viridis and Caryophyllia smithii are common on vertical surfaces with scattered bryozoan turf species such as Crisiidae. Grazers such as the gastropod Gibbula cineraria and the urchin Echinus esculentus are often present. L. ochroleuca occurs across a wide range of wave exposures (in common with L. hyperborea) and consequently it occurs at low abundance in other kelp biotopes (sheltered through to exposed) that occur in the South-West between Dorset to Lundy. In such cases, records should be considered as regional variations of the usual kelp biotopes. Records should only be assigned to this biotope when the canopy is dominated by L. ochroleuca alone, or by a mixture of both L. hyperborea and L. ochroleuca (though the latter is usually at greater abundance). L. ochroleuca commonly occurs on the Brittany and Normandy coasts.
Mixed Laminaria hyperborea and Laminaria saccharina on sheltered infralittoral rock
Mixed Laminaria hyperborea and Laminaria saccharina on bedrock and boulders in sheltered infralittoral habitats. Typically subject to weak tidal streams and rather silty conditions. Beneath the kelp is an associated under-storey flora of foliose red seaweeds including Plocamium cartilagineum, Cryptopleura ramosa and Callophyllis laciniata as well as the brown seaweeds Dictyota dichotoma, Cutleria multifida and Desmarestia aculeata. The stipes of L. hyperborea may be densely covered with red seaweeds such as Phycodrys rubens and Delesseria sanguinea as well as the solitary ascidian Clavelina lepadiformis and the featherstar Antedon bifida. The fronds are often epiphytised by the hydroid Obelia geniculata and the bryozoan Membranipora membranacea. Beneath the kelp canopy, the faunal component is generally less diverse than the more exposed kelp forests, dominated by the echinoderms Echinus esculentus and Asterias rubens, but the tops shells Gibbula cineraria and Calliostoma zizyphinum can be common as well. The crab Necora puber and the brittlestar Ophiothrix fragilis can be found in cracks and crevices, while the tube-building polychaete Pomatoceros triqueter and coralline crusts are present on the rock surface. Although there is a reduced number of species by comparison to the more exposed L. hyperborea forests (Lhyp.Ft), there are considerably more algae species than occur in the more sheltered L. saccharina forests (Lsac.Ft). This biotope is predominately found in the shelter of fjordic sealochs in Scotland. Where it does occur in south-west Britain the mixed kelp forest may also include the southern kelp Laminaria ochroleuca. Three variants has been described: The kelp forest in the upper infralittoral (LhypLsac.Ft), grading to a kelp park with increasing depth (LhypLsac.Pk) as well as a grazed variant (LhypLsac.Gz).
Mixed Laminaria hyperborea and Laminaria saccharina forest on sheltered upper infralittoral rock
Sheltered, often silted, upper infralittoral bedrock and boulder slopes with mixed kelps Laminaria hyperborea and Laminaria saccharina and red seaweeds beneath. The kelp at these sheltered sites often has large `cape-form' fronds, which form a dense canopy over the seabed and are often epiphytised by the hydroid Obelia geniculata and the bryozoan Membranipora membranacea. Beneath the kelp, red seaweeds such as Delesseria sanguinea and Cryptopleura ramosa occur on top of encrusting coralline algae. Often, a dense algal turf of Bonnemaisonia hamifera (tetrasporophyte) carpets the rock. The stipes of L. hyperborea may be densely covered with seaweeds such as Phycodrys rubens, Plocamium cartilagineum and Porphyropsis coccinea. There can also be a prominent faunal component on the stipes including the solitary ascidian Clavelina lepadiformis and the colonial ascidian Botryllus schlosseri. Brown seaweeds, occurring here in low abundance, include Dictyota dichotoma. The kelp Saccorhiza polyschides may also occur but rarely in equal abundance to L. hyperborea or L. saccharina. Beneath the kelp canopy, the faunal component is generally less diverse than the more exposed kelp forests (Lhyp). The silted rock supports a sparse fauna of gastropods Gibbula cineraria and Calliostoma zizyphinum, the tube-building polychaete Pomatoceros triqueter and occasional starfish Asterias rubens and the urchin Echinus esculentus. Steeper, less silted rock, may have the anthozoans Caryophyllia smithii and Alcyonium digitatum.Sheltered, often silted, upper infralittoral bedrock and boulder slopes with mixed kelps Laminaria hyperborea and Laminaria saccharina and red seaweeds beneath. The kelp at these sheltered sites often has large `cape-form' fronds, which form a dense canopy over the seabed and are often epiphytised by the hydroid Obelia geniculata and the bryozoan Membranipora membranacea. Beneath the kelp, red seaweeds such as Delesseria sanguinea and Cryptopleura ramosa occur on top of encrusting coralline algae. Often, a dense algal turf of Bonnemaisonia hamifera (tetrasporophyte) carpets the rock. The stipes of L. hyperborea may be densely covered with seaweeds such as Phycodrys rubens, Plocamium cartilagineum and Porphyropsis coccinea. There can also be a prominent faunal component on the stipes including the solitary ascidian Clavelina lepadiformis and the colonial ascidian Botryllus schlosseri. Brown seaweeds, occurring here in low abundance, include Dictyota dichotoma. The kelp Saccorhiza polyschides may also occur but rarely in equal abundance to L. hyperborea or L. saccharina. Beneath the kelp canopy, the faunal component is generally less diverse than the more exposed kelp forests (Lhyp). The silted rock supports a sparse fauna of gastropods Gibbula cineraria and Calliostoma zizyphinum, the tube-building polychaete Pomatoceros triqueter and occasional starfish Asterias rubens and the urchin Echinus esculentus. Steeper, less silted rock, may have the anthozoans Caryophyllia smithii and Alcyonium digitatum.
Grazed, mixed Laminaria hyperborea and Laminaria saccharina on sheltered infralittoral rock
Silted infralittoral rock with mixed Laminaria hyperborea and Laminaria saccharina kelp forest, intensively grazed by the echinoderm Echinus esculentus and the gastropods Gibbula cineraria and Calliostoma zizyphinum. Although both kelp species can occur in equal abundance (Common), L. hyperborea usually dominates. The grazing-resistant brown seaweed Desmarestia aculeata and Cutleria multifida may be present. A similar variety of red seaweeds to those found in the ungrazed kelp forest (LhypLsac.Ft) may occur beneath the kelp canopy, but in much lower abundance. As grazing intensity increases the seaweed cover decreases - and some sites are reduced to the bare appearance of encrusting brown and coralline algae beneath the kelp canopy. The L. hyperborea stipes generally support more seaweeds than the rock beneath, including Cryptopleura ramosa, Delesseria sanguinea, Phycodrys rubens and Bonnemaisonia hamifera. The stipes may also support sometimes dense ascidians Clavelina lepadiformis and Ciona intestinalis and the echinoderm Antedon bifida. The kelp fronds are often densely covered by the hydroid Obelia geniculata. At the most intensively grazed sites even the kelp stipes are bare. Although the rock appears bare, between boulders and in crevices there are often the brittlestar Ophiothrix fragilis and the crabs Necora puber and Pagurus bernhardus. The tube-building Pomatoceros triqueter and bryozoan crusts are commonly found on any vertical surfaces.
Mixed Laminaria hyperborea and Laminaria saccharina park on sheltered lower infralittoral rock
Sheltered silted, bedrock and boulders with a park of mixed Laminaria hyperborea and Laminaria saccharina. Both kelp species are sparse in the park (Frequent). Beneath the often 'cape-form' kelp canopy, foliose red seaweeds such as Delesseria sanguinea, Cryptopleura ramosa, Heterosiphonia plumosa and Brongniartella byssoides are often present at high densities on the silted rock. Other red seaweeds such as encrusting coralline algae, Phycodrys rubens, Callophyllis laciniata, Bonnemaisonia asparagoides and Plocamium cartilagineum can be present. Other brown seaweeds include Dictyota dichotoma and Desmarestia aculeata. The animal component of this biotope is generally richer than the upper infralittoral mixed kelp forest (LhypLsac.Ft). A variety of hydroids such as Obelia geniculata grow epiphytically on the kelp fronds along with the bryozoan Membranipora membranacea. The echinoderm Antedon bifida and ascidians such as Clavelina lepadiformis attach to the kelp stipes, above the silted rock. The rock itself supports anthozoans such as Caryophyllia smithii and Urticina felina as well as the tube-building polychaete Pomatoceros triqueter and the crap Necora puber. Grazers include the prominent echinoderm Echinus esculentus and the gastropods Gibbula cineraria and Calliostoma zizyphinum. Where pockets of sediment occur, there may be an increase in infaunal species such as the burrowing anthozoan Cerianthus lloydii, the brittlestar Ophiura albida, and starfish Asterias rubens. Although there is a decrease in the number of algal species in the kelp park, the abundance remains relatively high.
Laminaria saccharina on very sheltered infralittoral rock
Very sheltered infralittoral rock dominated by the kelp Laminaria saccharina. Typically very silty and often with few associated seaweeds due to siltation, grazing or shading from the dense kelp canopy. The most commonly occurring red seaweeds are Delesseria sanguinea, Phycodrys rubens, Bonnemaisonia hamifera and coralline crusts. In addition to the kelp the brown seaweed Chorda filum and Ectocarpaceae are often present. As well as lacking Laminaria hyperborea, the Lsac biotopes have fewer foliose and filamentous red seaweed species by comparison to LhypLsac biotopes. A depauperate assemblage of animals is present (by comparison to Lhyp.Ft and Lhyp.Pk) predominantly consisting of the encrusting polychaetes Pomatoceros triqueter, the crabs Carcinus maenas and Pagurus bernhardus and the ubiquitous gastropod Gibbula cineraria. The echinoderms Antedon bifida, starfish Asterias rubens, brittlestar Ophiothrix fragilis and urchin Echinus esculentus occur in low abundance. Ascidians are commonly found in all the Lsac biotopes, but the large solitary ascidian Ascidia mentula are most prolific in very sheltered conditions of L. saccharina forests (Lsac.Ft). This biotope is most commonly associated with the sheltered fjordic sealochs of Scotland where sublittoral hard substrata can be found at the sheltered head of the lochs. Similarly the sheltered loughs of Ireland (Lough Hyne, Strangford Lough and Carlingford Lough). It is also found where suitable hard substrata exist in the sheltered inlets of south-west Britain, such as Milford Haven or Plymouth Sound. 4 variants has been described: A mixture of L. saccharina and Laminaria digitata (Lsac.Ldig), dense L. saccharina forest in the upper infralittoral (Lsac.Ft), sparse L. saccharina in the lower infralittoral (Lsac.Pk) and urchin-grazed (Lsac.Gz).
Laminaria saccharina forest on very sheltered upper infralittoral rock
Sheltered to extremely sheltered sublittoral fringe and infralittoral bedrock, boulders and cobbles characterised by a dense canopy of the kelp Laminaria saccharina. In such sheltered conditions, a distinct sublittoral fringe is not always apparent and this biotope can therefore extend from below the Fucus serratus zone (Fserr) into the upper infralittoral zone, though there may be a mixed L. saccharina and Laminaria digitata zone (Lsac.Ldig) in between. There is a relatively low species diversity and species density due to a combination of heavy siltation of the habitat and the lack of light penetrating through the dense kelp canopy. Only a few species of red seaweeds are present compared with Lsac.Ldig or LhypLsac. The most commonly occurring red seaweeds are Delesseria sanguinea, Phycodrys rubens, Bonnemaisonia hamifera and coralline crusts. Brown seaweeds are also sparse and generally comprise Chorda filum and ectocarpoids. At extremely sheltered sites, where there is a heavy silt cover on the rock and the kelp fronds, the sub-flora is reduced to a few specialised species able to tolerate these conditions, such as the cartilaginous seaweeds Polyides rotundus and Chondrus crispus. Ascidians such as Clavelina lepadiformis, Ascidiella aspersa and Ascidia mentula can remain prominent in such conditions, often occurring on steep or vertical rock which is subject to less siltation. The variety of red seaweeds is further reduced where grazers such as the urchin Echinus esculentus and the top shell Gibbula cineraria are present. The keelworm Pomatoceros triqueter, the crab Carcinus maenas and the hermit crab Pagurus bernhardus can be present. Geographical variations: Northern sites: in sheltered sealochs the most conspicuous fauna in these forests are the large solitary ascidians Ciona intestinalis, Ascidiella spp. and A. mentula which tend to occur in greater abundance than in the mixed kelp forests (LhypLsac). In common with mixed forests, echinoderms are consistently present in low abundance: the featherstar Antedon bifida, common starfish Asterias rubens, the brittlestar Ophiothrix fragilis and the urchin Echinus esculentus are typically present. Saddle oysters Pododesmus patelliformis and chitons Tonicella marmorea can occur in high abundance at some sites. The anthozoan Anemonia viridis is often more prevalent at the extremely sheltered sites. The communities of the sheltered voes and sounds of Shetland and Orkney are similar to those present in the mainland sealochs. Southern sites: Sheltered infralittoral rock is not commonly found outside of the fjordic sealochs. In south-west Britain, where sublittoral rock does occur in shallow marine inlets, the waters are more turbid than in the sealochs, generally limiting kelp to the sublittoral fringe zone. Echinoderms are rare or absent from the south-western L. saccharina forests. A far greater diversity of red seaweeds is associated with the south-western sites: Palmaria palmata, Gracilaria gracilis, Phyllophora pseudoceranoides, Cystoclonium purpureum, Rhodophyllis divaricata, Ceramium nodulosum and Polyneura bonnemaisonii typically occur.
Grazed Laminaria saccharina with Echinus, brittlestars and coralline crusts on sheltered infralittoral rock
Coralline encrusted rock with scattered tufts of red seaweed and a relatively high abundance of grazing echinoderms which typically include the urchin Echinus esculentus and/or the brittlestars Ophiothrix fragilis or Ophiocomina nigra. The rock often looks bare, with few conspicuous species present although Laminaria saccharina may occur it is generally in low abundance (Rare or Occasional). The red seaweeds, reduced to small tufts through grazing, include Phycodrys rubens, Delesseria sanguinea and Brongniartella byssoides and although these seaweeds also occur in Lsac.Pk they are far less frequent in this biotope. Brown seaweeds, such as Desmarestia viridis, Chorda filum and Cutleria multifida, may be present. Grazing molluscs, such as Gibbula cineraria and can be common. Under-boulder habitats can harbour the crabs Necora puber and Pagurus bernhardus, terebellid polychaetes and the polychaete Pomatoceros spp. with ascidians Ascidia mentula. and Clavelina lepadiformis on the open rock along with the echinoderm Asterias rubens and the hydroids Kirchenpauria pinnata and Obelia dichotoma.
Laminaria saccharina and Laminaria digitata on sheltered sublittoral fringe rock
Sheltered bedrock and boulders in the sublittoral fringe characterised by a mixed canopy of the kelp Laminaria digitata (usually in its broad-fronded cape-form) and Laminaria saccharina - both species are generally Frequent or greater. Beneath the kelp canopy, the understorey of red seaweeds often includes Chondrus crispus, Dumontia contorta, Bonnemaisonia hamifera and Plocamium cartilagineum. The surface of the rock is usually covered with encrusting coralline algae as well as non-calcified red crusts and the tube-building polychaete Pomatoceros triqueter. The brown seaweeds Chorda filum, Ectocarpaceae and Fucus serratus can be present along with the green seaweeds Ulva lactuca and Enteromorpha intestinalis. Patches of the sponge Halichondria panicea can frequently be found in cracks and crevices. Beneath and between boulders a variety of mobile crustaceans such as Carcinus maenas, the gastropod Gibbula cineraria and the starfish Asterias rubens are common.
Laminaria saccharina park on very sheltered lower infralittoral rock
Silty bedrock or boulders with a Laminaria saccharina park (often the cape-form). Beneath the canopy, the rock is covered by encrusting coralline algae, and the urchin Echinus esculentus is often present. Due to the amount of silt cover on the rock and the reduced light intensity beneath the broad-fronded kelp, only a few red seaweeds typically survive, the most common species being Phycodrys rubens, Delesseria sanguinea, Bonnemaisonia spp. and Brongniartella byssoides. The brown seaweeds Dictyota dichotoma and Cutleria multifida may be present in low abundance. Compared to the kelp forest zone above (Lsac.Ft) both the kelp and other seaweeds are sparse (Occasional). The most conspicuous animals are large solitary ascidians, particularly Ascidia mentula and Ciona intestinalis, together with the smaller Clavelina lepadiformis. In general, the faunal component of this biotope is similar to other sheltered kelp biotopes and includes a variety of mobile crustaceans such Carcinus maenas and Pagurus bernhardus, the keelworm Pomatoceros spp., terebellid worms, echinoderms Asterias rubens, Ophiothrix fragilis and the featherstar Antedon bifida. The hydroid Kirchenpauria pinnata, although only rare is often found in the kelp park along with the top shell Gibbula cineraria and the barnacle Balanus crenatus.
Sargassum muticum on shallow slightly tide-swept infralittoral mixed substrata
Mixed substrata from the sublittoral fringe to 5m below chart datum dominated by the brown seaweed Sargassum muticum. This invasive non-native brown seaweed can form a dense canopy on areas of mixed substrata (typically 0-10% bedrock on 90-100% sandy sediment). The substrate on which this S. muticum-dominated community is able to develop is highly variable, but particularly prevalent on broken rock and pebbles anchored in sandy sediment. The pebbles, cobbles and broken bedrock provide a substrate for alga such as the kelp Laminaria saccharina. During the spring, S. muticum has large quantities of epiphytic ectocarpales and may also support some epifauna e.g. the hydroid Obelia geniculata commonly found on kelp. The brown seaweed Chorda filum, which thrives well on these mixed substrata, is also commonly found with S. muticum during the summer months. In Strangford Lough, where this biotope occurs, the amphipod Dexamine spinosa has been recorded to dominate the epiphytic fauna (this is known to be commonly found in Zostera spp. beds). S. muticum is also found on hard, bedrock substrates within L. saccharina canopies. S. muticum plants on hard substrate area, under a dense L. saccharina canopy, are typically smaller and at a much lower density, especially where a lush, under-storey exists with red seaweeds such as Ceramium nodolosum, Gracilaria gracilis, Chylocladia verticillata, Pterosiphonia plumula and Polysiphonia elongata and the green seaweeds Cladophora sp., Ulva lactuca and Bryopsis plumosa. The anthozoan Anemonia viridis and the crab Necora puber can be present. More information is necessary to validate this description.
Very wave-sheltered bedrock, boulders and cobbles subject to only weak tidal streams in the sublittoral fringe and infralittoral zone, in areas of variable/reduced salinity. This biotope complex is characterised by the kelp Laminaria saccharina and coralline crusts such as Lithothamnion glaciale. Grazers such as the urchins Psammechinus miliaris and Echinus esculentus, and the gastropods Gibbula cineraria and Buccinum undatum may be present. The tube-dwelling polychaete Pomatoceros triqueter, the ascidians Ciona intestinalis, Corella parallelogramma and Ascidiella scabra, the barnacle Balanus crenatus, the starfish Asterias rubens and the brittlestar Ophiothrix fragilis may also be present. Red algal communities are composed primarily of Phycodrys rubens. The crabs Carcinus maenas and Pagurus bernhardus, and the bivalve Modiolus modiolus may also be observed.
Codium spp. with red seaweeds and sparse Laminaria saccharina on shallow, heavily-silted, very sheltered infralittoral rock
Very shallow, heavily-silted infralittoral rock characterised by dense stands of Codium spp., together with silt-tolerant red seaweeds, the green seaweed Ulva spp. and often only a sparse covering of the kelp Laminaria saccharina. This biotope appears to have a restricted distribution, being known at present only from the sheltered voes of Shetland, some Scottish lagoons and from the harbours of south-west England. These locations suggest the habitat is likely to be subject to reduced salinity conditions (although the habitat data indicate mostly fully marine records). Dense Codium spp. can occur at very sheltered sites, on cobbles or boulders, often in dense patches interspersed with filamentous red seaweeds Bonnemaisonia hamifera, Antithamnionella spirographidis and Ceramium spp. Where sediment is present the red seaweed Polyides rotundus is commonly found along the rock-sediment interface, and the sponge Dysidea fragilis often occurs on the rock. Other red seaweeds that may be present include Chondrus crispus, Callophyllis laciniata, Gelidium latifolium, Corallina officinalis and coralline crusts. The brown seaweeds Halidrys siliquosa, Desmarestia viridis or Chorda filum may be present in high abundance and although kelp L. saccharina may occur, it is usually sparse. There are no conspicuous fauna that typify this biotope, though polychaetes such as terebellids and spirorbids may occur. The opisthobranch Elysia viridis may be locally abundant on the seaweeds and is known to favour Codium fragilis in particular. Large stands of Codium sp. (generally Common abundance) are accompanied by red seaweeds such as G. latifolium, C. laciniata and A. spirographidis on the rock beneath. Cod has been reported to occur in the shallows of The Fleet, Bembridge Ledges, Pagham Harbour and Jersey (Tittley et al. 1985). In Ireland, species-poor shallow, silted bedrock in the North Water of Mulroy Bay, Co. Donegal, is characterised by Griffithsia corallinoides (Common) and Codium tomentosum (Frequent) forming a narrow band below the kelp zone (Lsac.Ft). Cod has not been described from any other sites in Ireland. If Codium spp. is less than Common amongst dense L. saccharina and Chorda filum, it should not be recorded as Cod.
Laminaria saccharina with Phyllophora spp. and filamentous green seaweeds on variable or reduced salinity infralittoral rock
Shallow infralittoral bedrock or boulder slopes, in reduced or low salinity conditions, characterised by the kelp Laminaria saccharina with dense stands of silted filamentous green seaweeds and red seaweeds Phyllophora crispa, Phyllophora pseudoceranoides and Phycodrys rubens. The filamentous green seaweeds e.g. Chaetomorpha melagonium and Cladophora spp. can form a blanket cover amongst the L. saccharina in the upper zone, which is under greater influence of freshwater input. In deeper water the green seaweeds are replaced by red seaweed Phyllophora spp. or Polysiphonia fucoides which may form a distinct sub-zone in the biotope. Coralline crust can be present. The solitary ascidians Corella parallelogramma and Ascidiella scabra are often epiphytic on the seaweed (particularly Phyllophora spp.) and dominate the animal community along with the starfish Asterias rubens. The small ascidian Dendrodoa grossularia, the barnacle Balanus crenatus and the tube-building polychaete Pomatoceros triqueter occur on the rock surface. More mobile species include the crab Carcinus maenas, the hermit crab Pagurus bernhardus and the whelk Buccinum undatum. Bryozoans Electra pilosa and Spirorbis sp. may cover kelp fronds. The red seaweed Odonthalia dentata may be present in the north.
Laminaria saccharina and Psammechinus miliaris on variable salinity grazed infralittoral rock
Sheltered bedrock, boulders and cobbles, in areas of reduced salinity, with kelp Laminaria saccharina, and depauperate coralline-encrusted rock supporting few foliose seaweeds but many grazing urchins Psammechinus miliaris and Echinus esculentus. The coralline crusts are typically Lithothamnion glaciale, while the brown crusts can be Pseudolithoderma extensum. Encrusting polychaetes Pomatoceros triqueter, resistant to the grazing, are also present on most of the rock. The grazing fauna are a significant component of this biotope; large numbers of P. miliaris are typically present, although where absent the brittlestar Ophiothrix fragilis may occur. Other grazers prevalent on the rock include the chiton Tonicella marmorea, the limpet Tectura testudinalis and the gastropod Gibbula cineraria. A combination of grazing pressure and lowered salinity maintains a low diversity of species in this biotope, with foliose and filamentous seaweeds generally absent or reduced to small tufts by grazing. In stark contrast to the range of seaweeds present in the L. saccharina forests (Lsac.Ft) the only red seaweed consistently found in this biotope is Phycodrys rubens. The range of fauna is similarly low, with a conspicuous absence of hydroids and bryozoans. Bedrock and boulders provide a firm substrate on which ascidians Ciona intestinalis and Ascidia mentula and the bivalve Modiolus modiolus can attach. The crabs Pagurus bernhardus and Carcinus maenas can usually be found here, though Necora puber typically is absent due to the brackish conditions. The starfish Asterias rubens along with the whelk Buccinum undatum can be present. The substratum on which this biotope occurs varies from bedrock to boulders or cobbles on sediment. The kelp band is relatively narrow and shallow (upper 5 m) compared to Lsac.Ft, although the grazed coralline encrusted rock extends deeper. This depth limit becomes shallower towards the heads of the sealochs. Geographical distribution This biotope is restricted to the west coast of Scotland, usually near the head of fjordic sealochs, which are influenced by freshwater run-off.
Submerged fucoids, green or red seaweeds (low salinity infralittoral rock)
Very shallow submerged rocky habitats in lagoons, subject to reduced or permanently low salinity conditions. These particular conditions lead to a variety of seaweed-dominated communities, which include fucoids and green filamentous species. The fucoids, more typical of intertidal habitats, penetrate into the subtidal under the reduced salinity conditions which are not tolerated by kelps.
Ascophyllum nodosum with epiphytic sponges and ascidians on variable salinity infralittoral rock
Dense subtidal stands of Ascophyllum nodosum, heavily epiphytised by sponges and ascidians in lagoon-like habitats. The wracks Fucus vesiculosus and Fucus serratus can be present along with the brown seaweed Chorda filum and the red seaweed Polyides rotundus. The crab Carcinus maenas can be present between the A. nodosum holdfasts along with the shrimps Mysidae.
Mixed fucoids, Chorda filum and green seaweeds on reduced salinity infralittoral rock
Permanently submerged mixed fucoids on rock in lagoons. The main species are the wracks Fucus serratus and Fucus vesiculosus, but the brown seaweeds Chorda filum, Ascophyllum nodosum and Ectocarpaceae can be present as well. Red seaweeds are normally present and include Mastocarpus stellatus, Polyides rotundus, Chondrus crispus, Ceramium spp. and coralline crusts. A variety of green seaweeds is also present and include Enteromorpha spp., while dense patches of Cladophora rupestris may occur on vertical rock faces. The faunal component is restricted to the mussel Mytilus edulis, the polychaete Arenicola marina and the crab Carcinus maenas. Opossum shrimps Mysidae can be present as well. The kelp Laminaria saccharina is absent, possibly due to the low salinity conditions.
Fucus ceranoides and Enteromorpha spp. on low salinity infralittoral rock
Permanently submerged lagoon fringes with dense communities of the wrack Fucus ceranoides and the green seaweed Enteromorpha spp. There is typically a very limited associated biota due to low salinity conditions, and may include the opossum shrimps Mysidae and the freshwater/brackish gastropod Potamopyrgus antipodarum.
Polyides rotundus and/or Furcellaria lumbricalis on reduced salinity infralittoral rock
Bedrock and boulders characterised by a dense turf of the red seaweeds Polyides rotundus and/or Furcellaria lumbricalis, often with a dense mat of filamentous brown and green seaweeds including Ectocarpaceae and Cladophora spp. Other red seaweeds presents include Chondrus crispus, Gracilaria gracilis and coralline crusts as well as the odd brown seaweed Chorda filum or Laminaria spp. Associated with these seaweeds are a variety of ascidians including Clavelina lepadiformis, Ascidiella aspersa, Ascidiella scabra and Ciona intestinalis as well as the anemones Anemonia viridis and Actinia equina and the sponge Halichondria panicea. More mobile fauna include the starfish Asterias rubens, the crab Carcinus maenas, the hermit crab Pagurus bernhardus, the opossum shrimps Mysidae and the gastropod Littorina littorea. Attached to the rock or cobbles are spirorbid polychaetes and the mussel Mytilus edulis. Please notice that part of this diversity is due to large differences between sites.
This habitat complex occurs on predominantly moderately wave-exposed bedrock and boulders, subject to moderately strong to weak tidal streams. On the bedrock and stable boulders there is typically a narrow band of kelp Laminaria digitata in the sublittoral fringe which lies above a Laminaria hyperborea forest and park. Associated with the kelp are communities of seaweeds, predominantly reds and including a greater variety of more delicate filamentous types than found on more exposed coasts (KFaR).
Kelp and red seaweeds (moderate energy infralittoral rock)
Infralittoral rock subject to moderate wave exposure, or moderately strong tidal streams on more sheltered coasts. On bedrock and stable boulders there is typically a narrow band of kelp Laminaria digitata in the sublittoral fringe which lies above a Laminaria hyperborea forest and park. Associated with the kelp are communities of seaweeds, predominantly reds and including a greater variety of more delicate filamentous types than found on more exposed coasts (KFaR). The faunal component of the understorey is also less prominant than in KFaR.
Hiatella arctica and seaweeds on vertical limestone / chalk
This biotope is found in the infralittoral zone on moderately exposed vertical limestone/chalk surfaces in weak tidal streams, and has been recorded most frequently between 0-10m. This biotope is characterised by abundant Hiatella arctica and a rich sponge community including Cliona celata, Dysidea fragilis and Pachymatisma johnstonia. Other species that may be frequent in this biotope are the crab Necora puber, the sea squirt Clavelina lepadiformis, and the top shell Calliostoma zizyphinum, although these species are found in other vertical rock biotopes, however in lesser abundance.
Laminaria digitata on moderately exposed sublittoral fringe rock
Exposed to moderately exposed sublittoral fringe rock characterised by the kelp Laminaria digitata with coralline crusts covering the rock beneath the kelp canopy. Foliose red seaweeds such as Palmaria palmata, Membranoptera alata, Chondrus crispus and Mastocarpus stellatus are often present along with the calcareous Corallina officinalis. The brown seaweed Fucus serratus and the green seaweeds Cladophora rupestris and Ulva lactuca can be present as well. The sponge Halichondria panicea can be found among the kelp holdfasts or underneath overhangs. Also present on the rock are the tube-building polychaete Pomatoceros triqueter, the gastropods Patella vulgata and Gibbula cineraria. The bryozoan Electra pilosa can form colonies on especially C. crispus, M. stellatus and F. serratus while the hydroid Dynanema pumila are more common on the kelp. Three variants of this biotope are described: L. digitata forest on rocky shores (Ldig.Ldig). L. digitata on boulder shores (Ldig.Bo) and soft rock supporting L. digitata, such as the chalk found in south-east England (Ldig.Pid). For L. digitata in sheltered, tide-swept conditions see LdigT.
Laminaria digitata and under-boulder fauna on sublittoral fringe boulders
This Laminaria digitata biotope is found predominantly on moderately exposed boulder shores and occasionally also on exposed or sheltered shores. Upper surfaces of the boulders are colonised by dense L. digitata though other kelp such as Laminaria hyperborea and Laminaria saccharina or the wrack Fucus serratus can be present at lower abundance. The kelp fronds can be colonised by the bryozoan Membranipora membranacea. Beneath the kelp canopy are a variety of red seaweeds such as Mastocarpus stellatus, Chondrus crispus, Palmaria palmata, Membranoptera alata, Corallina officinalis and coralline crusts. Green seaweeds include Cladophora rupestris and Ulva lactuca. Where space is available beneath the boulders (i.e. they are not buried in sediment) there may be a rich assemblage of animals. Characteristic species include the crabs Porcellana platycheles, Pisidia longicornis and juvenile Cancer pagurus. Also present beneath the boulders are often high densities of the barnacle Balanus crenatus, the tube-building polychaete Pomatoceros triqueter, spirorbid worms, the polychaete Harmotho‰ sp., gammarid amphipods and a few gastropods such as Gibbula cineraria. The encrusting bryozoans Electra pilosa and Umbonula littoralis and encrusting colonies of the sponges Halichondria panicea and Halisarca dujardini are also typical of this habitat. The richest examples also contain a variety of echinoderms such as Asterias rubens, colonial ascidians such as Botryllus schlosseri and small hydroids.
Laminaria digitata on moderately exposed sublittoral fringe bedrock
Exposed to sheltered sublittoral fringe bedrock dominated by a dense canopy of Laminaria digitata, often with a wide range of filamentous and foliose red seaweeds beneath. The most frequently occurring red seaweeds are Palmaria palmata, Corallina officinalis, Mastocarpus stellatus, Chondrus crispus, Lomentaria articulata and Membranoptera alata. Generally the rocky substratum is covered by encrusting coralline algae, on which occasional limpets Patella vulgata and topshells Gibbula cineraria graze. A wide variety of fauna occurs, some of the most commonly occurring species being the sponge Halichondria panicea and the tube-building polychaete Pomatoceros triqueter. Kelp holdfasts provide a refuge for a varied assemblage of species such as sponges and the limpet Helcion pellucidum, while encrusting bryozoans such as Electra pilosa more often are found on the fronds of foliose red seaweeds. Solitary ascidians may be locally abundant where overhanging or vertical rock occurs, while the hydroid Dynamena pumila can be abundant on Fucus serratus and Laminaria sp. fronds. On exposed, wave-surged shores, the robust red seaweeds M. stellatus, C. crispus and C. officinalis can form a dense turf beneath the kelp along with the occasional green seaweed Ulva lactuca. Similarly on such shores the mussel Mytilus edulis can occur in extremely dense aggregations on the rock, beneath the kelp canopy.
Laminaria digitata and piddocks on sublittoral fringe soft rock
Soft rock, such as chalk, in the sublittoral fringe characterised by Laminaria digitata and rock-boring animals such as piddocks Barnea candida and Pholas dactylus, the bivalve Hiatella arctica and worms Polydora spp. Beneath the kelp forest, a wide variety of foliose red seaweeds occur such as Palmaria palmata, Chondrus crispus, Membranoptera alata and Halurus flosculosus. Filamentous red seaweeds often present are Polysiphonia fucoides and Ceramium nodulosum, while coralline crusts cover available rock surface. The bryozoan Membranipora membranacea and the hydroid Dynanema pumila can form colonies on the kelp fronds, while the bryozoan Electra pilosa more often occur on the foliose red seaweeds. Empty piddock burrows are often colonised by the polychaete Sabellaria spinulosa or in more shaded areas the sponges Halichondria panicea and Hymeniacidon perleve. The undersides of small chalk boulders are colonised by encrusting bryozoans, colonial ascidians and the tube-building polychaete Pomatoceros lamarcki. The boulders and any crevices within the chalk provide a refuge for small crustaceans such as Carcinus maenas, the mussel Mytilus edulis or the barnacle Semibalanus balanoides. The echinoderm Asterias rubens is present as well.
Laminaria hyperborea and foliose red seaweeds on moderately exposed infralittoral rock
Moderately exposed infralittoral bedrock and boulders characterised by a canopy of the kelp Laminaria hyperborea beneath which is an under-storey of foliose red seaweeds and coralline crusts. Some red seaweeds can be found as epiphytes on the kelp stipes and include Delesseria sanguinea and Phycodrys rubens. Other red seaweeds present include the Plocamium cartilagineum, Callophyllis laciniata, Cryptopleura ramosa and the brown seaweeds Dictyota dichotoma and Cutleria multifida. The kelp fronds can be colonised by the hydroid Obelia geniculata or the bryozoans Membranipora membranacea. The echinoderm Antedon bifida, the ascidian Clavelina lepadiformis, the tube-building polychaete Pomatoceros triqueter, the anthozoans Alcyonium digitatum and Urticina felina can be found on the rock beneath the canopy. Mobile species often present include the gastropods Gibbula cineraria and Calliostoma zizyphinum and the echinoderms Echinus esculentus and Asterias rubens. Five variants has been described: Kelp forest (Lhyp.Ft), kelp park (Lhyp.Pk), grazed kelp forest (Lhyp.GzFt), grazed kelp park (Lhyp.GzPk) and kelp with Sabellaria spinulosa reefs (Lhyp.Sab). This suite of biotopes differs from the wave exposed L. hyperborea biotopes (KFaR) by having a lower diversity of cushion-forming faunal species. The foliose red seaweed component of the two suites of biotopes may also differ in composition with a tendency for Lhyp to include some more delicate filamentous species.
Laminaria hyperborea forest and foliose red seaweeds on moderately exposed upper infralittoral rock
Moderately exposed upper infralittoral bedrock and boulders characterised by a dense forest of Laminaria hyperborea with dense foliose red seaweeds beneath the canopy. These include Callophyllis laciniata, Plocamium cartilagineum, Cryptopleura ramosa and Delesseria sanguinea. Kelp stipes are usually covered in a rich mixture of red seaweeds of which Palmaria palmata, Phycodrys rubens and Membranoptera alata are often present. Small kelp plants can also be found on the larger kelp stipes. Kelp fronds may be covered with a hydroid growth of Obelia geniculata or the bryozoans Membranipora membranacea and Electra pilosa. The kelp holdfasts can be colonised by bryozoans Scrupocellaria spp. and/or crisiids and colonial ascidians such as Botryllus schlosseri. The rock surface between the kelp plants is generally covered by encrusting coralline algae, often with sponge crusts Halichondria panicea. Small vertical surfaces within the kelp forest generally lack kelp plants, instead being characterised by foliose red seaweeds such as Dictyota dichotoma, the anthozoans Alcyonium digitatum, Urticina felina and Caryophyllia smithii, the tube-building polychaete Pomatoceros triqueter and gastropods including Calliostoma zizyphinum and Gibbula cineraria. Many grazers are found in the kelp forest, the most commonly occurring being the gastropods Gibbula cineraria and Calliostoma zizyphinum and the echinoderm Echinus esculentus. Other echinoderms present include Asterias rubens and Antedon bifida which can be locally abundant, particularly in the north-west.
Grazed Laminaria hyperborea forest with coralline crusts on upper infralittoral rock
Exposed to moderately exposed Laminaria hyperborea forest is in some areas intensely grazed by the urchin Echinus esculentus. The rock surface lacks a significant turf of foliose seaweeds and generally looks bare, though encrusting algae cover the rock. In addition to these encrusting coralline algae, non-calcareous crusts such as Cruoria pellita and brown algal crusts also occur. The kelp stipes may or may not be grazed; in the most extremely grazed areas, the stipes are also devoid of seaweeds. More usually, however, the stipes offers a refuge from grazing, and are characterised by dense turfs of red seaweeds, especially Phycodrys rubens, Callophyllis laciniata, Plocamium cartilagineum and Delesseria sanguinea. The hydroid Obelia geniculata and the bryozoan Membranipora membranacea colonise the kelp fronds. On the rock itself certain brown seaweeds such as Cutleria multifida may persist in this grazed environment. Fast-growing species such as the kelp Laminaria saccharina may be present at sites recovering from grazing, opportunistically colonising the rock surfaces that have been cleared by grazing. The fauna within a grazed kelp forest is also relatively sparse and is mostly confined to cracks, crevices and under-boulders. Species such as the ascidian Clavelina lepadiformis can often be found on vertical rock. Also found on the rock surface are the anthozoans Urticina felina and Alcyonium digitatum. Encrusting species such as the tube-building polychaete Pomatoceros triqueter are resistant to grazing and may occur in abundance. The grazers present include the echinoderm Echinus esculentus and the gastropods Calliostoma zizyphinum and Gibbula cineraria. Other echinoderms present include Asterias rubens and Antedon bifida which can be abundant in the north-west. Moderate grazing occurs within many kelp forests; records should only be assigned to this biotope where the community has been intensively grazed leaving algal-encrusted rock with very few epilithic algae.
Grazed Laminaria hyperborea park with coralline crusts on lower infralittoral rock
Exposed to moderately exposed Laminaria hyperborea kelp park in some areas is intensively grazed by the urchin Echinus esculentus. The rock surface lacks a significant turf of foliose seaweeds and generally looks bare, though coralline algal crusts and some grazing-resistant animals such as the tube-building polychaete Pomatoceros triqueter cover it. The kelp stipes may or may not be grazed; in the most extremely grazed areas, the stipes are also devoid of seaweeds. More usually, however, the stipes offers a refuge from grazing, and are characterised by dense turfs of red seaweeds, especially Phycodrys rubens and Delesseria sanguinea. Brown seaweeds present include Cutleria multifida, Laminaria saccharina and Dictyota dichotoma. The fauna within a grazed kelp park is also relatively sparse, though some species will survive in cracks and crevices or under boulders including the ascidian Clavelina lepadiformis. The encrusting bryozoan Parasmittina trispinosa and the anthozoans Alcyonium digitatum, Urticina felina and Caryophyllia smithii often characterise vertical or overhanging rock. Mobile species include the gastropods Gibbula cineraria and Calliostoma zizyphinum and the hermit crab Pagurus bernhardus The echinoderms Ophiocomina nigra, Ophiothrix fragilis and Crossaster papposus, generally absent from the kelp forest, can be found in these kelp parks along with Asterias rubens and Antedon bifida.
Laminaria hyperborea park and foliose red seaweeds on moderately exposed lower infralittoral rock
Below the dense kelp forest (Lhyp.Ft) on moderately exposed lower infralittoral bedrock and boulders, the kelp thins out to form a park. Beneath the kelp, the rock and kelp stipes are covered by an often dense turf of foliose red seaweeds such as Callophyllis laciniata, Plocamium cartilagineum, Delesseria sanguinea, Hypoglossum hypoglossoides, Cryptopleura ramosa, Callophyllis laciniata and Phycodrys rubens. Coralline crusts are often present on the rock surface. Many species of red seaweed found in this biotope occur at greater abundance in the shallower kelp forest. Other seaweeds, such as the red seaweeds Bonnemaisonia asparagoides and Hypoglossum hypoglossoides as well as the brown seaweed Dictyota dichotoma are more abundant in this zone than the upper infralittoral. The faunal component of this biotope is similar to that found below the kelp in the upper infralittoral zone and include the hydroid Obelia geniculata, the ascidian Clavelina lepadiformis, the anthozoans Urticina felina, Alcyonium digitatum and Caryophyllia smithii, the tube-building polychaete Pomatoceros triqueter and the gastropods Calliostoma zizyphinum and Gibbula cineraria. The gastropods Gibbula cineraria and Calliostoma zizyphinum and the echinoderm Echinus esculentus can be found grazing on the rock. Other echinoderms present include Asterias rubens and Antedon bifida which can be locally abundant, particularly in the north-west.
Sabellaria spinulosa with kelp and red seaweeds on sand-influenced infralittoral rock
Laminaria hyperborea kelp forest on shallow infralittoral bedrock and boulders characterised by encrustations of Sabellaria spinulosa tubes which cover much of the rock, together with sand-tolerant red seaweeds such as Phyllophora pseudoceranoides, Dilsea carnosa and Polysiphonia elongata and Polysiphonia fucoides. Red seaweeds such as Plocamium cartilagineum and Delesseria sanguinea may also be found beneath the kelp canopy, although typically low in abundance. They can be colonised by the ascidian Botryllus schlosseri. The cowrie Trivia arctica can also be found here. Much of the available rock is covered with encrusting coralline algae together with patches of the encrusting sponge Halichondria panicea and the anthozoan Urticina felina. More mobile fauna include the echinoderms Asterias rubens, Henricia sanguinolenta, Echinus esculentus, and Ophiothrix fragilis, the gastropod Gibbula cineraria and the hermit crab Pagurus bernhardus. The scouring effect of mobile sand adjacent to the rock maintains a reduced underflora and fauna compared to the association of species found in non-scoured kelp forests (Lhyp.Ft). Scour-resistant fauna such as the barnacle Balanus crenatus can be locally abundant on the rock, while the bivalve Pododesmus patelliformis can be found seeking shelter underneath the cobbles. Above the effect of scour, kelp stipes may be densely colonised by red seaweeds such as Phycodrys rubens, Palmaria palmata and Membranoptera alata, together with some sponges and ascidians.
Laminaria hyperborea on tide-swept, infralittoral rock
Wave exposed to moderately wave exposed, tide-swept bedrock and boulders with Laminaria hyperborea, characterised by a rich under-storey and stipe flora of foliose seaweeds including the brown seaweed Dictyota dichotoma. The kelp stipes support epiphytes such as Cryptopleura ramosa and Phycodrys rubens. At some sites, instead of being covered by red seaweeds, the kelp stipes are heavily encrusted by the ascidian Botryllus schlosseri. Epilithic seaweeds Delesseria sanguinea, Plocamium cartilagineum Heterosiphonia plumosa, Hypoglossum hypoglossoides, Callophyllis laciniata, Kallymenia reniformis, Brongniartella byssoides and crustose seaweeds commonly occur beneath the kelp. The kelp fronds are often covered with growth of the hydroid Obelia geniculata or the bryozoan Membranipora membranacea. On the rock surface, a rich fauna comprising the bryozoan Electra pilosa, the sponge Pachymatisma johnstonia, anthozoans such as Alcyonium digitatum, Sagartia elegans and Urticina felina, colonial ascidians such as Clavelina lepadiformis, the calcareous tubeworm Pomatoceros triqueter and the barnacle Balanus crenatus occur. More mobile species include the gastropod Calliostoma zizyphinum, the crab Cancer pagurus and the echinoderms Asterias rubens and Echinus esculentus. Two variants have been described: Tide-swept kelp forest (LhypT.Ft) and tide-swept kelp park (LhypT.Pk).
Laminaria hyperborea forest, foliose red seaweeds and a diverse fauna on tide-swept upper infralittoral rock
Exposed to moderately exposed, tide-swept bedrock and boulders, with dense Laminaria hyperborea forest, characterised by a rich under-storey and stipe flora of foliose seaweeds. The kelp stipes support epiphytes such as Callophyllis laciniata, Corallina officinalis, Cryptopleura ramosa, Membranoptera alata, and Phycodrys rubens. At some sites, instead of being covered by red seaweeds, the kelp stipes are heavily encrusted by the ascidians Botryllus schlosseri and in the south-west Distomus variolosus. Epilithic seaweeds (Dilsea carnosa, Hypoglossum hypoglossoides, Delesseria sanguinea, Plocamium cartilagineum, Brongniartella byssoides, and Dictyota dichotoma ) and crustose seaweeds commonly occur beneath the kelp. The kelp fronds are often covered with growth of the hydroid Obelia geniculata or the bryozoan Membranipora membranacea. Although these species are also found in most kelp forests, in this biotope they are particularly dense. On the rock surface, a rich fauna comprising of the sponges Pachymatisma johnstonia, Halichondria panicea, Esperiopsis fucorum and Dysidea fragilis, anthozoans such as Urticina felina, Alcyonium digitatum and Caryophilia smithii, the barnacle Balanus crenatus, colonial ascidians such as Clavelina lepadiformis, and the gastropods Calliostoma zizyphinum and Gibbula cineraria, occur. Also found on the rock is the echinoderm Asterias rubens and the crab Cancer pagurus.
Laminaria hyperborea park with hydroids, bryozoans and sponges on tide-swept lower infralittoral rock
Exposed to moderately wave-exposed, strongly tide-swept, rock with Laminaria hyperborea park characterised by a rich under-storey and stipe flora of foliose seaweeds such as Phycodrys rubens, Plocamium cartilagineum, Hypoglossum hypoglossoides, Kallymenia reniformis, Cryptopleura ramosa and Delesseria sanguinea. The red seaweed Heterosiphonia plumosa can be present. The foliose brown seaweed Dictyota dichotoma and coralline crust are often present as well. Amongst the red seaweeds is a rich fauna comprising sponges (Pachymatisma johnstonia, Stelligera rigida, Esperiopsis fucorum and Dysidea fragilis), anthozoans (Alcyonium digitatum and Caryophyllia smithii), hydroids (Aglaophenia pluma and Nemertesia antennina), colonial ascidians (Clavelina lepadiformis and Morchellium argus) and bryozoans such as Electra pilosa. Both the flora and fauna of this biotope are similar to the wave exposed kelp park (LhypR.Pk), but LhypT.Pk has a greater faunal component including the barnacle Balanus crenatus, the echinoderm Asterias rubens and the crab Necora puber.
Laminaria hyperborea on tide-swept infralittoral mixed substrata
Wave-exposed through to wave-sheltered, tide-swept infralittoral mixed substrata with Laminaria hyperborea forest/park and other kelp species such as Laminaria saccharina. The rich under-storey and stipe flora is characterised by foliose seaweeds including the brown algae Dictyota dichotoma. The kelp stipes support epiphytes such as Cryptopleura ramosa, Callophyllis laciniata and Phycodrys rubens. At some sites, instead of being covered by red seaweeds, the kelp stipes are heavily encrusted by the ascidians Botryllus schlosseri and the bryozoan Alcyonidium diaphanum. Epilithic seaweeds such as Desmerestia aculeata, Odonthalia dentate, Delesseria sanguinea, Plocamium cartilagineum, Callophyllis laciniata, and crustose seaweeds commonly occur beneath the kelp. The kelp fronds are often covered with growths of the hydroid Obelia geniculata or the bryozoan Membranipora membranacea. On the rock surface, a rich fauna comprising anthozoans such as Alcyonium digitatum and Urticina felina, colonial ascidians such as Clavelina lepadiformis and the calcareous tubeworm Pomatoceros triqueter occurs. More mobile species include the gastropods Gibulla cineria and Calliostoma zizyphinum, the crab Cancer pagurus and the echinoderms Crossaster papposus, Henricia oculata, Asterias rubens and Echinus esculentus. Two variants are described; tide-swept kelp forest on upper infralittoral mixed substrata (LhypTX.Ft) and tide-swept kelp park on lower infralittoral mixed substrata (LhypTX.Pk).
Laminaria hyperborea forest and foliose red seaweeds on tide-swept upper infralittoral mixed substrata
Moderately wave-exposed to wave sheltered, tide-swept mixed substrata, with dense Laminaria hyperborea forest and sparser Laminaria saccharina, characterised by an under-storey and stipe flora of foliose seaweeds. The kelp stipes support epiphytes such as Palmaria palmata Callophyllis laciniata, Cryptopleura ramosa, Membranoptera alata, and Phycodrys rubens. At some sites, instead of being covered by red seaweeds, the kelp stipes are heavily encrusted by the ascidians Botryllus schlosseri and in the south-west Distomus variolosus. Epilithic seaweeds (Delesseria sanguinea, Plocamium cartilagineum, Odonthalia dentata, Dictyota dichotoma and Desmarestia aculeata) and crustose seaweeds commonly occur beneath the kelp. The kelp fronds are often covered with growth of the hydroid Obelia geniculata or the bryozoan Membranipora membranacea. Although these species are also found in most kelp forests, in this biotope they are particularly dense. On the rock surface, a rich fauna comprising anthozoans such as Urticina felina, the barnacle Balanus crenatus, the calcareous tubeworm Pomatoceros triqueter, colonial ascidians such as Clavelina lepadiformis, the gastropods Calliostoma zizyphinum and Gibbula cineraria, and the bryozoans Electra pilosa and Alcyonidium diaphanum occur. Also found on the rock are the echinoderms Echinus esculentus, Asterias rubens and Ophiothrix fragilis, and the crabs Cancer pagurus, Pagurus bernhardus and Necora puber.
Laminaria hyperborea park and foliose red seaweeds on tide-swept lower infralittoral mixed substrata
Exposed to moderately wave-exposed, tide-swept, Infralittoral mixed substrata with Laminaria hyperborea park characterised by an under-storey and stipe flora of foliose seaweeds such as Phycodrys rubens, Plocamium cartilagineum, Hypoglossum hypoglossoides, Kallymenia reniformis, Cryptopleura ramosa and Delesseria sanguinea. Epilithic seaweeds (Bonnemaisonia asparagoides, Callophyllis laciniata, Lomentaria orcadensis and Brongniartella byssoides) and crustose seaweeds commonly occur beneath the kelp. The foliose brown seaweed Dictyota dichotoma is often present as well. Amongst the red seaweeds is a fairly diverse fauna comprising sponges (Scypha ciliate), anthozoans (Alcyonium digitatum, Urticina felina and Caryophyllia smithii), hydroids (Tubularia indivisa, Halecium halecinum, Sertularia argentea and Nemertesia antennina), colonial ascidians (Botryllus schlosseri) and bryozoans such as Alcyonium diaphanum. On the rock surface, the calcareous tubeworm Pomatoceros triqueter, the crab Cancer pagurus and the gastropods Gibbula cineraria and Calliostoma zizyphinum may be found. A diverse range of echinoderms are also found in this biotope: Crossaster papposus, Henricia oculata, Asterias rubens, Echinus esculentus and Ophiothrix fragilis.
Laminaria hyperborea on moderately exposed vertical rock
LhypVt is found on moderately exposed coasts in moderately strong to weak tidal streams generally in 0-20m water depth. It is characterised by the kelp Laminaria hyperborea, the soft coral Alcyonium digitatum and crinoid Antedon bifida. This biotope is relatively species poor when compared to similar biotopes in more exposed environments e.g. LhypRVt. The urchin Echinus esculentus may be frequently observed grazing the vertical rock face. This biotope may have 2 sub-biotopes. One is characterised by the frequent occurrence of the sea squirt Clavelina lepadiformis and the red seaweeds Phycodrys rubens and Cryptopleura ramosa. The brown seaweed Dictyota dichotoma may also be frequent in this sub-biotope. The second sub-biotope is more species poor than the previous one and is characterised by the common occurrence of Alcyonium digitatum, which is only occasional in the other variant.
Dense foliose red seaweeds on silty moderately exposed infralittoral rock
Upward-facing surfaces of shallow, infralittoral bedrock and boulders in areas of turbid water dominated by dense red seaweeds, with the notable absence of kelp. The stable rock, which can be cobbles or boulders but is more typically bedrock, is usually silted. Individual species of foliose red seaweeds such as Plocamium cartilagineum or Calliblepharis ciliata often dominate. Other red seaweeds likely to be present include Phyllophora crispa, Rhodymenia holmesii, Halurus flosculosus, Cryptopleura ramosa, Hypoglossum hypoglossoides, Heterosiphonia plumosa and coralline crusts. The brown seaweed Dictyota dichotoma is sometimes present, although never abundant. This biotope does not generally occur below kelp park but rather occurs on shallow, silted rock on which kelp would normally grow in less turbid conditions. The fauna can be variable but is generally typified by the presence of silt-tolerant animals such as encrusting sponges, particularly Dysidea fragilis and Halichondria panicea, the hydroid Tubularia indivisa, bryozoan crusts and scattered Sabellaria spinulosa and Balanus crenatus. In the summer months the seaweeds can become heavily encrusted with the bryozoan Electra pilosa and the ascidian Molgula manhattensis which can also form dense mats on the rock. The polychaete Lanice conchilega can be present, where sandy and muddy patches occur. Where this biotope occurs on chalk bedrock, such as off the Sussex coast, the piddock Pholas dactylus is often found bored into the rock. This biotope is recorded from the English Channel, off Kent, Sussex and the Isle of Wight. Please notice that individual sites of this biotope can vary significantly in the species composition.
Kelp and seaweed communities in tide-swept sheltered conditions
Sheltered infralittoral rock exposed to strong tidal streams. In the sublittoral fringe dense Laminaria digitata is found together with erect seaweeds, sponges, ascidians and bryozoans (LdigT). Below this, on bedrock and stable boulders a canopy of mixed kelp (primarily Laminaria hyperborea and Laminaria saccharina) occurs with foliose red seaweeds, sponges and ascidians (XKT). This biotope is typically found in the sheltered narrows and sills of Scottish sealochs. Mixed substrata of boulders, cobbles, pebbles and gravel, that also occurs in the tidal rapids of Scottish sealochs, supports a reduced kelp canopy (L. hyperborea and L. saccharina; typically Frequent), with a rich red seaweed component and maerl at some sites (XKTX). In south-west Britain, sheltered, tide-swept rock is restricted to estuarine conditions where variable salinity and increased turbidity of the water have a significant effect on the biota, limiting the infralittoral zone to very shallow depths. Unlike the tide-swept channels in sealochs, the rock in these estuaries is characterised by a relatively low abundance of L. saccharina (< Common) with foliose red seaweeds, sponges and ascidians (LsacT). L. hyperborea is rarely present.
Filamentous red seaweeds, sponges and Balanus crenatus on tide-swept variable-salinity infralittoral rock
Tide-swept infralittoral rock subject to variable salinity and turbid waters occurs in the mid to upper reaches of the rias of south-west Britain, where riverine freshwater input reduces the salinity. Very shallow rock under these conditions is characterised by a covering of filamentous red seaweed such as Callithamnion spp., Antithamnion spp., Ceramium spp., Griffithsia devoniensis, Pterothamnion plumula and Polysiphonia fucoides, as well as the filamentous green seaweed Cladophora spp. Foliose red seaweeds such as Hypoglossum hypoglossoides, Cryptopleura ramosa and Erythroglossum laciniatum commonly occur, as does the foliose green seaweed Ulva lactuca. Although Laminaria saccharina is often present it is usually in very low abundance (Occasional). The fluctuating salinity limits the number of species able to exist in this habitat. The animal community is dominated by the sponges Halichondria panicea and Hymeniacidon perleve and the barnacle Balanus crenatus. The ascidians Clavelina lepadiformis and Dendrodoa grossularia can be locally abundant at some sites. The crab Carcinus maenas is usually present, as is the mussel Mytilus edulis. The bryozoan Bugula plumosa is sometimes present. Where vertical rock is present, the seaweeds Ceramium nodulosum, P. plumula, C. ramosa, H. hypoglossoides and E. laciniatum are typically found.
Laminaria digitata, ascidians and bryozoans on tide-swept sublittoral fringe rock
Sheltered bedrock, boulders and cobbles that are subject to moderate to strong tidal water movement characterised by dense Laminaria digitata, coralline crusts and sponges such as Halichondria panicea. Other seaweeds present include the foliose red seaweeds Chondrus crispus, Palmaria palmata, Cryptopleura ramosa and Mastocarpus stellatus as well as the calcareous Corallina officinalis. Green seaweeds present include Ulva lactuca, Enteromorpha intestinalis and Cladophora rupestris. The increased water movement encourages several filter-feeding faunal groups to occur. The sponges Leucosolenia spp., Scypha ciliata and Hymeniacidon perleve frequently occur on steep and overhanging rock faces. The bryozoans Electra pilosa, Membranoptera membranipora and Alcyonidium hirsutum encrust the kelp and other foliose seaweeds. In addition, ascidians such as Ascidiella scabra, Dendrodoa grossularia and colonial ascidians Botryllus byssoides and Botryllus leachi often thrive in this environment encrusting both the rock and the seaweeds. The tube-building polychaete Pomatoceros triqueter can be found on the rock and on the kelp holdfasts along with the barnacle Balanus crenatus. More mobile species such as the gastropods Gibbula cineraria and Calliostoma zizyphinum, the crab Carcinus maenas and the starfish Asterias rubens are also common. Areas where increased tidal movement influences this community can be found in the narrows and/or intertidal sills of sealochs.
Laminaria saccharina with foliose red seaweeds and ascidians on sheltered tide-swept infralittoral rock
Sheltered, tide-swept rock in south-western Britain tends to be restricted to estuarine conditions, where variable salinity and increased turbidity have a significant effect on the biota. Due to the turbidity of the water, the infralittoral zone is restricted to very shallow depths. Unlike the tide-swept channels in sealochs, which support a mixed kelp canopy, the rock in these estuaries is characterised by Laminaria saccharina alone, occurring in relatively low abundance (Frequent). The brown alga Desmarestia ligulata can occur in this biotope, though never dense, along with the non-native brown seaweed Sargassum muticum. Beneath the sparse kelp, cobbles and boulders, often surrounded by sediment, are encrusted by fauna and often a dense turf of red seaweed. The foliose red seaweeds associated with this biotope include Callophyllis laciniata, Nitophyllum punctatum, Kallymenia reniformis, Gracilaria gracilis, Gymnogongrus crenulatus, Hypoglossum hypoglossoides, Rhodophyllis divaricata, Chylocladia verticillata, Cryptopleura ramosa and Erythroglossum laciniatum as well as the filamentous Ceramium nodulosum and Pterothamnion plumula. Green seaweeds Ulva lactuca, Bryopsis plumosa and Cladophora spp. may be locally abundant. The dominating faunal species vary from site to site but include sponges such as Halichondria panicea, Esperiopsis fucorum, Dysidea fragilis and Hymeniacidon perleve as well as ascidians, particularly Dendrodoa grossularia and Morchellium argus, which can cover the rocks. Also present is the anthozoan Anemonia viridis, the barnacle Balanus crenatus and the tube-building polychaete Pomatoceros triqueter. The hydroid Plumularia setacea can cover rocks and seaweed fronds Of the range of solitary ascidians found in the north-west, only Ascidiella aspersa tends also to be present in these south-western inlets. There is also a general absence of echinoderms. Where there is vertical rock present, it tends to support more fauna, including barnacles Balanus crenatus, the ascidians Clavelina lepadiformis and Botryllus schlosseri and sometines the featherstar Antedon bifida. Where soft rock allows, such as the limestone in Plymouth Sound, rock-boring organisms such as Polydora sp. may be locally abundant. Sheltered, tide-swept rock is generally restricted to the narrows or tidal rapids of marine inlets. The clear tide-swept waters of Scottish sealochs are significantly different to the marine inlets of south-west Britain. This biotope deals with the latter.
Mixed kelp with foliose red seaweeds, sponges and ascidians on sheltered tide-swept infralittoral rock
Stable, tide-swept rock characterised by dense kelp Laminaria hyperborea and/or Laminaria saccharina forest on scoured, coralline-encrusted rock. This biotope occurs in the sheltered narrows and sills of Scottish sealochs, where there is an increase in tidal flow. Although L. hyperborea (typically Common) generally occurs in greater abundance than L. saccharina (Frequent), either kelp may dominate, sometimes to the exclusion of the other. (This biotope should not be confused with sheltered, but silted LhypLsac). Large stands of the brown seaweed Halidrys siliquosa may also occur amongst the kelp along with Dictyota dichotoma on bedrock and boulders. In contrast to the scoured rock surface the kelp stipes themselves often support prolific growths of foliose red seaweeds such as Phycodrys rubens, Membranoptera alata, Delesseria sanguinea and Plocamium cartilagineum. Other foliose seaweeds may be present among the kelp holdfasts include Chondrus crispus and Dilsea carnosa. The scoured rock surface is characterised by encrusting coralline algae, barnacles Balanus crenatus and the tube-building polychaete Pomatoceros triqueter. The sponge Halichondria panicea, anthozoans Urticina felina, Anemonia viridis and Sagartia elegans can also occur on the scoured rock. Sponges, particularly Halichondria panicea and colonial and solitary ascidians Botryllus schlosseri and Ascidiella aspersa encrust the stipes, whilst hydroid growth of Obelia geniculata and seamats Membranoptera membranacea can cover the fronds, optimising the increased tidal flow. Mobile species such as the gastropod Gibbula cineraria can often be found on and around the kelp. The echinoderms Asterias rubens, Ophiothrix fragilis and Echinus esculentus can be found underneath the kelp canopy on the rock along with the crab Carcinus maenas. Where some protection is afforded from the scour anthozoans may occur on the rock such as Alcyonium digitatum or Metridium senile.
Mixed kelp and red seaweeds on infralittoral boulders, cobbles and gravel in tidal rapids
Mixed substrata of boulders, cobbles, pebbles and gravel, typically found in tidal rapids with kelp Laminaria saccharina and Laminaria hyperborea and red seaweeds. L. saccharina usually dominates this habitat although L. hyperborea may occur in equal abundance at some sites. The kelp in these tidal rapids does not form the same dense canopies associated with stable tide-swept bedrock, but generally occurs at lower abundance (Frequent). Other brown seaweeds occur in significant amounts in these tidal rapids including Dictyota dichotoma, Halidrys siliquosa and Chorda filum. These mixed substrata support a greater diversity of species than scoured bedrock narrows (XKT). In particular, there is an increase in red algal species such as Corallina officinalis, Bonnemaisonia hamifera and Ceramium nodulosum, although none occur in any great abundance. Red seaweeds common to both XKT and this biotope include Chondrus crispus, Delesseria sanguinea, Plocamium cartilagineum and Phycodrys rubens. Good examples of this biotope often have maerl gravel (Lithothamnion sp.) or rhodoliths between cobbles and boulders. Where maerl dominates, the biotope should be recorded as a maerl bed (SS.SMP.Mrl). The sponges associated with more stable, tide-swept conditions are generally absent, but the anthozoan Anemonia viridis might be present. Cobbles and pebbles are encrusted by the ubiquitous polychaete Pomatoceros triqueter and provide shelter for scavenging crabs such as Carcinus maenas and the hermit crab Pagurus bernhardus, gastropods such as Gibbula cineraria and echinoderms such as Echinus esculentus, Asterias rubens, Ophiocomina nigra and Ophiothrix fragilis which favour these sites of increased water movement. Additional infaunal species, inhabiting the sediment pockets, include Lanice conchilega and Sabella pavonina, which can be locally abundant.
Littoral rock (and other hard substrata)
Littoral rock includes habitats of bedrock, boulders and cobbles which occur in the intertidal zone (the area of the shore between high and low tides) and the splash zone. The upper limit is marked by the top of the lichen zone and the lower limit by the top of the laminarian kelp zone. There are many physical variables affecting rocky shore communities - wave exposure, salinity, temperature and the diurnal emersion and immersion of the shore. Wave exposure is most commonly used to characterise littoral rock, from 'extremely exposed' on the open coast to 'extremely sheltered' in enclosed inlets. Exposed shores tend to support faunal-dominated communities of barnacles and mussels and some robust seaweeds. Sheltered shores are most notable for their dense cover of fucoid seaweeds, with distinctive zones occurring down the shore. In between these extremes of wave exposure, on moderately exposed shores, mosaics of seaweeds and barnacles are more typical.
Littoral rock features includes lichens and algae crusts (LIC) in the supralittoral zone and rockpools (Rkp), ephemeral algae (Eph) and caves (CvOv) in the intertidal zone (the area of the shore between high and low tides). These features are present throughout the littoral rock zone from the upper limit at the top of of the lichen zone and the lower limit by the top of the laminarian kelp zone. These features can be found on most rocky shores regardless of wave exposure. Lichens can be found in the supralittoral zone on shores with suitable substratum. The lichen band is wider and more distinct on more exposed shores. Rockpools occur where the topography of the shore allows seawater to be retained within depressions in the bedrock producing 'pools' on the retreat of the tide. As these rockpool communities are permanently submerged they are not directly affected by height on the shore and normal rocky shore zonation patterns do not apply allowing species from the sublittoral to survive. Ephemeral seaweeds occur on disturbed littoral rock in the lower to upper shore. The shaded nature of caves and overhangs diminishes the amount of desiccation suffered by biota during periods of low tides which allows certain species to proliferate. In addition, the amount of scour, wave surge, sea spray and penetrating light determines the unique community assemblages found in upper, mid and lower shore caves, and on overhangs on the lower shore.
Where caves and overhangs occur on rocky shores, the shaded nature of the habitat diminishes the amount of desiccation suffered by biota during periods of low tides which allows certain species to proliferate. In addition, the amount of scour, wave surge, sea spray and penetrating light determines the unique community assemblages found in upper, mid and lower shore caves and overhangs on the lower shore. Biotopes from the surrounding shore such as MytB, Sem or any of the fucoid communities occasionally extend into cave entrances. Sem often extends some way into the cave. Other open shore biotopes may also be found within caves, such as the green seaweed Prasiola stipitata on cave roofs where birds roost (Pra), and localised patches of green algae where freshwater seepage influences the rock (Ent). Rockpools containing encrusting coralline algae (Cor), fucoids and kelp (FK) and hydroids and littorinid molluscs may occur also on the floor of cave entrances. The cave biotope descriptions are largely based on data obtained from surveys of Berwickshire caves (ERT,2000), chalk caves from the Thanet coast (Tittley et al, 1998; Tittley & Spurrier 2001) and data from Wales (CCW Phase 1 data). In general, the biomass and diversity of algal species found in upper and mid-shore littoral caves decreases with increasing depth into the cave as the light levels diminish. Fucoids are usually only found at the entrances to caves, but red algae, and filamentous and encrusting green algae are able to penetrate to lower light intensities towards the back of the cave, and mats of the turf forming red seaweed Audouinella purpurea and/or patches of the green seaweed Cladophora rupestris may occur on the upper walls (AudCla). Brownish velvety growths of the brown algae Pilinia maritima occurring in mats with the red alga A. purpurea on cave walls and upper littoral levels of cliffs (AudPil) should not be confused with the green (GCv) or golden brown algal stains often found above this zone on the ceilings of the caves (AudPil; ChrHap). Below is a zone of Verrucaria mucosa and/or Hildenbrandia rubra on the inner and outer reaches (VmucHil). Fauna usually only occur on the lower and mid walls of the caves and generally comprise barnacles, anemones and tube-forming polychaetes (ScrFa; FaCr) depending on the level of boulder scour or wave surge. Where the floors of caves consist of mobile cobbles and small boulders, little algae and fauna occur due to the effects of scouring (BarCv). Vertical or steeply sloping cave walls and overhangs on the mid and lower shore, subject to wave-surge but without scour, support a rich biota of sponges, hydroids, ascidians and shade-tolerant red algae (SByAs, SR or SR.Den).
Audouinella purpurea and Cladophora rupestris on upper to mid-shore cave walls
Vertical and steeply-sloping upper walls at the entrances and inner reaches of upper to mid-shore caves that are partially sheltered from direct wave action characterised by a turf of the 'velvety' red seaweed Audouinella purpurea. Patches of green filamentous seaweed Cladophora rupestris can be present. The fauna is generally limited to limpets Patella spp., the winkle Littorina saxatilis and the barnacle Semibalanus balanoides, while they usually occur in low abundance. Filamentous or crust forming brown seaweeds may occur mixed with A. purpurea, often becoming a zone in its own right (AudPil) above the AudCrup biotope. Other shade-tolerant red seaweed such as Catenella caespitosa and Lomentaria articulata may occur (but at lower abundance), and where freshwater seepage occurs, Enteromorpha intestinalis can form patches. Some variation in the species composition of the individual caves must be expected depending on local conditions. A. purpurea can be the only seaweed present in caves on the Thanet coast in south-east England. This biotope is known to occur in hard rock caves in north-east England and chalk caves in south-east England. Received after deadline: A. purpurea has changed name to Rhodochorton purpurea.
Audouinella purpurea and Pilinia maritima crusts on upper and mid-shore cave walls and ceilings
Golden brown velvety growths of the brown algae Pilinia maritima occurring in mats with the red alga Audouinella purpurea forming on cave walls and upper littoral levels of cliffs. Fauna is sparse and limited to occasional individuals of the winkle Littorina saxatilis and spirorbid polychaetes. This assemblage is thought to be is widespread throughout Britain, although there are currently few records available. More information are needed to validate this description, which is based on information from the Thanet intertidal survey (Tittley & Spurrier 2001). Received after deadline: A. purpurea has changed name to Rhodochorton purpurea and P. maritima has changed name to Pleurocladia lacustris.
Barren and/or boulder-scoured littoral cave walls and floors
Mid and upper shore mobile boulders/cobbles on cave floors and the lower reaches of cave walls which are subject to scour are generally devoid of macro-fauna and flora. However, where light is available around the cave entrances, encrusting coralline algae may cover the rock and boulder surfaces. In some instances they may support sparse fauna such as the limpet Patella spp. and the winkle Littorina saxatilis.
Chrysophyceae and Haptophyceae on vertical upper littoral fringe soft rock
Orange, brownish or blackish gelatinous bands of algae at high tide and supralittoral levels on open cliff faces and on upper walls and ceilings at entrances and to the rear of upper and mid-shore hard and soft rock (chalk) caves. This dark brown band consists of an assemblage of Haptophyceae such as Apistonema spp., Pleurochrysis carterae and the orange Chrysotila lamellosa, but other genera and species of Chrysophyceae, Haptophyceae and Prasinophyceae are likely to be present as well. Species such as Entodesmis maritima and Thallochrysis littoralis and the filamentous green alga Epicladia perforans are often associated with Apistonema spp. and the latter can form a green layer beneath the Apistonema spp. Associated with this splash zone algal community is an assemblage of animals of terrestrial origin, with red mites, insects and centipedes commonly found. These species descend into the community as the tide falls and retreat as the tide rises. The most common truly 'marine' species is the small winkle Melarhaphe neritoides.
Faunal crusts on wave-surged littoral cave walls
The inner walls of caves, predominantly in the mid shore in wave-surged conditions dominated by barnacles Semibalanus balanoides, and Verruca stroemia, with patches of encrusting sponges such as Halichondria panicea and Grantia compressa and occasional patches of the mussel Mytilus edulis. Increased moisture allows a denser faunal population than ScrFa to develop within the cave. The limpet Patella vulgata and spirorbid tube-forming polychaetes can be present. The hydroid Dynamena pumila and anemones such as Metridium senile and Actinia equina may occur towards the lower reaches of the cave. Where a dense faunal turf of barnacles or bryozoan crusts covers the cave walls, the biotope can also extend to cover the ceiling and may be accompanied by the bryozoan Alcyonidium diaphanum. Variations of this biotope may occur in mid and lower shore scoured caves in south Wales the rock is dominated by dense Sabellaria alveolata. In south-west England the rock can be completely covered by the barnacle Balanus perforatus. There may be a variation in the species composition from cave to cave, depending on local conditions.
Green algal films on upper and mid-shore cave walls and ceilings
The upper walls and ceilings of upper and mid-shore hard and soft rock (chalk) dominated by a band of green algal films (or 'stains'). Other encrusting algae including the non-calcified Hildenbrandia rubra may be present. In chalk caves, on the east and south-east coasts of England, a distinctive assemblage of species occurs, including the brown alga Pilinia maritima and the bright green algae Pseudendoclonium submarinum and Entocladia perforans that often covers the cave ceilings. Fauna is generally sparse and limited to limpets such as Patella vulgata and the winkle Littorina saxatilis. The species forming a green algal film that covers upper shore caves in Berwickshire were not identified. More information required to validate this biotope description.
Sparse fauna (barnacles and spirorbids) on sand/pebble-scoured rock in littoral caves
Upper to lower shore sand- or pebble-scoured cave walls characterised by an impoverished faunal assemblage which may include bryozoan crusts, scattered sponges Halichondria panicea, barnacles such as Semibalanus balanoides or often large Balanus crenatus and the limpet Patella vulgata. The isopod Ligia oceanica may seek refuge in crevices in the rock, and due to the decreased effect of desiccation in these damp caves, other species such as the anemone Actinia equina and spirorbid polychaetes are able to extend further up the shore than normally found on open rock. The lower section of the wall which is subject to greatest scour may be characterised by a band of Pomatoceros triqueter and spirorbid tube-forming polychaetes. In wave sheltered conditions, this biotope may extend to the cave ceiling. The rear of caves on the lower shore may support only sparse fauna consisting of spirorbid polychaetes and barnacles such as Chthamalus montagui with scattered Pomatoceros sp., scattered bryozoan and coralline crusts and in the south-west, occasional Sabellaria alveolata. Shade-tolerant red algae such as Lomentaria articulata may occasionally occur. Due to the low species abundance in this biotope, there may be a variation from cave to cave, depending on local conditions.
Sponges, bryozoans and ascidians on deeply overhanging lower shore bedrock or caves
Overhanging, and shaded vertical, bedrock on the lower shore and in lower shore caves, which is not subject to appreciable wave-surge, characterised by crusts of bryozoans including Umbonula littoralis, sponges such as Grantia compressa, Halichondria panicea, Scypha ciliata and Hymeniacidon perleve and the ascidian Botryllus schlosseri. On overhangs, the hydroid Dynamena pumila hangs in distinct form from overhanging rock. The barnacles Balanus crenatus, Balanus perforatus (sometimes at high densities) and Semibalanus balanoides, and the calcareous tube-forming polychaetes Spirorbis spp. and Pomatoceros triqueter can be present as well. Certain species which are generally confined to the sublittoral, including the anemones Metridium senile and Corynactis viridis, may be found in the lower shore caves and overhangs. Littoral species such as Actinia equina are also present. The only algae present are coralline crusts. The list of characterising species partly reflects the variation in the species composition between individual overhangs and caves although this biotope can have a high species richness.
Sponges and shade-tolerant red seaweeds on overhanging lower eulittoral bedrock and in cave entrances
Overhanging shaded bedrock on the open lower shore and at the entrance to inner reaches of caves (where light availability permits), which is not subject to appreciable wave-surge, characterised by a shade-tolerant red seaweed community. It includes foliose species such as Plumaria plumosa, Palmaria palmata, Mastocarpus stellatus, Membranoptera alata and Osmundea pinnatifida, but Lomentaria articulata and coralline crusts are usually present as well. The foliose green seaweed Ulva lactuca can be present. The rock surface often supports dense populations of calcareous tube-forming polychaetes Spirorbis spp. and Pomatoceros spp., while sponges such as Grantia compressa, Halichondria panicea and Hymeniacidon perleve can be common. The hydroid Dynamena pumila (normally found on fucoids) hangs in distinct form from overhanging rock. Colonies of the ascidian Botryllus schlosseri can be found on the rock, along with the mussel Mytilus edulis and the barnacles Semibalanus balanoides and Balanus perforatus (the latter may occur at high densities in the south and west), while the anemone Actinia equina thrives in the permanently damp pits and crevices. The whelk Nucella lapillus can be found among the barnacles and mussels, preying on them. The long list of characterising species is partly due to the difference in the species composition and does not solely reflect a high species richness.
Sponges, shade-tolerant red seaweeds and Dendrodoa grossularia on wave-surged overhanging lower eulittoral bedrock and caves
Overhanging bedrock on the lower shore, at cave entrances, to and on inner walls of caves, subject to wave surge and low light levels, and characterised by a high density of small groups of the solitary ascidian Dendrodoa grossularia. The sponges Grantia compressa, Halichondria panicea and Hymeniacidon perleve are common on the rock surface, while the hydroid Dynamena pumila (normally found on fucoids) hangs in distinct form from overhanging rock. Found on the rock surface are the calcareous tube-forming polychaetes Spirorbis spp. and Pomatoceros spp. along with the barnacles Semibalanus balanoides. The anemone Actinia equina thrives in the permanently damp pits and crevices. Where sufficient light is available a sparse community of shade-tolerant red seaweeds. These include Membranoptera alata, Lomentaria articulata, Audouinella spp. and coralline crusts.
Verrucaria mucosa and/or Hildenbrandia rubra on upper to mid shore cave walls
The upper walls and ceilings of the entrances and inner reaches of upper shore caves affected by direct wave action (and therefore moistened by sea spray), characterised by a mosaic of the olive green lichen Verrucaria mucosa and the non-calcified encrusting red alga Hildenbrandia rubra. The black lichen Verrucaria maura and red coralline algae can be present, though not dominating. The fauna in these upper shore caves is generally limited, due to problems of desiccation. However, where conditions remain sufficiently moist, and particularly in crevices and fissures, the barnacle Semibalanus balanoides, the limpet Patella vulgata and winkles Littorina saxatilis may occur, particularly towards the rear of the cave. Although the characterising species of this biotope also occur on the shore, they do not generally occur in a distinct band other than in moist dark caves. The turf-forming red seaweed Audouinella purpurea may occasionally occur in low abundance (where A. purpurea covers an extensive area, generally on softer rock such as chalk, the biotope should be recorded as AudCla).
Ephemeral green or red seaweed communities (freshwater or sand-influenced)
Ephemeral seaweeds on disturbed littoral rock in the lower to upper shore. Dominant green seaweeds include Enteromorpha intestinalis, Ulva lactuca and the red seaweeds Rhodothamniella floridula and Porphyra purpurea. Winkles such as Littorina littorea and Littorina saxatilis, the limpet Patella vulgata and the barnacles Semibalanus balanoides can occur, though usually in low abundance. The crab Carcinus maenas can be found where boulders are present, while the barnacle Elminius modestus is usually present on sites subject to variable salinity. On moderately exposed shores, the biotope is Enteromorpha spp. on freshwater-influenced or unstable upper shore rock (Ent) or P. purpurea and/or Enteromorpha spp. on sand-scoured mid to lower eulittoral rock (EntPor). Eulittoral mixed substrata subject to variations in salinity and/or siltation characterised by dense blankets of ephemeral green and red seaweeds (EphX), or if the substratum is too mobile or disturbed to support a seaweed community (BLitX). These are biotopes with a low species diversity and the relatively high number of species in the characterising species list are due to a variation in the species composition from site to site, not to high species richness on individual sites.
Barnacles and Littorina spp. on unstable eulittoral mixed substrata
The eulittoral zone, particularly the mid shore zone, of sheltered to extremely sheltered mixed substrata shores is often characterised by flat banks or scards of cobbles and pebbles (on sediment) which are either too small or unstable to support a seaweed community. The boulders and larger cobbles are usually colonised by the barnacles Semibalanus balanoides or in areas with variable salinity Elminius modestus and often dense aggregations of the winkles Littorina littorea and Littorina saxatilis are present as well. Between the cobbles and pebbles the mussel Mytilus edulis occasionally occurs, but always at low abundance. Juvenile crabs Carcinus maenas and gammarids may occur between and underneath the pebbles and cobbles. Brown seaweeds are rare, although the wrack Fucus vesiculosus may occasionally occur on larger cobbles and small boulders in the mid and upper shore zones. Ephemeral green seaweeds such as Enteromorpha intestinalis may also be present. Shallow pools and patches of standing water may occur in low-lying areas and may contain amphipods and filamentous green seaweeds. Due to the unstable nature of the substratum the diversity and density of flora and fauna is characteristically low.
Enteromorpha spp. on freshwater-influenced and/or unstable upper eulittoral rock
Upper shore hard substratum that is relatively unstable (e.g. soft rock) or subject to considerable freshwater runoff is typically very species poor and characterised by a dense mat of Enteromorpha spp., though Ulva lactuca can occur as well. It occurs in a wider zone spanning from the supralittoral down to the upper eulittoral, across a wide range of wave exposures range. This biotope is generally devoid of fauna, except for occasional limpets Patella vulgata, winkles Littorina littorea or Littorina saxatilis and barnacles Semibalanus balanoides.
Porphyra purpurea and Enteromorpha spp. on sand-scoured mid or lower eulittoral rock
Exposed and moderately exposed mid-shore bedrock and boulders occurring adjacent to areas of sand which significantly affects the rock. As a consequence of sand-abrasion, wracks such as Fucus vesiculosus or Fucus spiralis are scarce and the community is typically dominated by ephemeral red or green seaweeds, particularly the foliose red seaweed Porphyra purpurea and green seaweeds such as Enteromorpha spp. Under the blanket of ephemeral seaweeds, the barnacles Semibalanus balanoides or Elminius modestus and the limpet Patella vulgata may occur in the less scoured areas, along with the occasional winkles Littorina littorea and Littorina saxatilis. Few other species are present.
Ephemeral green and red seaweeds on variable salinity and/or disturbed eulittoral mixed substrata
Eulittoral mixed substrata (pebbles and cobbles overlying sand or mud) that are subject to variations in salinity and/or siltation, characterised by dense blankets of ephemeral green and red seaweeds. The main species present are Enteromorpha intestinalis, Ulva lactuca and Porphyra spp., along with colonial diatoms covering the surface of the substratum. Small numbers of other species such as barnacles Semibalanus balanoides and Elminius modestus are confined to any larger cobbles and pebbles or on the shells of larger individuals of the mussel Mytilus edulis. The crab Carcinus maenas and the winkle Littorina littorea can be present among the boulders, cobbles and seaweeds, while gammarids can be found in patches underneath the cobbles. In common with the other biotopes found on mixed substrata, patches of sediment are typically characterised by infaunal species including bivalves, for example, Cerastoderma edule and the polychaete Arenicola marina and the polychaete Lanice conchilega.
Lichens or small green algae on supralittoral and littoral fringe rock
Lichen communities typically form a distinct zone or band in a 'splash' zone on most rocky shores. This splash zone occurs above the main intertidal zone (i.e. that subject to regular covering by the tide) and blends into angiosperm-dominated communities of coastal (terrestrial) habitats at its upper limits. The width of the splash zone varies considerably, depending on the degree of exposure of the shore to wave action. On very exposed coasts the zone is very wide, extending 10s of meters up cliffs, whilst in very sheltered sites it may be only a metre or so high. Several biotopes have been identified. Yellow and grey lichens such as Xanthoria parietina, Caloplaca marina, Caloplaca thallincola or Ramalina sp. dominate the supralittoral rock (YG) with the distinctive black band of Verrucaria maura occurring below in the littoral fringe (Ver.Ver; Ver.B). Small green seaweeds can sometimes be found in this splash zone, where localised conditions allow growth in what would otherwise be inhospitable conditions for seaweeds. Such an example is the green seaweed Prasiola stipitata which occurs in areas of nitrate enrichment from nearby roosting seabirds (Pra). The littoral fringe on soft rock can be characterised by the green seaweed Blidingia minima (Bli) while steep and vertical rock influenced by freshwater in the littoral fringe can be dominated by the green seaweeds Ulothrix flacca, Urospora penicilliformis and Urospora wormskioldii (UloUro). The winkle Littorina saxatilis is one of the few 'marine' species found in this environment. [Note: in EUNIS, this habitat is placed within Coastal habitats section B, as it strictly speaking occurs above the marine environment. In the UK marine surveys have traditionally included the lichen zone within intertidal surveys, so the habitat is retained here for UK purposes.]
Blidingia spp. on vertical littoral fringe soft rock
Vertical soft rock in the littoral fringe may be characterised by a band of the green seaweeds Blidingia minima and Blidingia marginata. Unbranched filamentous green seaweeds, including Ulothrix flacca and Urospora wormskioldii, are found amongst the Blidingia spp. The siphonous Xanthophyceae Vaucheria spp. can also occur in high abundance in this biotope, where they can form dense mats. During low tide terrestrial fauna such as red mites, insects and centipedes migrate into this zone. More information is needed to improve this description.
Prasiola stipitata on nitrate-enriched supralittoral or littoral fringe rock
Exposed to moderately exposed bedrock and large boulders in the supralittoral and littoral fringe that receives nitrate enrichment from nearby roosting sea birds and is characterised by a band or patches of the ephemeral tufty green seaweed Prasiola stipitata or Prasiola spp. This typically grows over the black lichen Verrucaria maura in the littoral fringe or yellow and grey lichens in the supralittoral zone. In damp pits and crevices, species such as the winkle Littorina saxatilis, amphipods and halacarid mites are occasionally found. Pra often covers a smaller area than 5m x 5m and care should be taken to notice/record this biotope. The biotope can be associated with artificial substrata such as septic tanks, and in supralittoral areas influenced by sewage seeps or agricultural run-off.
Ulothrix flacca and Urospora spp. on freshwater-influenced vertical littoral fringe soft rock
An assemblage of the small un-branched filamentous green seaweeds Ulothrix flacca, Urospora penicilliformis and Urospora wormskioldii at High Water Spring Tide level on steep and vertical rock often influenced by freshwater. The community is also present in areas with freshwater seepage. It is visually recognised as a closely adherent, often shiny, green mat of filamentous growth. Associated species include the green seaweeds Blidingia minima and Enteromorpha prolifera, the barnacle Semibalanus balanoides and the limpet Patella vulgata, but these species are not common. Although this biotope does occur on rock other than chalk, this description has been derived from chalk coast sites. More information is needed to improve this description.
Verrucaria maura on littoral fringe rock
Bedrock or stable boulders and cobbles in the littoral fringe which is covered by the black lichen Verrucaria maura. This lichen typically covers the entire rock surface giving a distinct black band in the upper littoral fringe. The winkle Littorina saxatilis is usually present. Two variants are defined which both occur in a wide range of wave exposures. On exposed shores V. maura may occur with sparse barnacles such as Chthamalus spp. or Semibalanus balanoides and may be covered by a band of ephemeral seaweeds such as Porphyra umbilicalis or Enteromorpha spp. (Ver.B). Above Ver.B or on more sheltered shores is a species poor community consisting mainly of V. maura and L. saxatilis (Ver.Ver).
Verrucaria maura and sparse barnacles on exposed littoral fringe rock
The littoral fringe of very exposed to moderately exposed rocky shores with a sparse covering of the barnacles Semibalanus balanoides and/or Chthamalus montagui over the black lichen Verrucaria maura. Winkles Littorina saxatilis and Melarhaphe neritoides are usually present although M. neritoides tends to be found on more exposed shores. The limpet Patella vulgata is often present though at a low abundance (Occasional). This biotope can be dominated by ephemeral seaweeds including the red seaweed Porphyra umbilicalis, the green seaweeds Enteromorpha spp. or, particulary in the north, microscopic blue-green algae (Cyanophyceae), which overgrow V. maura. The wrack Pelvetia canaliculata (Rare) may also be present, becoming increasingly more common with greater shelter (see PelB). Geographical variation: On northern and eastern shores the barnacle is usually S. balanoides, which is normally restricted to the lower littoral fringe, with a band of V. maura only in the upper littoral fringe. On south-west and western shores the barnacle is usually C. montagui which may extend over the whole of the littoral fringe zone.
Verrucaria maura on very exposed to very sheltered upper littoral fringe rock
Upper littoral fringe bedrock, boulders and stable cobbles on very exposed to very sheltered shores which have a blanket covering of the black lichen Verrucaria maura. The winkle Littorina saxatilis is often present. Due to the nature of this biotope it is species poor, but occasionally a range of species may be present in low abundance. These species include the yellow lichen Caloplaca marina and the winkle Melarhaphe neritoides, the barnacles Chthamalus montagui and Semibalanus balanoides or the ephemeral seaweeds Porphyra umbilicalis and Enteromorpha spp. can be present in low abundance (see Ver.B). If one or more of these species is present compare with Ver.B. On northern shores Littorina saxatilis var. rudis can dominate along with the occasional presence of the lichens Verrucaria mucosa and Xanthoria parietina. V. maura can be found overlying stable mud in N. Ireland sea loughs.
Yellow and grey lichens on supralittoral rock
Vertical to gently sloping bedrock and stable boulders in the supralittoral (or splash zone) of the majority of rocky shores are typically characterised by a diverse maritime community of yellow and grey lichens, such as Xanthoria parietina, Caloplaca marina, Lecanora atra and Ramalina spp. The black lichen Verrucaria maura is also present, but usually in lower abundance than in the littoral fringe zone. In wave exposed conditions, where the effects of sea-spray extend further up the shore, the lichens generally form a wide and distinct band. This band then becomes less distinct as wave exposure decreases, and in sheltered locations, cobbles and pebbles may also support the biotope. Pools, damp pits and crevices in the rock are occasionally occupied by winkles such as Littorina saxatilis and halacarid mites may also be present.
Rockpools occur where the topography of the shore allows seawater to be retained within depressions in the bedrock producing 'pools' on the retreat of the tide. As these rockpool communities are permanently submerged they are not directly affected by height on the shore and normal rocky shore zonation patterns do not apply. For this reason rockpools have been dealt with as a separate biotope complex, apart from the scheme of wave exposure and shore height. Four main rockpool biotopes have been described, and although it is accepted that an enormous variety of rockpool communities exist, it is hoped that these biotope descriptions are broad enough to adequately encompass most types. It would be meaningless to include the characterising species in a description at the biotope complex level. Rockpools on the upper shore which are subject to rainwater influence and wide fluctuations in temperature are typically dominated by green seaweeds such as Enteromorpha spp. and Cladophora spp. (G). Shallow rockpools in the mid to upper shore characterised by encrusting coralline algae and Corallina officinalis (Cor); several variants of these coralline pools occur in south-west Britain and Ireland (Cor.Par, Cor.Bif and Cor.Cys). Deeper rockpools on the mid to lower shore can support fucoids and some sublittoral species such as kelp (FK). Those rockpools influenced by the presence of sand are characterised by sand-tolerant seaweed such as Furcellaria lumbricalis and Polyides rotundus (SwSed). Where more stable sand occurs in the base of the rockpool sea-grass beds can occur (SwSed). Shallow rockpools on mixed cobbles, pebbles, gravel and sand may be characterised by hydroids (H). A very rough guideline to the terms "shallow" and "deep" rockpools: "shallow" rockpools do not support kelp, whereas "deep" rockpools do. This rockpool complex (LR.FLR.Rkp) does not include shallow standing water on compacted sediment or mixed substrata.
Coralline crust-dominated shallow eulittoral rockpools
Shallow and smaller rockpools throughout the eulittoral zone in a wide range of wave exposures characterised by a covering of encrusting coralline algae on which Corallina officinalis often forms a dense turf. The bottom of these pools can be covered in coarse gravel and cobbles. These 'coralline' pools have a striking appearance as they are dominated by red seaweeds. Foliose red seaweeds found in these pools include Mastocarpus stellatus, Chondrus crispus and the filamentous Ceramium nodulosum. The ephemeral green seaweeds Cladophora rupestris, Ulva lactuca and Enteromorpha spp. can also occur in high abundance. The pools may hold large numbers of grazing molluscs, particularly the winkle Littorina littorea (which often occur in exceptionally high densities in upper shore pools) and the limpet Patella vulgata. Gastropods may graze these pools to such an extent that they is devoid of any foliose red seaweeds, and the flora are reduced to encrusting coralline algae and large numbers of gastropods. Large brown seaweeds are generally absent. Within the pools, pits and crevices are often occupied by the anemone Actinia equina and small individuals of the mussel Mytilus edulis. The whelk Nucella lapillus can be found on the rock surface preying on the barnacles and mussels. A number of variants have been identified. Pools dominated by coralline algae and foliose red seaweeds with a distribution throughout the UK (see Cor.Cor). In Ireland, the sea urchin Paracentrotus lividus can dominate these shallow coralline pools (see Cor.Par). In south-west Britain, the brown seaweed Bifurcaria bifurcata (Cor.Bif) or Cystoseira spp. (Cor.Cys) can be regionally dominant.
Bifurcaria bifurcata in shallow eulittoral rockpools
Eulittoral rockpools in south-west Britain on very exposed to moderately exposed shores dominated by the brown seaweed Bifurcaria bifurcata and encrusting coralline algae and Corallina officinalis. Kelps are present and include the species Laminaria digitata, Laminaria saccharina and the wrack Himanthalia elongata. Underneath the canopy formed by these species is a high diversity of red seaweeds including the foliose species Chondrus crispus, Palmaria palmata, Osmundea pinnatifida and Mastocarpus stellatus. Other red seaweeds include Gastroclonium ovatum, Ceramium nodulosum, Calliblepharis jubata and Mesophyllum lichenoides. The green seaweeds Ulva lactuca and Enteromorpha intestinalis occur where space allows. Often found in small cracks and crevices are the anemones Actinia equina and Anemonia viridis, while the limpet Patella vulgata can be found on the rock surface. Coarse gravel, cobbles and mobile boulders often cover the bottom of these rockpools, where Gibbula umbilicalis can be found.
Coralline crusts and Corallina officinalis in shallow eulittoral rockpools
Shallow and smaller rockpools throughout the eulittoral zone in a wide range of wave exposures characterised by a covering of encrusting coralline algae on which Corallina officinalis often forms a dense turf. The bottom of these pools can be covered in coarse gravel and cobbles. These 'coralline' pools have a striking appearance as they are dominated by red seaweeds. Foliose red seaweeds found in these pools include Mastocarpus stellatus, Chondrus crispus and the filamentous Ceramium nodulosum. The ephemeral green seaweeds Cladophora rupestris, Ulva lactuca and Enteromorpha spp. can also occur in high abundance. The pools may hold large numbers of grazing molluscs, particularly the winkle Littorina littorea (which often occurs in exceptionally high densities in upper shore pools), the limpet Patella vulgata and top shell Gibbula cineraria. Gastropods may graze these pools to such an extent that they is devoid of any foliose red seaweeds, and the flora are reduced to encrusting coralline algae and large numbers of gastropods. Large brown seaweeds are generally absent. Within the pools, pits and crevices are often occupied by the anemone Actinia equina and small individuals of the mussel Mytilus edulis, while the barnacle Semibalanus balanoides can be found on the rock surface. The whelk Nucella lapillus can be found on the rock surface preying on the barnacles and mussels.
Eulittoral rockpools on exposed to moderately exposed south-western shores dominated by the brown alga Cystoseira spp. (including Cystoseira tamariscifolia), coralline crusts and Corallina officinalis. These pools generally support dense red algal growth comprising: Ceramium spp., Calliblepharis jubata, Chondrus crispus, Osmundea pinnatifida and Gelidium latifolium. Wracks such as Himanthalia elongata and the epiphytic brown seaweed Colpomenia peregrina are present while the kelp Laminaria digitata can occupy the deeper parts of the pool. The green seaweeds Enteromorpha intestinalis and Ulva lactuca are usually present as well. The pools usually contain some sand and pebbles at the base of the pool while spirorbid polychaetes and Pomatoceros spp. build their tubes on any small boulders present. In addition, these pools can support high numbers of grazing gastropods including the top shells Gibbula cineraria and Gibbula umbilicalis but also the limpet Patella vulgata, while sponges such Hymeniacidon perleve and Halichondria panicea can be found overgrowing the small boulders or on and around the seaweeds. The shanny Lipophrus pholis is present hiding underneath boulder and cobbles, while the anemone Actinia equina is found in cracks and crevices. number of available records and care should be taken not to interpret this solely as a very high species richness.
Coralline crusts and Paracentrotus lividus in shallow eulittoral rockpools
Shallow and relatively smal rockpools throughout the eulittoral zone on very exposed to exposed shores, characterised by a covering of encrusting coralline algae on which Corallina officinalis forms a dense turf. The bottom of these pools can be covered in coarse gravel and cobbles. In south and west Ireland these coralline pools may be dominated by the sea urchin Paracentrotus lividus and the seaweed diversity is generally low due to the grazing pressure of P. lividus, the top shells Gibbula cineraria and Gibbula umbilicalis, and winkles such as Littorina littorea. Within the pools, pits and crevices are often occupied by the anemone such as Actinia equina and Anemonia viridis and small individuals of the mussel Mytilus edulis. The siphonous green seaweed Codium spp. can also be present along with the wrack Himanthalia elongata and the brown seaweed Leathesia difformis and the filamentous red seaweed Ceramium spp. The barnacle Semibalanus balanoides is either absent or occurs at low abundance in these rockpools, presumably due to the grazing pressure on the larval stage and the predation pressure from the whelk Nucella lapillus. Soft bedrock, such as limestone, allows P. lividus to bore into the rock.
Fucoids and kelp in deep eulittoral rockpools
Deep or larger rockpools in the mid to lower eulittoral zone on exposed to moderately exposed shores characterised by the wrack Fucus serratus and the kelp Laminaria digitata and the red seaweed Corallina officinalis while encrusting coralline algae cover the rock surface. Other large brown seaweeds, including the kelp Laminaria saccharina and Halidrys siliquosa may also occur. A wide variety of filamentous and foliose seaweeds occur beneath the brown algal canopy. The species includes the red seaweeds Palmaria palmata, Chondrus crispus, Mastocarpus stellatus, Ceramium nodulosum and Dumontia contorta, but green seaweeds such as Enteromorpha intestinalis, Ulva lactuca and Cladophora rupestris can be present as well. Algal-free vertical and overhanging faces often support the sponge Halichondria panicea and anemones including Actinia equina and Urticina felina. Grazing molluscs including the limpet Patella vulgata, the top shell Gibbula cineraria and the winkle Littorina littorea are present on the rock surface while the mussel Mytilus edulis can be found in cracks and crevices. The whelk Nucella lapillus can be found preying on the mussels. Where boulders occur in these pools they provide a greater variety of micro-habitats which support a variety of fauna. Mobile crustaceans including the crabs Pagurus bernhardus and Carcinus maenas, brittlestars such as Ophiothrix fragilis and Amphipholis squamata, encrusting bryozoans and ascidians are typically found beneath and between boulders.
Sargassum muticum in eulittoral rockpools
Shallow rockpools throughout the eulittoral zone on exposed to moderately exposed shores dominated by the brown seaweed Sargassum muticum and the red seaweed Corallina officinalis. Other brown seaweeds, including the kelp Laminaria saccharina, Laminaria digitata and the wrack Fucus serratus may occur along with Dictyota dichotoma, but S. muticum always dominates. Underneath the canopy is a rich red seaweed community which includes both foliose and filamentous species such as Palmaria palmata, Chondrus crispus, Lomentaria articulata, Osmundea pinnatifida, Ceramium spp. and Dumontia contorta. Encrusting coralline algae and Hildenbrandia rubra often cover the rock surface. The foliose green seaweed Ulva lactuca is usually present in high abundance growing on the mobile gravel and boulders on the bottom of the rockpools, often along with other ephemeral green seaweeds such as Cladophora rupestris and Enteromorpha intestinalis. The winkle Littorina littorea, the limpet Patella vulgata and the top shells Gibbula cineraria and Gibbula umbilicalis can often be found grazing on the biofilm of the rock surface or the seaweeds. Crevices and fissures in the rock provide cover for anemones such as Actinia equina and Anemonia viridis, cover while the prawn Palaemon serratus often can be found in large numbers hiding underneath the seaweed canopy or along the boulders on the bottom. Some sand scour can affect these rockpools.
Green seaweeds (Enteromorpha spp. and Cladophora spp.) in shallow upper shore rockpools
Rockpools in the littoral fringe or upper eulittoral zone subject to widely fluctuating temperatures and salinity are characterised by ephemeral green alga of the genus Enteromorpha, along with Cladophora spp. and Ulva lactuca. Due to the physical stress imposed on these upper shore pools, grazing molluscs such as the limpet Patella vulgata and the winkles Littorina littorea and Littorina saxatilis are generally in lower abundance than eulittoral pools, allowing the green seaweeds to proliferate under reduced grazing pressures. The bright orange copepod Tigriopus fulvus is tolerant of large salinity fluctuations and may occur in large numbers in these upper shore pools, along with gammarid amphipods.
Hydroids, ephemeral seaweeds and Littorina littorea in shallow eulittoral mixed substrata pools
Shallow pools on mixed cobbles, pebbles, gravel and sand characterised by abundant hydroids. Species present may include Obelia geniculata, O. dichotoma, O. longissima, Sertularia cupressina, Tublaria indivisa and Thuiaria thuja. The difficulty in identifying hydroids suggests many more species may be also be present. Other species typically found in this biotope include ephemeral green algae (Enteromorpha spp. and Ulva sp.), red algae (Chondrus crispus and Coralline algae) and the winkle Littorina littorea. Within the pools, patches of sand may be occupied by the lugworm Arenicola marina and sand mason worms Lanice conchilega. These pools are often associated with mussel beds (MytX), with Mytilus edulis frequently recorded within the pools. Barnacles (Semibalanus balanoides and Elminius modestus) and the keel worm Pomatoceros triqueter may be attached to shells and small stones. Mobile species typical of rock pool habitats, such as Crangon crangon and Pomatoschistus minutus will also be found within the pool.
Seaweeds in sediment-floored eulittoral rockpools
Rockpools with sediment (mud, sand, gravel) floors support distinct communities of scour-tolerant seaweeds. Deep pools with sediment are similar to FK, and are typically dominated by fucoids and kelp (Fucus serratus, Laminaria digitata, Laminaria saccharina and Saccorhiza polyschides). Areas of hard substrata near to the interface with the sediment are, however, characterised by a range of sand-tolerant seaweeds such as Furcellaria lumbricalis, Polyides rotundus, Ahnfeltia plicata and Rhodochorton purpureum (compare with FK). Chorda filum may occur attached to pebbles and shells embedded within the sediment while the top shell Gibbula cineraria can be found underneath or among the pebbles. In pools with large areas of sand, infaunal species such as Arenicola marina and Lanice conchilega often occur. The seagrass Zostera spp. may occur in some pools where stable sand is present. Shallow rockpools with cobble and pebble floors, often with an underlying layer of sediment, support red algal tufts consisting of coralline crust, Corallina officinalis, Chondrus crispus, Mastocarpus stellatus mixed with Ceramium spp. and the green seaweeds Cladophora spp. and Enteromorpha intestinalis. The long list of characterising species is partly due to low similarity between the available records and care should be taken not to interpret this solely as a very high species richness.
Extremely exposed to moderately exposed or tide-swept bedrock and boulder shores. Extremely exposed shores dominated by mussels and barnacles, occasionally with robust fucoids or turfs of red seaweed. Tide-swept shores support communities of fucoids, sponges and ascidians on the mid to lower shore. Three biotope complexes have been described: Communities on very exposed to moderately exposed upper and mid eulittoral bedrock and boulders dominated by the mussel Mytilus edulis, barnacles Chthamalus spp. and/or Semibalanus balanoides and the limpets Patella spp. (MusB); red and brown seaweeds able to tolerate the extreme conditions of exposed rocky shores, primarily the physical stresses caused by wave action (FR), and tide-swept shores in more sheltered areas (such as narrow channels in sea loch) with canopy forming fucoids and a rich filter-feeding community (FT).
Robust fucoid and/or red seaweed communities
This biotope complex encompasses those seaweeds that are able to tolerate the extreme conditions of very exposed to moderately exposed rocky shores. The physical stresses caused by wave action often results in dwarf forms of the individual seaweeds. The strong holdfasts and short tufts structure of the wracks Fucus distichus and Fucus spiralis f. nana allow these fucoids to survive on extremely exposed shores in the north and north-west (Fdis). Another seaweed able to tolerate the wave-wash is the red seaweed Corallina officinalis, which can form a dense turf on the mid to lower shore (Coff). The wrack Himanthalia elongata occurs on the lower shore and can extend on to moderately exposed shores (Him). The red seaweed Mastocarpus stellatus is common on both exposed and moderately exposed shores, where it may form a dense turf (particularly on vertical or overhanging rock faces, Mas). Very exposed to moderately exposed lower eulittoral rock can support a pure stand of the red seaweed Palmaria palmata. It is found either as a dense band or in large patches above the main sublittoral fringe (Pal). Exposed to moderately exposed lower eulittoral rock characterised by extensive areas or a distinct band of Osmundea pinnatifida (Osm). Outcrops of fossilised peat in the eulittoral are soft enough to allow a variety of piddocks, such as Barnea candida and Petricola pholadiformis, to bore into them (RPid). This biotope is rare. Other species such as the anemone Halichondria panicea, the barnacle Semibalanus balanoides, the limpet Patella vulgata, the mussel Mytilus edulis and the whelk Nucella lapillus can be present as well, but they are never dominant as in the MusB-complex. There is also a higher number of seaweeds present including the red Palmaria palmata, Lomentaria articulata, Ceramium spp. and the brown seaweeds Laminaria digitata and Fucus serratus. The green seaweeds Enteromorpha intestinalis, Ulva lactuca and Cladophora rupestris are occasionally present.
Corallina officinalis on exposed to moderately exposed lower eulittoral rock
Very exposed to moderately exposed lower eulittoral rock that supports a dense turf of the red seaweed Corallina officinalis, often on wave surged rocky slopes. There is usually a low abundance of other turf-forming red seaweeds including Lomentaria articulata, Mastocarpus stellatus, Palmaria palmata and Osmundea pinnatifida. Other seaweeds that occur in low abundance includes the wrack Himanthalia elongata, Laminaria digitata while the brown seaweed Leathesia difformis can be found growing on and around the other seaweeds. The green seaweeds Enteromorpha intestinalis, Ulva lactuca and Cladophora rupestris are present as well. A number of invertebrates are present on the bedrock underneath the coralline turf, including the barnacle Semibalanus balanoides, the mussel Mytilus edulis, the sponges Halichondria panicea and Hymeniacidon perleve, the anemone Actinia equina and the limpets Patella ulyssiponensis and Patella vulgata. The brown seaweed Bifurcaria bifurcata and the barnacle Balanus perforatus may occur in the extreme south-west. Two variants have been described: C. officinalis and kelp (Coff.Coff) and C. officinalis, H. elongata and the limpet P. ulyssiponensis (Coff.Puly).
Corallina officinalis and Mastocarpus stellatus on exposed to moderately exposed lower eulittoral rock
Exposed lower eulittoral rock or moderately exposed lower eulittoral vertical rock that supports a dense turf of the red seaweed Corallina officinalis, often on wave surged rocky slopes. There is usually a low abundance of other turf-forming red seaweeds such as Lomentaria articulata, Mastocarpus stellatus, Palmaria palmata and Osmundea pinnatifida. Other seaweeds that occur in low abundance includes the wrack Himanthalia elongata and the kelp Laminaria digitata, while the brown seaweed Leathesia difformis can be found growing on and around the other seaweeds. Green seaweeds such as Enteromorpha intestinalis, Ulva lactuca and Cladophora rupestris are also present. The coralline turf creates a micro-habitat for small animals such as the colonial tube building polychaete Pomatoceros sp. and the barnacle Semibalanus balanoides. The mussel Mytilus edulis is often found in small cracks and crevices while the sponges Halichondria panicea and Hymeniacidon perleve can be found in shaded areas or on overhangs. The limpets Patella ulyssiponensis and Patella vulgata can be found on the bedrock underneath the turf. The brown seaweed Bifurcaria bifurcata and the barnacle Balanus perforatus may occur in the extreme south-west.
Corallina officinalis, Himanthalia elongata and Patella ulyssiponensis on very exposed lower eulittoral rock
Very exposed to exposed lower eulittoral bedrock shores in the south-west can support a dense turf of the red seaweed Corallina officinalis found underneath the long erect fronds of the wrack Himanthalia elongata. The rock surface is pitted with the limpet Patella ulyssiponensis. Also found on the bedrock is the barnacle Chthamalus stellatus or the limpet Patella vulgata, while numerous cracks and crevices provide shelter for anemones such as Actinia equina or the mussel Mytilus edulis. Other turf-forming red seaweeds include Lomentaria articulata, Mastocarpus stellatus, Palmaria palmata, Gastroclonium ovatum, Ceramium spp. and Osmundea pinnatifida which can be found along with the kelp Laminaria digitata. Foliose green seaweeds such as Enteromorpha intestinalis and Ulva lactuca may also be present along with siphonous Codium spp. Sponges such as Grantia compressa, Halichondria panicea and Hymeniacidon perleve may be present in shaded areas. The brown seaweed Bifurcaria bifurcata and the barnacle Balanus perforatus may occur in the extreme south-west.
Fucus distichus and Fucus spiralis f. nana on extremely exposed upper shore rock
Extremely exposed gently or steeply sloping upper shore bedrock which supports a mixture of the wracks Fucus distichus and Fucus spiralis f. nana, the latter often at the top of the zone. On some sites F. distichus dominates and F. spiralis is not present. Other seaweeds normally found on exposed coasts are common in this biotope. These include ephemeral species such as the foliose red Porphyra umbilicalis and the green Enteromorpha spp. The winkles Melarhaphe neritoides and Littorina saxatilis can be found grazing on the bedrock or on the fucoids, while red crusts of Hildenbrandia rubra and the mussel Mytilus edulis are restricted to moist cracks and crevices. A sparse covering of the black lichens Verrucaria maura and Verrucaria mucosa can be found in the upper part of this biotope competing for space with barnacle Semibalanus balanoides and the limpet Patella vulgata. This biotope is very rare and restricted to the far north and west coasts.
Himanthalia elongata and red seaweeds on exposed to moderately exposed lower eulittoral rock
Exposed to moderately exposed lower eulittoral bedrock characterised by the wrack Himanthalia elongata with a dense turf of red seaweeds beneath. H. elongata may occur on tide-swept, sheltered shores in sea lochs (e.g. Loch Maddy). The wrack Fucus serratus is normally present as well. The predominant red seaweeds are usually Mastocarpus stellatus, Osmundea pinnatifida, Corallina officinalis and Palmaria palmata that tend to grow over a crust of the pink coralline algae Lithothamnion spp. Any patches between the algal turf may be colonised by barnacles Semibalanus balanoides, or Balanus perforatus in the south-west, and by the limpet Patella vulgata. Pits and crevices in the rock often provide a refuge for the whelk Nucella lapillus, the winkle Littorina spp. and small individuals of the mussel Mytilus edulis. Besides the dominant seaweeds there are a number of other red, brown and green seaweeds present. These include species such as the red seaweeds Dumontia contorta, Lomentaria articulata, Porphyra spp., the kelp Laminaria digitata and the green seaweeds Enteromorpha intestinalis, Ulva lactuca and Cladophora rupestris.
Mastocarpus stellatus and Chondrus crispus on very exposed to moderately exposed lower eulittoral rock
Exposed to moderately exposed lower eulittoral vertical to almost horizontal bedrock characterised by a dense turf of Mastocarpus stellatus and Chondrus crispus (either together or separately). Beneath these foliose seaweeds the rock surface is covered by encrusting coralline algae and the barnacle Semibalanus balanoides, the limpet Patella vulgata and spirorbid polychaetes. Other seaweeds including the red Lomentaria articulata and Osmundea pinnatifida, Palmaria palmata, Corallina officinalis and coralline crusts. The wrack Fucus serratus and the green seaweeds Enteromorpha intestinalis and Ulva lactuca may also be present though usually at a low abundance. Although both M. stellatus and C. crispus are widespread in the lower eulittoral and the sublittoral fringe, they occur only infrequently in a distinct band, or in large enough patches, to justify separation from Fser.R. Consequently, where only small patches of these species occur within a larger area of mixed red algal turf, then records should be assigned to more general mixed red algal turf biotope (Coff; Him). M. stellatus can be present in high abundance in a number of biotopes (Coff: Him; Fser.R etc.) found on the shore. At least one other species normally co-dominates and records should be assigned to the appropriate biotope. Caution should be taken regarding the characterising species list due to the low number of records. More information needed to validate this description.
Osmundea pinnatifida on moderately exposed mid eulittoral rock
Exposed to moderately exposed lower eulittoral rock characterised by extensive areas or a distinct band of Osmundea pinnatifida and Gelidium pusillum (either together or separately). This community usually occurs on shores on which a fucoid canopy is reduced in extent, or even absent. Other turf-forming red seaweeds, such as Corallina officinalis, Mastocarpus stellatus, Ceramium spp. and Callithamnion hookeri may be present, although O. pinnatifida always dominate. On flatter, more sheltered shores, Osmundea hybrida may also occur. Small patches of bare rock amongst the algal turf are occupied by barnacles Semibalanus balanoides, the limpet Patella vulgata, the whelk Nucella lapillus and small individuals of the mussel Mytilus edulis. The winkles Littorina littorea and Littorina saxatilis can be present on the rock or among the seaweeds. A variation of this biotope has been described for the chalk platforms in Kent where extensive turfs of G. pusillum occur in the mid eulittoral above the main O. pinnatifida zone.
Palmaria palmata on very exposed to moderately exposed lower eulittoral rock
Very exposed to moderately exposed lower eulittoral rock which supports a pure stand of dulse Palmaria palmata as a dense band or in large patches above the main kelp zone. P. palmata favours shaded or overhanging rock and often forms a band at the top of overhanging rock. Relatively low abundance of other seaweeds, such as the red seaweed Porphyra umbilicalis or the green seaweeds Enteromorpha intestinalis, Ulva lactuca and Cladophora rupestris may also occur in this biotope although P. palmata always dominates. On the rock underneath the seaweed turf are the barnacle Semibalanus balanoides and the limpet Patella vulgata and the olive-green lichen Verrucaria mucosa.. Sites should only be recorded as Pal where P. palmata forms a distinct band or occurs in large patches on the shore.
Ceramium sp. and piddocks on eulittoral fossilised peat
Outcrops of fossilised peat in the eulittoral are soft enough to allow a variety of piddocks such as Barnea candida and Petricola pholadiformis to bore into them. The surface of the peat can be characterised by a dense algal mat, predominantly the red seaweed Ceramium spp. and with the green seaweeds Ulva lactuca and Enteromorpha intestinalis. Damp areas in the algal mat are covered by aggregations of the polychaetes Lanice conchilega and Polydora sp. The crabs Carcinus maenas and Cancer pagurus occur in crevices in the peat. Small pools on the peat may contain hydroids, such as Obelia longissima and Kirchenpaueria pinnata, the brown alga Dictyota dichotoma and the crustacean Crangon crangon. Description derived largely from sites in north Norfolk and this community could possibly be found on other "soft" substrata. Further records of this community are required in order to validate the description.
Biotope complex description Fucoid seaweeds in tide-swept conditions on sheltered to extremely sheltered mid eulittoral to lower eulittoral rocky shores, such as narrow channels in sea lochs. The middle shore can be dominated by the wrack Ascophyllum nodosum (AscT), while Fucus serratus is dominating the lower shore (FserT, FserTX). The high levels of water movement encourages a rich associated fauna including several filter-feeding groups. These include the sponges Grantia compressa, Halichondria panicea and Hymeniacidon perleve which frequently occur on steep and overhanging faces of boulders and bedrock. It also includes the sea squirts Dendrodoa grossularia and Ascidiella scabra, which occur on steep surfaces and beneath boulders. Hydroids such as the pink Clava multicornis can form colonies on A. nodosum while Dynamena pumila is more often found on Fucus vesiculosus or F. serratus. Underneath the canopy formed by the brown seaweeds is a diverse community of the red seaweeds Gelidium pusillum, Chondrus crispus, Lomentaria articulata, Membranoptera alata and coralline crusts, but the green seaweeds Enteromorpha intestinalis, Ulva lactuca and Cladophora rupestris can be present. The filamentous red seaweed Polysiphonia lanosa can usually be found growing on A. nodosum. On the rock beneath are the limpet Patella vulgata and the barnacle Semibalanus balanoides, while the crab Carcinus maenas and a variety of winkles including Littorina littorea, Littorina mariae and Littorina obtusata can be found on or among the boulders. The whelk Nucella lapillus can either be found in cracks and crevices.
Ascophyllum nodosum, sponges and ascidians on tide-swept mid eulittoral rock
Very sheltered to extremely sheltered areas of mid eulittoral rock that are subject to strong to moderate tidal streams, such as the narrows in sea lochs, and characterised by the wrack Ascophyllum nodosum. The wracks Fucus vesiculosus and Fucus serratus are occasionally present. The increased water movement encourages a rich associated fauna including several filter-feeding groups. These include the sponges Leucosolenia spp., Grantia compressa, Halichondria panicea and Hymeniacidon perleve which frequently occur on steep and overhanging faces of boulders and bedrock. It also includes the sea squirts Dendrodoa grossularia and Ascidiella scabra, which occur on steep surfaces and beneath boulders. Hydroids such as the pink Clava multicornis can form colonies on A. nodosum while Dynamena pumila is more often found on F. vesiculosus or F. serratus. Underneath the canopy formed by the brown seaweeds is a diverse community of the red seaweeds Gelidium pusillum, Chondrus crispus, Lomentaria articulata, Membranoptera alata and coralline crusts, but the green seaweeds Enteromorpha intestinalis, Ulva lactuca and Cladophora rupestris can be present. The filamentous red seaweed Polysiphonia lanosa can usually be found growing on A. nodosum. On the rock beneath are the limpet Patella vulgata and the barnacle Semibalanus balanoides, while the crab Carcinus maenas and a variety of winkles including Littorina littorea, Littorina mariae and Littorina obtusata can be found on or among the boulders. The whelk Nucella lapillus can either be found in cracks and crevices or preying on the barnacles.
Fucus serratus, sponges and ascidians on tide-swept lower eulittoral rock
Sheltered to extremely sheltered lower eulittoral bedrock, boulders and cobbles that are subject to increased tidal water movement and characterised by the wrack Fucus serratus and a rich assemblage of filter-feeding fauna. This community is encouraged by the increased water movement. It includes species such as the sponges Halichondria panicea and Hymeniacidon perleve, which occur frequently on steep and overhanging faces. Underneath the F. serratus canopy is a diverse flora of foliose red seaweeds including Mastocarpus stellatus, Lomentaria articulata, Membranoptera alata and Chondrus crispus. The green seaweeds Cladophora spp., Enteromorpha intestinalis and Ulva lactuca and the wrack Ascophyllum nodosum are present though usually in small numbers. On the rock underneath the seaweed canopy, species such as the limpet Patella vulgata, the barnacles Semibalanus balanoides and Balanus crenatus and the whelk Nucella lapillus can be found though in lower abundance than higher up the shore. Also present on the rock are the tube-forming polychaetes Pomatoceros triqueter and spirorbids and more mobile species such as the winkles Littorina mariae and Littorina littorea, the top shell Gibbula cineraria and the crab Carcinus maenas. Lastly, several species of bryozoans are usually present including Electra pilosa and Alcyonidium gelatinosum, all competing for space with the hydroid Dynamena pumila, which can form dense populations on the F. serratus fronds.
Fucus serratus with sponges, ascidians and red seaweeds on tide-swept lower eulittoral mixed substrata
Sheltered lower shore boulders, cobbles and pebbles on muddy sediments that are subject to enhanced tidal water movement and characterised by a species rich community. Dominant species include the sponges Halichondria panicea and Hymeniacidon perleve, the sea squirts Ascidiella aspera, Ascidiella scabra, Styela clava and Botryllus schlosseri. A number of filamentous red seaweeds including Halurus flosculosus, Ceramium spp., Gracilaria gracilis, Polysiphonia fucoides and foliose seaweeds Mastocarpus stellatus and Chondrus crispus are usually present. The brown seaweed Dictyota dichotoma and the wrack Fucus serratus with colonies of the hydroid Dynamena pumila, and Ectocarpus sp. may be found on more stable substrata. Boulders and large cobbles provide substrata for the top shell Gibbula cineraria, the whelk Nucella lapillus and barnacles such as Semibalanus balanoides, Balanus crenatus, or in areas with variable salinity Elminius modestus, and the tube-forming polychaete Pomatoceros triqueter. Patches of sand or mud are often characterised by the polychaete Lanice conchilega and the polychaete Sabella pavonina. Aggregations of the mussel Mytilus edulis and, in southern and eastern England the limpet Crepidula fornicata, may be found attached to cobbles and pebbles. Sites in Scottish sea lochs may support maerl Lithothamnion spp. and bivalves Venerupis senegalensis (see also VsenMtru).
Communities on very exposed to moderately exposed upper and mid eulittoral bedrock and boulders dominated by the mussel Mytilus edulis (MytB), barnacles Chthamalus spp. and/or Semibalanus balanoides and limpets Patella spp. (Cht, Sem). Several variants are identified. Some shores are characterised by dense bands of the barnacle Semibalanus balanoides and the limpet Patella vulgata (Sem). The barnacles may be covered by Porphyra umbilicalis on the upper shore of exposed sites. Cracks and crevices in the rock provide a refuge for small individuals of the mussel M. edulis, winkles Littorina saxatilis and the whelk Nucella lapillus. Red seaweeds also frequently occupy damp crevices, particularly Ceramium shuttleworthianum, Corallina officinalis, Osmundea pinnatifida and encrusting coralline algae, but the non-vesiculate form of the wrack Fucus vesiculosus might be present (Sem.FvesR). Large numbers of the winkle Littorina littorea often dominate fields of large boulders or shores with a more mixed substratum (Sem.LlitX). There is much regional variation affecting the zonation of barnacles in the British Isles. In the north-west C. montagui and/or C. stellatus can form a distinct band above S. balanoides. In the south-west C. montagui and/or C. stellatus can be the dominant barnacles throughout the eulittoral zone (Cht.Cht). On the east coasts S. balanoides is able to extend to the upper shore due to the absence of Chthamalus spp. and thereby any competition. The lichen Lichina pygmaea may be prominent, especially in the south, where it can form distinct patches or even a separate zone among the Chthamalus spp. (Cht.Lpyg). In areas of soft rock (e.g. shales), the barnacles may be scarce or absent and the rock dominated by P. vulgata.
Chthamalus spp. on exposed eulittoral rock
Very exposed to moderately exposed upper and mid eulittoral bedrock and boulders characterised by a dense community of barnacles, including Chthamalus montagui, Chthamalus stellatus and Semibalanus balanoides, and the limpet Patella vulgata. Damp cracks and crevices in the rock provide a refuge for small individuals of the mussel Mytilus edulis and the winkles Melarhaphe neritoides and Littorina saxatilis. These crevices can also be occupied by encrusting coralline algae and the anemone Actinia equina. Black patches of the lichen Verrucaria maura may be found in this zone. There is much regional variation in the distribution and zonation of Chthamalus spp. On the west coast Chthamalus spp. dominate the upper eulittoral, often forming a distinct white band above a darker band of S. balanoides in the mid eulittoral zone. C. montagui is better adapted to resist desiccation and, therefore, extends further up the shore. On some shores, particularly in the south-west, Chthamalus spp. is the dominant barnacle throughout the eulittoral zone (Cht.Cht). On other shores, particularly in the south, Lichina pygmaea can form a distinct zone (Cht.Lpyg).
Chthamalus spp. on exposed upper eulittoral rock
Very exposed to moderately exposed upper and mid eulittoral bedrock and boulders characterised by a dense community of barnacles, including Chthamalus montagui, Chthamalus stellatus and Semibalanus balanoides, and the limpet Patella vulgata. Damp cracks and crevices in the rock provide a refuge for small individuals of the mussel Mytilus edulis, and the winkles Melarhaphe neritoides and Littorina saxatilis. These crevices can also be occupied by encrusting coralline algae and the anemone Actinia equina. Patches of the black lichen Verrucaria maura and the green seaweed Enteromorpha intestinalis may be present, though in low abundance (Occasional). Shaded vertical littoral fringe and upper eulittoral bedrock may be characterised by the shade-tolerant red seaweeds Catenella caespitosa, Bostrychia scorpioides and/or Lomentaria articulata. Where the turf of C. caespitosa is well established, barnacles are rare. Geographical variation: There is much regional variation in the distribution and zonation of Chthamalus spp. On the west coast Chthamalus spp. dominate the upper eulittoral, often forming a distinct white band above a darker band of S. balanoides in the mid eulittoral zone (Sem). C. montagui is better adapted to resist desiccation and, therefore, extends further up the shore. In the south-west Chthamalus spp. can be the dominant barnacles throughout the eulittoral zone.
Chthamalus spp. and Lichina pygmaea on steep exposed upper eulittoral rock
Areas of steep and vertical rock in the upper eulittoral on very exposed to moderately exposed shores characterised by tufts of the dark brownish lichen Lichina pygmaea and the barnacles Chthamalus montagui and Chthamalus stellatus, although long-established patches of L. pygmaea ultimately exclude barnacles. The rigid branching thallus of L. pygmaea provides an ideal habitat for the bivalve Lasaea adasoni, the winkles Littorina saxatilis and Melarhaphe neritoides. The anemone Actinia equina and the mussel Mytilus edulis are confined to moist cracks and crevices, while the limpet Patella vulgata is found on the open bedrock. In the south-west the top shell Gibbula umbilicalis can be found on L. pygmaea. On the north-east coast this biotope does not have Chthamalus spp., L. pygmaea being the most important characterising species on these sites.
Mytilus edulis and barnacles on very exposed eulittoral rock
On very exposed to exposed rocky shores the eulittoral zone, particularly the mid and lower shore, is typically characterised by patches of small individuals of the mussel Mytilus edulis interspersed with patches of the barnacle Semibalanus balanoides and individuls of the limpet Patella vulgata. Amongst the mussels small individuals of red seaweeds including Ceramium spp., Corallina officinalis and Mastocarpus stellatus can be found. The foliose red seaweeds Porphyra umbilicalis and Palmaria palmata are commonly found as epiphytes on M. edulis where they can form luxuriant growths. The abundance of the red seaweeds generally increases down the shore and in the lower eulittoral they may form a distinct zone in which mussels or barnacles are scarce (FR, Coff.Coff or Him). Where M. edulis occurs on steep rock, red seaweeds are scarce and restricted to the lower shore. The whelk Nucella lapillus and a few winkles such as Littorina spp. can occur where cracks and crevices provide a refuge in the rock. Fucoids are generally absent, although some non-vesiculate Fucus vesiculosus may occur where the shore slopes more gently. This biotope also occurs on steep moderately exposed shores which experience increased wave energy.
Semibalanus balanoides on exposed to moderately exposed or vertical sheltered eulittoral rock
Exposed to moderately exposed mid to upper eulittoral bedrock and large boulders characterised by dense barnacles Semibalanus balanoides and the limpet Patella vulgata. The community has a relatively low diversity of species though occasional cracks and crevices in the rock can provide a refuge for small individuals of the mussel Mytilus edulis, the winkle Littorina saxatilis and the whelk Nucella lapillus. Seaweeds are usually not found in high numbers though fissures and crevices in the bedrock can hold a sparse algal community including the green seaweed Enteromorpha intestinalis. On some shores the olive green lichen Verrucaria mucosa can be present in some abundance (Frequent). Three variants have been described: A S. balanoides and P. vulgata dominated community on bedrock (Sem.Sem); S. balanoides and sparse Fucus vesioculosus and red seaweeds (Sem.FvesR); and barnacles and L. littorea eulittoral boulders and cobbles (Sem.LlitX).
Semibalanus balanoides, Fucus vesiculosus and red seaweeds on exposed to moderately exposed eulittoral rock
Exposed and moderately exposed upper and mid eulittoral bedrock characterised by the barnacle Semibalanus balanoides, the limpet Patella vulgata and the whelk Nucella lapillus with a sparse community of seaweeds. Turfs of the wrack Fucus vesiculosus can be present on the more horizontal parts of the shore though usually in low abundance (Occasional). Individuals of F. vesiculosus can lack the characteristic twin air bladders due to environmental stress (i.e. wave exposure). A sparse seaweed community consisting of foliose red seaweeds such as Osmundea pinnatifida and Mastocarpus stellatus are usually present along with the Corallina officinalis and the green seaweed Enteromorpha intestinalis. The algal community is usually restricted to fissures and cracks in the bedrock surface. Moist cracks and crevices also provide a refuge for small individuals of the mussel Mytilus edulis and the winkles Littorina saxatilis and Littorina littorea. These crevices can also be occupied by encrusting coralline algae and the anemone Actinia equina.
Semibalanus balanoides and Littorina spp. on exposed to moderately exposed eulittoral boulders and cobbles
Large patches of boulders, cobbles and pebbles in the eulittoral zone on exposed to moderately exposed shores colonised by the barnacle Semibalanus balanoides and, on larger rocks, the limpet Patella vulgata. The winkles Littorina littorea and Littorina saxatilis and the whelk Nucella lapillus are typically found in high numbers on and around cobbles and smaller boulders, while the anemone Actinia equina occurs in damp areas between and underneath larger boulders. Between the cobbles and pebbles, the mussel Mytilus edulis occasionally occurs, but always at low abundance, as do the crab Carcinus maenas and gammarid amphipods. Ephemeral green seaweeds such as Enteromorpha intestinalis may cover cobbles and boulders. The foliose red seaweeds Chondrus crispus, Mastocarpus stellatus and Osmundea pinnatifida as well as the wrack Fucus vesiculosus may also occur in low abundance on cobbles and boulders. The top shells Gibbula cineraria and Gibbula umbilicalis can, on more sheltered shores, be found among the seaweeds or underneath the boulders. The barnacle Elminius modestus is present on some shores.
Semibalanus balanoides, Patella vulgata and Littorina spp. on exposed to moderately exposed or vertical sheltered eulittoral rock
Very exposed to sheltered mid to upper eulittoral bedrock and large boulders characterised by dense barnacles Semibalanus balanoides and the limpet Patella vulgata. The community has a relatively low diversity of species though occasional cracks and crevices in the rock can provide a refuge for small individuals of the mussel Mytilus edulis, the winkle Littorina spp. and the whelk Nucella lapillus. Seaweeds are usually not found in high numbers though fissures and crevices in the bedrock can hold a sparse algae community, though patches of the red seaweed Osmundea pinnatifida can be present throughout the zone. On some shores the olive green lichen Verrucaria mucosa can be present in some abundance (Frequent). Records should not be assigned to this species impoverished biotope if there is a significant number or abundance of seaweeds.
Sheltered to extremely sheltered rocky shores with very weak to weak tidal streams are typically characterised by a dense cover of fucoid seaweeds which form distinct zones (the wrack Pelvetia canaliculata on the upper shore through to the wrack Fucus serratus on the lower shore). Where salinity is reduced (such as at the head of a sea loch or where streams run across the shore) Fucus ceranoides may occur. Fucoids also occur on less stable, mixed substrata (cobbles and pebbles on sediment) although in lower abundance and with fewer associated epifaunal species; beds of mussels Mytilus edulis are also common. In summer months, dense blankets of ephemeral green and red seaweeds can dominate these mixed shores. Two biotope complexes have been described: Dense blankets of fucoid seaweeds dominating sheltered, fully marine littoral rocky shores (F) and fucoids dominating variable salinity rocky shores (FVS).
Dense blankets of fucoid seaweeds dominating sheltered to extremely sheltered rocky shores and/or in locally sheltered patches on exposed to moderately exposed rocky shores. Typically, the wrack Pelvetia canaliculata (Pel) occurs on the upper shore, with the wrack Fucus spiralis (Fspi) below. The middle shore is dominated by vast areas of the wrack Ascophyllum nodosum or the wrack Fucus vesiculosus (Asc, Fves) or a mixture of both. The wrack Fucus serratus covers lower shore bedrock and boulders (Fser). Sheltered to very sheltered mixed substrata (pebbles and cobbles overlying muddy sand and gravel) shores can support fucoid communities (Fspi.X; Fves.X; Asc.X; Fserr.X).
Ascophyllum nodosum on very sheltered mid eulittoral rock
Sheltered to extremely sheltered mid eulittoral rock with the wrack Ascophyllum nodosum. The red seaweed Polysiphonia lanosa is often found growing as an epiphyte on the A. nodosum fronds while disturbed areas among the A. nodosum is colonised by the wrack Fucus vesiculosus and the green seaweed Enteromorpha intestinalis.e barnacle Semibalanus balanoides, the limpet Patella vulgata and Littorina littorea can all be found on the bedrock underneath the A. nodosum canopy along with coralline crusts. The whelk Nucella lapillus can be found preying on the barnacles and limpets. Three variants of this biotope are described. These are: full salinity (Asc.FS), mixed substrata (Asc.X) and the loose lying growth form A. nodosum ecad mackaii found on very sheltered shores (Asc.mac). To other biotopes has been identified as well tide-swept (AscT) and variabel salinity (AscVS).
Ascophyllum nodosum on full salinity mid eulittoral rock
Bedrock, stable boulders and cobbles in the mid-eulittoral zone of moderately exposed to extremely sheltered shores, in fully marine conditions, characterised by a dense canopy of the wrack Ascophyllum nodosum. Another wrack Fucus vesiculosus may in some places co-dominate the canopy. The hydroid Dynamena pumila can form colonies on the wracks F. vesiculosus and Fucus serratus. Variations in the ratio of A. nodosum and F. vesiculosus in the overlying canopy have little effect on the under-storey species. Beneath the canopy are a diverse array of filamentous and foliose red seaweeds, including Mastocarpus stellatus, Chondrus crispus, Gelidium pusillum and coralline crusts. The filamentous red seaweed Polysiphonia lanosa is usually present on A. nodosum as an epiphyte. A few green seaweeds including Cladophora rupestris and Enteromorpha spp. are also present in moderate to low densities. On the bedrock and boulders beneath the seaweed canopy is a fauna including the barnacle Semibalanus balanoides, the limpet Patella vulgata, tube-forming spirorbid polychaetes and the anemone Actinia equina. The latter can be present in damp cracks and crevices. On and among the seaweeds are mobile species including the winkles Littorina littorea and Littorina obtusata, the whelk Nucella lapillus or even the crab Carcinus maenas. At the top of the A. nodosum zone there might be the occasional presence of the olive green lichen Verrucaria mucosa.
Ascophyllum nodosum on full salinity mid eulittoral mixed substrata
Sheltered to extremely sheltered full salinity mixed substrata (cobbles, boulders and pebbles on sediment) characterised by a canopy formed by a mosaic of the wracks Ascophyllum nodosum and Fucus vesiculosus. The red seaweed Polysiphonia lanosa can often be found as an epiphyte on the A. nodosum. The mussel Mytilus edulis often occurs in clumps, and provides further suitable substrata for the attachment of fucoids and red and green seaweeds such as Polysiphonia spp. and Enteromorpha intestinalis or the barnacle Semibalanus balanoides. Winkles are common and Littorina littorea and Littorina obtusata/mariae may occur in high densities, while species such as the limpet Patella vulgata, the crab Carcinus maenas and the whelk Nucella lapillus may occur on and around the boulders. Gammarids can be found underneath the boulders or among the seaweeds, while tube-forming spirorbids are found on the boulders, shells or on the F. vesiculosus. Infaunal species including the polychaetes Arenicola marina and Lanice conchilega may occur in the sediment between the cobbles.
Fucus serratus on sheltered lower eulittoral rock
Sheltered to extremely sheltered lower eulittoral rock with Fucus serratus (for detailed description of the rich associated community please see Fserr.FS). Two variants of this biotope have been described. Fully marine conditions (Fserr.FS) and mixed substrata (Fserr.X). Please notice that three other biotopes with a F. serratus dominance have been described: Variable salinity (FserVS), tide-swept (FserT) and tide-swept on mixed substrata (FserXT).
Fucus serratus on full salinity sheltered lower eulittoral rock
Sheltered lower eulittoral rock subject to fully marine conditions characterised by a dense canopy of the wrack Fucus serratus. There is a wide range of associated species found on the surface of the rock underneath the canopy, including the barnacle Semibalanus balanoides, limpets Patella vulgata, winkles Littorina littorea, and even mussels Mytilus edulis can be present in cracks and crevices. These species are usually found in higher abundance further up on the shore. There may also be a number of other seaweeds present, including the red Corallina officinalis and Mastocarpus stellatus, the wrack Fucus vesiculosus and the green Enteromorpha intestinalis, Ulva lactuca or Cladophora rupestris, though these usually are present in low numbers if present at all. The sponge Halichondria panicea can be present underneath the F. serratus canopy in moist cracks or minor overhangs. Polychaetes such as Pomatoceros triqueter and Spirorbis spp. are present in their white calcareous tubes on the rock.
Fucus serratus on full salinity lower eulittoral mixed substrata
Sheltered to extremely sheltered full salinity lower eulittoral mixed substrata with dense stands of the wrack Fucus serratus. The crab Carcinus maenas and a large number of winkles such as Littorina littorea and Littorina obtusata/mariae can be found amongst the pebbles and cobbles as well as large individuals of the mussel Mytilus edulis, commonly occurring in clumps. On these mussels and on larger cobbles are the barnacle Semibalanus balanoides and the limpet Patella vulgata. Red algae such as coralline crusts including Lithothamnion spp. and the tube-forming polychaetes Pomatoceros triqueter and Spirorbis spp. can be found on cobbles and boulders. Spirorbis spp. can also be found on the F. serratus fronds. Sediment in the spaces between the loose substrata may support infauna including the polychaete Arenicola marina. The red seaweed Mastocarpus stellatus and the wrack Ascophyllum nodosum can occur in patches, while the green seaweeds Enteromorpha intestinalis and Cladophora spp. can be found among the mussels and underneath the F. serratus canopy.
Fucus spiralis on sheltered upper eulittoral rock
Sheltered upper eulittoral bedrock is typically characterised by a band of the spiral wrack Fucus spiralis overlying the black lichen Verrucaria maura. Underneath the fronds of F. spiralis and the occasional Pelvetia canaliculata is a community consisting of the limpet Patella vulgata, the winkles Littorina saxatilis and Littorina littorea and the barnacle Semibalanus balanoides. The rock surface can often be covered by the red crust Hildenbrandia rubra. During the summer months the ephemeral green seaweed Enteromorpha intestinalis can be common. Two variants have been described: Upper eulittoral bedrock characterised by F. spiralis, the black lichen Verrucaria maura and the olive green lichen Verrucaria mucosa (Fspi.FS). Upper eulittoral mixed substrata characterised by F. spiralis with occasional clumps of the wrack Pelvetia canaliculata (Fspi.X). Note that a F. spiralis biotope in variable salinity conditions (FspiVS) has also been descibed.
Fucus spiralis on full salinity sheltered upper eulittoral rock
Sheltered upper eulittoral bedrock characterised by a band of the spiral wrack Fucus spiralis overlying the black lichen Verrucaria maura and the olive green lichen Verrucaria mucosa. Underneath the fronds of F. spiralis is a community consisting of the limpet Patella vulgata, the winkles Littorina saxatilis and Littorina littorea and sparse individuals of the barnacle Semibalanus balanoides while the mussel Mytilus edulis can be found attached in cracks and crevices. A variety of red algae including Hildenbrandia rubra may be present underneath the fronds. During the summer months ephemeral green seaweeds such as Enteromorpha intestinalis can be common.
Fucus spiralis on full salinity upper eulittoral mixed substrata
Moderately exposed to sheltered full salinity upper eulittoral mixed substrata characterised by a band of the wrack Fucus spiralis. Occasional clumps of the wrack Pelvetia canaliculata can be overgrowing the black lichen Verrucaria maura and the olive green lichen Verrucaria mucosa. On the more stable boulders underneath the fronds the red crust Hildenbrandia rubra can be found along with the barnacle Semibalanus balanoides and the limpet Patella vulgata. The winkles Littorina littorea and Littorina saxatilis can be found on and among the boulders and cobbles, while amphipods and the crab Carcinus maenas can be present either underneath the boulders or among the brown seaweeds. The green seaweed Enteromorpha intestinalis can occur in some abundance especially during the summer.
Fucus vesiculosus on moderately exposed to sheltered mid eulittoral rock
Moderately exposed to very sheltered mid eulittoral bedrock and large boulders characterised by a dense canopy of the wrack Fucus vesiculosus (Abundant to Superabundant). Beneath the seaweed canopy the rock surface has a sparse covering of the barnacle Semibalanus balanoides and the limpet Patella vulgata. The mussel Mytilus edulis is confined to pits and crevices. A variety of winkles including Littorina littorea and Littorina saxatilis can be found grazing on the fucoid fronds. The whelk Nucella lapillus is found beneath the seaweed canopy. In areas of localised shelter the wrack Ascophyllum nodosum may occur, though never at high abundance. The crab Carcinus maenas may be present in pools or among the boulders. Two variants have been described: Bedrock and large boulders (Fves.FS) and mixed substrata (Fves.X). Please notice that a F. vesioculosus biotope subject to variable salinity (FvesVS) has been identified.
Fucus vesiculosus on full salinity moderately exposed to sheltered mid eulittoral rock
Moderately exposed to sheltered mid eulittoral bedrock and large boulders characterised by a dense canopy of the wrack Fucus vesiculosus (Abundant to Superabundant). Beneath the seaweed canopy the rock surface has a sparse covering of the barnacle Semibalanus balanoides and the limpet Patella vulgata. The mussel Mytilus edulis is confined to pits and crevices. A variety of winkles including Littorina littorea, Littorina saxatilis and the whelk Nucella lapillus are found beneath the seaweeds, whilst Littorina obtusata/mariae graze on the fucoid fronds. The calcareous tube-forming polychaete Spirorbis spirorbis may also occur epiphytically on the fronds. In areas of localised shelter the wrack Ascophyllum nodosum may occur, though never at high abundance. Damp cracks and crevices often contain patches of the red seaweed Mastocarpus stellatus and even the wrack Fucus serratus may be present. The crab Carcinus maenas may be present in pools or among the boulders.
Fucus vesiculosus on mid eulittoral mixed substrata
Sheltered and very sheltered mid eulittoral pebbles and cobbles lying on sediment in fully marine conditions typically characterised by the wrack Fucus vesiculosus. The wrack Ascophyllum nodosum can occasionally be found on larger boulders while the barnacle Semibalanus balanoides and the limpet Patella vulgata also can be present on the cobbles with the whelk Nucella lapillus preying on the barnacles and on the mussel Mytilus edulis. Winkles, particularly Littorina littorea and Littorina obtusata, commonly graze the biofilm on the seaweeds, while Littorina saxatilis can be found in crevices. Ephemeral seaweeds such as Enteromorpha intestinalis may be present in this biotope. The sediment between patches of hard substrata often contains the polychaete Arenicola marina or the polychaete Lanice conchilega, while a variety of gastropods and the crab Carcinus maenas occur on and under cobbles.
Pelvetia canaliculata on sheltered littoral fringe rock
Lower littoral fringe bedrock or stable boulders and mixed substrata in sheltered to extremely sheltered conditions characterised by a dense cover of the wrack Pelvetia canaliculata. The biotope may be present in localised sheltered patches on moderately exposed shores. P. canaliculata overgrows a crust of black lichens Verrucaria maura or the non-calcified red algae Hildenbrandia rubra on very sheltered shores. Individuals of the wrack Fucus spiralis can usually be found among the P. canaliculata and/or in lower part of the biotope. This biotope lacks the density of barnacles found amongst the P. canaliculata on more exposed shores. The winkle Littorina saxatilis occurs, as do a variety of amphipods. The red alga Catenella caespitosa can be present especially in more shaded areas while the green seaweed Enteromorpha spp. can be present in moist areas.
Blankets of fucoid seaweeds dominating sheltered to extremely sheltered rocky shores with variable salinity. The wrack Pelvetia canaliculata (PelVS) occurs on the upper shore, with the wrack Fucus spiralis (FspiVS) below. The middle shore is dominated by vast areas of the wrack Ascophyllum nodosum or the wrack Fucus vesiculosus (AscVS, FvesVS) or a mixture of both. The wrack Fucus serratus covers lower shore bedrock and boulders (FserVS). Fucus ceranoides can be found on extremly sheltered shores with variable or low salinity (Fcer). The variable salinity communities are species impoverished compared to fucoids in full salinity or in tide-swept conditions as red seaweeds and sponges are usually absent. Underneath the canopy are a few green seaweeds including Enteromorpha intestinalis and Cladophora spp., while the red seaweed Polysiphonia lanosa can be found as an epiphyte on A. nodosum. On the rock and among the boulders are the winkles Littorina littorea and Littorina saxatilis, the crab Carcinus maenas, the barnacles Semibalanus balanoides and Elminius modestus and even the occasional mussel Mytilus edulis.
Ascophyllum nodosum and Fucus vesiculosus on variable salinity mid eulittoral rock
Very sheltered to extremely sheltered mid eulittoral bedrock, boulders or cobbles subject to variable salinity characterised by an impoverished community dominated by a mixture of the wracks Ascophyllum nodosum and Fucus vesiculosus. Underneath the canopy are a few green seaweeds including Enteromorpha intestinalis and Cladophora spp., while the red seaweed Polysiphonia lanosa can be found as an epiphyte on A. nodosum. On the rock and among the boulders are the winkles Littorina littorea and Littorina saxatilis, the crab Carcinus maenas, the barnacles Semibalanus balanoides and Elminius modestus and even the occasional mussel Mytilus edulis. Among the seaweeds and underneath the boulders a variety of gammarids can be found.
Ascophyllum nodosum ecad mackaii beds on extremely sheltered mid eulittoral mixed substrata
Extremely sheltered mid shore mixed substrata, usually subject to variable salinity due to freshwater runoff, which support beds of the non-attached growth form of the wrack Ascophyllum nodosum ecad mackaii. Cobbles and other hard substrata are often characterised by the normal form of A. nodosum with the red seaweed Polysiphonia lanosa growing as an epiphyte and other fucoids such as Fucus vesiculosus. The loose mats of A. nodosum ecad mackaii provide a cryptic and humid habitat for mobile species including gammarids, the crab Carcinus maenas and the winkles Littorina littorea, Littorina obtusata and Littorina saxatilis. The barnacle Semibalanus balanoides and the mussel Mytilus edulis are commonly attached to pebbles and cobbles on the sediment, while the infauna may contain the polychaetes Arenicola marina and Lanice conchilega. NB: This biotope is a BAP-habitat.
Fucus ceranoides on reduced salinity eulittoral rock
Very sheltered to extremely sheltered bedrock and stable boulders in the eulittoral zone that are subject to reduced salinity and characterised by the wrack Fucus ceranoides. Species richness is typically low in this biotope. The green seaweeds Enteromorpha intestinalis and Ulva lactuca may be present together with the crab Carcinus maenas and the occasional barnacle Elminius modestus and Semibalanus balanoides.
Fucus serratus and large Mytilus edulis on variable salinity lower eulittoral rock
Areas of very sheltered lower eulittoral rock or mixed substrata subject to variable salinity, which support an impoverished community dominated by the wrack Fucus serratus. The hydroid Dynamena pumila can form colonies on the F. serratus and clumps of large individuals of the mussel Mytilus edulis may be present on the bedrock beneath. The canopy of F. serratus is not usually as dense as in the other F. serratus dominated biotopes due the presence of the wracks Ascophyllum nodosum and Fucus vesiculosus, which are better adapted to the variable salinity. A few red seaweeds are present which includes the species Mastocarpus stellatus, Chondrus crispus and coralline crusts. Underneath the canopy is a sparse fauna consisting of barnacles Semibalanus balanoides, Balanus crenatus and Elminius modestus, the limpet Patella vulgata or the occasional presence of the winkles Littorina obtusata and Littorina mariae and the crab Carcinus maenas. The tube-forming polychaetes Pomatoceros triqueter or spirorbid polychaetes can be found. In areas (such as the Scottish sea lochs) where variable salinity water passes through tide-swept narrows and the associated biota is impoverished such records should be classified as FserVS rather than FserT.
Fucus spiralis on sheltered variable salinity upper eulittoral rock
Sheltered to extremely sheltered upper eulittoral bedrock or mixed substrata (boulders, large cobbles or shells on mud) in variable salinity conditions characterised by a band of the spiral wrack Fucus spiralis. The ephemeral green seaweed Enteromorpha intestinalis is usually found in this species poor biotope. The barnacles Semibalanus balanoides and Elminius modestus can be found where suitable substrata are available, while gammarids can be found underneath the fronds of F. spiralis and/or underneath the boulders and cobbles. Also found underneath the fronds and among the boulders are the winkles Littorina saxatilis and Littorina littorea and the crab Carcinus maenas.
Fucus vesiculosus on variable salinity mid eulittoral boulders and stable mixed substrata
Sheltered to extremely sheltered mid eulittoral pebbles and cobbles lying on sediment subject to variable salinity and characterised by the wrack Fucus vesiculosus. The wrack Ascophyllum nodosum can occasionally be found on larger boulders, while the barnacles Semibalanus balanoides and Elminius modestus and the mussel Mytilus edulis can be present on cobbles. Winkles, particularly Littorina littorea, commonly graze on the seaweeds, while Littorina saxatilis can be found in crevices. Ephemeral seaweeds such as Enteromorpha intestinalis can occupy available space. Patches of sediment found between the hard substrata often contains the lugworm Arenicola marina or the sand mason Lanice conchilega, while the crab Carcinus maenas, gammarids and amphipods occur on and under cobbles.
Pelvetia canaliculata on sheltered variable salinity littoral fringe rock
Lower littoral fringe bedrock or stable boulders and mixed substrata on very sheltered to extremely sheltered variable salinity shores characterised by a dense cover of the wrack Pelvetia canaliculata, which often overgrows a crust of black lichens Verrucaria maura. The wrack Fucus spiralis can be present among the P. canaliculata. This biotope lacks the density of barnacles found among the P. canaliculata on more exposed shores though the occasional Semibalanus balanoides or Elminius modestus can be found. The winkle Littorina saxatilis occurs, as do a variety of amphipods. The red alga Catenella caespitosa can be present in more shaded areas as well as the green seaweed Enteromorpha intestinalis.
Moderately exposed shores (bedrock, boulders and cobbles) characterised by mosaics of barnacles and fucoids on the mid and upper shore; with fucoids and red seaweed mosaics on the lower shore. Where freshwater or sand-scour affects the shore ephemeral red or green seaweeds can dominate. Other shores support communities of mussels and fucoids in the mid to lower shore. Two biotope complexes have been described: Mussels and fucoids (MusF) and barnacles and fucoids (BF).
Barnacles and fucoids on moderately exposed shores
Moderately exposed rocky shores characterised by a mosaic of fucoids and barnacles on bedrock and boulders, where the extent of the fucoid cover is typically less than the blanket cover associated with sheltered shores. Other species are normally present as well in this habtat including the winkle Littorina littorea, the whelk Nucella lapillus and the red seaweed Mastocarpus stellatus. Beneath the band of yellow and grey lichens at the top of the shore is a zone dominated by the wrack Pelvetia canaliculata, scattered barnacles, while the black lichen Verrucaria maura covers the rock surface (PelB). Below, on the mid shore the wrack Fucus vesiculosus generally forms a mosaic with the barnacle Semibalanus balanoides and the limpet Patella vulgata (FvesB). Finally, the wrack Fucus serratus, dominates the lower shore, while a variety of red seaweeds can be found underneath the F. serratus canopy (Fser). A number of variants have been described: lower shore bedrock and boulders characterised by mosaics of F. serratus and turf-forming red seaweeds (Fser.R); where the density of F. serratus is greater (typically Common - Superabundant) and the abundance of red seaweeds less Fserr.FS should be recorded. The presence of boulders and cobbles on the shore can increase the micro-habitat diversity, which often results in a greater species richness. Although the upper surface of the boulders may bear very similar communities to Fserr.FS there is often an increase in fauna (crabs, tube-forming polychaetes, sponges and bryozoans) and Fser.Bo should be recorded. Sand-influenced exposed to moderately exposed lower shore rock can be characterised by dense mats of Rhodothamniella floridula (Rho).
Fucus serratus on moderately exposed lower eulittoral rock
Lower eulittoral bedrock and stable boulders on moderately exposed to sheltered shores with a canopy of the wrack Fucus serratus and an associated fauna consisting of the limpet Patella vulgata, the barnacle Semibalanus balanoides, the whelk Nucella lapillus, the anemone Actinia equina and the sponge Halichondria panicea. Green seaweeds such as Enteromorpha intestinalis and Ulva lactuca are usually present among/beneath the F. serratus canopy. Three variants of this biotope are described. These are: F. serratus with red seaweeds (Fser.R) and F. serratus with under-boulder communities (Fser.Bo) with sponges. Lastly, a F. serratus and piddocks community on soft rock has been identified (Fser.Pid). Dense F. serratus with fewer red seaweeds occurs on more sheltered shores (Fserr).
Fucus serratus and under-boulder fauna on exposed to moderately exposed lower eulittoral boulders
Exposed to moderalety exposed lower eulittoral boulders with the wrack Fucus serratus community of a high species richness as the presence of the boulders increases the micro-habitat diversity. The upper surfaces of the boulders are colonised by a very similar fauna to the other F. serratus biotopes, including species such as the limpet Patella vulgata, the whelk Nucella lapillus, the anemone Actinia equina and the barnacle Semibalanus balanoides. The shaded sides of the boulders are, depending on environmental conditions, often colonised by a variety of foliose red seaweeds, including Mastocarpus stellatus, Lomentaria articulata, Osmundea pinnatifida, Palmaria palmata and Chondrus crispus. Coralline algae such as Corallina officinalis and coraline crusts, as well as the green seaweeds Enteromorpha intestinalis and Ulva lactuca, can be found underneath the F. serratus canopy or in patches on the boulders. The species composition underneath the boulders varies considerably depending on the underlying substratum. On muddy shores the fauna living under the boulders may be limited to a few infaunal species, such as the polychaete Cirratulus cirratus. Where more space is available beneath the boulders there may be a rich assemblage of animals. Characteristic mobile species include the crabs Porcellana platycheles and Carcinus maenas. Also present on and beneath the boulders are the tube-forming polychaete Pomatoceros triqueter, spirorbid polychaetes and a few winkles such as Littorina obtusata/mariae and Littorina littorea or even the top shell Gibbula cineraria. Encrusting colonies of the sponge Halichondria panicea are also typical of the undersides of boulders, while the hydroid Dynamena pumila colonies can be found on the F. serratus fronds. The richest examples of this biotope also contain a variety of brittlestars, ascidians and small hydroids.
Fucus serratus and piddocks on lower eulittoral soft rock
The lower eulittoral zone on soft rock shores (e.g. chalk) characterised by the wrack Fucus serratus. Much of the community associated with this biotope is the same as the biotope Fserr.FS, but certain taxa are specific to the soft underlying substrata. Rock-boring fauna including the piddocks Barnea spp., Pholas dactylus and Hiatella arctica can occur in dense aggregations. Burrowing polychaetes such as Polydora spp. can also occur in high numbers only visible due to their long, slender palps waving in the water as they occupy holes in the top few centimetres of the rock. A dense red algal turf occurs beneath the F. serratus and includes Gelidium pusillum, Osmundea pinnatifida, Palmaria palmata, Lomentaria articulata and Rhodothamniella floridula, but also calcareous algae such as Corallina officinalis and coralline crusts including the red-violet encrusting algae Phymatolithon lenormandii are present. Infaunal taxa such as various amphipods may be common amongst the seaweeds. The empty piddock holes may provide a refuge for species such as the anemone Actinia equina and the mussel Mytilus edulis while the barnacle Semibalanus balanoides, the limpet Patella vulgata can be present on the surface of the soft rock. The whelk Nucella lapillus, the winkles Littorina littorea and Littorina mariae and the top shell Gibbula cineraria are all present on the soft rock among the seaweeds. The high number of characterising species is partly caused by the low number of records used to define this biotope. The high % frequency of occurrence is partly a result of the low number of records. More data is needed to validate this biotope description.
Fucus serratus and red seaweeds on moderately exposed lower eulittoral rock
Moderately exposed lower eulittoral bedrock characterised by mosaics of the wrack Fucus serratus and turf-forming red seaweeds including Osmundea pinnatifida, Mastocarpus stellatus or Corallina officinalis. The hydroid Dynamena pumila can occur in dense populations on the F. serratus fronds whilst the sponge Halichondria panicea can cover the bedrock beneath. Underneath the canopy a number of other red seaweeds may be present including Palmaria palmata, Lomentaria articulata,Membranoptera alata and Chondrus crispus. Green seaweeds such as Cladophora rupestris, Enteromorpha intestinalis and Ulva lactuca are present though usually in small numbers. In addition, such shores provide a greater number of permanently damp refuges between the stones and underneath the seaweed canopy. Within these micro-habitats species such as the limpet Patella vulgata, the barnacle Semibalanus balanoides or the whelk Nucella lapillus can be found in lower abundance than higher up the shore. If a few boulders are present then the winkle Littorina littorea and the crab Carcinus maenas can be found on or underneath the boulders.
Fucus spiralis on exposed to moderately exposed upper eulittoral rock
Exposed to moderately exposed upper eulittoral bedrock characterised by a band of the spiral wrack Fucus spiralis overlying the black lichen Verrucaria maura and the olive green lichen Verrucaria mucosa. Underneath the fronds of F. spiralis is a community consisting of the limpet Patella vulgata, the winkles Littorina saxatilis and Littorina littorea, the mussel Mytilus edulis and the barnacle Semibalanus balanoides. The whelk Nucella lapillus can be found in cracks and crevices preying on the mussels and barnacles. During the summer months ephemeral green seaweeds such as Enteromorpha intestinalis can be common. The insect Anurida maritima can be present in this zone taking shelter in cracks and crevices when the tide comes in.
Fucus vesiculosus and barnacle mosaics on moderately exposed mid eulittoral rock
Exposed to moderately exposed mid eulittoral bedrock and boulders are frequently characterised by a mosaic of the barnacle Semibalanus balanoides and the wrack Fucus vesiculosus. The limpet Patella vulgata and the whelk Nucella lapillus are typically present, whilst the anemone Actinia equina and small individuals of the mussel Mytilus edulis are confined to crevices. Underneath the F. vesiculosus is a community of red seaweeds, including Corallina officinalis, Mastocarpus stellatus and Osmundea pinnatifida, usually with the winkles Littorina littorea and Littorina spp. present. Opportunistic seaweeds such as Enteromorpha intestinalis may occur in patches recently cleared on the rock or growing on the M. edulis.
Pelvetia canaliculata and barnacles on moderately exposed littoral fringe rock
Exposed to moderately exposed steep, lower littoral fringe rock and mixed substrata characterised by the wrack Pelvetia canaliculata and sparse barnacles Chthamalus montagui and Semibalanus balanoides. On sheltered shores the biotope is restricted to vertical faces. The limpet Patella vulgata and the wrack Fucus spiralis are usually present as well. P. canaliculata typically overgrows a crust of the black lichen Verrucaria maura or on occasion Verrucaria mucosa, in contrast to the red crust Hildenbrandia rubra on very sheltered shores. The winkle Littorina saxatilis is frequently present underneath the fronds of P. canaliculata. Some geographical variation are present and southern and western shores are typically characterised by the barnacle C. montagui or Chthamalus stellatus while S. balanoides dominates on northern and eastern shores. On mixed substrata the barnacle Elminius modestus may be present.
Rhodothamniella floridula on sand-scoured lower eulittoral rock
Lower eulittoral and sublittoral fringe bedrock and boulders subject to mild sand-scouring characterised by a canopy of the wracks Fucus serratus or Fucus vesiculosus, beneath which a mat of the sand-binding red seaweed Rhodothamniella floridula occurs. These mats can form distinct areas without F. serratus. The small hummocks of R. floridula also contain a diversity of other red seaweeds tolerant of sand scour, e.g. Palmaria palmata, Chondrus crispus, coralline crusts and Mastocarpus stellatus. The brown seaweed Cladostephus spongiosus or the ephemeral green seaweed Enteromorpha intestinalis, Ulva lactuca or Cladophora rupestris may occur. The hydroid Dynamena pumila can form colonies on the F. serratus fronds. The barnacle Semibalanus balanoides, the limpet Patella vulgata, the anemone Actinia equina and the polychaete Pomatoceros triqueter may be present where bedrock are available along with a few winkles such as Littorina littorea. In addition, polychaetes and amphipods may burrow into the R. floridula mat, while the mussel Mytilus edulis is restricted to small crevices in the bedrock. The species diversity of this biotope is normally low and there can be much variation in the species composition from site to site.
Mussels and fucoids on moderately exposed shores
Mid and lower eulittoral exposed to moderately exposed bedrock, often with nearby sediment, may be densely covered by large individuals of the mussel Mytilus edulis. Three biotopes have been described: In the mid eulittoral, the mussels may form a band or large patches with scattered bladder wrack Fucus vesiculosus (MytFves). In the lower eulittoral a range of red seaweeds including Mastocarpus stellatus and Palmaria palmata occur amongst the mussels (in higher abundance than the mid eulittoral) (MytFR). Clay outcrops in the mid to lower eulittoral may be bored by a variety of piddocks including Pholas dactylus, Barnea candida and Petricola pholadiformis, while the surface is characterised by small clumps of the mussel M. edulis, the barnacle Elminius modestus and the winkle Littorina littorea (MytPid). Ephemeral green seaweeds such as Enteromorpha intestinalis and Ulva lactuca commonly occur on the shells of the mussels. Barnacles are common on both the mussel valves and on patches of bare rock, where the limpet Patella vulgata is found as well, often at high abundance. The whelk Nucella lapillus and a range of littorinids also occur within the mussel bed. A dense M. edulis community may be found on more sheltered coasts on mixed substrata (Myt).
Mytilus edulis, Fucus serratus and red seaweeds on moderately exposed lower eulittoral rock
Lower eulittoral moderately exposed bedrock covered by a dense community of large individuals of the mussel Mytilus edulis, often with a scarce covering of the wrack Fucus serratus and red seaweeds. The red seaweeds may include Palmaria palmata, Mastocarpus stellatus, Ceramium spp., Audouinella spp. and Chondrus crispus. Ephemeral green seaweeds such as Enteromorpha intestinalis and Ulva lactuca commonly occur on the shells of the mussels. The barnacle Semibalanus balanoides is common on both the mussel valves and on patches of bare rock, where the limpet Patella vulgata is also found, often at high abundance. The whelk Nucella lapillus and the winkle Littorina littorea occur within the mussel bed, as well as the polychaete Pomatoceros triqueter and the crab Carcinus maenas. The anemone Actinia equina is present in cracks and crevices. These moist areas can be overgrown by coralline crusts.
Mytilus edulis and Fucus vesiculosus on moderately exposed mid eulittoral rock
Mid eulittoral exposed to moderately exposed bedrock, often with nearby sediment, covered by a dense band or large patches of the mussel Mytilus edulis. The community often supports scattered Fucus vesiculosus and occasional foliose red seaweeds such as Porphyra umbilicalis, Osmundea pinnatifida, Mastocarpus stellatus, Palmaria palmata or the calcareous algae Corallina officinalis . The ephemeral green seaweeds Enteromorpha intestinalis and Ulva lactuca commonly occur on the shells of the mussels. The barnacle Semibalanus balanoides is common on both the mussel valves and on patches of bare rock, where the limpet Patella vulgata also can be found. The whelk Nucella lapillus and the winkle Littorina littorea can be found within the mussel bed.
Mytilus edulis and piddocks on eulittoral firm clay
Clay outcrops in the mid to lower eulittoral which are bored by a variety of piddocks including Pholas dactylus, Barnea candida and Petricola pholadiformis. The surface of the clay is characterised by small clumps of the mussel Mytilus edulis, the barnacle Elminius modestus and the winkle Littorina littorea. Seaweeds are generally sparse on the clay, although small patches of the red seaweeds Mastocarpus stellatus, Halurus flosculosus and Ceramium spp. can occur, usually attached to loose-lying cobble or mussel shells. Also the green seaweeds Enteromorpha spp. and Ulva lactuca may be present. The sand mason Lanice conchilega can sometimes be present in the clay, while the shore crab Carcinus maenas is present as well. More data are required to validate this description.
Littoral sediment includes habitats of shingle (mobile cobbles and pebbles), gravel, sand and mud or any combination of these which occur in the intertidal zone. Littoral sediment is defined further using descriptions of particle sizes - mainly gravel (16-4 mm), coarse sand (4-1 mm), medium sand (1-0.25 mm), fine sand (0.25-0.063 mm) and mud (less than 0.063 mm) and various admixtures of these (and coarser) grades - muddy sand, sandy mud and mixed sediment (cobbles, gravel, sand and mud together). Littoral sediments support communities tolerant to some degree of drainage at low tide and often subject to variation in air temperature and reduced salinity in estuarine situations. Very coarse sediments tend to support few macrofaunal species because these sediments tend to be mobile and subject to a high degree of drying when exposed at low tide. Finer sediments tend to be more stable and retain some water between high tides, and therefore support a greater diversity of species. Medium and fine sand shores usually support a range of oligochaetes, polychaetes, and burrowing crustaceans, and even more stable muddy sand shores also support a range of bivalves. Very fine and cohesive sediment (mud) tends to have a lower species diversity, because oxygen cannot penetrate far below the sediment surface. A black, anoxic layer of sediment develops under these circumstances, which may extend to the sediment surface and in which few species can survive. Some intertidal sediments are dominated by angiosperms, e.g. eelgrass (Zostera noltii) beds on the mid and upper shore of muddy sand flats, or saltmarshes which develop on the extreme upper shore of sheltered fine sediment flats.
The Littoral Biogenic Reefs habitat complex contains two biotope complexes (littoral Sabellaria reefs, and mixed sediment shores with mussels), encompassing the littoral biotope dominated by the honeycomb worm Sabellaria alveolata, and littoral Mytilus edulis- dominated communities. S. alveolata can form honeycomb reefs on mid to lower shore on exposed coasts, where there is a plentiful supply of sediment. The underlying substratum may consist primarily of rock or stable cobbles and boulders, or of cobbles and boulders on sand. Mixed sediment shores characterised by beds of adult mussels Mytilus edulis occur principally on mid and lower eulittoral mixed substrata (mainly cobbles and pebbles on muddy sediments) in a wide range of exposure conditions. In high densities the mussels bind the substratum and provide a habitat for many infaunal and epifaunal species.
Sediment shores characterised by beds of adult mussels Mytilus edulis occur principally on mid and lower eulittoral mixed substrata (mainly cobbles and pebbles on muddy sediments) in a wide range of exposure conditions. In high densities the mussels bind the substratum and provide a habitat for many infaunal and epifaunal species. This biotope is also found in lower shore tide-swept areas, such as in the tidal narrows of Scottish sealochs. A fauna of dense juvenile mussels may be found in sheltered firths, attached to algae on shores of pebbles, gravel, sand, mud and shell debris with a strandline of fucoid algae.
Mytilus edulis beds on littoral sediments
Dense aggregations of Mytilus edulis on the mid and lower shore, on mixed substrata (mainly cobbles and pebbles on fine sediments), on sand, or on sheltered muddy shores. In high densities the mussels bind the substratum and provide a habitat for many infaunal and epifaunal species. The wrack Fucus vesiculosus is often found attached to either the mussels or cobbles and it can be abundant. The mussels are often encrusted with the barnacles Semibalanus balanoides, Elminius modestus or Balanus crenatus. Where boulders are present they can support the limpet Patella vulgata. The winkles Littorina littorea and L. saxatilis and small individuals of the crab Carcinus maenas are common amongst the mussels, whilst areas of sediment may contain the lugworm Arenicola marina, the sand mason Lanice conchilega, the cockle Cerastoderma edule, and other infaunal species. The characterising species list shown below is based on data from epifaunal sampling only. Three sub-biotopes are recognised for this biotope, distinguished principally on the basis of the sediment type associated with the mussel beds. The three types of intertidal mussel beds may be part of a continuum on an axis that is most strongly influenced by the amount of pseudofaeces that accumulate amongst the mussels. The differences may not always be directly connected to the underlying substratum on which the mussel bed may have started a long time ago. It should be noted that there are few data available for the muddy (Myt.Mu) and sandy (Myt.Sa) sub-biotopes, therefore there are no characterising species lists or comparative tables for these two sub-biotopes.
Dense mussel beds found in sheltered conditions on mud. There is a build up of pseudofaeces that results in a bed that is very soft to walk on, and sediment which is anoxic to the surface. Pools are often present in the mussel bed but they tend to contain few species. The sediment infauna is very poor as a result of anoxic conditions. The mussel valves are usually clean, without epifaunal growth. Where this biotope occurs naturally, all age classes are found within the mussel bed. This biotope also includes commercially laid mussel beds on soft sediments, which tend to be of uniform age structure. The species diversity of this sub-biotope is a lot lower than that of the other Myt sub-biotopes.
Mytilus edulis beds on littoral mixed substrata
Mid and lower shore mixed substrata (mainly cobbles and pebbles on fine sediments) in a wide range of exposure conditions and with aggregations of the mussel Mytilus edulis colonising mainly the sediment between cobbles, though they can extend onto the cobbles themselves. The mussel aggregations can be very dense and support various age classes. In high densities the mussels bind the substratum and provide a habitat for many infaunal and epifaunal species. The wrack Fucus vesiculosus is often found attached to either the mussels or the cobbles and it can occur at high abundance. The mussels are also usually encrusted with the barnacles Semibalanus balanoides, Elminius modestus or Chtamalus spp., especially in areas of reduced salinity. The winkles Littorina littorea and L. saxatilis and small individuals of the crab Carcinus maenas are common amongst the mussels, whilst areas of sediment may contain the lugworm Arenicola marina, the sand mason Lanice conchilega and other infaunal species. Pools are often found within the mussel beds that support algae such as Chondrus crispus. Where boulders are present they can support the limpet Patella vulgata, the dogwhelk Nucella lapillus and the anemone Actinia equina. Ostrea edulis may occur on the lowest part of the shore. There are few infaunal samples for this biotope, hence the characterising species list below shows only epifauna. Where infaunal samples have been collected for this biotope, they contain a highly diverse range of species including nematodes, Anaitides mucosa, Hediste diversicolor, Polydora spp., Pygospio elegans, Eteone longa, oligochaetes such as Tubificoides spp., Semibalanus balanoides, a range of gammarid amphipods, Corophium volutator, Jaera forsmani, Crangon crangon, Carcinus maenas, Hydrobia ulvae and Macoma balthica.
This sub-biotope occurs on mid to lower shore sand and muddy sand. Mussels Mytilus edulis grow attached to shell debris and live cockles Cerastoderma edule, forming patches of mussels on consolidated shell material, and often growing into extensive beds. The mussel valves are usually encrusted with barnacles such as Elminius modestus and Semibalanus balanoides, and the mussel bed provides a habitat for a range of species including Littorina littorea. The sediment infaunal community is usually rich and very similar to that of cockle beds (CerPo), including cockles Cerastoderma edule, the baltic tellin Macoma balthica, and a range of burrowing crustaceans and polychaetes typical for CerPo. Further species may be present are the sand mason Lanice conchilega, the sand gaper Mya arenaria, the peppery furrow shell Scrobicularia plana, Nephtys spp., and the ragworm Hediste diversicolor. Scattered fronds of eelgrass Zostera noltii may occur.
Littoral Sabellaria honeycomb worm reefs
The sedentary polychaete Sabellaria alveolata (honeycomb worm) builds tubes from sand and shell. On exposed shores, where there is a plentiful supply of sediment, S. alveolata can form honeycomb reefs on boulders and low-lying bedrock on the mid to lower shore. These S. alveolata reefs are quite distinct from the mosaic of seaweeds and barnacles or red seaweeds (FK; MB) generally associated with moderately exposed rocky shores though many of the same species are present. These include the anemone Actinia equina, the barnacles Semibalanus balanoides and Elminius modestus, the limpet Patella vulgata, the top shell Gibbula cineraria and the winkle Littorina littorea. The whelk Nucella lappilus and the mussel Mytilus edulis is also present on the boulders whereas the polychaete Lanice conchilega is restricted to the associated sediment areas. Scour resistent red seaweeds including Palmaria palmata, Corallina ifficinalis, Mastocarpus stellatus, Chondrus crispus, Ceramium nodulosum, Osmundea pinnatifida, Polysiphonia spp. and coralline crusts can also be present where suitable substrata exsist. Brown and green seaweeds also present include Fucus serratus, Fucus vesioculosus, Cladostephus spongiosus, Enteromorpha intestinalis and Ulva lactuca.
Sabellaria alveolata reefs on sand-abraded eulittoral rock
Exposed to moderately exposed bedrock and boulders in the eastern basin of the Irish Sea (and as far south as Cornwall) characterised by reefs of the polychaete Sabellaria alveolata. The sand based tubes formed by S. alveolata form large reef-like hummocks, which serve to stabilise the boulders and cobbles. Other species in this biotope include the barnacles Semibalanus balanoides and Elminius modestus and the limpet Patella vulgata, the winkle Littorina littorea, the mussel Mytilus edulis and the whelk Nucella lapillus. The anemone Actinia equina and the crab Carcinus maenas can be present in cracks and crevices on the reef. Low abundance of seaweeds tend to occur in areas of eroded reef. The seaweed diversity can be high and may include the foliose red seaweeds Palmaria palmata, Mastocarpus stellatus, Osmundea pinnatifida, Chondrus crispus and some filamentous species e.g. Polysiphonia spp. and Ceramium spp. Coralline crusts can occur in patches. Wracks such as Fucus vesiculosus, Fucus serratus and the brown seaweed Cladostephus spongiosus may occur along with the ephemeral green seaweeds Enteromorpha intestinalis and Ulva lactuca. On exposed surf beaches in the south-west S. alveolata forms a crust on the rocks, rather than the classic honeycomb reef form, and may be accompanied by the barnacle Balanus perforatus (typically common to abundant). On wave-exposed shores in Ireland, the wrack Himanthalia elongata can also occur.
Littoral coarse sediments include shores of mobile pebbles, cobbles and gravel, sometimes with varying amounts of coarse sand. The sediment is highly mobile and subject to high degrees of drying between tides. As a result, few species are able to survive in this environment. Beaches of mobile cobbles and pebbles tend to be devoid of macroinfauna, while gravelly shores may support limited numbers of crustaceans, such as Pectenogammarus planicrurus.
Littoral shingle and gravel shores include shores of mobile pebbles and gravel, sometimes with varying amounts of coarse sand. The sediment is highly mobile and subject to high degrees of drying between tides. As a result, few species are able to survive in this environment. Beaches of mobile shingle tend to be devoid of macroinfauna, while gravelly shores may support limited numbers of crustaceans such as Pectenogammarus planicrurus.
Shingle or gravel shores, typically with sediment particle size ranging from 4 - 256 mm, sometimes with some coarse sand mixed in. This biotope is normally only found on exposed open coasts in fully marine conditions. Such shores tend to support virtually no macrofauna in their very mobile and freely draining substratum. The few individuals that may be found are those washed into the habitat by the ebbing tide, including the occasional amphipod or small polychaete.
Pectenogammarus planicrurus in mid shore well-sorted gravel or coarse sand
Shores of well-sorted gravel with a predominant particle size of 4.0 mm but ranging between 3 and 6 mm support dense populations of the amphipod Pectenogammarus planicrurus. Material finer than 2 mm reduces the ability of the amphipod to survive. The amphipod is tolerant of variable salinity, although a preference for a specific salinity regime has not been determined. As this habitat is regularly under-surveyed, its distribution is unclear.
Littoral macrophyte-dominated sediment biotopes include saltmarshes on the upper shore and seagrass beds on the mid and upper shore. These higher plant-dominated communities develop mostly on sheltered shores with fine, often muddy, sediments. The character of saltmarsh communities is affected by height up the shore, resulting in a zonation pattern related to the degree or frequency of immersion in seawater. Saltmarsh and seagrass bed vegetation is generally well studied; its classification is fully covered by the UK National Vegetation Classification, where 26 types are defined (Rodwell, 2000). Users are referred to the chapter on saltmarsh communities in Rodwell (2000) (this will be a hyperlink to an electronic copy of the mentioned chapter) for details on the plant communities which characterise the different littoral macrophyte-dominated biotopes.
Mid and upper shore wave-sheltered muddy fine sand or sandy mud with the narrow-leafed eel grass Zostera noltii at an abundance of frequent or above. Exactly what determines the distribution of Z. noltii is not entirely clear. It is often found in small lagoons and pools, remaining permanently submerged, and on sediment shores where the muddiness of the sediment retains water and stops the roots from drying out. An anoxic layer is usually present below 5 cm sediment depth. The infaunal community is characterised by polychaetes Scoloplos armiger, Pygospio elegans and Arenicola marina, oligochaetes, spire shell Hydrobia ulvae, and bivalves Cerastoderma edule and Macoma balthica. The green algae Enteromorpha spp. may be present on the sediment surface. The characterising species lists below give an indication both of the epibiota and of the sediment infauna that may be present in intertidal seagrass beds. The biotope is described in more detail in the National Vegetation Classification (see the chapter on saltmarsh communities in Rodwell, 2000).
Zostera noltii beds in littoral muddy sand
Mid and upper shore wave-sheltered muddy fine sand or sandy mud with narrow-leafed eel grass Zostera noltii at an abundance of frequent or above. It should be noted that the presence of Z. noltii as scattered fronds does not change what is otherwise a muddy sand biotope. Exactly what determines the distribution of Z. noltii is not entirely clear. It is often found in small lagoons and pools, remaining permanently submerged, and on sediment shores where the muddiness of the sediment retains water and stops the roots from drying out. An anoxic layer is usually present below 5 cm sediment depth. The infaunal community is characterised by the polychaetes Scoloplos armiger, Pygospio elegans and Arenicola marina, oligochaetes, the spire shell Hydrobia ulvae, and the bivalves Cerastoderma edule and Macoma balthica. The green algae Enteromorpha spp. may be present on the sediment surface. The characterising species lists below give an indication both of the epibiota and of the sediment infauna that may be present in intertidal seagrass beds. The biotope is described in more detail in the National Vegetation Classification (see the chapter on saltmarsh communities in Rodwell, 2000) (*** this will be a hyperlink to an electronic copy of the mentioned chapter).
Angiosperm-dominated stands of vegetation, occurring on the extreme upper shore of sheltered coasts and periodically covered by spring high tides. The vegetation develops on a variety of sandy and muddy sediment types and may have admixtures of coarser material. The character of the saltmarsh communities is affected by height up the shore, resulting in a zonation pattern related to the degree or frequency of immersion in seawater. Saltmarsh vegetation is generally well studied; its classification is fully covered by the UK National Vegetation Classification, where 26 types are defined (Rodwell, 2000). The species listed below give a general indication of the infaunal component of saltmarsh communities. Users are referred to the chapter on saltmarsh communities in Rodwell (2000) for details on the plant communities which characterise the different saltmarsh biotopes.
Shores of fine particulate sediment, mostly in the silt and clay fraction (particle size less than 0.063 mm in diameter), though sandy mud may contain up to 40% sand (mostly very fine and fine sand). Littoral mud typically forms extensive mudflats, though dry compacted mud can form steep and even vertical structures, particularly at the top of the shore adjacent to saltmarshes. Little oxygen penetrates these cohesive sediments, and an anoxic layer is often present within millimetres of the sediment surface. Littoral mud can support communities characterised by polychaetes, bivalves and oligochaetes. Most muddy shores are subject to some freshwater influence, as most of them occur along the shores of estuaries. Mudflats on sheltered lower estuarine shores can support a rich infauna, whereas muddy shores at the extreme upper end of estuaries and which are subject to very low salinity often support very little infauna.
Polychaete/bivalve-dominated mid estuarine mud shores
Mid estuarine shores of fine sediment, mostly in the silt and clay fraction (particle size less than 0.063 mm in diameter), though sandy mud may contain up to 40% sand (mostly very fine and fine sand). Littoral mud typically forms extensive mudflats, though dry compacted mud can form steep and even vertical structures, particularly at the top of the shore adjacent to saltmarshes. Little oxygen penetrates these cohesive sediments, and an anoxic layer is often present within millimetres of the sediment surface. Most mid estuarine muddy shores are subject to some freshwater influence, though at some locations more or less fully marine conditions may prevail. Mid estuarine muds support rich communities characterised by polychaetes, bivalves and oligochaetes.
Hediste diversicolor and Macoma balthica in littoral sandy mud
Mainly mid and lower shore sandy mud or mud in lower estuaries, sheltered bays and marine inlets, often subject to variable salinity. The main characterising species are the ragworm Hediste diversicolor, the baltic tellin Macoma balthica, and the oligochaetes Tubificoides benedii and T. pseudogaster. Further polychaetes that are often common or abundant include Pygospio elegans, Streblospio shrubsolii, Tharyx killariensis, Aphelochaeta marioni, Capitella capitata and Manayunkia aestuarina. The oligochaete Heterochaeta costata and the mud shrimp Corophium volutator may be abundant. The spire shell Hydrobia ulvae is often common. Other species which occur in a significant proportion of samples include the polychaetes Eteone longa and Nephtys hombergii, and bivalves such as the cockle Cerastoderma edule and Abra tenuis. The sand gaper Mya arenaria is superabundant in about a quarter of the samples for this biotope. M. arenaria is probably present in a higher proportion of areas of this biotope, but may be missed in core samples due to its size.
Hediste diversicolor, Macoma balthica and Scrobicularia plana in littoral sandy mud
Mainly mid shore mud or sandy mud subject to variable salinity on sheltered estuarine shores. Typically, the sediment is wet in appearance and has an anoxic layer below 1 cm depth. The surface of the mud has the distinctive 'crow's foot' pattern formed by the peppery furrow shell Scrobicularia plana. The infauna is additionally characterised by a range of polychaete and bivalve species, including the ragworm Hediste diversicolor, Pygospio elegans, Streblospio shrubsolii, Tharyx killariensis and the baltic tellin Macoma balthica. Oligochaetes, most notably Tubificoides benedii, and the spire shell Hydrobia ulvae may be abundant. Other species that sometimes occur in this biotope are the cockle Cerastoderma edule, the sand gaper Mya arenaria and the polychaetes Eteone longa and Nephtys hombergii.
Nephtys hombergii, Macoma balthica and Streblospio shrubsolii in littoral sandy mud
Soft mud with a fine sand fraction, in variable salinity conditions, typically close to the head of estuaries. The infauna is dominated by the polychaete worm Streblospio shrubsolii, the polychaete Nephtys hombergii, oligochaetes of the genus Tubificoides, and the Baltic tellin Macoma balthica. The ragworm Hediste diversicolor and the spire shell Hydrobia ulvae are often common or abundant.
Polychaete/oligochaete-dominated upper estuarine mud shores
Upper estuarine sandy mud and mud shores, in areas with significant freshwater influence. Littoral mud typically forms mudflats, though dry compacted mud can form steep and even vertical structures, particularly at the top of the shore adjacent to saltmarshes. Little oxygen penetrates these cohesive sediments, and an anoxic layer is often present within millimetres of the sediment surface. The upper estuarine mud communities support few infaunal species and are principally characterised by a restricted range of polychaetes and oligochaetes.
Mud and sandy mud shores in sheltered marine inlets and estuaries subject to variable or reduced salinity. The biotope is typically found on the mid and lower shores in the upper and mid estuary. If present on the upper shore, the sediment may become firm and compacted as water drains out, though usually the biotope occurs lower on the shore and the sediment remains water saturated during low tide. An anoxic layer occurs within the upper 5 cm of the sediment. The infauna is dominated by abundant or superabundant ragworms Hediste diversicolor. Other species that occur in a significant number of samples include oligochaetes such as Heterochaeta costata and Tubificoides spp., polychaetes such as Streblospio shrubsolii and Manayunkia aestuarina, the mud shrimp Corophium volutator, and the spire shell Hydrobia ulvae.
Hediste diversicolor and Corophium volutator in littoral mud
Sheltered estuarine shores of sandy mud, which may become firm and compacted if present in the upper shore where there is more time for drainage between high tides. An anoxic layer is usually present within the first 5 cm of the sediment. The infauna is very sparse, usually only the ragworm Hediste diversicolor and the amphipod Corophium volutator are present in any abundance. Occasionally, oligochaetes or the spire shell Hydrobia ulvae may be present. Corophium multisetosum may also be found. There may be organic pollution of the sediment.
Hediste diversicolor and oligochaetes in littoral mud
A species-poor community found in mud or slightly sandy mud in low salinity conditions, typically at the head of estuaries. The infauna is dominated by the ragworm Hediste diversicolor which is typically superabundant. Oligochaetes, including tubificids and Heterochaeta costata, can be abundant, as well as spionids. The peppery furrow shell Scrobicularia plana may be present in low abundances. The mud is often very soft and fluid, with a 'wet' surface appearance, or it may be compacted and form steep banks in the upper parts of macro-tidal estuaries and along saltmarsh creeks.
Hediste diversicolor and Streblospio shrubsolii in littoral sandy mud
Mud and sandy mud shores in sheltered marine inlets and estuaries subject to variable or reduced salinity. The biotope is typically found on the mid and lower shores and is often associated with shallow layers of cobbles and pebbles in the sediment in the upper and mid estuary. The sediment is anoxic close to the surface and remains water saturated during low tide. The infaunal polychaete community is dominated by dense Hediste diversicolor, as well as species with a limited salinity range tolerance such as Streblospio shrubsolii and Manayunkia aestuarina. Oligochaetes, including Heterochaeta costata and Tubificoides benedii are often abundant, and the amphipod Corophium volutator is often common.
Nephtys hombergii and Streblospio shrubsolii in littoral mud
Soft wet mud with a fine sand fraction, on the mid and lower shore of sheltered estuaries, usually with an anoxic layer present within the first 5 cm of the sediment. The infauna is relatively poor, dominated by the polychaetes Nephtys hombergii, Streblospio shrubsolii, and Aphelochaeta marioni. The oligochaete Tubificoides benedii is also characterising for this biotope, and Hediste diversicolor may be common.
Tubificoides benedii and other oligochaetes in littoral mud
Extreme upper estuarine fine sandy mud, sometimes with a fine sand fraction, in very sheltered conditions and subject to reduced salinity. An anoxic layer is usually present within the upper 3 cm of the sediment. The infaunal community is extremely poor, consisting almost exclusively of oligochaetes, including Tubificoides benedii and, more rarely, Heterochaeta costata. The only polychaete species that may occur is Capitella capitata, which may be common. The sediment may form steep banks in upper parts of macro-tidal estuaries or along saltmarsh creeks. Vaucheria species may form a film on the sediment surface along such creeks, and juvenile shore crabs Carcinus maenas may be common. At the very upper end of estuaries, the oligochaetes Limnodrilus spp. and Tubifex tubifex may be found.
Shores of mixed sediments ranging from muds with gravel and sand components to mixed sediments with pebbles, gravels, sands and mud in more even proportions. By definition, mixed sediments are poorly sorted. Stable large cobbles or boulders may be present which support epibiota such as fucoids and green seaweeds more commonly found on rocky and boulder shores. Mixed sediments which are predominantly muddy tend to support infaunal communities which are similar to those of mud and sandy mud shores.
Hediste-dominated gravelly sandy mud shores
Sheltered gravelly sandy mud, subject to reduced salinity, mainly on the mid and lower shore. The infaunal community is dominated by abundant ragworms Hediste diversicolor. Other species of the infauna vary for the sub-biotopes described. They include polychaetes such as Pygospio elegans, Streblospio shrubsolii, and Manayunkia aestuarina, oligochaetes such as Heterochaeta costata and Tubificoides spp., the mud shrimp Corophium volutator, the spire shell Hydrobia ulvae, the baltic tellin Macoma balthica and the peppery furrow shell Scrobicularia plana. Sub-biotopes described in HedMx have equivalent communities in soft muddy sediments, but the sediment here is much firmer due to the gravel component. There are relatively few records in each sub-type, leading to uncertainty over the precise nature of the habitat, particularly regarding sediment type and salinity regime.
Hediste diversicolor in littoral gravelly muddy sand and gravelly sandy mud
Hediste diversicolor, cirratulids and Tubificoides spp. in littoral gravelly sandy mud
Sheltered gravelly sandy mud, subject to variable salinity. The infaunal community consists of the ragworm Hediste diversicolor, Pygospio elegans, Streblospio shrubsolii, and cirratulid polychaetes such as Tharyx killariensis. Nematodes and oligochaetes occur, as well as the bivalve Macoma balthica. Given the low sample numbers for this biotope, more records are needed to confirm the characterising species list.
Hediste diversicolor and Corophium volutator in littoral gravelly sandy mud
Extremely sheltered gravelly sandy mud, subject to variable or reduced salinity. The infaunal community consists of the ragworm Hediste diversicolor, Streblospio shrubsolii, Capitella capitata and Manayunkia aestuarina. Oligochaetes and Corophium volutator are abundant. Given the low sample numbers for this biotope, more records are needed to confirm the characterising species list.
Hediste diversicolor and Macoma balthica in littoral gravelly mud
Sheltered gravelly mud shores, subject to reduced salinity. The infaunal community consists of the ragworm Hediste diversicolor, as well as the spire shell Hydrobia ulvae and the baltic tellin Macoma balthica. The presence of the gravel in the sediment is unlikely to have a large influence on the infaunal composition, which is driven mainly by the estuarine sandy mud conditions. Coarse material on the sediment surface may however enrich the biota with additional epifaunal species such as barnacles and algae. Given the low sample numbers for this biotope, more records are needed to confirm the characterising species list.
Hediste diversicolor and Scrobicularia plana in littoral gravelly mud
Extremely sheltered gravelly mud on the mid and lower shore, containing little sand with occasional cobbles. The infaunal community includes the ragworm Hediste diversicolor and the peppery furrow shell Scrobicularia plana, as well as a range of polychaetes, oligochaetes, and molluscs. Given the low sample numbers for this biotope, more records are needed to confirm the characterising species list.
Hediste diversicolor and Streblospio shrubsolii in littoral gravelly sandy mud
Extremely sheltered gravelly sandy mud, subject to variable salinity, on the mid and lower shore. The infaunal community consists of the ragworm Hediste diversicolor, Pygospio elegans, Streblospio shrubsolii, and Ampharete grubei, as well as oligochaetes and Corophium volutator. There are often low densities of Scrobicularia plana. Given the low sample numbers for this biotope, more records are needed to confirm the characterising species list.
Sheltered mixed sediments, usually subject to variable salinity conditions. The infauna is very diverse, dominated by a range of polychaetes including Exogone naidina, Sphaerosyllis taylori, Pygospio elegans, Chaetozone gibber, Cirriformia tentaculata, Aphelochaeta marioni, Capitella capitata, Mediomastus fragilis, and Melinna palmata. The oligochaete worms Tubificoides benedii and T. pseudogaster are abundant, as is the cockle Cerastoderma edule. A large range of amphipods may occur, including Melita palmata, Microprotopus maculatus, Aora gracilis and Corophium volutator. The bivalves Abra alba and A. nitida may occur. The barnacle Elminius modestus may be abundant where the sediment has stones on the surface.
Cirratulids and Cerastoderma edule in littoral mixed sediment
Sheltered mixed sediments, usually subject to variable salinity conditions. Banks of shell may be present. The infauna is very diverse, dominated by a range of polychaetes including Exogone naidina, Sphaerosyllis taylori, Pygospio elegans, Chaetozone gibber, Cirriformia tentaculata, Aphelochaeta marioni, Capitella capitata, Mediomastus fragilis, and Melinna palmata. The oligochaetes Tubificoides benedii and T. pseudogaster are abundant, as is the cockle Cerastoderma edule. A large range of amphipods may occur, including Melita palmata, Microprotopus maculatus, Aora gracilis and Corophium volutator. The bivalves Abra alba and A. nitida may occur. The barnacle Elminius modestus can be abundant where the sediment has stones on the surface. Epifaunal algae may occur attached to stable cobbles on the sediment surface.
Shores comprising clean sands (coarse, medium or fine-grained) and muddy sands with up to 25% silt and clay fraction. Shells and stones may occasionally be present on the surface. The sand may be duned or rippled as a result of wave action or tidal currents. Littoral sands exhibit varying degrees of drying at low tide depending on the steepness of the shore, the sediment grade and the height on the shore. The more mobile sand shores are relatively impoverished (MoSa), with more species-rich communities of amphipods, polychaetes and, on the lower shore, bivalves developing with increasing stability in finer sand habitats (FiSa). Muddy sands (MuSa), the most stable within this habitat complex, contain the highest proportion of bivalves.
Polychaete/amphipod-dominated fine sand shores
Shores of clean, medium to fine and very fine sand, with no coarse sand, gravel or mud present. Shells and stones may occasionally be present on the surface. The sand may be duned or rippled as a result of wave action or tidal currents. The degree of drying between tides is limited, and the sediment usually remains damp throughout the tidal cycle. Typically, no anoxic layer is present. Fine sand shores support a range of species including amphipods and polychaetes. On the lower shore, and where sediments are stable, bivalves such as Angulus tenuis may be present in large numbers. An exceptionally rich fine sand community has been recorded from very sheltered reduced salinity shores in Poole Harbour. Species recorded include Anaitides maculata, Hediste diversicolor, Scoloplos armiger, Pygospio elegans, Tharyx killariensis, oligochaetes, Gammarus locusta, Hydrobia ulvae, Cerastoderma edule and Mya truncata.
Moderately exposed or sheltered beaches of medium and fine, usually clean, sand, though the sediment may on rare occasions contain a small silt and clay fraction. The sediment is relatively stable, remains damp throughout the tidal cycle, and contains little organic matter. It is often rippled and typically lacks an anoxic sub-surface layer. Where an anoxic layer is present, it occurs at a depth below 10 cm and tends to be patchy. The biotope occurs mainly on the lower part of the shore, and relatively frequently on the mid shore. It is only rarely present above mid shore level, except where coastal defences cause backwash onto the upper shore. Conditions are usually fully marine, though the biotope can also occur in open lower estuarine conditions. The infaunal community is dominated by a range of polychaete species such as Nephtys cirrosa, Paraonis fulgens, Spio spp., Pygospio elegans, Ophelia rathkei and Scoloplos armiger. The presence of polychaetes may be seen as coloured burrows running down from the surface of the sediment, and Arenicola marina casts may be present on the sediment surface. The amphipods Bathyporeia spp. and Pontocrates arenarius frequently occur, and nemerteans are often present. On some North Wales shores, the presence of Arenicola species characterises the lowest part of the shore, with a range of species characteristic of the shallow sublittoral. These include sparsely distributed Echinocardium, Amphiura brachiata, Ensis siliqua and Fabulina fabula. The Po biotope is split into three sub-biotopes, between which there can be a large degree of overlap. The bivalve Angulus tenuis dominates the Po.Aten sub-biotope, which is characterised by slightly more stable and fine sediments than the other two sub-biotopes.
Polychaetes and Angulus tenuis in littoral fine sand
This biotope occurs on the mid and lower shore on moderately wave-exposed and sheltered coasts, with predominantly fine sand which remains damp throughout the tidal cycle. The sediment is often rippled, and an anoxic layer may occasionally occur below a depth of 10 cm, though it is often patchy. The infaunal community is dominated by the abundant bivalve Angulus tenuis together with a range of polychaetes. The presence of polychaetes may be seen as coloured burrows running down from the surface of the sediment. Polychaetes that are characterising for this biotope include Nephtys cirrosa, Paraonis fulgens and Spio filicornis. Burrowing amphipods Bathyporeia spp. may occur in some samples of this biotope.
Nephtys cirrosa-dominated littoral fine sand
This biotope occurs mainly on the mid and lower shore on moderately wave-exposed and sheltered coasts, with medium to fine clean sand which remains damp throughout the tidal cycle and contains little organic matter. The sediment is not usually well sorted and may contain a fraction of coarse sand. It is often rippled and typically lacks an anoxic sub-surface layer. The polychaete infauna is dominated by Nephtys cirrosa, Magelona mirabilis, Spio martinensis, Spiophanes bombyx and Paraonis fulgens. The presence of polychaetes may be seen as coloured burrows running down from the surface of the sediment. Nemertean worms may be present. The amphipods Pontocrates spp. and Bathyporeia spp., as well as Cumopsis goodsiri and the shrimp Crangon crangon are typically present. The bivalve Angulus tenuis is scarce or absent.
Polychaetes, including Paraonis fulgens, in littoral fine sand
This biotope occurs mainly on the mid and lower shore of moderately wave-exposed coasts, with medium and fine clean sand which remains damp throughout the tidal cycle and contains little organic matter. The sediment is often rippled and typically lacks an anoxic sub-surface layer. Polychaetes make up the greater part of the community, and are dominated by Paraonis fulgens, Capitella capitata, Pygospio elegans, Ophelia rathkei and Eteone longa. The presence of polychaetes may be seen as coloured burrows running down from the surface of the sediment. Nemerteans may also be present. The amphipods Bathyporeia pilosa and B. sarsi are often present.
Barren or amphipod-dominated mobile sand shores
Shores consisting of clean mobile sands (coarse, medium and some fine-grained), with little very fine sand, and no mud present. Shells and stones may occasionally be present on the surface. The sand may be duned or rippled as a result of wave action or tidal currents. The sands are non-cohesive, with low water retention, and thus subject to drying out between tides, especially on the upper shore and where the shore profile is steep. Most of these shores support a limited range of species, ranging from barren, highly mobile sands to more stable clean sands supporting communities of isopods, amphipods and a limited range of polychaetes. Species which can characterise mobile sand communities include Scolelepis squamata, Pontocrates arenarius, Bathyporeia pelagica, B. pilosa, Haustorius arenarius and Eurydice pulchra.
Amphipods and Scolelepis spp. in littoral medium-fine sand
Mobile clean sandy beaches on exposed and moderately exposed shores, with sediment grain sizes ranging from medium to fine, often with a fraction of coarser sediment. The sediment contains little or no organic matter, and usually no anoxic layer is present at all. It tends to be well-drained, retaining little water at low tide, though the sediment of the AmSco.Pon sub-biotope may remain damp throughout the tidal cycle. These beaches usually occur under fully marine conditions, though the AmSco.Eur sub-biotope may occur under moderately exposed lower estuarine conditions. The mobility of the sediment leads to a species-poor community, dominated by polychaetes, isopods and burrowing amphipods. Scolelepis spp. can tolerate well-drained conditions, and are often present in well-draining, coarser sand. Burrowing amphipods that often occur in this biotope include Bathyporeia spp., Pontocrates arenarius, and Haustorius arenarius. The isopod Eurydice pulchra is also often present. On semi-exposed beaches with a moderate tide range where there is a marked high-shore berm, there can be a marked seepage at the foot of the berm that probably carries the products of the organic matter derived from strand line breakdown. Here in a narrow zone, exceptionally high populations of Bathyporeia pilosa, sometimes above 10000 per square metre, may occur. The zone may be narrower than the strandline and could easily be missed on surveys were only a few levels are sampled. Three sub-biotopes are described for this biotope, based principally on differences in infaunal species composition.
Eurydice pulchra in littoral mobile sand
Well-draining beaches of medium- to fine-grained mobile sand, often (but not always) well sorted. Occasionally, a small fraction of coarse sand may be present. The biotope generally occurs on exposed open coasts, but sometimes in estuarine conditions, supporting populations of the isopod Eurydice pulchra and burrowing amphipods which frequently include Bathyporeia pilosa and Haustorius arenarius. The degree of drainage appears to be a critical factor in determining the presence of polychaetes, with only Scolelepis squamata capable of tolerating the well-drained sediments of this biotope. This biotope has two facies: drying upper and mid shore sands, and highly mobile lower shore and shallow sublittoral sand bars. Where this biotope occurs in estuarine conditions, H. arenarius is often highly abundant.
Pontocrates arenarius in littoral mobile sand
Mainly on the mid and lower shore on wave-exposed or moderately wave-exposed coasts of medium and fine sand, sometimes with a fraction of coarse sand, which remains damp throughout the tidal cycle and contains little organic matter. The sediment is often rippled and typically lacks an anoxic sub-surface layer. The infauna is dominated by burrowing amphipods, most notably Pontocrates arenarius, as well as Bathyporeia pelagica, Haustorius arenarius and the isopod Eurydice pulchra. The polychaete fauna is poor, dominated by Scolelepis squamata, which tolerates the exposed and mobile sediment conditions. The presence of polychaetes may be seen as coloured burrows running down from the surface of the sediment.
Exposed and moderately exposed shores of fully marine mobile clean sand, with particle sizes ranging from coarse to very fine. The sediment is not always well sorted, and may contain a subsurface layer of gravel or shell debris. Usually no anoxic layer is present. The mobility of the sediment leads to a species-poor community, dominated by the polychaetes Scolelepis squamata and S. foliosa. The amphipod Bathyporeia pilosa may be present. Further species that may be present in this sub-biotope include the amphipods B. pelagica and Haustorius arenarius, and the isopod Eurydice pulchra. The lugworm Arenicola marina may also occur.
Freely-draining sandy beaches, particularly on the upper and mid shore, which lack a macrofaunal community due to their continual mobility. Trial excavations are unlikely to reveal any macrofauna in these typically steep beaches on exposed coasts. Oligochaetes, probably mainly enchytraeids, and the isopod Eurydice pulchra may be found in extremely low abundances, but if present in any quantity should be classed as Ol or AmSco.Eur. Burrowing amphipods (Bathyporeia spp.) may be present on very rare occasions. Occasionally, other species may be left behind in low abundance by the ebbing tide.
A species-poor community of oligochaetes occurring in estuarine conditions where sands and gravel are associated with the lower shore river channel in estuaries. The sediment is relatively coarse and mobile due to strong river flow and subject to variable salinity. The biotope also occurs in fully marine conditions on open shores with mobile, medium to fine, usually clean, sand. Oligochaetes, including enchytraeid oligochaetes, constitute the infaunal assemblage. This biotope has been split into two sub-biotopes, based on the physical environment (a full-salinity and a variable salinity type).
Oligochaetes in full salinity littoral mobile sand
A species-poor community of oligochaetes occurring in fully marine conditions on open shores with mobile, medium to fine, usually clean, sand. Oligochaetes, including enchytraeid oligochaetes, constitute the infaunal assemblage. On rare occasions individuals of polychaete or crustacean species may be encountered (e.g. Nephtys spp., Eurydice pulchra, Bathyporeia spp.), though these are not characterising for the biotope and if present in any significant abundance, the area should be classed as AmSco.
Oligochaetes in variable salinity littoral mobile sand
A species-poor community of oligochaetes occurring in estuarine conditions where sands and gravel are associated with the lower shore river channel in estuaries. The sediment is relatively coarse and mobile due to strong river flow and subject to variable salinity. There is usually very little mud in the sediment. Oligochaetes, including enchytraeid oligochaetes, constitute the infaunal assemblage. Nemerteans may be present, and nematodes may be frequent.
Polychaete/bivalve-dominated muddy sand shores
Muddy sand or fine sand, often occurring as extensive intertidal flats on open coasts and in marine inlets. The sediment generally remains water-saturated during low water. The habitat may be subject to variable salinity conditions in marine inlets. An anoxic layer may be present below 5 cm of the sediment surface, sometimes seen in the worm casts on the surface. The infauna consists of a diverse range of amphipods, polychaetes, bivalves and gastropods.
Bathyporeia pilosa and Corophium arenarium in littoral muddy sand
Wave-sheltered, mainly upper and mid shore flats of medium to fine sand, often muddy sand. The salinity, although predominantly recorded as variable, probably varies little from fully marine in these broad estuaries. The infauna is characterised by the amphipods Bathyporeia pilosa, Corophium arenarium and C. volutator, and the spire shell Hydrobia ulvae. Polychaetes and bivalves are limited in their abundance and variety, though the Baltic tellin Macoma balthica may occur. Tidal streams may be strong during spring tides, accounting for the presence of amphipods B. pilosa that are more commonly associated with open coast sandflats.
Cerastoderma edule and polychaetes in littoral muddy sand
Extensive clean fine sand or muddy sand shores with abundant cockles Cerastoderma edule. The community consists of the polychaetes Eteone longa, Scoloplos armiger, Pygospio elegans, Spio filicornis and Capitella capitata, the crustaceans Bathyporeia sarsi, Bodotria arenosa arenosa and Crangon crangon, the spire shell Hydrobia ulvae, as well as the cockle C. edule and the baltic tellin Macoma balthica. This biotope carries commercially viable stocks of C. edule, and it is therefore possible to find areas of this habitat where the infauna may have been changed through recent cockle dredging. Cockle dredging can result in a reduced bivalve abundance and reduced densities of some polychaete species, including P. elegans (Moore, 1991). At the outer edges of large flats, there may be a zone between the cockle beds and more exposed sands, where there are fewer cockles and B. sarsi is the commoner species.
Hediste diversicolor, Macoma balthica and Eteone longa in littoral muddy sand
Fine to very fine muddy sand on the mid shore at the lower extreme of estuaries, and in moderately exposed and sheltered bays and marine inlets, sometimes subject to variable salinity. The infauna is characterised by the polychaetes Eteone longa, Hediste diversicolor (ragworm) and Pygospio elegans, oligochaetes (mostly Tubificoides benedii and T. pseudogaster), the crustaceans Corophium volutator and Crangon crangon, the spire shell Hydrobia ulvae and the baltic tellin Macoma balthica. The cockle Cerastoderma edule may be abundant, and the sand gaper Mya arenaria may be superabundant, though these species are not always present, or may be missed in core samples due to their large size. The polychaetes Arenicola marina, Polydora cornuta and Capitella capitata, the shrimp Crangon crangon, and the Mussel Mytilus edulis are sometimes present.
This biotope usually occurs on flats of medium fine sand and muddy sand, most often on the lower shore but sometimes also on waterlogged mid shores. The sand may contain a proportion of shell fragments or gravel. Lan can also occur on the lower part of predominantly rocky or boulder shores, where patches of sand or muddy sand occur between scattered boulders, cobbles and pebbles. Conditions may be tide-swept, and the sediment may be mobile, but the biotope usually occurs in areas sheltered from strong wave action. The sediment supports dense populations of the sand mason Lanice conchilega. Other polychaetes present are tolerant of sand scour or mobility of the sediment surface layers and include the polychaetes Anaitides mucosa, Eumida sanguinea, Nephtys hombergii, Scoloplos armiger, Aricidea minuta, Tharyx spp. and Pygospio elegans. The mud shrimp Corophium arenarium and the cockle Cerastoderma edule may be abundant. The baltic tellin Macoma balthica may be present. On boulder shores, and where pebbles and cobbles are mixed in with lower shore tide-swept sand with dense L. conchilega between the cobbles, the infaunal component is rarely sampled. The infaunal community under these circumstances, provided that the cobbles are not packed very close together, is likely to be similar to that in areas without the coarse material.
Macoma balthica and Arenicola marina in littoral muddy sand
Muddy sand or fine sand, often occurring as extensive intertidal flats both on open coasts and in marine inlets. The sediment is often compacted, with a rippled surface, areas of standing water, and generally remains water-saturated during low water. Scattered stones, cobbles and boulders with attached fucoids may be present. An anoxic layer is usually present within 5cm of the sediment surface and is often visible in worm casts. The habitat may be subject to variable salinity conditions in marine inlets. The species assemblage is characterised by the lugworm Arenicola marina and the Baltic tellin Macoma balthica. The polychaetes Scoloplos armiger and Pygospio elegans are typically superabundant and common, respectively. Oligochaetes, probably mainly Tubificoides benedii and T. pseudogaster, may be common, and the cockle Cerastoderma edule may be abundant.
The strandline is the shifting line of decomposing seaweed and debris which is typically left behind on sediment (and some rocky shores) at the upper extreme of the intertidal at each high tide. These ephemeral bands of seaweed often shelter communities of sandhoppers.A fauna of dense juvenile mussels may be found in sheltered firths, attached to algae on shores of pebbles, gravel, sand, mud and shell debris with a strandline of fucoid algae.
Mytilus edulis and Fabricia sabella in littoral mixed sediment
Pebbles, gravel, sand and shell debris with mud in sheltered Firths with a strandline of fucoid algae. The fauna is characterised by juvenile mussels Mytilus edulis, often in very high numbers. The nemertean worm Lineus spp. may be abundant and oligochaetes are common. Polychaetes such as Pygospio elegans, Scoloplos armiger and Fabricia sabella may be present in high densities. Fabricia sabella is typically found amongst algal holdfasts and between cobbles on rocky shores. The bivalves Macoma balthica and Cerastoderma edule, typical of muddy sediments, characterise the community. The validity of this biotope is uncertain, as the only available data, from the Dornoch Firth and the Moray Firth, are poor. Its position within the classification, as a strandline community, is also very uncertain, but there is not enough information available for a better description or classification at this stage.
Talitrids on the upper shore and strand-line
A community of sandhoppers (talitrid amphipods) may occur on any shore where driftlines of decomposing seaweed and other debris accumulate on the strandline. The biotope occurs most frequently on medium and fine sandy shores, but may also occur on a wide variety of sediment shores composed of muddy sediment, shingle and mixed substrata, or on rocky shores. The decaying seaweed provides cover and humidity for the sandhopper Talitrus saltator. In places on sand that regularly accumulate larger amounts of weed, Talorchestia deshayesii is often present. Oligochaetes, mainly enchytraeids, can occur where the stranded debris remains damp as a result of freshwater seepage across the shore or mass accumulation of weed in shaded situations. On shingle and gravel shores and behind saltmarshes the strandline talitrid species tend to be mainly Orchestia species. Abundances of the characterising species tend to be highly patchy. Two characterising species lists are presented below. They are derived from two sets of data, which were analysed separately. The first shows data from infaunal samples, the second shows data from epifaunal samples. The epifaunal lists contains no counts per square metre, as the data were collected on the SACFOR scale.
Sediment habitats in the sublittoral near shore zone (i.e. covering the infralittoral and circalittoral zones), typically extending from the extreme lower shore down to the edge of the bathyal zone (200m). Sediment ranges from boulders and cobbles, through pebbles and shingle, coarse sands, sands, fine sands, muds, and mixed sediments. Those communities found in or on sediment are described within this broad habitat type.
Sublittoral biogenic reef communities. This complex includes polychaete reefs, bivalve reefs (e.g. mussel beds) and cold water coral reefs. These communities develop in a range of habitats from exposed open coasts to estuaries, marine inlets and deeper offshore habitats and may be found in a variety of sediment types and salinity regimes.
The coral reef structures in UK waters are found in cold (12-4øC), largely aphotic waters, generally along the shelf edge and in offshore waters down to 2000m. In the north east Atlantic, Lophelia pertusa is the dominant colonial coral and is the characterising species of the biotope described under this biotope complex. Lophelia and its deep-water allies lack the symbiotic algae of their tropical relatives, so can live in the permanent darkness of the deep sea. These corals form colonies and can aggregate into patches and banks which may be described as reefs. These deep-sea corals can support and shelter hundreds of other species, including sponges, polychaete worms, echinoderms (starfish, sea urchins, brittle stars) and bryozoans (sea mats). Some 200-300 species can be found in one of these coral habitats, a number comparable to that found in other important deep-water habitats. Unlike tropical coral reef systems, they are dominated by only a few hard-coral species, and there are far fewer fish species.
Reefs of the coral Lophelia pertusa, typically supporting a range of other biota. Lophelia reefs are generally found in areas of elevated current. The coral provides a 3 dimensional structure and a variety of microhabitats that provide shelter and a surface of attachment for other species. Boring sponges, anemones, bryozoans, gorgonians including Paragorgia arborea, Paramuricea placomus, Primnoa resedaeformis, polychaetes, barnacles, squat lobsters (Munida sarsi) and bivalves have all been recorded within and among the corals (Wilson, 1979; Mortensen et al., 1995) Other hard corals such as Madrepora oculata and Solenosmilia variabilis may also be present. Mobile species present include the redfish (Sebastes viviparous and Sebastes marinus), Ling (Molva molva) and tusk (Brosme brosme) (Husebo et al., 2002).
Polychaete worm reefs (on sublittoral sediment)
Sublittoral reefs of polychaete worms in mixed sediments found in a variety of hydrographic conditions. Such habitats may range from extensive structures of considerable size to loose agglomerations of tubes. Such communities often play an important role in the structural composition or stability of the seabed and provide a wide range of niches for other species to inhabit. Consequently polychaete worm reefs often support a diverse flora and fauna.
Sabellaria alveolata on variable salinity sublittoral mixed sediment
Tide-swept sandy mixed sediments with cobbles and pebbles, in variable salinity or fully marine conditions, may be characterised by surface accumulations of the reef building polychaete Sabellaria alveolata. The presence of Sabellaria sp. has a strong influence on the associated infauna as the tubes bind the surface sediments together and provide increased stability. Such reefs may form large structures up to a metre in height although they are considerably less extensive than the intertidal reefs formed by this species (Salv). Other associated species may include the polychaete Melinna cristata, itself often as dense aggregations, mobile surface feeding polychaetes including Typosyllis armillary and Eulalia tripunctata. Other polychaetes may include Mediomastus fragilis and Pygospio elegans whilst amphipods such as Harpinia pectinata and tubificid oligochaetes may also be found.
Serpula vermicularis reefs on very sheltered circalittoral muddy sand
Large clumps (mini 'reefs') of the calcareous tubes of Serpula vermicularis, typically attached to stones on muddy sediment in very sheltered conditions in sealochs and other marine inlets. A rich associated biota attached to the calcareous tube may include Esperiopsis fucorum, thin encrusting sponges, and the ascidians Ascidiella aspersa, Ascidia mentula, Dendrodoa grossularia and Diplosoma listerianum. The echinoderms Ophiothrix fragilis and Psammechinus miliaris and the queen scallop (Aequipecten opercularis) are also found throughout this biotope. In shallow water dense Phycodrys rubens may grow on the 'reefs'. This biotope has been recorded in the U.K. from Loch Creran, where these reefs have been well studied (Moore 1996), and Loch Sween, where they are reported to have deteriorated. The only other known sites for this biotope are Salt Lake, Cliffden and Killary Harbour, Co. Galway.
Sabellaria spinulosa on stable circalittoral mixed sediment
The tube-building polychaete Sabellaria spinulosa at high abundances on mixed sediment. These species typically forms loose agglomerations of tubes forming a low lying matrix of sand, gravel, mud and tubes on the seabed. The infauna comprises typical sublittoral polychaete species such as Protodorvillea kefersteini, Pholoe synophthalmica, Harmothoe spp, Scoloplos armiger, Mediomastus fragilis, Lanice conchilega and cirratulids, together with the bivalve Abra alba, and tube building amphipods such as Ampelisca spp. The epifauna comprise a variety of bryozoans including Flustra foliacea, Alcyonidium diaphanum and Cellepora pumicosa, in addition to calcareous tubeworms, pycnogonids, hermit crabs and amphipods. The reefs formed by Sabellaria consolidate the sediment and allow the settlement of other species not found in adjacent habitats leading to a diverse community of epifaunal and infauna species. The development of such reefs is assisted by the settlement behaviour of larval Sabellaria which are known to selectively settle in areas of suitable sediment and particularly on existing Sabellaria tubes (Tait and Dipper, 1997; Wilson 1929). These reefs are particularly affected by dredging or trawling and in heavily dredged or disturbed areas an impoverished community may be left (e.g. Pkef) particularly if the activity or disturbance is prolonged. However, it is likely that reefs of S. spinulosa can recover quite quickly from short term or intermediate levels of disturbance as found by Vorberg (2000) in the case of disturbance from shrimp fisheries and recovery will be accelerated if some of the reef is left intact following disturbance as this will assist larval settlement of the species.
Sublittoral mussel beds (on sublittoral sediment)
Sublittoral mussel beds comprised of either the horse mussel Modiolus modiolus or the common mussel Mytilus edulis. These communities may be sublittoral extensions of littoral reefs or exist independently. Found in a variety of habitats ranging from sheltered estuaries and marine inlets to open coasts and offshore areas they may occupy a range of substrata, although due to the stabilising effect such communities have on the substratum muddy mixed sediments are typical. A diverse range of epibiota and infauna often exists in these communities.
Modiolus modiolus beds with Chlamys varia, sponges, hydroids and bryozoans on slightly tide-swept very sheltered circalittoral mixed substrata
Dense Modiolus modiolus beds, covered by hydroids and bryozoans, on soft gravelly, shelly mud with pebbles in areas of slight or moderate tidal currents. The variable scallop (Chlamys varia) is frequently found in large numbers amongst the Modiolus shells. Hydroids such as Halecium spp. and Kirchenpaueria pinnata and ascidians such as Ascidiella aspersa, Corella parallelogramma and Ciona intestinalis may be found attached to pebbles or mussel shells. The echinoderms Ophiothrix fragilis and Antedon bifida are often frequent in this biotope as is the encrusting polychaete Pomatoceros triqueter. Similar communities have been found on cobble and pebble plains in stable, undisturbed conditions in some sealochs, although not all these examples have Modiolus beds.
Modiolus modiolus beds with fine hydroids and large solitary ascidians on very sheltered circalittoral mixed substrata
Beds or scattered clumps of Modiolus modiolus in generally sheltered conditions with only slight tidal movement. Typically occurs in sealochs and the Shetland voes. Brittlestars Ophiothrix fragilis and Ophiocomina nigra, as well as Ophiopholis aculeata are often frequent, sometimes forming a dense bed as described in OphMx. The queen scallop Aequipecten opercularis is often present in moderate abundances. Large solitary ascidians (Ascidiella aspersa, Corella parallelogramma, Dendrodoa grossularia) and fine hydroids (Kirchenpaueria pinnata) are present attached to the mussel shells. Decapods such as hermit crabs (Pagurus bernhardus) and spider crabs (Hyas araneus) are typically present. Coralline algal crusts may be found on the mussel shells, with some red seaweeds in shallower water such as Phycodrys rubens. Little information on the infaunal component is given here although it is likely that it is very rich and may highlight more subtle differences in the Modiolus biotopes.
Modiolus modiolus beds on open coast circalittoral mixed sediment
Muddy gravels and coarse sands in deeper water of continental seas may contain venerid bivalves with beds of Modiolus modiolus. The clumping of the byssus threads of the M. modiolus creates a stable habitat that attracts a very rich infaunal community with a high density of polychaete species including Glycera lapidum, Paradoneis lyra, Aonides paucibranchiata, Laonice bahusiensis, Protomystides bidentata, Lumbrineris spp., Mediomastus fragilis and syllids such as Exogone spp. and Sphaerosyllis spp. Bivalves such as Spisula elliptica, Timoclea ovata and other venerid species are also common. Brittlestars such as Amphipholis squamata may also occur with this community. This biotope is very similar to SMX.PoVen and the 'boreal off-shore gravel association' and the 'deep Venus community' described by previous workers (Ford 1923; Jones 1951). Similar Modiolus beds (though with a less diverse infauna) on open coast stable boulders, cobbles and sediment are described under MCR.ModT.
Modiolus modiolus beds with hydroids and red seaweeds on tide-swept circalittoral mixed substrata
Modiolus beds on mixed substrata (cobbles, pebbles and coarse muddy sediments) in moderately strong currents or wave exposed areas, typically on the open coast but also in tide-swept channels of marine inlets. Ophiothrix fragilis are often common in this biotope along with the calcareous tubes of Pomatoceros triqueter, anemones such as Alcyonium digitatum and Urticina felina and hydroids such as Abietinaria abietina and Sertularia argentea. Buccinum undatum may also be important and in some areas the clam Chlamys varia may be frequent but not in the same abundances as in ModCvar. Little information on the infaunal component is given here although it is likely that it is very rich and may highlight more subtle differences in the Modiolus biotopes. This biotope is typified by examples off the north-west Lleyn Peninsula in N Wales and off Co. Down, Northern Ireland.
Mytilus edulis beds on sublittoral sediment
Shallow sublittoral mixed sediment, in fully marine coastal habitats or sometimes in variable salinity conditions in the outer regions of estuaries, are characterised by beds of the common mussel Mytilus edulis. Other characterising infaunal species may include the amphipod Gammarus salinus and oligochaetes of the genus Tubificoides. The polychaetes Harmothoe spp., Kefersteinia cirrata and Heteromastus filiformis are also important. Epifaunal species in addition to the M. edulis include the whelks Nucella lapillus and Buccinum undatum, the common starfish Asterias rubens the spider crab Maja squinado and the anemone Urticina felina. Relatively few records are available for this biotope and it is possible that as more data is accumulated separate estuarine and fully marine sub-biotopes may be described. Further clarification may also be required with regard to the overlap between littoral and sublittoral mussel beds and with regard to mussel beds biotopes on hard substratum.
Sublittoral coarse sediment (unstable cobbles and pebbles, gravels and coarse sands)
Coarse sediments including coarse sand, gravel, pebbles, shingle and cobbles which are often unstable due to tidal currents and/or wave action. These habitats are generally found on the open coast or in tide-swept channels of marine inlets. They typically have a low silt content and a lack of a significant seaweed component. They are characterised by a robust fauna including venerid bivalves.
Tide-swept circalittoral coarse sands, gravel and shingle generally in depths of over 15-20m. This habitat may be found in tidal channels of marine inlets, along exposed coasts and offshore. This habitat, as with shallower coarse sediments, may be characterised by robust infaunal polychaetes, mobile crustacea and bivalves. Certain species of sea cucumber (e.g. Neopentadactyla) may also be prevalent in these areas along with the lancelet Branchiostoma lanceolatum.
Branchiostoma lanceolatum in circalittoral coarse sand with shell gravel
Gravel and coarse sand with shell gravel often contains communities of robust venerid bivalves (SCS.MedLumVen). Shallower examples, such as the biotope presented here, may support a significant population of Branchiostoma lanceolatum. Other conspicuous infauna may include Echinocyamus pusillus, Glycera lapidum, Polygordius, Pisione remota and Arcopagia crassa (in the south of UK). Sessile epifauna are typically a minor component of this community. This biotope has been described from a limited number of records and as such may need revising when further data become available. This biotope is related to the 'Boreal Offshore Gravel Association' and 'Deep Venus Community' described by other workers (Ford 1923; Jones 1951), and may also be closely allied (the same?) as the 'Venus fasciata' community of Cabioch (Glemarec 1973). This biotope may be an epibiotic overlay of the biotope SCS.MoeVen or SCS.MedLumVen.
Mediomastus fragilis, Lumbrineris spp. and venerid bivalves in circalittoral coarse sand or gravel
Circalittoral gravels, coarse to medium sands, and shell gravels, sometimes with a small amount of silt and generally in relatively deep water (generally over 15-20m), may be characterised by polychaetes such as Mediomastus fragilis, Lumbrineris spp., Glycera lapidum with the pea urchin Echinocyamus pusillus. Other taxa may include Nemertea spp., Protodorvillea kefersteini, Owenia fusiformis, Spiophanes bombyx and Amphipholis squamata along with amphipods such as Ampelisca spinipes. This biotope may also be characterised by the presence of conspicuous venerid bivalves, particularly Timoclea ovata. Other robust bivalve species such as Moerella spp., Glycymeris glycymeris and Astarte sulcata may also be found in this biotope. Spatangus purpureus may be present especially where the interstices of the gravel are filled by finer particles, in which case, Gari tellinella may also be prevalent (Glemarec 1973). Venerid bivalves are often under-sampled in benthic grab surveys and as such may not be conspicuous in many infaunal datasets. Such communities in gravelly sediments may be relatively species-rich and they may also contain epifauna such as Hydroides norvegicus and Pomatoceros lamarcki. In sand wave areas this biotope may also contain elements of the FfabMag biotope, particularly Magelona species. This biotope has previously been described as the 'Deep Venus Community' and the 'Boreal Off-Shore Gravel Association' by other workers (Ford 1923; Jones 1950) and may also be part of the Venus community described by Thorson (1957) and in the infralittoral etage described by Glemarec (1973). SCS.MedLumVen may be quite variable over time and in fact may be closer to a biotope complex in which a number of biotopes or sub-biotopes may yet be defined. For example, Ford (1923) describes a 'Series A' and a 'Series B' characterised by Echinocardium cordatum-Chamelea gallina and Spatangus purpurea-Clausinella fasciata. Furthermore, mosaics of cobble and lag gravel often contain ridges of coarse gravelly sand and these localised patches are also characterised by robust veneriid and similar bivalves including Arcopagia crassa, Laevicardium crassum and others including Glycymeris glycymeris (E.I.S. Rees pers. comm.. 2002). This high porosity fine gravel or coarse sand may be a separate biotope.
Neopentadactyla mixta in circalittoral shell gravel or coarse sand
Sublittoral plains of clean, shell, maerl and / or stone gravels or sometimes coarse sands, with frequent Neopentadactyla mixta. Pecten maximus may occur occasionally along with Lanice conchilega. Other epifaunal species may include Ophiura albida, Pagurus spp. and Callionymus spp. These sediments may be thrown into dunes by wave action or tidal streams. Widespread species such as Cerianthus lloydii and Chaetopterus variopedatus are present in many examples of this biotope. Scarcely recorded species such as Molgula oculata, Ophiopsila annulosa and Amphiura securigera may also be found. O. annulosa only occurs in records from the south-west of the British Isles. It should be noted that Neopentadactyla may exhibit periodicity in its projection out of, and retraction into, the sediment (Picton 1993).This biotope may be an epibiotic overlay of the biotope MedLumVen.
Protodorvillea kefersteini and other polychaetes in impoverished circalittoral mixed gravelly sand
In coarse gravelly or shelly sand sometimes with a slight mud content, along open coasts in depths of 10 to 30m, and in shallower offshore areas, an impoverished community characterised by Protodorvillea kefersteini may be found. This biotope has a number of other species associated with it including Nemertea spp., Caulleriella zetlandica, Minuspio cirrifera, Glycera lapidum, Ampelisca spinipes and numerous other polychaete species all occurring at low abundances. The polychaete Sabellaria spinulosa is also found in low numbers in this biotope.
Pomatoceros triqueter with barnacles and bryozoan crusts on unstable circalittoral cobbles and pebbles
This biotope is characterised by a few ubiquitous robust and/or fast growing ephemeral species which are able to colonise pebbles and unstable cobbles and slates which are regularly moved by wave and tidal action. The main cover organisms tend to be restricted to calcareous tube worms such as Pomatoceros triqueter (or P. lamarcki), small barnacles including Balanus crenatus and Balanus balanus, and a few bryozoan and coralline algal crusts. Scour action from the mobile substratum prevents colonisation by more delicate species. Occasionally in tide-swept conditions tufts of hydroids such as Sertularia argentea and Hydrallmania falcata are present. This biotope often grades into SMX.FluHyd which is characterised by large amounts of the above hydroids on stones also covered in Pomatoceros and barnacles. The main difference here is that SMX.FluHyd, seems to develop on more stable, consolidated cobbles and pebbles or larger stones set in sediment in moderate tides. These stones may be disturbed in the winter and therefore long-lived and fragile species are not found.
Moderately exposed habitats with coarse sand, gravelly sand, shingle and gravel in the infralittoral, are subject to disturbance by tidal steams and wave action. Such habitats found on the open coast or in tide-swept marine inlets are characterised by a robust fauna of infaunal polychaetes such as Chaetozone setosa and Lanice conchilega, cumacean crustacea such as Iphinoe trispinosa and Diastylis bradyi, and venerid bivalves.
Cumaceans and Chaetozone setosa in infralittoral gravelly sand
In shallow medium-fine sands with gravel, on moderately exposed open coasts, communities dominated by cumacean crustaceans such as Iphinoe trispinosa and Diastylis bradyi along with the cirratulid polychaete Chaetozone setosa (agg.) may occur. Chaetozone setosa is a species complex so it is likely that some variability in nomenclature will be found in the literature. Other important taxa may include the polychaetes Anaitides spp., Lanice conchilega, Eteone longa and Scoloplos armiger. This community may be subject to periodical sedimentary disturbance, such that a sub-climactic community may develop with opportunistic taxa such as C. setosa and S. armiger often dominating the community (Allen 2000).
Glycera lapidum in impoverished infralittoral mobile gravel and sand
In infralittoral mixed slightly gravelly sands on exposed open coasts impoverished communities characterised by the polychaete Glycera lapidum (agg.) may be found. Glycera lapidum is a species complex and as such some variability in identification may be found in the literature. It is also quite widespread and may occur in a variety of coarser sediments and is often present in other SCS biotopes. However, it is rarely considered a characteristic species and where this is the case it is normally due to the exclusion of other species. Consequently it is considered that habitats containing this biotope may be subject to continual or periodic sediment disturbance from wave action, which prevents the establishment of a more stable community. Other taxa include spionid polychaetes such as Spio martinensis and Spiophanes bombyx, Nephtys spp. and in some areas the bivalve Spisula elliptica. It is possible that SCS.Glap it is not a true biotope, rather an impoverished, transitional community, which in more settled conditions develops into other more stable communities.
Halcampa chrysanthellum and Edwardsia timida on sublittoral clean stone gravel
Periodically (seasonally?) disturbed sublittoral stone gravel with small pebbles characterised by the presence of the anemones Halcampa chrysanthellum and Edwardsia timida. Associated species are often typical of a hydroid/bryozoan turf with polychaetes such as Pomatoceros spp. encrusting larger pebbles and low numbers of syllid and phyllodocid polychaetes living interstitially. In some areas this biotope may also contain opportunistic red seaweeds and infauna such as Sabella pavonina. It should be noted that this habitat may show considerable variation in community composition and it is possible that it is a sub-biotope of other gravel biotopes.
Hesionura elongata and Microphthalmus similis with other interstitial polychaetes in infralittoral mobile coarse sand
On infralittoral sandbanks and sandwaves and other areas of mobile medium-coarse sand, populations of interstitial polychaetes may be found. These habitats consist of loosely packed grains of sand forming waves up to several metres high often with gravel, or occasionally silt, in the troughs of the waves. This biotope is commonly found both inshore along the east coast of the UK e.g. around the Race Bank, Docking Shoal and Inner Dowsing banks (IECS, 1995; IECS, 1999), and in the Southern Bight of the North Sea and off the Belgian coast (Degraer et al. 1999; Vanosmael et al. 1982). These habitats support interstitial communities living in the spaces between the grains of sand, in particular hesionurid polychaetes such as Hesionura elongata and Microphthalmus similis, along with protodrilid polychaetes such as Protodrilus spp. and Protodriloides spp. Other important species may include Turbellaria spp. and larger deposit feeding polychaetes such as Travisia forbesii. An important feature of this biotope which is not reflected in much of the available data is the importance of the meiofaunal population which may exceed the macrofaunal population both in terms of abundance and biomass (Willems et al. 1982).
Moerella spp. with venerid bivalves in infralittoral gravelly sand
Infralittoral medium to coarse sand and gravelly sand which is subject to moderately strong water movement from tidal streams may be characterised by Moerella spp. with the polychaete Glycera lapidum (agg.) and venerid bivalves. Typical species include Moerella pygmaea or M. donacina with other robust bivalves such as Dosinia lupinus, Timoclea ovata, Goodallia triangularis and Chamelea gallina. Other infauna include nephtyd and spionid polychaetes and amphipod crustacea. Another important component of this biotope in some areas is the bivalve Spisula solida (see Khne & Rachnor 1996) which may be common or abundant. In conjunction with FfabMag this biotope may form part of the 'Shallow Venus Community', the 'Boreal Off-shore Sand Association' and the 'Goniadella-Spisula association' of previous workers (see Petersen 1918; Jones 1951; Thorson 1957; Salzwedel, Rachor & Gerdes 1985). Epifaunal communities may be reduced in this biotope when compared to FfabMag; both types may have surface sand waves which may be indicative of the presence of venerid bivalves (Warwick & Davies 1977). This hypothesis, however, requires testing. Remote grab sampling is likely to under-estimate venerid bivalves and other deep-burrowing and more dispersed species such as Paphia, Ensis and Spatangus. In southern areas of the UK and the North Sea, in slightly siltier sand and shelly sand, SCS.MoeVen may give way to the other Spisula biotope SSA.SsubNhom. Together these two biotopes replace the old biotope IGS.Sell.
Dense Lanice conchilega and other polychaetes in tide-swept infralittoral sand and mixed gravelly sand
Dense beds of Lanice conchilega occur in coarse to medium fine gravelly sand in the shallow sublittoral, where there are strong tidal streams or wave action. Several other species of polychaete also occur as infauna e.g. Spiophanes bombyx, Scoloplos armiger, Chaetozone setosa and Magelona mirabilis. Lanice beds are found in a wide range of habitats including muddier mixed sediment. The dense Lanice biotope (LGS.Lan) on certain lower shores may be a littoral extension of the current biotope. The presence of L. conchilega in high numbersmay, over time, stabilise the sediment to the extent where a more diverse community may develop (Wood, 1987). Possibly as a result of this, there is a high level of variation with regard the infauna found in SCS.SLan. It is likely that a number of sub-biotopes may subsequently be identified for this biotope. Offshore from the Wash and the North Norfolk coast Lanice beds are often found intermixed with Sabellaria spinulosa beds in muddier mixed sediment, particularly in the channels between the shallow sandbanks, which are so prevalent in this area (IECS, 1995; NRA, 1995). It is possible that the presence of Lanice has stabilised the habitat sufficiently to allow the deposition of finer material, which has subsequently assisted the development of S. spinulosa. It may be more accurate to define SLan as an epibiotic biotope which overlays a variety of infaunal biotopes (e.g. NcirBat in finer sands and AalbNuc or FfabMag in slightly muddier areas).
Sparse fauna on highly mobile sublittoral shingle (cobbles and pebbles)
Sublittoral clean shingle and pebble habitats with a lack of conspicuous fauna. Unstable, rounded pebbles and stones (as opposed to sub-angular cobbles, which are often found lying on or embedded in other sediment) that are strongly affected by tidal steams and/or wave action can support few animals and are consequently faunally impoverished. The species composition of this biotope may be highly variable seasonally and is likely to comprise of low numbers of robust polychaetes or bivalves with occasional epibiota including echinoderms and crustacea such as Liocarcinus spp. and Pagurus spp. In more settled periods there may be colonisation by anemones such as Urticina felina and small populations of hydroids and Bryozoa.
Offshore (deep) circalittoral habitats with coarse sands and gravel or shell. This habitat may cover large areas of the offshore continental shelf although there is relatively little quantitative data available. Such habitats are quite diverse compared to shallower versions of this habitat and generally characterised by robust infaunal polychaete and bivalve species. Animal communities in this habitat are closely related to offshore mixed sediments and in some areas settlement of Modiolus modiolus larvae may occur and consequently these habitats may occasionally have large numbers of juvenile M. Modiolus. In areas where the mussels reach maturity their byssus threads bind the sediment together, increasing stability and allowing an increased deposition of silt leading to the development of the biotope SBR.ModMx.
Glycera lapidum, Thyasira spp. and Amythasides macroglossus in offshore gravelly sand
Offshore (deep) circalittoral habitats with coarse sands and gravel, stone or shell and occasionally a little silt (<5%) may be characterised by the polychaetes Glycera lapidum and Amythasides macroglossus with the bivalve Thyasira spp. (particularly Thyasira succisa). Other taxa include polychaetes such as Exogone verugera, Notomastus latericeus, Spiophanes kroyeri,Aphelochaeta marioni (Tharyx marioni) and Lumbrineris gracilis and occasional numbers of the bivalve Timoclea ovata. This biotope bears some resemblance to the shallow SCS.Glap and also to the circalittoral and offshore venerid biotopes (SCS.MedLumVen and SMX.PoVen) but differs by the range of polychaete and bivalve fauna present. This biotope is notable for the presence of the rarely recorded ampharetid polychaete Amythasides macroglossus and also for the small ear file clam Limatula subauriculata which is common in some examples of this biotope.
Hesionura elongata and Protodorvillea kefersteini in offshore coarse sand
Offshore (deep) circalittoral habitats with coarse sand may support populations of the interstitial polychaete Hesionura elongata with Protodorvillea kefersteini. Other notable species include the phyllodocid polychaete Protomystides limbata and the bivalve Moerella pygmaea. This biotope was reported in the offshore northern North Sea by Eleftheriou and Basford (1989). Relatively little data exists for this biotope.
Sublittoral coarse sediment in variable salinity (estuaries)
Clean gravels that occur in the upper reaches of marine inlets, especially estuaries, where water movement is sufficiently strong to remove the silt content of the sediment. The habitat typically lacks a significant seaweed component and is characterised by a sparse but very robust brackish-water tolerant fauna.
Sublittoral macrophyte-dominated communities on sediments
This complex includes maerl beds, seaweed dominated mixed sediments (including kelps such as Laminaria saccharina and filamentous/foliose red and green algae), seagrass beds, and lagoonal angiosperm communities. These communities develop in a range of habitats from exposed open coasts to lagoons and are found in a variety of sediment types and salinity regimes.
Angiosperm communities in reduced salinity
Lagoon communities, subject to reduced or low salinity conditions, dominated by angiosperms, including Potamogeton pectinatus beds and fringing habitats with reeds Phragmites australis.
Low and variable salinity infralittoral mud with beds of Potamogeton pectinatus. Other associated species are broadly similar to that of Rup, with blankets of filamentous green algae such as Enteromorpha intestinalis, Cladophora liniformis and Rhizoclonium riparium. The grazing gastropod Potamopyrgus antipodarum is found in this biotope and juvenile Mytilus edulis have been observed settled on Potamogeton leaves and amongst the algae. The nationally scarce charaphyte Lamprothamnium papulosum may be found to some extent in this biotope but more often in neighbouring habitats (see Plaza & Sanderson 1997). Mysids, trout (Salmo trutta), and sticklebacks Gasterosteus aculeatus can be found swimming amongst the vegetation. Mya arenaria may be found in some examples of this biotope, but the infaunal component of this biotope requires further investigation but is likely to contain oligochaetes, Arenicola marina, Corophium volutator and Gammarus spp.
Phragmites australis swamp and reed beds
Permanently low salinity muds or peaty muddy sands with some gravel which supports Phragmites australis reed beds. These reed beds are often found in enclosed water bodies influenced by freshwater inflow and may have notable quantities of decaying reed material. The substratum may be mixtures of mud, peaty mud, sand and some gravel. Filamentous green algae and charaphytes such as Lamprothamnium papulosum and Chara aspera may also be found in association with this biotope as well as a the freshwater quillwort Myriophyllum spp. The infaunal component of this biotope is poorly known. This biotope is further described as NVC type S4 (Rodwell 1995).
Kelp and seaweed communities on sublittoral sediment
Shallow sublittoral sediments which support seaweed communities, typically including the kelp Laminaria saccharina, the bootlace weed Chorda filum and various red and brown seaweeds, particularly filamentous types. The generally sheltered nature of these habitats enables the seaweeds to grow on shells and small stones which lie on the sediment surface; some communities develop as loose-lying mats on the sediment surface.
Filamentous green seaweeds on low salinity infralittoral mixed sediment or rock
Shallow muddy sediments, often with boulders, cobbles and pebbles around the edges of lagoons, or other areas that are exposed to wide salinity variations are unsuitable for colonisation by many species. Such areas may be colonised by a dense blanket of ephemeral green algae such as Enteromorpha spp., Chaetomorpha linum, Cladophora liniformis or Rhizoclonium riparium. This biotope may also contain some red seaweeds, such as Furcellaria lumbricalis, but always at low abundance (compare with PolFur). Amongst the filamentous green algae, grazing molluscs and solitary ascidians may be present. Infauna may typically include Corophium volutator, Heterochaeta costata, Tubificoides benedeni and other taxa suited for low/variable salinity environments.
Laminaria saccharina and Chorda filum on sheltered upper infralittoral muddy sediment
Shallow kelp community found on sandy mud and gravelly sandy mud, in sheltered or extremely sheltered conditions, with very weak tidal currents. The community is characterised by a reasonable covering of Laminaria saccharina and Chorda filum. Beneath the kelp canopy, Ulva lactuca is often frequent and some filamentous and foliose red algae may be present, along with filamentous brown ectocarpoid algae although in much lower abundance than in the LsacR biotopes. At the sediment surface ubiquitous fauna such as Asterias rubens, crabs such as Pagurus bernhardus, Carcinus maenas, and the gastropod Gibbula cineraria may be visable and in some areas Sabella pavonina may be present. Given the nature of the sediment it is likely that a wide range of infaunal bivalves and polychaetes are present including Arenicola marina, Mediomastus fragilis and Anaitides mucosa. In more tideswept areas with coarser and generally less muddy sediments SMP.LsacCho may be replaced by one of the sub biotopes of SMP.LsacR.
Laminaria saccharina, Gracilaria gracilis and brown seaweeds on full salinity infralittoral sediment
Shallow kelp community found on muddy sand, in moderately exposed or sheltered, fully marine conditions, with weak tidal currents. The community is characterised by a reasonable covering of Laminaria saccharina. Frequent Chorda filum may also form part of the canopy although not at the abundance in LsacCho. Beneath the canopy the community is characterised by the red algae Gracilaria gracilis, and various brown algal species particularly Dictyota dichotoma. Other members of the understory may include a variety of other filamentous and foliose red algae in particular Ceramium nodulosum and the green alga Ulva. The muddy sand substrate supports a variety of faunal species including polychaetes (Lanice conchilega) and gastropods (Hinia reticulata).
Laminaria saccharina and Gracilaria gracilis with sponges and ascidians on variable salinity infralittoral sediment
Shallow kelp community found on stony sediment, in extremely sheltered, variable salinity conditions, with moderately strong tidal currents. The community is characterised by a more sparse covering of Laminaria saccharina, particularly when compared to the fully marine version of this sub biotope (SMP.LsacGraFS). Beneath the canopy the community is characterised by the red algae Gracilaria gracilis, and a variety of faunal species in particular sponges (Suberites ficus and Halichondria panacea) and ascidians (Ascidiella aspersa and Dendrodoa grossularia). The stony substrate provides a surface for attachment for these and many other filter and suspension feeding species, particularly barnacles (Balanus crenatus), hydroids (Urticina feline and Hydractinia echinata) and anemones. Other members of the understory may include a variety of filamentous and foliose red algae in particular Pterothamnion plumula, and the green alga Ulva.
Laminaria saccharina with Psammechinus miliaris and/or Modiolus modiolus on variable salinity infralittoral mixed sediment
Shallow kelp community found on stoney mixed sediment, in full or variable salinity, in sheltered or moderately exposed conditions, with weak or very weak tidal currents. The community is characterised by a dense covering of Laminaria saccharina. Beneath the kelp canopy, frequent Psammechinus miliaris may be found grazing the algal turf and scattered Modiolus modiolus are characteristic of this biotope. Encrusting the suface of stones and pebbles are Pomatoceros triqueter and in the sediment between the stones, the burrowing anemone Cerianthus lloydii may also be present. Small patches of Lithothamnion glaciale may be found in this biotope, although these patches do not form distict beds as in SBR.Lgla. In addition, a more ubiquitous fauna such as Asterias rubens and Pagurus bernhardus are also present. This biotope is generally found in sealochs.
Laminaria saccharina and red seaweeds on infralittoral sediments
On infralittoral mixed muddy substrata communities characterised by the kelp Laminaria saccharina and mixed filamentous and foliose red algae can be found. This biotope contains a number of sub-biotopes distinguished by the degree of either wave or tidal exposure. In moderately strong tidal streams in exposed areas Laminaria is sparse and dense stands of red seaweeds are found attached to the boulders and cobbles that make up a large proportion of the sediment (LsacR.CbPb). As the degree of wave and/or tidal exposure decreases there is a change in community structure, with the density of Laminaria and the diversity of red algal species increasing (LsacR.Gv). As the environment becomes more stable a number of brown algal species are able to inhabit this environment and a rich infauna develops (LsacR.Sa). In the most sheltered examples of this biotope a diverse muddy sediment infauna can be found and the 'Trailliella' phase of Bonnemaisonia hamifera may develop (LsacR.Mu).
Red seaweeds and kelps on tide-swept mobile infralittoral cobbles and pebbles
Shallow mixed substrata of cobbles and pebbles swept by moderately strong tidal streams in exposed areas, and characterised by dense stands of red seaweeds. Tide-swept infralittoral cobbles and pebbles which may be highly mobile, create an environment that is difficult for many algae to survive in. Foliose and filamentous seaweeds with an encrusting phase in their life history, or those that are able to withstand rolling of the substratum and scouring, can form dense turfs of seaweed in the more settled summer months. Characteristic red seaweeds include Halarachnion ligulatum which is able to survive attached to the pebbles and cobbles. Ephemeral algae grow rapidly in periods of relative stability. Other characteristic red seaweeds include Plocamium cartilagineum, Hypoglossum hypoglossoides, Bonnemaisonia asparagoides and Brongniartella byssoides. Coralline encrusting algae cover many of the cobbles and pebbles; some areas of cobbles may be quite barren, dominated only by encrusting coralline algae and brittlestars. Of the brown seaweeds scattered Laminaria spp. and Desmarestia spp. may be present on more stable large boulders or bedrock outcrops. Chorda filum and Halidrys siliquosa may be present in low abundance but where these seaweeds occur in greater abundance (typically >Frequent) refer to MIR.LsacChoR and MIR.HalXK respectively. Although the faunal component of this biotope is usually relatively sparse it can include a wide variety of species. Turfs of hydroids (Nemertesia spp., Aglaophenia tubulifera) and bryozoans (Crisia spp. and Bugula spp.) are the major components but sponges and anemones may also occur. Brittlestars, sea-urchins, hydroids and solitary ascidians are more prominent in the Scottish examples of this biotope, which tend to occur in deeper water, due in part to clearer waters.
Laminaria saccharina and robust red algae on infralittoral gravel and pebbles
Shallow kelp community found on gravel and gravelly sand in slightly less exposed areas than SMP.LsacR.CbPb but in moderately strong tidal currents, and characterised by occasional Laminaria saccharina with an undergrowth of robust red seaweeds. Characteristic red seaweeds, as with LsacR.CbPb, include Plocamium cartilagineum, Halarachnion ligulatum and Brongniartella byssoides; however the greater stability of this biotope allows a slightly more diverse range of red seaweeds to become established including Polyides rotundus, Rhodophyllis divaricata, Delesseria sanguinea and Nitophyllum punctatum. Coralline encrusting algae may be found covering the larger pebbles. Laminaria hyperborea may also be present within this biotope, although at low densities. Other brown algal species present include Desmarestia spp., Dictyota dichotoma and Chorda filum, all at low abundance. The ubiquitous green seaweed Ulva sp. may be found attached to larger pebbles.
Laminaria saccharina with red and brown seaweeds on lower infralittoral muddy mixed sediment
Slightly deeper kelp community in the lower infralittoral, found on sandy gravelly mud, in sheltered and very sheltered conditions, with very weak tidal currents. The community is characterised by occasional Laminaria saccharina with an undergrowth of red and brown algae. Characteristic red seaweeds, as with other LsacR biotopes include Plocamium cartilagineum and Phycodrys rubens. However, the sheltered conditions of this biotope allow the 'Trailliella' phase of Bonnemaisonia hamifera to develop (although not to the extent of forming distinct mats as in SMP.Tra), and the related species Bonnemaisonia asparagoides. Brown algal species present, as with other LsacR biotopes, include Desmarestia spp at low abundance. The ubiquitous green seaweed Ulva sp. may also be present. The muddy substrate is home to a variety of typical mud dwelling fauna including the burrowing anemone Cerianthus lloydii. The gravelly component of this biotope provides a substrate for encrusting species such as the polychaete Pomatoceros triqueter and coralline encrusting algae.
Laminaria saccharina and filamentous red algae on infralittoral sand
Shallow kelp community found on sand and slightly gravelly sand, in moderately exposed and sheltered conditions, with weak tidal currents. The community is characterised by occasional Laminaria saccharina with an undergrowth of red algae. Characteristic red seaweeds, as with LsacR.Gv, include Plocamium cartilagineum, Polyides rotundus, Polysiphonia elongate and Lomentaria clavellosa. Coralline encrusting algae is much less important in this biotope as a result of a lack of suitable substrate. Brown algal species present, as with other LsacR biotopes, include Desmarestia spp., Dictyota dichotoma and Chorda filum, all at low abundance. The ubiquitous green seaweed Ulva sp. may also be present. The sandy substrate is home to a variety of typical sand dwelling infauna including polychaetes (Scoloplos armiger, Exogone hebes, and Aricidea minuta), amphipods (Ampelisca brevicornis), and bivalves (Lucinoma borealis and Abra alba). Arenicola worm casts and Lanice worm tubes may be visible at the sediment surface.
Loose-lying mats of Phyllophora crispa on infralittoral muddy sediment
Infralittoral muddy sand and sandy mud, sometimes with some shells or pebbles, and a dense, loose-lying cover of Phyllophora crispa. This biotope occurs in very sheltered conditions such as those found in sealochs and voes. SMP.Pcri is similar to other biotopes described with dense, loose-lying algae but has been less frequently recorded, and from the few records available, appears to occur in slightly deeper infralittoral waters primarily between 10m to 30m and typically in fully saline waters. The seaweeds in this biotope may be epiphytised by ascidians such as Ascidiella aspera. Kelp such as Laminaria saccharina and red seaweeds including Plocamium cartilagineum may be present in some areas. The scallops Pecten maximus and Aequipecten opercularis may also be found occasionally in this biotope and Trailliella/Bonnemaisonia hamifera may also be present but not at the levels found in SMP.Tra.
Mats of Trailliella on infralittoral muddy gravel
Dense loose-lying beds of the 'Trailliella' phase of Bonnemaisonia hamifera may occur in extremely sheltered shallow muddy environments. Beds of this alga are often 10 cm thick but may reach 100 cm at some sites. Other loose-lying algae may also occur such as Audouinella floridula, Phyllophora crispa and species of Derbesia. Often the mud is gravelly or with some cobbles and may be black and anoxic close to the sediment surface. This biotope is widely distributed in lagoons, sealochs and voes but should only be described as SMP.Tra when a continuous mat is found. It is likely that the infaunal component of this biotope may be considerably modified by the overwhelming quantity of loose-lying algae.
Beds of maerl in coarse clean sediments of gravels and clean sands, which occur either on the open coast or in tide-swept channels of marine inlets (the latter often stony). In fully marine conditions the dominant maerl is typically Phymatolithon calcareum (SMP.Pcal), whilst under variable salinity conditions in some sealochs beds of Lithothamnion glaciale (SMP.Lgla) may develop.
Lithothamnion corallioides maerl beds on infralittoral muddy gravel
Live maerl beds in sheltered, silty conditions which are dominated by Lithothamnion corallioides with a variety of foliose and filamentous seaweeds. Live maerl is at least common but there may be noticeable amounts of dead maerl gravel and pebbles. Other species of maerl, such as Phymatolithon calcareum and Phymatolithon purpureum, may also occur as a less abundant component. Species of seaweed such as Dictyota dichotoma, Halarachnion ligulatum. and Ulva spp. are often present, although are not restricted to this biotope, whereas Dudresnaya verticillata tends not to occur on other types of maerl beds. The anemones Anemonia viridis and Cerianthus lloydii, the polychaetes Notomastus latericeus and Caulleriella alata, the isopod Janira maculosa and the bivalve Hiatella arctica are typically found in SMP.Lcor where as Echinus esculentus tends to occur more in other types of maerl. The seaweeds Laminaria saccharina and Chorda filum may also be present in some habitats. Lcor has a south-western distribution in Britain and Ireland. Sheltered, stable, fully saline maerl beds in the north of Great Britain (where L. corallioides has not been confirmed to occur) may need to be described as an analogous biotope to Lcor (see Pcal).
Lithophyllum fasciculatum maerl beds on infralittoral mud
Shallow, sheltered infralittoral muddy plains with Lithophyllum fasciculatum maerl. This rarely recorded maerl species forms flattened masses or balls several centimetres in diameter (Irvine & Chamberlain 1994). Lfas may be found on mud and muddy gravel mixed with shell. Species of anemone typical of sheltered conditions may be found in association, for example, Anthopleura ballii, Cereus pedunculatus and Sagartiogeton undatus. Polychaetes such as Myxicola infundibulum and terebellids, also characteristic of sheltered conditions, may be present as may hydroids such as Kirchenpaueria pinnata. Occasional Chlamys varia and Thyone fuscus are present in all records of this biotope and red seaweeds such as Plocamium cartilagineum, Calliblepharis jubata and Chylocladia verticillata are often present.
Lithothamnion glaciale maerl beds in tide-swept variable salinity infralittoral gravel
Upper infralittoral tide-swept channels of coarse sediment in full or variable salinity conditions support distinctive beds of Lithothamnion glaciale maerl 'rhodoliths'. Phymatolithon calcareum may also be present as a more minor maerl component. Associated fauna and flora may include species found in other types of maerl beds (and elsewhere), e.g. Pomatoceros triqueter, Cerianthus lloydii, Sabella pavonina, Chaetopterus variopedatus, Lanice conchilega, Mya truncata, Plocamium cartilagineum and Phycodrys rubens. Lgla, however, also has a fauna that reflects the slightly reduced salinity conditions, e.g. Psammechinus miliaris is often present in high numbers along with other grazers such as chitons and Tectura spp. Hyas araneus, Ophiothrix fragilis, Ophiocomina nigra and the brown seaweed Dictyota dichotoma are also typically present at sites. In Scottish lagoons this biotope may show considerable variation but the community falls within the broad description defined here.
Phymatolithon calcareum maerl beds in infralittoral clean gravel or coarse sand
Maerl beds characterised by Phymatolithon calcareum in gravels and sands. Associated epiphytes may include red algae such as Dictyota dichotoma, Halarachnion ligulatum, Callophyllis laciniata, Cryptopleura ramosa, Brongniartella byssoides and Plocamium cartilagineum. Algal species may be anchored to the maerl or to dead bivalve shells amongst the maerl. Polychaetes, such as Chaetopterus variopedatus, Lanice conchilega, Kefersteinia cirrata, Mediomastus fragilis, Chone duneri, Parametaphoxus fultoni and Grania may be present. Gastropods such as Gibbula cineraria, Gibbula magus, Calyptraea chinensis Dikoleps pusilla and Onoba aculeus may also be present. Liocarcinus depurator and Liocarcinus corrugatus are often present, although they may be under-recorded; it would seem likely that robust infaunal bivalves such as Circomphalus casina, Mya truncata, Dosinia exoleta and other venerid bivalves are more widespread than available data currently suggests. It seems likely that stable wave-sheltered maerl beds with low currents may be separable from SMP.Pcal; having a generally thinner layer of maerl overlying a sandy /muddy substratum with a diverse cover of epiphytes (e.g. Bosence 1976; Blunden et al. 1977; 1981; Davies & Hall-Spencer 1996) but insufficient data currently exists on a national scale. Wave and current-exposed maerl beds, where thicker depths of maerl accumulate, frequently occur as waves and ridge / furrows arrangements (see Bosence 1976; Blunden et al. 1977; 1981; Irvine & Chamberlain 1994; Hall-Spencer 1995). At some sites where Pcal occurs, there may be significant patches of maerl gravel containing the rare burrowing anemone Halcampoides elongatus; this may be a separate biotope, but insufficient data exists at present. Northern maerl beds in the UK do not appear to contain L. corallioides but in south-west England and Ireland L. corallioides may occur to some extent in Pcal as well as Lcor, where it dominates.
Phymatolithon calcareum maerl beds with Neopentadactyla mixta and other echinoderms in deeper infralittoral clean gravel or coarse sand
Lower infralittoral maerl beds characterised by Phymatolithon calcareum in gravels and sand with a variety of associated echinoderms. The echinoderm Neopentadactyla mixta is frequently observed in this biotope. Other echinoderms such as Echinus esculentus, Ophiura albida and rarely Luidia ciliaris may also be present. Red seaweed such as Plocamium cartilagineum may be present but at a much lower abundance than in Pcal.R and with fewer species present. Other, more ubiquitous echinoderms such as Asterias rubens may also be found in low numbers throughout Pcal biotopes.
Phymatolithon calcareum maerl beds with red seaweeds in shallow infralittoral clean gravel or coarse sand
Upper infralittoral maerl beds characterised by Phymatolithon calcareum in gravels and sand with a wide variety of associated red seaweeds. These algae typically include Dictyota dichotoma, Plocamium cartilagineum, Phycodrys rubens, Chondrus crispus, Halarachnion ligulatum, Chylocladia verticillata, Hypoglossum hypoglossoides and Nitophyllum punctum. These species are not restricted to maerl beds but their abundance on maerl beds differentiates this biotope from Pcal.Nmix. Anthozoans and echinoderms are much less common in this biotope than in Pcal.Nmix, which typically occurs deeper than Pcal.R.
Beds of seagrass (Zostera marina or Ruppia spp.) in shallow sublittoral sediments. These communities are generally found in extremely sheltered embayments, marine inlets, estuaries and lagoons, with very weak tidal currents. They may inhabit low, variable and full salinity marine habitats. Whilst generally found on muds and muddy sands they may also occur in coarser sediments, particularly marine examples of Zostera communities.
Ruppia maritima in reduced salinity infralittoral muddy sand
In sheltered brackish muddy sand and mud, beds of Ruppia maritima and more rarely Ruppia spiralis may occur. These beds may be populated by fish such as Gasterosteus aculeatus which is less common on filamentous algal-dominated sediments. Seaweeds such as Chaetomorpha spp., Enteromorpha spp., Cladophora spp., and Chorda filum are also often present in addition to occasional fucoids. In some cases the stoneworts Lamprothamnium papulosum and Chara aspera occur. Infaunal and epifaunal species may include mysid crustacea, the polychaete Arenicola marina, the gastropod Hydrobia ulvae, the amphipod Corophium volutator and oligochaetes such as Heterochaeta costata. In some areas Zostera marina may also be interspersed with the Ruppia beds.
Zostera marina/angustifolia beds on lower shore or infralittoral clean or muddy sand
Expanses of clean or muddy fine sand and sandy mud in shallow water and on the lower shore (typically to about 5 m depth) can have dense stands of Zostera marina/angustifolia [Note: the taxonomic status of Z. angustifolia is currently under consideration]. In Zmar the community composition may be dominated by these Zostera species and therefore characterised by the associated biota. Other biota present can be closely related to that of areas of sediment not containing Zostera marina, for example, Laminaria saccharina, Chorda filum and infaunal species such as Ensis spp. and Echinocardium cordatum (e.g. Bamber 1993). From the available data it would appear that a number of sub-biotopes may be found within this biotope dependant on the nature of the substratum and it should be noted that sparse beds of Zostera marina may be more readily characterised by their infaunal community. For example, coarse marine sands with seagrass have associated communities similar to MoeVen, SLan or Glap whilst muddy sands may have infaunal populations related to EcorEns, AreISa and FfabMag. Muddy examples of this biotope may show similarities to SundAasp, PhiVir, Are or AfilMysAnit. At present the data does not permit a detailed description of these sub-biotopes but it is likely that with further study the relationships between these assemblages will be clarified. Furthermore, whilst the Zostera biotope may be considered an epibiotic overlay of established sedimentary communities it is likely that the presence of Zostera will modify the underlying community to some extent. For example, beds of this biotope in the south-west of Britain may contain conspicuous and distinctive assemblages of Lusitanian fauna such as Laomedea angulata, Hippocampus spp. and Stauromedusae. In addition, it is known that seagrass beds play an important role in the trophic status of marine and estuarine waters, acting as an important conduit or sink for nutrients and consequently some examples of Zostera marina beds have markedly anoxic sediments associated with them.
Sublittoral cohesive mud and sandy mud communities
Sublittoral mud and cohesive sandy mud extending from the extreme lower shore to offshore, circalittoral habitats. This biotope is predominantly found in sheltered harbours, sealochs, bays, marine inlets and estuaries and stable deeper/offshore areas where the reduced influence of wave action and/or tidal streams allow fine sediments to settle. Such habitats are often by dominated by polychaetes and echinoderms, in particular brittlestars such as Amphiura spp. Seapens such as Virgularia mirabilis and burrowing megafauna including Nephrops norvegicus are common in deeper muds. Estuarine muds tend to be characterised by infaunal polychaetes and oligochaetes.
Sublittoral muds, occurring below moderate depths of 15-20 m, either on the open coast or in marine inlets such as sealochs. The seapens Virgularia mirabilis and Pennatula phosphorea are characteristic of this biotope complex together with the burrowing anemone Cerianthus lloydii and the ophiuroid Amphiura spp. The relatively stable conditions often lead to the establishment of communities of burrowing megafaunal species, such as Nephrops norvegicus.
Brissopsis lyrifera and Amphiura chiajei in circalittoral mud
Mud in deep offshore, or shallower stable nearshore, waters can be characterised by the urchin Brissopsis lyrifera and the brittle star Amphiura chiajei. Where intense benthic dredge fishing activity occurs, populations of the indicator species, Brissopsis lyrifera may be depressed, although broken tests may still remain (E.I.S. Rees pers. comm. 1997; M. Costello pers. comm. 1997). Low numbers of the seapen Virgularia mirabilis may be found in many examples of this biotope. In addition, in certain areas of the UK such as the northern Irish Sea, this community may also contain Nephrops norvegicus and can consequently be the focus for fishing activity (Mackie, Oliver & Rees 1995). Infaunal species in this community are similar to those found in SpnMeg and include the polychaetes Nephtys hystricis, Pectinaria belgica, Glycera spp. and Lagis koreni and the bivalves Myrtea spinifera and Nucula sulcata. This community is the 'Boreal Offshore Mud Association' and 'Brissopsis - Chiajei' communities described by other workers (Petersen 1918; Jones 1950).
Burrowing megafauna and Maxmuelleria lankesteri in circalittoral mud
In circalittoral stable mud distinctive populations of megafauna may be found. These typically include Nephrops norvegicus, Calocaris macandreae and Callianassa subterranea. Large mounds formed by the echiuran Maxmuelleria lankesteri are also frequent in this biotope. The seapen Virgularia mirabilis may occur occasionally in this biotope but not in the same abundance as SpnMeg to which MegMax is closely allied. Infaunal species may include Nephtys hystricis, Chaetozone setosa, Amphiura chiajei and Abra alba.
Seapens and burrowing megafauna in circalittoral fine mud
Plains of fine mud at depths greater than about 15 m may be heavily bioturbated by burrowing megafauna; burrows and mounds may form a prominent feature of the sediment surface with conspicuous populations of seapens, typically Virgularia mirabilis and Pennatula phosphorea. The burrowing crustacea present typically include Nephrops norvegicus, which is frequently recorded from surface observations although grab sampling may fail to sample this species. Indeed, some forms of sampling may also fail to indicate seapens as characterising species. This biotope also seems to occur in deep offshore waters in the North Sea, where densities of Nephrops norvegicus may reach 68 per 10 m-2 (see Dyer et al. 1982, 1983), and the Irish Sea. The burrowing anemone Cerianthus lloydii and the ubiquitous epibenthic scavengers Asterias rubens, Pagurus bernhardus and Liocarcinus depurator are present in low numbers in this biotope whilst the brittlestars Ophiura albida and Ophiura ophiura are sometimes present, but are much more common in slightly coarser sediments. Low numbers of the anemone Pachycerianthus multiplicatus may also be found, and this species, which is scarce in the UK, appears to be restricted to this habitat (Plaza & Sanderson 1997). The infauna may contain significant populations of the polychaetes Pholoe spp., Glycera spp., Nephtys spp., spionids, Pectinaria belgica and Terebellides stroemi, the bivalves Nucula sulcata, Corbula gibba and Thyasira flexuosa, and the echinoderm Brissopsis lyrifera.
Seapens, including Funiculina quadrangularis, and burrowing megafauna in undisturbed circalittoral fine mud
Deep muds, especially in sealochs, support forests of the nationally scarce Funiculina quadrangularis, in addition to populations of the seapens Virgularia mirabilis and Pennatula phosphorea. The sediment is usually extensively burrowed by crustaceans, the most common of which is Nephrops norvegicus, but Calocaris macandreae and Callianassa subterranea may also be present (the latter is likely to be under-recorded by grab sampling because it is deep burrowing). The burrowing anemone Cerianthus lloydii is present in low numbers in this biotope and the rare anemone Pachycerianthus multiplicatus may also be found occasionally. Amphiura spp. are also often present in high densities.
Circalittoral, cohesive sandy mud, typically with over 20% silt/clay, generally in water depths of over 10m, with weak or very weak tidal streams. This habitat is generally found in deeper areas of bays and marine inlets or offshore from less wave exposed coasts. Sea pens such as Virgularia mirabilis and brittlestars such as Amphiura spp. are particularly characteristic of this habitat whilst infaunal species include the tube building polychaetes Lagis koreni and Owenia fusiformis, and deposit feeding bivalves such as Mysella bidentata and Abra spp.
Amphiura filiformis, Mysella bidentata and Abra nitida in circalittoral sandy mud
Cohesive sandy mud off wave exposed coasts with weak tidal streams can be characterised by super-abundant Amphiura filiformis with Mysella bidentata and Abra nitida. This community occurs in muddy sands in moderately deep water (Hiscock 1984; Picton et al. 1994) and may be related to the 'off-shore muddy sand association' described by other workers (Jones 1951; Thorson 1957; Mackie 1990) and is part of the infralittoral etage described by Glemarec. This community is also characterised by the sipunculid Thysanocardia procera and the polychaetes Nephtys incisa, Phoronis sp. and Pholoe sp., with cirratulids also common in some areas. Other taxa such as Nephtys hombergii, Echinocardium cordatum, Nucula nitidosa, Callianassa subterranea and Eudorella truncatula may also occur in offshore examples of this biotope (e.g. Knitzer et al. 1992).
Amphiura filiformis and Nuculoma tenuis in circalittoral and offshore sandy mud
In cohesive and non-cohesive sandy mud, off moderately exposed coasts in deep water dense populations of Amphiura filiformis with the bivalve Nuculoma tenuis may occur. This biotope together with AfilMysAnit, ThyNten and OfusAfil may be part of the Amphiura filiformis dominated infralittoral etage described by Glemarec (1973) and part of the 'off-shore muddy sand association' described by other workers (Jones 1951; Mackie 1990). Other species characteristic of this biotope may include the echinoderms Ophiura albida and Echinocardium flavescens and the bivalve Mysella bidentata. Phaxas pellucidus, Owenia fusiformis and Virgularia mirabilis may also be present. At the sediment surface the hydroid Sertularia argentea may be present although only at very low abundances. Variations of this biotope exist in the northern North Sea (see below) and it is possible that more than one entity exists for this biotope.
Lagis koreni and Phaxas pellucidus in circalittoral sandy mud
In stable circalittoral sandy mud dense populations of the tube building polychaete Lagis koreni may occur. Other species found in this habitat typically include bivalves such as Phaxas pellucidus, Mysella bidentata and Abra alba and polychaetes such as Mediomastus fragilis, Spiophanes bombyx, Owenia fusiformis and Scalibregma inflatum. At the sediment surface easily visible fauna include Lagis koreni and Ophiura ophiura. Lagis koreni is an important source of food for commercially important demersal fish, especially dab and plaice (Macer, 1967; Lockwood, 1980 and Basimi & Grove, 1985).
Thyasira spp. and Nuculoma tenuis in circalittoral sandy mud
Circalittoral cohesive sandy muds with small quantities of gravel, off sheltered or moderately exposed coasts may support populations characterised by Thyasira spp. and in particular Thyasira flexuosa. Other characteristic taxa may include Nuculoma tenuis, Goniada maculate and in some areas Rhodine gracilior. Mysella bidentata, Abra alba, Harpinia antennaria and Amphiura filiformis may be abundant in some examples of this biotope. Whilst moderately diverse, animal abundances are often low and it is possible that the biotope is the result of sedimentary disturbance e.g. from trawling and is possibly an impoverished version of AfilNten. Collectively the biotopes ThyNten, AfilMysAnit, AfilNten and OfusAfil, may form the Amphiura dominated components of the 'off-shore muddy sand association' described by other workers (Jones 1951; Thorson 1957; Mackie 1990) and the infralittoral etage described by Glemarec (1973).
Virgularia mirabilis and Ophiura spp. with Pecten maximus on circalittoral sandy or shelly mud
Circalittoral fine sandy mud may contain Virgularia mirabilis and Ophiura spp. A variety of species may occur, and species composition at a particular site may relate, to some extent, to the proportions of the major sediment size fractions. Several species are common to most sites including Virgularia mirabilis which is present in moderate numbers, Ophiura albida and Ophiura ophiura which are often quite common, and Pecten maximus which is usually only present in low numbers. Virgularia mirabilis is usually accompanied by occasional Cerianthus lloydii, Liocarcinus depurator and Pagurus bernhardus. Amphiura chiajei and Amphiura filiformis may occur in some examples of this biotope. Polychaetes and bivalves are generally the main components of the infauna, although the nemerteans, Edwardsia claparedii, Phoronis muelleri and Labidoplax buski may also be widespread. Of the polychaetes Goniada maculata, Nephtys incisa, Minuspio cirrifera, Chaetozone setosa, Notomastus latericeus and Owenia fusiformis are often the most widespread species whilst Myrtea spinifera, Lucinoma borealis, Mysella bidentata, Abra alba and Corbula gibba are typical bivalves in this biotope. This biotope is primarily identified on the basis of its epifauna and may be an epibiotic overlay over other closely related biotopes such as SpnMeg, AfilMysAnit and AfilNten.
Virgularia mirabilis and Ophiura spp. with Pecten maximus, hydroids and ascidians on circalittoral sandy or shelly mud with stones
Circalittoral fine sandy mud with shell gravel and notable quantities of shells or small stones scattered over the sediment surface. These sediments, like SMU.VirOphPmax, may contain Virgularia mirabilis, Pecten maximus and Ophiura spp. but shells and small stones scattered over the sediment surface provided sufficient stable substrata for a variety of sessile epifaunal species to occur. Of these the hydroids Kirchenpaueria pinnata, Nemertesia antennina and Nemertesia ramosa are most common with solitary ascidians such as Corella parallelogramma and Ascidia mentula also present. The anemone Cerianthus lloydii is often found in the sediment together with occasional Lanice conchilega. The serpulids Protula tubularia, Serpula vermicularis and Pomatoceros triqueter and the barnacles Balanus balanus and Balanus crenatus are also often present on pebbles and shells. Munida rugosa are occasionally found under larger stones. All these species are typical of more rocky habitats in such sheltered conditions. As with SMU.VirOphPmax this biotope is primarily identified on the basis of its epifauna and may be an epibiotic overlay over other closely related biotopes such as AfilMysAnit and AfilNten.
Shallow sublittoral muds, extending from the extreme lower shore to about 15-20 m depth in fully marine or near marine conditions, predominantly in extremely sheltered areas with very weak tidal currents. Such habitats are found in sealochs and some rias and harbours. Populations of the lugworm Arenicola marina may be dense, with anemones, the opisthobranch Philine aperta and synaptid holothurians also characteristic in some areas. The extent of the oxidised layer may be shallow with some areas being periodically or permanently anoxic. In these areas bacterial mats may develop on the sediment surface. Infaunal records for this biotope complex are limited encompassing only one biotope. They are therefore not representative of the full suit of infaunal species found in this biotope.
In very shallow, extremely sheltered, very soft muds Arenicola marina may form very conspicuous mounds and casts. This biotope may also contain synaptid holothurians such as Labidoplax media and Leptosynapta bergensis or L. inhaerens. However these species may be under recorded (possibly due to periodicity in feeding) and are not considered characteristic of this biotope. Other conspicuous fauna may include Carcinus maenas, Asterias rubens and Pagurus bernhardus whilst the scallop Pecten maximus and the turret shell Turritella communis may also be present in some areas.
Beggiatoa spp. on anoxic sublittoral mud
Sublittoral soft anoxic mud, often in areas with poor water exchange with the open sea, can have a conspicuous bacterial mat covering of Beggiatoa spp. The anoxia may be a result of natural conditions of poor water exchange in some sealochs (and many Scandinavian fjords) or artificially under fish farm cages from nutrient enrichment. The fauna is normally impoverished at such sites, with few elements of the infaunal communities present in other muddy biotopes. Scavenging species such as Asterias rubens and Carcinus maenas are typically present where the habitat is not too anoxic along with occasional Arenicola marina but in extreme conditions of anoxia little survives other than the Beggiatoa. The polychaete Ophiodromus flexuosus occurs in high densities at the interface between oxygenated and deoxygenated sediments (in Norwegian fjords).
Cerastoderma edule with Abra nitida in infralittoral mud
Sheltered shallow sublittoral muds and gravelly muds in marine embayments, inlets or harbours may contain populations of the edible cockle Cerastoderma edule with Abra nitida. Other taxa may include the gastropod Hydrobia ulvae, cirraltulid polychaetes such as Caulleriella spp. and other polychaetes including Hediste diversicolor and Aphelochaeta marioni. Available data for this biotope are limited to parts of Southampton Water, Chichester Harbour and also in the Wash. The species list given here may therefore be far from complete. It is not known at this stage whether this biotope is a sublittoral extension of intertidal cockle beds (e.g. LSA.CerPo) or whether it exists independently of intertidal populations of C. edule.
Ocnus planci aggregations on sheltered sublittoral muddy sediment
Dense aggregations of Ocnus planci [?brunneus] on various substrata, typically muddy but occasionally with stones or shells, in sheltered conditions such as sealochs. Philine aperta also characterises this biotope but is present in lower abundances than in PhiVir. Other associated species vary but are typical of very sheltered muddy habitats and include the ophiuroids Ophiura spp. and Ophiothrix fragilis. Melanella alba, which parasitises holothurians, has been found in large numbers at one site.
Philine aperta and Virgularia mirabilis in soft stable infralittoral mud
Physically very stable muds, occasionally with small stones, with a high proportion of fine material (typically greater than 80 %) may contain the opisthobranch Philine aperta and the seapen Virgularia mirabilis. These muds typically occur in shallow water down to about 12-15 m where significant seasonal variation in temperature is presumed to occur. This habitat is restricted to the most sheltered basins in, for example, sealochs. Although most records suggest full salinity conditions are prevalent, some sites may be subject to variable salinity. Philine aperta is the most characteristic species of this habitat, occurring in high densities at many sites, whilst Virgularia mirabilis, a species found more widely in muddy sediments, appears to reach its highest densities in this shallow mud but may not be present in all examples of this biotope. Other conspicuous species found in this shallow muddy habitat include Cerianthus lloydii, Pagurus bernhardus, Sagartiogeton spp. and Hydractinia echinata. Burrowing crustacean megafauna, characteristic of deeper mud, are rare or absent from this shallow sediment although Nephrops norvegicus may sometimes be recorded. This biotope has been primarily recorded on the basis of its epifauna and a few conspicuous infauna. Little data exists on the infaunal component of this biotope but it may include Nephtys spp., spionid polychaetes, Ampelisca spp. and the bivalves Nucula spp., Thyasira flexuosa, Mysella bidentata and Abra spp. In the south of Great Britain, the polychaete Sternaspis scutata is also characteristic of this biotope. This polychaete is rare in Great Britain (Sanderson 1996). Indeed, this southern variant of the biotope is very restricted in the UK to Portland Harbour but is known to occur further south in the Gulf of Gascony and the Mediterranean (Glemarec 1973; Dauvin et al. 1994).
Infralittoral, cohesive sandy mud, typically with over 20% silt/clay, in depths of less than 15-20m. This habitat is generally found in sheltered bays or marine inlets and along sheltered areas of open coast. Typical species include a rich variety of polychaetes including Melinna palmate, tube building amphipods (Ampelisca spp.) and deposit feeding bivalves such as Macoma balthica and Mysella bidentata. Sea pens such as Virgularia mirabilis and brittlestars such as Amphiura spp. may be present but not in the same abundances as found in deeper circalittoral waters.
Ampelisca spp., Photis longicaudata and other tube-building amphipods and polychaetes in infralittoral sandy mud
Sublittoral stable cohesive sandy muds occurring over a wide depth range may support large populations of semi-permanent tube-building amphipods and polychaetes. In particular large numbers of the amphipods Ampelisca spp. and Photis longicaudata may be present along with polychaetes such as Lagis koreni. Other important taxa may include bivalves such as Nucula nitidosa, Chamelea gallina, Abra alba and Mysella bidentata and the echinoderms Echinocardium cordatum and Amphiura brachiata. In some areas polychaetes such as Spiophanes bombyx and Polydora ciliata may also be conspicuously numerous. This community is poorly known, appearing to occur in restricted patches. In some areas it is possible that AmpPlon may develop as a result of moderate organic enrichment. A similar community in mud has also been reported in the Baltic which is characterised by large populations of amphipods such as Ampelisca spp., Corophium spp. and Haploops tubicola (see Petersen 1918; Thorson 1957) and it is not known if SMU.AmpPlon is a UK variant of this biotope.
Capitella capitata in enriched sublittoral muddy sediments
The polychaete Capitella capitata (agg.) a widely-occurring, opportunist species complex that is particularly associated with organically enriched and polluted sediments (Warren 1977; Pearson & Rosenberg 1978) where it may be superabundant. In very polluted/disturbed areas only Capitella, Nematodes and occasional Malacoceros fuliginosus may be found whilst in slightly less enriched areas and estuaries species such as Tubificoides, Cirriformia tentaculata, Pygospio elegans and Polydora ciliata may also be found. In some areas e.g. the Tees estuary, high numbers of the polychaete Ophryotrocha may also be present. Cap may become established as a result of anthropogenic activities such as fish farming and sewerage effluent but may also occur with natural enrichment as a result of, for example, coastal bird roosts. This biotope may also occur to some extent in the intertidal and in estuaries.
Melinna palmata with Magelona spp. and Thyasira spp. in infralittoral sandy mud
In infralittoral cohesive sandy mud, in sheltered marine inlets, and occasionally variable salinity environments, dense populations of the polychaete Melinna palmata may occur, often with high numbers of Magelona spp. and the bivalve Thyasira flexuosa. Other important taxa may include Chaetozone gibber, Nephtys hombergii, Galathowenia oculata, Euclymene oerstedii, Ampelisca tenuicornis, Ampharete lindstroemi, Abra alba, and Phoronis sp. In addition the polychaete Aphelochaeta spp. and the gastropod Turritella communis may be common or abundant in some areas. At the sediment surface visible taxa may include occasional Virgularia mirabilis, and mobile epifauna such as Pagurus bernhardus. This biotope is characteristic in many southern UK marine inlets and in some areas e.g. Plymouth Sound during high levels of recruitment when M. palmata often occurs in abundances between 500 to 1000 per m2 moderate numbers of the species often 'overspill' into adjacent biotopes (Allen et al. 2001).
Mysella bidentata and Abra spp. in infralittoral sandy mud
Cohesive sandy mud, sometimes with a small quantity of shell in shallow water may contain the bivalves Mysella bidentata and Abra spp. (typically A. alba and A. nitida). Other characteristic taxa may include Scoloplos armiger, Mya sp., and Thyasira flexuosa. Tube building amphipods are also characteristic of this biotope in particular Ampelisca spp. and Aoridae such as Microprotopus maculatus.
Nephtys hombergii and Macoma balthica in infralittoral sandy mud
Near-shore shallow sandy muds and muds, and sometimes mixed sediments, may be characterised by the presence of the polychaete Nephtys hombergii and the bivalve Macoma balthica. Abra alba, and Nucula nitidosa may also be important although they may not necessarily occur simultaneously or in high numbers. Other taxa include Spiophanes bombyx, Lagis koreni, and Echinocardium cordatum. In some areas Scoloplos armiger and Crangon crangon may also be present. The community appears to be quite stable (Dewarumez et al. 1992) and the substratum is typically rich in organic content. This community has been included in the 'Boreal Offshore Muddy Sand Association' of Jones (1950) and is also described by several other authors (Petersen 1918; Cabioch & Gla‡on 1975). A similar community may occur in deep water in the Baltic (Thorson 1957). This biotope may occur in slightly reduced salinity estuarine conditions where Mya sp. may become a significant member of the community (Thorson 1957).
Sagartiogeton undatus and Ascidiella aspersa on infralittoral sandy mud
Sheltered sublittoral mud or sandy mud in shallow water with relatively few conspicuous species may be characterised by the anemone Sagartiogeton undatus in low numbers and the tunicate Ascidiella aspersa. Other taxa may include Carcinus maenas, Pagurus bernhardus and terebellid polychaetes. The burrowing anemones Cerianthus lloydii may also be found occasionally. The status of this biotope is uncertain at present as it is not known whether it is an impoverished, disturbed or epifaunal variant of other sheltered, shallow mud biotopes such as PhiVir or if the areas in which it has been recorded have been incompletely surveyed.
In mud and cohesive sandy mud in the offshore circalittoral zone, typically below 50-70 m, a variety of faunal communities may develop, depending upon the level of silt/clay and organic matter in the sediment. Communities are typically dominated by polychaetes but often with high numbers of bivalves such as Thyasira spp., echinoderms and foraminifera.
Ampharete falcata turf with Parvicardium ovale on cohesive muddy sediment near margins of deep stratified seas
Dense stands of Ampharete falcata tubes which protrude from muddy sediments, appearing as a turf or meadow in localised areas. These areas seem to occur on a crucial point on a depositional gradient between areas of tide-swept mobile sands and quiescent stratifying muds. Dense populations of the small bivalve Parvicardium ovale occur in the superficial sediment. Other infauna in this diverse biotope includes Lumbrineris scopa, Levinsenia sp., Prionospio steenstrupi, Diplocirrus glaucus and Praxillella affinis although a wide variety of other infaunal species may also be found. Both the brittlestars Amphiura filiformis and Amphiura chiajei may be present together with Nephrops norvegicus in higher abundance than the BlyrAchi or AfilEcor biotopes. Substantial populations of mobile epifauna such as Pandalus montagui and smaller fish also occur, together with those that can cling to the tubes, such as Macropodia spp. A similar turf of worm tubes formed by the maldanid polychaete Melinna cristata has been recorded from Northumberland (Buchanan 1963). Nephrops trawling may severely damage this biotope and it is possible that such activity has destroyed examples of this biotope in the Irish Sea (E.I.S. Rees pers. comm. 2002).
Capitella capitata and Thyasira spp. in organically-enriched offshore circalittoral mud and sandy mud
In circalittoral and deep offshore mud and sandy mud adjacent to oil or gas platforms, organic enrichment from drill cuttings leads to the development of communities dominated by the Capitella capitata, an opportunist especially associated with organically enriched and polluted sediments as described for Cap (Warren 1977; Pearson & Rosenberg 1978). The bivalves Thyasira flexuosa or T. sarsi may also be found in moderate numbers at some sites. Other taxa may be present in low numbers in areas of less severe enrichment including Pholoe inornata, Lagis koreni, Philine scabra, Anaitides groenlandica, Mediomastus fragilis and Paramphinome jeffreysii.
Capitella capitata, Thyasira spp. and Ophryotrocha dubia in organically-enriched offshore circalittoral sandy mud
In deep offshore sandy mud adjacent to oil or gas platforms, organic enrichment from drill cuttings leads to the development of communities dominated by the pollution tolerant opportunist Capitella capitata and the polychaete Ophryotrocha dubia (or other species of Ophryotrocha). These species are generally found in extremely high abundances and accompanied by Thyasira spp., Raricirrus beryli, Paramphinome jeffreysii and Chaetozone setosa. Other taxa including Exogone verugera, Pholoe inornata and Idasola simpsoni may also be present.
Foraminiferans and Thyasira sp. in deep circalittoral fine mud
In deep water and soft muds of Boreal and Arctic areas, a community dominated by foraminiferans and the bivalve Thyasira sp. (e.g. T. croulinensis and T. pygmaea) may occur (Thorson 1957; Knitzer et al. 1992). Foraminiferans such as Saccammina, Psammosphaera, Haplophragmoides, Crithionina and Astorhiza are important components of this community with dead tests numbering thousands per m2 (see Stephen 1923; McIntyre 1961) and sometimes visible from benthic photography (Mackie, Oliver & Rees 1995). It is likely that a community dominated by Astorhiza in fine sands in the Irish Sea may be another distinct biotope (E.I.S. Rees pers. comm. 2002). Polychaetes, e.g. Paraonis gracilis, Myriochele heeri, Spiophanes kroyeri, Tharyx sp., Lumbrineris tetraura, are also important components of this biotope. These communities appear to have no equivalent on the continental plateau further south (Glemarec 1973) but are known from the edge of the Celtic Deep in the Irish Sea (Mackie, Oliver & Rees 1995). The benthos in these offshore areas has been shown to be principally Foraminifera and similar, rich communities may exist in Scottish sealochs (McIntyre 1961). Communities from yet deeper (northern) waters at the extremes of the North Sea may be reminiscent, although dissimilar to ForThy (see Pearson et al. 1996) reflecting a higher proportion of silt/clay. A fully Arctic version of this biotope has also been described (Thorson 1934, 1957) although it should be noted that Jones (1950) considered this Boreal foraminiferan community to be part of a 'Boreal Deep Mud Association'.
Levinsenia gracilis and Heteromastus filifirmis in offshore circalittoral mud and sandy mud
In deep offshore mud and sandy mud a community characterised by the polychaetes Levinsenia gracilis and Heteromastus filiformis may occur. Other important taxa may include Paramphinome jeffreysii, Nephtys hystricis and N. incisa, Spiophanes kroyeri, Orbinia norvegica, Terebellides stroemi, Thyasira gouldi and T. equalis. Burrowing megafauna such as Calocaris macandreae may also be found in this biotope. This biotope has been found in the central and northern North Sea. A similar community, dominated by L. gracilis but accompanied by Glycera spp. (particularly Glycera rouxii) and Monticellina dorsobranchialis, has also been reported from the Irish Sea. This Irish community also contains Calocaris macandreae, Mediomastus fragilis, Tubificoides amplivasatus, Nephtys incisa, Ancistrosyllis groenlandica, Nucula sulcata, Litocorsa stremma and Minuspio sp. and it is not known at present whether this represents a separate biotope or whether it is a geographic variant of a wider Levinsenia biotope.
Myrtea spinifera and polychaetes in offshore circalittoral sandy mud
Deep, offshore habitats with cohesive sandy mud (>20% mud) may support communities characterised by infaunal polychaetes and the bivalve Myrtea spinifera. Polychaetes typically include Chaetozone setosa, Paramphinome jeffreysii, Levinsenia gracilis, Aricidea catherinae and Prionospio malmgreni. The bivalves Thyasira spp. and Abra nitida may also be found as may seapens, such as Pennatula phosphorea. Some examples of the biotope AfilNten contain Myrtea spinifera (Mackie 1990) in lower numbers but these habitats are generally sandier than those in MyrPo.
Paramphinome jeffreysii, Thyasira spp. and Amphiura filiformis in offshore circalittoral sandy mud
Deep, offshore cohesive sandy mud communities characterised by the polychaete Paramphinome jeffreysii, bivalves such as Thyasira equalis and T. gouldi and the brittlestar Amphiura filiformis. Other taxa may include Laonice cirrata, the sea cucumber Labidoplax buski and the polychaetes Goniada maculata, Spiophanes kroyeri and Aricidea catherinae. Amphiura chiajei may be occasional in this biotope as may Philine scabra, Levinsenia gracilis and Pholoe inornata. This biotope along with SMU.ThyNten, SMU.AfilMysAnit, SMU.AfilNten and SSA.OfusAfil, may comprise the Amphiura dominated components of the 'off-shore muddy sand association' (Jones 1951; Mackie 1990) and the infralittoral etage described by Glemarec (1973).
Styela gelatinosa, Pseudamussium septemradiatum and solitary ascidians on sheltered deep circalittoral muddy sediment
This biotope is known only from deep water in Loch Goil (Clyde sealochs) in fine mud at 65 m with terrigenous debris. Large numbers of solitary ascidians, including Styela gelatinosa, Ascidia conchilega, Corella parallelogramma and Ascidiella spp., are characteristic of this biotope together with the bivalve Pseudamussium septemradiatum. Terebellid worms, the bivalve Abra alba and the polychaete Glycera tridactyla may also occur. It is possibly an ice age relict biotope.
Sublittoral mud in low or reduced salinity (lagoons)
Shallow, typically anoxic, muddy and sandy mud sediments in areas of low or reduced, although stable, salinity (may vary annually) with largely ephemeral faunal communities. Characterised by Arenicola marina and blue-green algae with other species, including mysids, Carcinus maenas and Corophium volutator which commonly occur in lagoons. Important infaunal species may include Hediste diversicolor, Heterochaeta costata and chironomids; however infaunal records for this biotope are limited.
Sublittoral mud in variable salinity (estuaries)
Shallow sublittoral muds, extending from the extreme lower shore into the subtidal in variable salinity (estuarine) conditions. Such habitats typically support communities characterised by oligochaetes, and polychaetes such as Aphelochaeta marioni. In lowered salinity conditions the sediments may include a proportion of coarser material, where the silt content is sufficient to yield a similar community to that found in purer muds.
Aphelochaeta marioni and Tubificoides spp. in variable salinity infralittoral mud
Variable salinity cohesive muddy sediment (sometimes with some coarser material) dominated by the polychaete Aphelochaeta marioni (or other Aphelochaeta species e.g. A. amplivasatus) and the oligochaete Tubificoides spp. These taxa are generally accompanied by Nephtys hombergii whilst the polychaetes Capitella capitata and Melinna palmata may also occur in high numbers in some areas. Other members of the cirratulid polychaete group e.g. Caulleriella zetlandica. and Tharyx spp. may also occur in high numbers, sometimes replacing A. marioni as the dominant polychaete. However, there is still inconsistency in the identification of the cirratulid group which is further compounded by fragmentation during sample processing. This biotope is very common in stable muddy environments and may extend from reduced salinity to fully marine conditions.
Capitella capitata and Tubificoides spp. in reduced salinity infralittoral muddy sediment
Reduced or variable salinity muddy sediment characterised by the Capitella capitata species complex with a relatively low species richness. Large numbers of the oligochaetes Tubificoides spp. may be found in conjunction with C. capitata, along with other species such as Marenzellaria sp, Macoma balthica, Arenicola marina and Eteone longa. In some estuaries this biotope may also include high numbers of the polychaete Ophryotrocha. This biotope usually has a moderate organic content, and is found away from tidal channels in estuaries. The presence of dense Capitella has classically been associated with organically enriched and physically disturbed habitats in the marine environment (Warren 1977; Pearson & Rosenberg 1978) and areas of higher organic loads in estuaries will typically fall into the biotope Cap. Where Capitella is less abundant and accompanied by other typical estuarine species the dominance of Capitella may be associated with other natural factors including the occurrence of a competitive refuge for C. capitata in the reduced-salinity environment (Wolff 1973).
Limnodrilus hoffmeisteri, Tubifex tubifex and Gammarus spp. in low salinity infralittoral muddy sediment
Upper estuary muddy sediments with very low fluctuating salinity, characterised by the oligochaetes Limnodrilus hoffmeisteri and Tubifex tubifex. Other taxa may include Marenzelleria wireni, Gammarus zaddachi, Paranais litoralis and Heterochaeta costata. The biotope contains elements of both freshwater and brackish communities.
Fluid mobile mud suspended and deposited on each tide. In areas with very high quantities of suspended particulate material in the water column it may become deposited around slack water when tidal currents fall. This can form fluid mud layers up to several metres thick (Warwick & Uncles 1980) becoming a transient habitat in its own right. Species present within this biotope will be those washed in from other communities such as Nephtys hombergii or Capitella capitata. This biotope may be under-recorded due to sampling problems, and also where sediment descriptions are absent from field data.
Nephtys hombergii and Tubificoides spp. in variable salinity infralittoral soft mud
Variable salinity soft infralittoral mud and sandy mud characterised by the polychaete Nephtys hombergii and oligochaetes of the genus Tubificoides. Other characterising species that may be present are the polychaetes Streblospio shrubsolii and Aphelochaeta marioni, and the cumacean Diastylis rathkei typica.
Oligochaetes in variable or reduced salinity infralittoral muddy sediment
Reduced or variable salinity muddy and sandy mud sediments characterised by oligochaetes, particularly of the genus Tubificoides or from the group Enchytraeidae. The abundance of the oligochaetes may vary by several orders of magnitude but very few other species will be present. Organic loading and poor water-exchange within the sediment lead to anoxic conditions which may explain the low species richness within this biotope.
Polydora ciliata and Corophium volutator in variable salinity infralittoral firm mud or clay
Variable salinity clay and firm mud characterised by a turf of the polychaete Polydora ciliata along with the amphipod Corophium volutator. Other important taxa include the polychaetes Pygospio elegans, Hediste diversicolor, Streblospio shrubsolii and the oligochaete Tubificoides benedii. P. ciliata also occurs in high densities elsewhere (see MCR.Pol) and may be a specific feature of the Humber Estuary in these conditions. This biotope occurs only in very firm mud and clay and possibly submerged relict saltmarsh with a high detrital content. It is characterised, and can be separated from other biotopes, by a combination of the sediment characteristics and the very high density of Polydora ciliata. In some areas, such as the Humber estuary, cyclical behaviour with regard its characteristic taxa has been reported with either P. ciliata or C. volutator increasing in dominance at the expense of the other (Gameson 1982). It is possible that changes in water quality or the sediment regime may be responsible for this.
Sublittoral mixed (heterogeneous) sediments found from the extreme low water mark to deep offshore circalittoral habitats. These habitats incorporate a range of sediments including heterogeneous muddy gravelly sands and also mosaics of cobbles and pebbles embedded in or lying upon sand, gravel or mud. There is a degree of confusion with regard nomenclature within this complex as many habitats could be defined as containing mixed sediments, in part depending on the scale of the survey and the sampling method employed. The BGS trigon can be used to define truly mixed or heterogeneous sites with surficial sediments which are a mixture of mud, gravel and sand. However, another 'form' of mixed sediment includes mosaic habitats such as superficial waves or ribbons of sand on a gravel bed or areas of lag deposits with cobbles/pebbles embedded in sand or mud and these are less well defined and may overlap into other habitat or biotope complexes. These habitats may support a wide range of infauna and epibiota including polychaetes, bivalves, echinoderms, anemones, hydroids and Bryozoa. Mixed sediments with biogenic reefs or macrophyte dominated communities are classified separately in the SBR and SMP habitat complexes respectively.
Mixed (heterogeneous) sediment habitats in the circalittoral zone (generally below 15-20m) including well mixed muddy gravelly sands or very poorly sorted mosaics of shell, cobbles and pebbles embedded in or lying upon mud, sand or gravel. Due to the variable nature of the seabed a variety of communities can develop which are often very diverse. A wide range of infaunal polychaetes, bivalves, echinoderms and burrowing anemones such as Cerianthus lloydii are often present in such habitat and the presence of hard substrata (shells and stones) on the surface enables epifaunal species to become established, particularly hydroids such as Nemertesia spp and Hydrallmania falcata. The combination of epifauna and infauna can lead to species rich communities. Coarser mixed sediment communities may show a strong resemblance, in terms of infauna, to biotopes within the SCS complex. However, infaunal data for this biotope complex is limited to that described under the biotope MysThyMx, and so are not representative of the infaunal component of this biotope complex.
Sparse Modiolus modiolus, dense Cerianthus lloydii and burrowing holothurians on sheltered circalittoral stones and mixed sediment
Pebbles and cobbles on mud or muddy gravel in sealochs with frequent Cerianthus lloydii and occasional Modiolus modiolus. Large burrowing holothurians may include Psolus phantapus, Paracucumaria hyndmani, Thyonidium commune, Thyone fusus and Leptopentacta elongate. Many of these species only extend their tentacles above the sediment surface seasonally and are likely to be under recorded by epifaunal surveys. Other more conspicuous characterising taxa include Pagurus bernhardus, Asterias rubens, and Buccinum undatum. This biotope is well developed in the Clyde sealochs, although many examples are rather species-poor. Some examples in south-west Scottish sealochs have greater quantities of boulders and cobbles and therefore have a richer associated biota (compared with other sheltered Modiolus bed biotopes such as ModHAs). Examples in Shetland are somewhat different in having the cucumber Cucumaria frondosa amongst sparse Modiolus beds and a slightly different balance in abundance of other species; for example the brittlestar Ophiopholis aculeata is more abundant in these far northern examples in the voes and narrows.
Cerianthus lloydii and other burrowing anemones in circalittoral muddy mixed sediment
Circalittoral plains of sandy muddy gravel may be characterised by burrowing anemones such as Cerianthus lloydii. Other burrowing anemones such as Cereus pedunculatus, Mesacmaea mitchellii and Aureliania heterocera may be locally abundant. Relatively few conspicuous species are found in any great number in this biotope but typically they include ubiquitous epifauna such as Asterias rubens, Pagurus bernhardus and Liocarcinus depurator with occasional terebellid polychaetes such as Lanice conchilega and also the clam Pecten maximus. Ophiura albida may be frequent in some areas, and where surface shell or stones are present ascidians such as Ascidiella aspersa may occur in low numbers.
Cerianthus lloydii with Nemertesia spp. and other hydroids in circalittoral muddy mixed sediment
In sheltered muddy sandy gravel with appreciable quantities of surficial cobbles, pebbles and shells a community similar to ClloMx may develop with frequent Cerianthus lloydii and other burrowing anemones. However, the pebbles and cobbles embedded in the sediment are colonised by hydroids and in particular Nemertesia antennina and N. ramosa. Other hydroids may include Kirchenpaueria pinnata and Halecium halecinum whilst ascidians such as Ascidiella aspersa or Corella parallelogramma may also be present locally. Pecten maximus and Pomatoceros triqueter may also be frequent in certain areas.
Flustra foliacea and Hydrallmania falcata on tide-swept circalittoral mixed sediment
This biotope represents part of a transition between sand-scoured circalittoral rock where the epifauna is conspicuous enough to be considered as a biotope and a sediment biotope where an infaunal sample is required to characterise it and is possibly best considered an epibiotic overlay. Flustra foliacea and the hydroid Hydrallmania falcata characterise this biotope; lesser amounts of other hydroids such as Sertularia argentea, Nemertesia antennina and occasionally Nemertesia ramose, occur where suitably stable hard substrata is found. The anemone Urticina feline and the soft coral Alcyonium digitatum may also characterise this biotope. Barnacles Balanus crenatus and tube worms Pomatoceros triqueter may be present and the robust bryozoans Alcyonidium diaphanum and Vesicularia spinosa appear amongst the hydroids at a few sites. Sabella pavonina and Lanice conchilega may be occasionally found in the coarse sediment around the stones. In shallower (i.e. upper circalittoral) examples of this biotope scour-tolerant robust red algae such as Polysiphonia nigrescens, Calliblepharis spp. and Gracilaria gracilis are found.
Mysella bidentata and Thyasira spp. in circalittoral muddy mixed sediment
In moderately exposed or sheltered, circalittoral muddy sands and gravels a community characterised by the bivalves Thyasira spp. (often Thyasira flexuosa), Mysella bidentata and Prionospio fallax may develop. Infaunal polychaetes such as Lumbrineris gracilis, Chaetozone setosa and Scoloplos armiger are also common in this community whilst amphipods such as Ampelisca spp. and the cumacean Eudorella truncatula may also be found in some areas. The brittlestar Amphiura filiformis may also be abundant at some sites. Conspicuous epifauna may include encrusting bryozoans Escharella spp. particularly Escharella immersa and, in shallower waters, maerl (Phymatolithon calcareum), although at very low abundances and not forming maerl beds.
Ophiothrix fragilis and/or Ophiocomina nigra brittlestar beds on sublittoral mixed sediment
Circalittoral sediment dominated by brittlestars (hundreds or thousands m-2) forming dense beds, living epifaunally on boulder, gravel or sedimentary substrata. Ophiothrix fragilis and Ophiocomina nigra are the main bed-forming species, with rare examples formed by Ophiopholis aculeate. Brittlestar beds vary in size, with the largest extending over hundreds of square metres of sea floor and containing millions of individuals. They usually have a patchy internal structure, with localized concentrations of higher animal density. Ophiothrix fragilis or Ophiocomina nigra may dominate separately or there may be mixed populations of the two species. Ophiothrix beds may consist of large adults and tiny, newly-settled juveniles, with animals of intermediate size living in nearby rock habitats or among sessile epifauna. Unlike brittlestar beds on rock, the sediment based beds may contain a rich associated epifauna (Warner, 1971; Allain, 1974; Davoult & Gounin, 1995). Large suspension feeders such as the octocoral Alcyonium digitatum, the anemone Metridium senile and the hydroid Nemertesia antennina are present mainly on rock outcrops or boulders protruding above the brittlestar-covered substratum. The large anemone Urticina feline may be quite common. This species lives half-buried in the substratum but is not smothered by the brittlestars, usually being surrounded by a 'halo' of clear space (Brun, 1969; Warner, 1971). Large mobile animals commonly found on Ophiothrix beds include the starfish Asterias rubens, Crossaster papposus and Luidia ciliaris, the urchins Echinus esculentus and Psammechinus miliaris, edible crabs Cancer pagurus, swimming crabs Necora puber, Liocarcinus spp., and hermit crabs Pagurus bernhardus. The underlying sediments also contain a diverse infauna including the bivalve Abra alba. Warner (1971) found that numbers and biomass of sediment dwelling animals were not significantly reduced under dense brittlestar patches.
Shallow mixed (heterogeneous) sediments in fully marine or near fully marine conditions, supporting various animal-dominated communities, with relatively low proportions of seaweeds. This habitat may include well mixed muddy gravelly sands or very poorly sorted mosaics of shell, cobbles and pebbles embedded in mud, sand or gravel. Due to the quite variable nature of the sediment type, a widely variable array of communities may be found, including those characterised by bivalves (SMX.VsenAsquAps, SMX.CreAsAn, and SMX.Ost), polychaetes (SMX.SpavSpAn) and file shells (SMX.Lim). This has resulted in many species being described as characteristic of this biotope complex all contributing only a small percentage to the overall similarity (see below). This biotope complex may also include a newly proposed Chaetopterus biotope (Rees pers com.) recently found in the eastern English Channel. This biotope is characterised by an undescribed Chaetopterus sp. and small Lanice conchilega. Further sampling is need in order to assess and fully characterise this potential biotope. As a result, the Chaetopterus biotope has not been included in this revision. Infaunal data for this biotope complex are limited to that described in the biotope SMX.VsenAsquAps and so are not representative of the infaunal component of the whole biotope complex.
Crepidula fornicata with ascidians and anemones on infralittoral coarse mixed sediment
Medium-coarse sands with gravel, shells, pebbles and cobbles on moderately exposed coasts may support populations of the slipper limpet Crepidula fornicata with ascidians and anemones. C. fornicata is common in this biotope though not as abundant as in the muddier estuarine biotope CreMed to which this is related. Anemones such as Urticina felina and Alcyonium digitatum and ascidians such as Styela clava are typically found in this biotope. Bryozoans such as Flustra foliacea are also found along with polychaetes such as Lanice conchilega. Little information is available with regard the infauna of this biotope but given the nature of the sediment the infaunal communities are liable to resemble those in biotopes from the SCS habitat complex. As with FluHyd this biotope could be considered a superficial or epibiotic overlay but more data is required to support this.
Limaria hians beds in tide-swept sublittoral muddy mixed sediment
Mixed muddy gravel and sand often in tide-swept narrows in the entrances or sills of sealochs with beds or 'nests' of Limaria hians. The Limaria form woven 'nests' or galleries from byssus and fragments of seaweeds so that the animals themselves cannot be seen from above the seabed. Modiolus modiolus sometimes occur at the same sites lying over the top of the Limaria bed. Other fauna associated with this biotope include echinoderms (Ophiothrix fragilis, Ophiocomina nigra and Asterias rubens), Buccinum undatum, mobile crustaceans (e.g. Pagurus bernhardus), Alcyonium digitatum and hydroids such as Plumularia setacea, Kirchenpaueria pinnata and Nemertesia spp. Sometimes red seaweeds such as Phycodrys rubens occur if the beds are in shallow enough water.
Ostrea edulis beds on shallow sublittoral muddy mixed sediment
Dense beds of the oyster Ostrea edulis can occur on muddy fine sand or sandy mud mixed sediments. There may be considerable quantities of dead oyster shell making up a substantial portion of the substratum. The clumps of dead shells and oysters can support large numbers of Ascidiella aspersa and Ascidiella scabra. Sponges such as Halichondria bowerbanki may also be present. Several conspicuously large polychaetes, such as Chaetopterus variopedatus and terebellids, as well as additional suspension-feeding polychaetes such as Myxicola infundibulum and Sabella pavonina may be important in distinguishing this biotope, whilst the Opisthobranch Philine aperta may also be frequent in some areas. A turf of seaweeds such as Plocamium cartilagineum, Nitophyllum punctatum and Spyridia filamentosa may also be present. This biotope description may need expansion to account for oyster beds in England.
Sabella pavonina with sponges and anemones on infralittoral mixed sediment
Muddy gravelly sand with pebbles off shallow, sheltered or moderately exposed coasts or embayments may support dense populations of the peacock worm Sabella pavonina. This community may also support populations of sponges such as Esperiopsis fucorum, Haliclona oculata and Halichondria panicea and anemones such as Sagartia elegans, Cerianthus lloydii and Urticina felina. Hydroids such as Hydrallmania falcata and the encrusting polychaete Pomatoceros triqueter are also important. This biotope may have an extremely diverse epifaunal community. Less is known about its infaunal component, although it is likely to include polychaetes such as Nephtys spp., Harmothoe spp., Glycera spp., syllid and cirratulid polychaetes, bivalves such as Abra spp., Aoridae amphipods and brittlestars such as Amphipholis squamata.
Venerupis senegalensis, Amphipholis squamata and Apseudes latreilli in infralittoral mixed sediment
Sheltered muddy sandy gravel and pebbles in marine inlets, estuaries or embayments with variable salinity or fully marine conditions, support large populations of the pullet carpet shell Venerupis senegalensis with the brittlestar Amphipholis squamata and the tanaid Apseudes latreilli. This biotope may be found at a range of depths from 5m to 30m although populations of V. senegalensis may also be found on the low shore. Other common species within this biotope include the gastropod Calyptraea chinensis, a range of amphipod crustacea such as Corophium sextonae and Maera grossimana and polychaetes such as Mediomastus fragilis, Melinna palmata, Aphelochaeta marioni, Syllids and tubificid oligochaetes. Many of the available records for this biotope are from southern inlets and estuaries such as Plymouth Sound and Milford Haven but V. senegalensis has a much wider distribution and it should be noted that northern versions of this biotope may a have a much lower species diversity than reported here.
Offshore (deep) circalittoral habitats with slightly muddy mixed gravelly sand and stones or shell. This habitat may cover large areas of the offshore continental shelf although there is relatively little data available. Such habitats are often highly diverse with a high number of infaunal polychaete and bivalve species. Animal communities in this habitat are closely related to offshore gravels and coarse sands and in some areas populations of the horse mussel Modiolus modiolus may develop in these habitats (see SBR.ModMx). Only one biotope is currently described under this biotope complex.
Polychaete-rich deep Venus community in offshore mixed sediments
In offshore circalittoral slightly muddy mixed sediments, a diverse community particularly rich in polychaetes with a significant venerid bivalve component may be found. Typical species include the polychaetes Glycera lapidum, Aonides paucibranchiata, Laonice bahusiensis, Mediomastus fragilis, Lumbrineris gracilis, Pseudomystides limbata, Protomystides bidentata and syllid species and bivalves such as Timoclea ovata, Glycymeris glycymeris, Spisula elliptica and Goodallia triangularis. This biotope has been recorded on surveys of the Lambay and Codling Deeps and other areas of the Irish Sea and collectively with MedLumVen comprise the 'Deep Venus Community' and the 'Boreal Off-Shore Gravel Association' as defined by other workers (Ford 1923; Jones 1950). Some examples of this biotope may have abundant juvenile Modiolus modiolus.
Sublittoral mixed sediment in low or reduced salinity (lagoons)
Shallow, muddy mixed sediments in areas of low or reduced, although stable, salinity (may vary annually) with largely ephemeral faunal communities. Characterised infaunally by oligochaetes, including Heterochaeta costata and members of the Enchytraeidae, polychaetes such as Hediste diversicolor, Polydora ciliata and Pygospio elegans,and bivalves such as Mya arenaria and the lagoon cockle Cerastoderma glaucum. These bivalve species may also form conspicuious members of the epifauna together with more ubiquitous species like the common goby Pomatoschistus microps.
Sublittoral mixed sediment in variable salinity (estuaries)
Shallow sublittoral mixed sediments in estuarine conditions, often with surface shells or stones, enabling the development of diverse epifaunal communities, e.g. Crepidula fornicata (IMX.CreAph), as well as infaunal communities. This biotope complex is therefore often quite species rich, compared with purer sediments.
Aphelochaeta spp. and Polydora spp. in variable salinity infralittoral mixed sediment
In sheltered muddy mixed sediments in estuaries or marine inlets with variable or reduced/low salinity communities characterised by Aphelochaeta marioni and Polydora ciliata may be present. Other important taxa may include the polychaetes Nephtys hombergii, Caulleriella zetlandica and Melinna palmata, tubificid oligochaetes and bivalves such as Abra nitida. Conspicuous epifauna may include members of the bivalve family Cardiidae (cockles) and the slipper limpet Crepidula fornicata. This biotope is often found in polyhaline waters.
Crepidula fornicata and Mediomastus fragilis in variable salinity infralittoral mixed sediment
Variable salinity mixed sediment characterised by the slipper limpet Crepidula fornicata and the polychaetes Mediomastus fragilis and Aphelochaeta marioni. Other numerically important taxa include the oligochaetes Tubificoides benedii, syllids such as Exogone naidina and Sphaerosyllis, and Nephtys hombergii. Lepidonotus squamatus and Scoloplos armiger may also be common. Shell debris and cobbles are colonised by the ascidians Ascidiella aspersa, Ascidiella scabra, Molgula sp. and Dendrodoa grossularia (the ascidians may not be recorded adequately by remote infaunal survey techniques).
Clean medium to fine sands or non-cohesive slightly muddy sands on open coasts, offshore or in estuaries and marine inlets. Such habitats are often subject to a degree of wave action or tidal currents which restrict the silt and clay content to less than 15%. This habitat is characterised by a range of taxa including polychaetes, bivalve molluscs and amphipod crustacea.
Clean fine sands with less than 5% silt/clay in deeper water, either on the open coast or in tide-swept channels of marine inlets in depths of over 15-20m. The habitat may also extend offshore and is characterised by a wide range of echinoderms (in some areas including the pea urchin Echinocyamus pusillus), polychaetes and bivalves. This habitat is generally more stable than shallower, infralittoral sands and consequently supports a more diverse community.
Abra prismatica, Bathyporeia elegans and polychaetes in circalittoral fine sand
In circalittoral and offshore medium to fine sands between 25m and 100m a community characterised by the bivalve Abra prismatica, the amphipod Bathyporeia elegans and polychaetes such as Scoloplos armiger, Spiophanes bombyx, Aonides paucibranchiata, Chaetozone setosa, Ophelia borealis and Nephtys longosetosa may be found. Crustacea such as the cumacean Eudorellopsis deformis and the opheliid polychaetes such as Ophelia borealis, Travisia forbesii or Ophelina neglecta are often present in this biotope and the brittlestar Amphiura filiformis may also be common at some sites. This biotope has been reported in the central and northern North Sea ( Basford and Eleftheriou, 1989; Knitzer et al., 1992).
Echinocyamus pusillus, Ophelia borealis and Abra prismatica in circalittoral fine sand
Circalittoral and offshore medium to fine sand (from 40m to 140m) characterised by the pea urchin Echinocyamus pusillus, the polychaete Ophelia borealis and the bivalve Abra prismatica. Other species may include the polychaetes Spiophanes bombyx, Pholoe sp., Exogone spp., Sphaerosyllis bulbosa, Goniada maculata, Chaetozone setosa, Owenia fusiformis, Glycera lapidum, Lumbrineris latreilli and Aricidea cerrutii and the bivalves Thracia phaseolina and Moerella pygmaea and to a lesser extent Spisula elliptica and Timoclea ovata. This biotope has been found in the central and northern North Sea.
Circalittoral non-cohesive muddy sands with the silt content of the substratum typically ranging from 5% to 20%. This habitat is generally found in water depths of over 15-20m and supports animal-dominated communities characterised by a wide variety of polychaetes, bivalves such as Abra alba and Nucula nitidosa, and echinoderms such as Amphiura spp and Ophiura spp., and Astropecten irregularis. These circalittoral habitats tend to be more stable than their infralittoral counterparts and as such support a richer infaunal community.
Abra alba and Nucula nitidosa in circalittoral muddy sand or slightly mixed sediment
Non-cohesive muddy sands or slightly shelly/gravelly muddy sand characterised by the bivalves Abra alba and Nucula nitidosa. Other important taxa include Nephtys spp., Chaetozone setosa and Spiophanes bombyx with Fabulina fabula also common in many areas. The echinoderms Ophiura albida and Asterias rubens may also be present. The epibiotic biotope EcorEns may overlap this biotope. This biotope is part of the Abra community defined by Thorson (1957) and the infralittoral etage described by Glemarec (1973).
Amphiura brachiata with Astropecten irregularis and other echinoderms in circalittoral muddy sand
In shallow, circalittoral non-cohesive muddy sand (typically less than 20% silt/clay) abundant populations of the brittlestar Amphiura brachiata may occur with other echinoderms such as Astropecten irregularis, Asterias rubens, Ophiura ophiura and Echinocardium cordatum. Other infaunal species typically include Mysella bidentata, Lanice conchilega and Magelona filiformis. This biotope is likely to form part of the non-cohesive/cohesive muddy sand communities, which make up the 'off-shore muddy sand association' described by other workers (Jones 1951; Mackie 1990). It is possible that in some areas this biotope forms an epifaunal overlay which may cover a range of biotopes in years of good recruitment but does not develop into a settled or established community.
Clean sands which occur in shallow water, either on the open coast or in tide-swept channels of marine inlets. The habitat typically lacks a significant seaweed component and is characterised by robust fauna, particularly amphipods (Bathyporeia) and robust polychaetes including Nephtys cirrosa and Lanice conchilega.
Infralittoral mobile clean sand with sparse fauna
Medium to fine sandy sediment in shallow water, often formed into dunes, on exposed or tide-swept coasts often contains very little infauna due to the mobility of the substratum. Some opportunistic populations of infaunal amphipods may occur, particularly in less mobile examples in conjunction with low numbers of mysids such as Gastrosaccus spinifer, the polychaete Nephtys cirrosa and the isopod Eurydice pulchra. Sand eels Ammodytes sp. may occasionally be observed in association with this biotope (and others). This biotope is more mobile than SSA.NcirBat and may be closely related to LSa.BarSa on the shore. Common epifaunal species such as Pagurus bernhardus, Liocarcinus depurator, Carcinus maenas and Asterias rubens may be encountered and are the most conspicuous species present.
Nephtys cirrosa and Bathyporeia spp. in infralittoral sand
Well-sorted medium and fine sands characterised by Nephtys cirrosa and Bathyporeia spp. (and sometimes Pontocrates spp.) which occur in the shallow sublittoral to at least 30 m depth. This biotope occurs in sediments subject to physical disturbance, as a result of wave action (and occasionally strong tidal streams). The magelonid polychaete Magelona mirabilis may be frequent in this biotope in more sheltered, less tideswept areas whilst in coarser sediments the opportunistic polychaete Chaetozone setosa may be commonly found. The faunal diversity of this biotope is considerably reduced compared to less disturbed biotopes (such as FfabMag) and for the most part consists of the more actively-swimming amphipods. Sand eels Ammodytes sp. may occasionally be observed in association with this biotope (and others) and spionid polychaetes such as Spio filicornis and S. martinensis may also be present. Occasional Lanice conchilega may be visible at the sediment surface.
Sertularia cupressina and Hydrallmania falcata on tide-swept sublittoral sand with cobbles or pebbles
Shallow sands with cobbles and pebbles, exposed to strong tidal streams, with conspicuous colonies of hydroids, particularly Hydrallmania falcata and to a lesser extent Sertularia cupressina and S. argentea. These hydroids are tolerant to periodic submergence and scour by sand. Both diving and dredge surveys will easily record this biotope. Flustra foliacea, Balanus crenatus and Alcyonidium diaphanum may also occur on the more stable cobbles and pebbles, with Urticina felina and occasional Lanice conchilega present in the sand. Infaunal components of the other biotopes in the SSA or SCS complex may occur in this biotope as may elements of the 'Venus' associations; indeed, this biotope may be at one extreme of the spectrum of such associations (E.I.S. Rees pers. comm. 1997) and this biotope may be best considered an epibiotic overlay.
Semi-permanent tube-building amphipods and polychaetes in sublittoral sand
Sublittoral marine sand in moderately exposed or sheltered inlets and voes in shallow water may support large populations of semi-permanent tube-building amphipods and polychaetes. Typically dominated by Corophium crassicorne with other tube building amphipods such as Ampelisca spp. also common. Other taxa include typical shallow sand fauna such as Spiophanes bombyx, Urothoe elegans, Bathyporeia spp. along with various polychaetes including Exogone hebes and Lanice conchilega. Polydora ciliata may also be abundant in some areas. At the sediment surface, Arenicola marina worm casts may be visible and occasional seaweeds such as Laminaria saccharina may be present. As many of the sites featuring this biotope are situated near to fish farms it is possible that it may have developed as the result of moderate nutrient enrichment. The distribution of this biotope is poorly known and like the muddier SMU.AmpPlon, to which it is related, appears to have a patchy distribution.
Non-cohesive muddy sand (with 5% to 20% silt/clay) in the infralittoral zone, extending from the extreme lower shore down to more stable circalittoral zone at about 15-20 m. The habitat supports a variety of animal-dominated communities, particularly polychaetes (Magelona mirabilis, Spiophanes bombyx and Chaetozone setosa), bivalves (Fabulina fibula and Chamelea gallina) and the urchin Echinocardium cordatum.
Echinocardium cordatum and Ensis spp. in lower shore and shallow sublittoral slightly muddy fine sand
Sheltered lower shore and shallow sublittoral sediments of sand or muddy fine sand in fully marine conditions, support populations of the urchin Echinocardium cordatum and the razor shell Ensis siliqua or Ensis ensis. Other notable taxa within this biotope include occasional Lanice conchilega, Pagurus and Liocarcinus spp. and Asterias rubens. This biotope has primarily been recorded by epifaunal dive, video or trawl surveys where the presence of relatively conspicuous taxa such as E. cordatum and Ensis spp. have been recorded as characteristic of the community. However, these species, particularly E. cordatum have a wide distribution and are not necessarily the best choice for a characteristic taxa (Thorson, 1957). Furthermore, detailed quantitative infaunal data for this biotope is often rather scarce, possibly as a result of survey method as remote grab sampling is likely to under-estimate deep-burrowing species such as Ensis sp. (Warwick & Davis 1977). Consequently, it may be better to treat this biotope as an epibiotic overlay which is likely to overlap a number of other biotopes such as FfabMag, NcirBat and AalbNuc with infaunal components of these biotopes occurring within EcorEns. The precise nature of this infaunal community will be related to the nature of the substratum, in particular the quantity of silt/clay present. Infaunal species may include the polychaetes Spiophanes bombyx, Magelona mirabilis, Nephtys cirrosa and Chaetozone setosa and the amphipod Bathyporeia spp. This biotope is currently broadly defined and needs further consideration as to whether it should be placed at biotope or biotope complex level. AreISa is another biotope based primarily on epibiotic data. It is likely that this biotope and EcorEns form a wider epibiotic sand /muddy sand community with EcorEns biased towards sandier areas and SSA.AreISa towards slightly muddier areas.
Fabulina fabula and Magelona mirabilis with venerid bivalves and amphipods in infralittoral compacted fine muddy sand
In stable, fine, compacted sands and slightly muddy sands in the infralittoral and littoral fringe, communities occur that are dominated by venerid bivalves such as Chamelea gallina. This biotope may be characterised by a prevalence of Fabulina fabula and Magelona mirabilis or other species of Magelona (e.g. M. filiformis). Other taxa, including the amphipod Bathyporeia spp. and polychaetes such as Chaetozone setosa, Spiophanes bombyx and Nephtys spp. are also commonly recorded. In some areas the bivalve Spisula elliptica may also occur in this biotope in low numbers. The community is relatively stable in its species composition, however, numbers of Magelona and F. Fabulina tend to fluctuate. Around the Scilly Isles numbers of F. fabulina in this biotope are uncommonly low whilst these taxa are often found in higher abundances in muddier communities (presumably due to the higher organic content). Consequently it may be better to revise this biotope on the basis of less ubiquitous taxa such as key amphipod species (E.I.S. Rees pers. comm. 2002) although more data is required to test this. FfabMag and MoeVen are collectively considered to be the 'shallow Venus community' or 'boreal off-shore sand association' of previous workers (see Petersen 1918; Jones 1950; Thorson 1957). These communities have been shown to correlate well with particular levels of current induced 'bed-stress' (Warwick & Uncles 1980). The 'Arctic Venus Community' and 'Mediterranean Venus Community' described to the north and south of the UK (Thorson 1957) probably occur in the same habitat and appears to be the same biotope described as the Ophelia borealis community in northern France and the central North Sea (Knitzer et al. 1992). Sites with this biotope may undergo transitions in community composition. The epibiotic biotopes EcorEns and AreISa may also overlay this biotope in some areas.
Spisula subtruncata and Nephtys hombergii in shallow muddy sand
In shallow non-cohesive muddy sands, in fully marine conditions, a community characterised by the bivalve Spisula subtruncata and the polychaete Nephtys hombergii may occur. The sediments in which this community is found may vary with regard silt content but they generally have less than 20% silt/clay and in some areas may contain a degree of shell debris. This biotope falls somewhere between SSA.FfabMag and SSA.AalbNuc with regard sediment type (i.e. somewhat muddier than SSA.FfabMag and less muddy than SSA.AalbNuc) and may have species in common with both. As a result, other important species in this community include Abra alba, Fabulina fabula spp. and Mysella bidentata spp. In addition, Diastylis rathkei/typical, Philine aperta (in muddier sediments), Ampelisca spp., Ophiura albida, Phaxas pellucidus and occasionally Bathyporeia spp, may also be important, although this is not clear from the data available. In areas of slightly coarser, less muddy sediment S. solida or S. elliptica may appear occasionally in this biotope. Abundances of Spisula subtruncata in this biotope are often very high and distinguish it from other closely related biotopes. Extensive areas of this community to the north east of the Dogger Bank were recorded in the 1950s, but these seem to have declined since then (Kroncke 1990). More information is required with regard the status of this biotope.
Offshore (deep) circalittoral habitats with fine sands or non-cohesive muddy sands. Very little data is available on these habitats however they are likely to be more stable than their shallower counterparts and characterised by a diverse range of polychaetes, amphipods, bivalves and echinoderms.
Maldanid polychaetes and Eudorellopsis deformis in offshore circalittoral sand or muddy sand
In deep offshore sand or non-cohesive muddy sand dense populations of maldanid polychaetes such as Maldane sarsi and the cumacean Eudorellopsis deformis may be found. Accompanying these species are abundant ophiuroids including Amphiura filiformis, polychaetes such as Terebellidae sp., Chaetozone setosa, Levinsenia gracilis, Scoloplos armiger, the amphipod Harpinia antennaria and the bivalves Nuculoma tenuis and Parvicardium minimum. This biotope is similar to the Maldane sarsi-Ophiura sarsi community defined by Glemarec (1973).
Owenia fusiformis and Amphiura filiformis in offshore circalittoral sand or muddy sand
Areas of slightly muddy sand (generally <20% mud) in offshore waters may be characterised by high numbers of the tube building polychaete Owenia fusiformis often with the brittlestar Amphiura filiformis. Whilst O. fusiformis is also found in other circalittoral or offshore biotopes it usually occurs in lower abundances than in SSA.OfusAfil. Other species found in this community are the polychaetes Goniada maculata, Pholoe inornata, Diplocirrus glaucus, Chaetozone setosa and Spiophanes kroyeri with occasional bivalves such as Timoclea ovata and Thyasira equalis. The sea cucumber Labidoplax buski and the cumacean Eudorella truncatula are also commonly often found in this biotope.
Sublittoral sand in low or reduced salinity (lagoons)
Shallow sand and muddy sand in areas of low or reduced, although relatively stable salinity (may vary annually), with largely ephemeral faunal communities. The species are often similar to that found in SMuLS and are characterised by Arenicola marina with other species, including mysids, tubificoid and enchytraeid oligochaetes, Corophium volutator, Hediste diversicolor, Pygospio elegans, Hydrobia ulvae and Cerastoderma glaucum, which commonly occur in lagoons. Filamentous green algae such as Chaetomorpha linum may also be present. In some examples of this biotope the polychaete Fabricia sabella may be super-abundant and the isopod Sphaeroma hookeri common.
Sublittoral sand in variable salinity (estuaries)
Clean sands that occur in the upper reaches of marine inlets, especially estuaries, where water movement is moderately strong, allowing the sedimentation of sand but not the finer silt fraction. The habitat typically lacks a significant seaweed component and is characterised by brackish-water tolerant fauna, particularly amphipods, polychaetes and mysid shrimps.
Infralittoral mobile sand in variable salinity (estuaries)
Very mobile sand in areas of strong tidal currents and variable salinity. No stable community is able to develop within this extremely mobile and abrasive habitat. The fauna encountered in this habitat consists of epifaunal crustaceans or relatively low numbers of robust species, such as the isopod Eurydice pulchra or Mesopodopsis slabberi. The polychaete Capitella capitata may occur frequently in some areas. Other taxa such as the polychaetes Eteone spp. and Arenicola marina, the mysid Neomysis integer and the amphipods Bathyporeia spp. and Haustorius arenarius may also be washed in from adjacent communities. This biotope is found in tidal channels of estuaries and areas where water movement keeps silt and mud in suspension, and excludes even the more robust infauna. If oligochaetes, polychaetes and bivalves are present in any numbers within this habitat type then care must be taken to avoid the inclusion of juvenile or spat recruitment counts which may mask the presence of this biotope. This is particularly relevant as sampling usually occurs at slack water periods when settlement takes place.
Nephtys cirrosa and Macoma balthica in variable salinity infralittoral mobile sand
Mobile sand in variable salinity conditions where tidal currents create an unstable shifting habitat. Characteristic species include the polychaetes Nephtys cirrosa and Scoloplos armiger along with amphipods of the genus Bathyporeia and Haustorius arenarius. The bivalve Macoma balthica may occur in more stable examples of this biotope, although not in the abundances found in the NhomMac. The biotope contains relatively few species, each typically in low to moderate abundance. It is found in tidal channels with moderate tidal streams. Care should be taken in identification of this biotope due to the presence juveniles and species washed in during slack water.
Neomysis integer and Gammarus spp. in fluctuating low salinity infralittoral mobile sand
Upper estuary mobile fine muddy sands with very low fluctuating salinity characterised by the mysid shrimp Neomysis integer (see Arndt 1991) and amphipods of the genus Gammarus spp. This habitat has a rather sparse infauna and species such as N. integer will most likely be found on the sediment surface or just above it whilst Gammarus may be under loose weed, stones or other detritus on the sediment surface. The harsh physicochemical regime imposed by such environmental conditions in the upper estuary leads to a relatively impoverished community but high densities of the mobile, salinity-tolerant, crustaceans can occur. The biotope is found in the transitional zone between freshwater and brackish environments, relying on the decreased freshwater input during the summer for penetration of the brackish species up-stream. As such this biotope may also contain elements of freshwater communities.
Arenicola marina in infralittoral fine sand or muddy sand
In shallow fine sand or non-cohesive muddy sand in fully marine conditions (or occasionally in variable salinity) a community characterised by the polychaete Arenicola marina may occur. This biotope appears quite faunally sparse. Those other taxa present however, include scavenging crustacea such as Pagurus bernhardus and Liocarcinus depurator, terebellid polychaetes such as Lanice conchilega and the burrowing anemone Cerianthus lloydii. Occasional Sabella pavonina and frequent Ensis spp. may also be observed in some areas. The majority of records for this biotope are derived from epifaunal surveys and consequently there is little information available for the associated infaunal species. It is possible that this biotope, like EcorEns (to which it is broadly similar) is an epibiotic overlay on other biotopes from the SSA complex.