Circalittoral offshore rock (and other hard substrata)
Ampharete falcata turf with Parvicardium ovale on cohesive muddy very fine sand 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 Parvicardium ovale occur in the superficial sediment. Both Amphiura filiformis and A. chiajei may be present together with Nephrops norvegicus in higher abundance than the CMU.BriAchi or CMS.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 Melinna cristata, a maldanid worm, has been recorded from Northumberland (Buchanan 1963).
Foramaniferans and Thyasira sp. in deep circalittoral soft mud
In deep water and soft muds of Boreal and Arctic areas, a community dominated by foraminiferans and the bivalve Thyasira sp. may occur (Thorson 1957; Künitzer et al. 1992). This community typically occurs in water deeper than 100 m in the northern North Sea (Künitzer et al. 1992) and have been referred to as 'Foraminifera communities' by other workers (e.g. Stephen 1923; Thorson 1957; McIntyre 1961). Foraminiferans such as Saccammina, Psammosphaera, 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 the Irish Sea is another distinct biotope (E.I.S. Rees pers. comm. 1997). Polychaetes, e.g. Paraonis gracilis, Myriochee 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 (Glémarec 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 Formanifera and similar, rich communities may exist in Scottish sealochs (McIntyre 1961). Shallower water may give rise to a Brissopsis-dominated communities (CMU.BriAchi). Communities from yet deeper (northern) waters at the extremes of the North Sea may be reminiscent, although dissimilar to COS.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'.
Styela gelatinosa and other 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., occur together with terebellid worms and the bivalve Pseudamussium septemradiatum. It is possibly an ice age relict biotope.
Circalittoral rock (and other hard substrata)
Sponges, cup corals and Parerythropodium coralloides 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 though 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. Likely to need further splitting with analysis and data from west coast of Ireland.
Alcyonium-dominated communities (tide-swept/vertical)
Alcyonium-dominated communities (tide -swept/ vertical)
Alcyonium digitatum, Pomatoceros triqueter, algal and bryozoan crusts on vertical exposed circalittoral rock
Often found on exposed bedrock walls with dense Alcyonium digitatum, having the appearance of being grazed and is sometimes species poor on North Sea coasts. Pomatoceros can be highly abundant in some situations, sometimes covering far more rock than the Alcyonium digitatum. Other species include Parasmittina trispinosa, coralline crusts, Sagartia elegans, Abietinaria abietina, Leptasterias muelleri, Antedon bifida, Filograna/Salmacina and sometimes tufts of Tubularia. Vertical faces of wrecks may have a similar community or with a greater density of anemones, particularly Metridium senile. This biotope includes some records where dense Alcyonium occurs with Metridium and brittlestars in narrows in sealochs. This biotope does not usually have many of the larger sponges as in AlcMaS and has far less Tubularia than AlcTub or TubS. Where very grazed and in slower tides or less wave action the faunal and algal crusts (FaAlC) biotope predominates.
Alcyonium digitatum with massive sponges (Cliona celata and Pachymatisma johnstonia) and Nemertesia antennina on moderately tide-swept exposed circalittoral rock
Variable amounts of Alcyonium digitatum but with large growths of Cliona celata and Pachymatisma johnstonia in moderately strong tides. In some locations Myxilla incrustans forms cushions amongst the other sponges. This biotope also has many hydroids (Nemertesia spp., tufts of Tubularia indivisa, sometimes Aglaophenia spp. and Gymnangium montagui) and bryozoans (Bugula plumosa, Scrupocellaria), which form a short turf. Antedon, Flustra, Caryophyllia, Corynactis and Actinothoe may be present. Usually lacks many branching sponges, although Stelligera spp. and Raspailia spp. are often present, particularly in deeper water at the same sites.
Alcyonium digitatum with Securiflustra securifrons on weakly tide-swept or scoured moderately exposed circalittoral rock
Found on generally moderately exposed bedrock and boulders with Alcyonium digitatum, often appearing fairly clean and grazed but with more erect species than FaAlC, including Securiflustra securifrons and Flustra foliacea. Pomatoceros is abundant at some sites, and other species include Parasmittina trispinosa, coralline crusts, Sagartia elegans, Abietinaria abietina, Leptasterias muelleri, Antedon bifida, Filograna/Salmacina and sometimes Tubularia. This biotope tends to occur in areas which are less turbid/silty than Flu.Flu and is found mainly in south-east Scotland and just across the border as well as in some sealochs. ECR.AlcC has fewer species with less Alcyonium.
Alcyonium digitatum with dense Tubularia indivisa and anemones on strongly tide-swept circalittoral rock
Occurs mainly in sounds, narrows and around tide-swept promontories in accelerated tidal streams. Alcyonium digitatum forms an almost continuous cushion in some locations with dense tufts to continuous cover of Tubularia indivisa on exposed edges and ridges. Actinothoe sphyrodeta, Sagartia elegans, Cliona celata and Corynactis viridis are often prominent components of the community. Hydroids, such as Sertularia argentea and Abietinaria abietina, and the horn wrack Flustra foliacea may be present. In some situations, e.g. Kyle Rhea, Strangford Narrows, Skye and the Mull of Galloway, the sponge and anemone component is more prominent (may warrant inclusion in AlcMaS). In increased tidal flow species richness falls and a Balanus crenatus biotope (ECR.BalTub) develops. In weaker tides, and in some parts of the country in similar habitat conditions (e.g. Welsh coasts), Alcyonium can still be fairly dense but a more species-rich biotope prevails (ECR.AlcMaS). In some cases dense Tubularia is found growing through sheets of sponges (see ECR.TubS).
Barnacle, cushion sponge and Tubularia communities (very tide-swept/wave-sheltered)
Barnacle, cushion sponge and Tubularia communities (very tide-swept / sheltered)
Balanus crenatus, Halichondria panicea and Alcyonidium diaphanum on extremely tide-swept sheltered circalittoral rock
Strong tides of variable to low salinity water run through the narrows such as parts of the Menai Strait and the Falls of Lora in Loch Etive with dense Balanus crenatus covering most surfaces. Few other species are present other than large growths of Halichondria panicea a few tufts of Tubularia indivisa and often dense Alcyonidium diaphanum (see CuSH). In these extreme conditions species richness is generally low and limited to those species which can tolerate variable salinity and hang on to the substratum (hence this biotope often has shore species such as Nucella lapillus and Carcinus maenas). In slightly less strong tides and/or less variable salinity dense Tubularia indivisa (ECR.BalTub) and/or dense cushions of sponge (ECR.CuSH) develops.
Balanus crenatus and Tubularia indivisa on extremely tide-swept circalittoral rock
Dense Balanus crenatus covering most surfaces in extremely tide-swept conditions, with short turfs of Tubularia indivisa in localised tide-sheltered spots. There also may be areas of Mytilus edulis, Corynactis viridis, Sertularia argentea and Clathrina coriacea although the cover of these species varies between locations. Very large Balanus balanus are associated with this community on the extremely tide-swept pinnacle in the Gulf of Coryvreckan, Firth of Lorne. Alcyonium digitatum is often found at the same sites with these extreme conditions although not on the most tide-exposed parts of the habitat. See also TubS and AlcTub which occur in strong, but not as strong, tides as this biotope.
Cushion sponges, hydroids and ascidians on very tide-swept sheltered circalittoral rock
Often turbid variable salinity water in straits or sounds with low wave exposure where circalittoral communities occur in relatively shallow water. This biotope seems to have close links with the sponge and Alcyonium-rich biotope AlcTub but has been modified by high turbidity, possible organic enrichment and some (slight?) freshwater influence which when combined encourage luxuriant, fast-growing sponges. Large growths of Halichondria bowerbanki, often with Haliclona oculata (although large H. oculata are characteristic of slightly more sheltered conditions in the biotope Flu.Hocu) and Esperiopsis fucorum, various hydroids (particularly Nemertesia spp. and Tubularia indivisa) and ascidians. Typically this biotope occurs where hard substrata is present in the tide-swept narrows / sounds of marine inlets and in particular in the Menai Strait.
Halichondria bowerbanki, Eudendrium arbusculum and Eucratea loricata on reduced salinity tide-swept circalittoral mixed substrata
Circalittoral mixed substrata (bedrock, boulders, cobbles and pebbles) in reduced salinity conditions and strong tidal streams. Halichondria bowerbanki, Mycale lobata, Eudendrium arbusculum and Alcyonidium diaphanum are particularly characteristic of these conditions. This biotope is only known from Loch Etive, a very impoverished low salinity version is present in the upper basin of Loch Etive.
Tubularia indivisa, sponges and other hydroids on tide-swept circalittoral bedrock
This biotope falls somewhere between the extremely tide-swept rock with little more than Tubularia and Balanus crenatus (BalTub) and the biotope characterised by large cushion sponges and/or dense Alcyonium and Tubularia (AlcTub). It is found in strongly tide-swept and exposed locations where turbidity levels are consistently high. This biotope does not include the Tubularia/Halichondria communities (CuSH and BalHpan) as found in the Menai Strait but does include the examples of dense Tubularia growing through sheets of Myxilla rosacea as well as patches of dense Jassa tubes and Dendrodoa grossularia as found off the Skerries, Anglesey. There is relatively little Alcyonium digitatum in this biotope, particularly around the Welsh coast, although in the few examples surveyed so far Actinothoe sphyrodeta is often frequent to common.
Faunal crusts or short turfs (wave-exposed rock)
Faunal crusts or short turfs (exposed rock)
Coralline crusts, Parasmittina trispinosa, Caryophyllia smithii, Haliclona viscosa, polyclinids and sparse Corynactis viridis on very exposed circalittoral rock
Sparse Corynactis viridis, encrusting bryozoans and coralline algae on clean, often deep circalittoral rock. The fauna is often sparse and has the appearance of being grazed but may also be effected by violent wave action working into deep water during winter storms. Other species include large specimens of the sponge Haliclona viscosa, the bryozoan Parasmittina, the sea cucumber Holothuria sp., the cup coral Caryophyllia and sparse hydroids such as Schizotricha frutescens and Nemertesia antennina. This biotope also contains polyclinid ascidians. There appears to be a northern (Shetland/Orkney) variant of this biotope which is virtually devoid of sponges, whilst Caryophyllia is less common than in the south and west and grazing by Echinus seems to have a marked effect. This biotope may require re-splitting although this is made difficult through the lack of characterising species.
Corynactis viridis and a crisiid/Bugula/Cellaria turf on steep or vertical exposed circalittoral rock
Wave exposed steep or vertical bedrock, often subject to moderate or strong tidal streams, with dense aggregations of the jewel anemone Corynactis viridis and a short bryozoan turf of Crisia spp., Cellaria spp. and Bugula spp. Occasional large growths of the sponge Cliona celata and the soft coral Alcyonium digitatum present. Caryophyllia smithii is often frequent and anemones, such as Sagartia elegans and Metridium senile, and the featherstar Antedon bifida are often common. Alcyonium glomeratum and Parazoanthus axinellae may be present in the south-west. Branching sponges are typically scarce or absent.
Pomatoceros triqueter, Balanus crenatus and bryozoan crusts on mobile circalittoral cobbles and pebbles
Cobbles and pebbles with Balanus crenatus, Pomatoceros and a few bryozoan and coralline algal crusts are often found at the base of exposed cliff faces where scour action 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 Flu.SerHyd which is characterised by large amounts of the above hydroids on stones also covered in Pomatoceros and barnacles. The main difference here is that Flu.SerHyd seems to develop on more stable, consolidated cobbles and pebbles in moderate tides - these stones may be disturbed in the winter and therefore long-lived species are not found.
Antedon bifida and a bryozoan/hydroid turf on steep or vertical circalittoral rock
Steep and vertical slopes of bedrock in slightly tide-swept conditions with dense aggregations of Antedon bifida, in some locations with a bryozoan turf. The dense aggregations of Antedon also extend into infralittoral where they occur on kelp stipes (see EIR.LhypR). Bugula spp., Abietinaria abietina and Nemertesia antennina are often found at the same sites and there are also examples with dense Ciona intestinalis and Pomatoceros triqueter. Some examples are particularly impoverished with little beneath the feather stars other than coralline crusts (e.g. Summer Isles and Loch Broom). High densities of Antedon are widely found, sometimes also in sheltered, silty conditions. Further consideration required of this biotope.
Bugula spp. and other bryozoans on vertical moderately exposed circalittoral rock
Vertical rock faces in the circalittoral (often at same depth as lower infralittoral biotopes as well as deeper) with a dense turf of Bugula spp. and Scrupocellaria spp. and the sponges Tethya aurantium, Pachymatisma johnstonia, Hemimycale columella and occasionally Dercitus bucklandi in crevices are often present. Also patches of Nemertesia antennina and Crisia eburnea. Most surfaces also with a thin cover of Cryptopleura, Rhodophyllis 'spiky' and Plocamium. Some areas may have large patches of Clavelina and a few areas with Perophora, Polycarpa scuba and Ascidia mentula. Antedon bifida also occurs in crevices. Bugula turbinata tends to predominate in shallower records of this biotope, whereas deeper records have a mixture of at least three Bugula spp., dominated by B. plumosa. Many of the records with this biotope have been recorded as parts of other habitat records despite the clarity in which this biotope occupies vertical faces of almost any size in some parts of the country, particularly in Wales and further south in the Irish Sea. Softer rock faces bored by Hiatella arctica (IR.AlcByH.Hia) tend to be more species-rich, reflecting the large number of niches and holes inhabited by small cryptic species.
Molgula manhattensis and Polycarpa spp. with erect sponges on tide-swept moderately exposed circalittoral rock
This biotope occurs in the shallower reaches of the circalittoral (upper and lower) at depths of around 8 to 13 m with the main ascidian cover of Molgula manhattensis with some Polycarpa pomaria and a wide variety of other ascidians mixed in. Sponge species associated with this biotope include Tethya, Cliona, Stelligera rigida, Stelligera stuposa, Raspailia ramosa, Esperiopsis, Hemimycale and Dysidea. There are also several records with Axinella dissimilis and Axinella infundibuliformis. Nemertesia antennina occurs at most sites, also with Alcyonium digitatum and Actinothoe. Flustra is common in all these ascidian biotopes, but Chartella is only found in this one. Red algae associated with the upper circalittoral occur sporadically - more an artefact of the way in which the habitat records have been split. This biotope has some parallels with the erect sponge biotopes (e.g. ErSPbolSH), although it appears to be far siltier at most sites.
Dense ascidians, bryozoans and hydroids on a crust of Sabellaria spinulosa on tide-swept circalittoral rock
Tide-swept rock in areas with high levels of suspended sand with a Sabellaria spinulosa crust which supports a wide variety of other species. A dense carpet of ascidians Molgula manhattensis, Polycarpa spp. and Polyclinum aurantium, a turf of bryozoans (Cellaria sinuosa, Bugula plumosa and Flustra foliacea) and sponges such as Scypha ciliata and Polymastia spp., bryozoans Alcyonidium diaphanum and Scrupocellaria sp. and Antedon bifida may also be present. In some cases this biotope occurs adjacent to MolPol although in deeper water and more tide-swept (scour/turbulent) conditions.
Stolonica socialis and/or Polyclinum aurantium with Flustra foliacea on slightly sand-scoured tide-swept moderately exposed circalittoral rock
Polyclinum aurantium and/or Stolonica socialis on silty, slightly sand-scoured, tide-swept rock with a turf of bryozoans such as Flustra foliacea and Chartella. There are several ascidian-dominated biotopes with Flustra - North Wales/Irish Sea variants with Sabellaria spinulosa or branching sponges and this more northern Irish Sea/Flamborough variant with generally fewer species. Some examples from Ireland include Synoicum incrustatum and Polycarpa scuba. Moderately strong tides also encourage tufts of Tubularia. Other ascidians such as Pycnoclavella aurilucens common in some areas. Hydroids often abundant in the strong / moderately strong tidal streams.
Ophiothrix fragilis and/or Ophiocomina nigra beds on slightly tide-swept circalittoral rock or mixed substrata
Moderately exposed or sheltered slightly tide-swept rock or mixed substrata with dense brittlestar beds, usually dominated by Ophiothrix fragilis but often with Ophiocomina nigra amongst them. At some sites O. nigra was found in larger numbers at some sites particularly in deeper water than the main Ophiothrix bed. Brittle star beds tend to be rather species-poor with coralline crusts, Pomatoceros triqueter, Bolocera tuediae, Urticina felina, Urticina eques, occasional Metridium senile, a few hydroids such as Abietinaria abietina and echinoderms such as Luidia ciliaris and Crossaster papposus fairly typical of the biotope. Alcyonium digitatum may be present, especially on protruding rocks. In the far north of Britain (Shetland, NW Scotland) and part of Ireland Ophiopholis aculeata often replaces Ophiothrix as the dominant brittlestar occurring in dense aggregations (Oph.Oacu).
Ophiopholis aculeata beds on slightly tide-swept circalittoral rock or mixed substrata
Sheltered, slightly tide-swept rock or mixed substrata with dense beds of the brittlestar Ophiopholis aculeata. These brittlestar beds occur in very similar conditions to Ophiothrix / Ophiocomina beds and may very well be a northern variant. Tends to be rather species-poor with coralline crusts, Pomatoceros triqueter, and several ubiquitous scavenging species such as Pagurus bernhardus and Buccinum undatum present in most of the records. The horse mussel Modiolus modiolus is often found amongst dense Ophiopholis and there may well be overlaps with the Modiolus biotopes. There are also a few species typical of these northern locations, although not necessarily confined to this biotope, such as the urchin Strongylocentrotus droebachiensis and holothurian Cucumaria frondosa. The most representative examples of this biotope are known from Shetland, with other examples found in Loch Alsh and from Ireland.
Bryozoan/hydroid turfs (sand-influenced)
Flustra foliacea and other hydroid/bryozoan turf species on slightly scoured circalittoral rock or mixed substrata
A widespread biotope which has been split into several related entities. The biotope is characterised by silt- and scour-tolerant species which occur in varying proportions around the country, but Flustra foliacea tends to dominate. This biotope is characteristic of silty rocky habitats, tending to be moderately exposed to wave action and with a moderate tidal flow which create the slight scour conditions (compared to silted rocky habitats in sheltered conditions). The species associated with and therefore characterising the different Flustra biotopes vary from region to region, ranging from the relatively low species-rich Flu.Flu found on North Sea coasts to the similar but far richer biotopes with sponges and hydroids on the west of Britain and Irish Sea coasts (Flu.HByS). There are also several other related biotopes: these include the Urticina (Urt.Urt) and Ciocalypta (Urt.Cio) biotopes which occur at rock-sediment interfaces; ascidian-dominated biotopes with Flustra (StoPaur) and several other biotopes characterised by other slight scour-tolerant or turbid-water species such as Sabellaria spinulosa which include Flustra (Sspi and MolPol.Sab) and Alcyonidium diaphanum (SNemAdia). Only use this biotope if records do not fit into other categories.
Flustra foliacea on slightly scoured silty circalittoral rock or mixed substrata
The biotope is characterised by the silt/scour-tolerant species Flustra foliacea. It is characteristic of the large bedrock terraces along the Northumberland coast which are generally fairly species-poor compared to similar situations on the west coasts which have more sponges, hydroids and bryozoans. Thuiaria thuja is often present, as are patches of Sabellaria spinulosa (see also Sspi). With increased turbidity, species-richness is lower, although the abundance of Flustra foliacea remains high. Similar assemblages occur on mixed substrata although these tend to be dominated by ephemeral hydroids (see Flu.SerHyd and SNemAdia). Other similar biotope include those dominated by ascidians (As), also characteristic of slight scour and turbidity, although they usually occur in different regions of the country tending to the west/Irish Sea. In increased tides, but more shelter, a similar biotope dominated by Flustra and a variety of sponges such as Haliclona oculata and Halichondria panicea occurs (Flu.Hocu).
Flustra foliacea with hydroids, bryozoans and sponges on slightly tide-swept circalittoral mixed substrata
Often dense Flustra foliacea with a variety of slightly scour/silt-tolerant species forming a dense turf on bedrock, boulders, cobbles and mixtures of sediment. This biotopes does not include the ascidians found in the silty biotope StoPaur although it can have similar suite of 'ubiquitous' species and the more scour-tolerant ascidian Polyclinum aurantium. Other species can include Alcyonidium diaphanum (see SNemAdia which has more hydroids and less Flustra), various robust hydroids such as Abietinaria abietina and Nemertesia antennina and sponges such as Dysidea fragilis, Polymastia boletiformis and Cliona celata. Has been recorded adjacent to exposed circalittoral rock communities with dense Corynactis viridis, although the data has not always been recorded separately. Securiflustra securifrons often occurs in this biotope.
Haliclona oculata and Flustra foliacea with a rich faunal turf on tide-swept sheltered circalittoral boulders or cobbles
Localised areas of relative shelter in tide-swept sounds and inlets with large 'finger' growths of Haliclona oculata amongst dense Flustra foliacea. Also polyclinid ascidians, patches of large Halichondria panicea, Esperiopsis fucorum and a hydroid turf. Some areas also have Alcyonidium diaphanum. Generally in the upper circalittoral although borders with the lower infralittoral at some sites. This biotope is more species-rich than Flu.Flu and occurs on west coasts in similarly silty conditions, although its distribution may overlap with the dense ascidian biotopes (e.g. StoPaur and MolPol). This biotope is typically found in locations such as the Menai Strait, Plymouth Sound, Milford Haven and Lune Deep area.
Sertularia argentea, S. cupressina and Hydrallmania falcata on tide-swept circalittoral cobbles and pebbles
Circalittoral cobbles and pebbles amongst clean sand or shell gravel in strong tides were covered in hydroids over Balanus crenatus. Sabella pavonina and Lanice conchilega were often common in the coarse sediment around the stones. With increased scouring S. cupressina becomes more common (see ScupHyd) although eventually, as tidal stream strength increases to a point at which the stones are kept mobile, all hydroids are scoured off leaving just Pomatoceros, bryozoan crusts, Balanus crenatus and coralline algae (PomByC).
Sparse sponges, Nemertesia spp., Alcyonidium diaphanum and Bowerbankia spp. on circalittoral mixed substrata
Mixed substrata of cobbles and coarse silty sediment with occasional boulders and small outcrops of bedrock. A variety of small sponges including erect sponges and fast growing cushions such as Esperiopsis fucorum, ephemeral and robust hydroids and bryozoans tolerant of some silt such as Nemertesia spp., Cellaria spp., Bugula spp., Bowerbankia spp. and sparse Flustra. There are also some records with Epizoanthus couchii and Isozoanthus sulcatus. This biotope sits somewhere between the Polymastia and erect sponge biotope (ErSPbolSH) which occurs on fairly stable substrata and the ephemeral hydroids biotope Flu.SerHyd which cannot develop further presumably because of periodic disturbance from wave and/or tide-scouring action. It therefore has a mixture of scour-tolerant species, ephemeral species and a few 'stable' substratum species on the larger or more consolidated rocks and boulders. Large areas of cobbly seabed in open but moderately exposed bays (e.g. Cardigan Bay) may comprise this biotope.
Urticina felina on sand-affected circalittoral rock
Urticina felina frequently occurs on rocks at the sand-rock interface where scour levels are high and few other species seem to be able to colonise. This biotope is only occasionally recorded as a separate entity. More often the Urticina are included as part of whatever biotope occurs on the nearby hard substrata. These neighbouring biotopes vary considerably but often include other scour-tolerant species. Most data has been assigned to Urt.Urt and Urt.Cio.
Urticina felina and Ciocalypta penicillus on sand-covered circalittoral rock
Sand-covered low-lying rock with some scouring effect which has dense Urticina felina with Ciocalypta penicillus attached to the underlying rock. Polymastia spp., particularly P. mamillaris and sometimes P. agglutinans are also present. Has links with the ephemeral hydroid (Flu.SerHyd) and Pomatoceros and bryozoan crust biotopes (PomByC) and can occur adjacent to them. Not regularly recorded as a separate entity but is often recognisable in this habitat where rock and coarse sediment interface.
Urticina felina on sand-scoured circalittoral rock
Urticina felina on boulder or sand-scoured rock often adjacent to sandy sediment plains. On more open coasts sand-covered rock often has Ciocalypta penicillus (Urt.Cio) whereas this biotope seems to occur in more coastal conditions where turbidity is higher and scour possibly greater. This biotope occurs in tide-swept conditions at many sites, but seems to be rarely recorded as a separate entity from adjacent rocky substrata. The inclusion of data from this sediment-interface biotope often distorts the adjacent rocky biotope's species composition.
Sabellaria spinulosa crusts on silty turbid circalittoral rock
Bedrock in moderately exposed, slightly tide-swept conditions with high turbidity with an almost entire crust of Sabellaria spinulosa tubes; few other species present. Ciona celata, Alcyonium digitatum and Hypoglossum hypoglossoides present in NE England, very extensive Mytilus edulis in South Wales (Gower). The fauna attached to the Sabellaria crust in many cases seem to reflect the biotopes on nearby rock.
Grazed fauna (moderately exposed or sheltered rock)
Faunal and algal crusts, Echinus esculentus, sparse Alcyonium digitatum and grazing-tolerant fauna on moderately exposed circalittoral rock
Moderately exposed circalittoral rock in slight tides with a rather barren appearance (reminiscent of a brittlestar bed after the brittlestars have moved elsewhere - brittlestars Ophiothrix fragilis recorded in moderate abundance). Can be sand/sediment scoured or grazed. Usually small Alcyonium digitatum, some Abietinaria abietina and sparse Nemertesia spp. present. Also Urticina felina, often associated with patches of muddy shell gravel and sand, or on North Sea coasts Urticina eques. Most of rock surface with coralline or non-coralline red algal crusts as well as patches of bryozoan crusts such as Parasmittina trispinosa. Echinus esculentus common in some areas and Pomatoceros triqueter found throughout, especially on vertical faces. The richer examples of this biotope also have Caryophyllia smithii, Antedon bifida, delicate hydroids, ascidians such as Ascidia mentula and holothurians such as Aslia lefevrei and Pawsonia saxicola, which may appear seasonally, in more cryptic habitats. Regional variants occur - e.g. with Thuiaria thuja and Bolocera tuediae on North Sea coasts. Under-boulders and crevices often have Pawsonia saxicola, Galathea spp., encrusting sponges, terebellids, Pododesmus patelliformis and Munida rugosa.
Faunal and algal crusts, Echinus esculentus, sparse Alcyonium digitatum, Abietinaria abietina and other grazing-tolerant fauna on moderately exposed circalittoral rock
Moderately exposed circalittoral rock in slight tides with a rather barren appearance (reminiscent of a brittlestar bed after the brittlestars have moved elsewhere - brittlestars Ophiothrix fragilis recorded in moderate abundance). Can be sand/sediment scoured or grazed. Usually small Alcyonium digitatum, frequent or more Abietinaria abietina and other more ephemeral hydroids. This biotope is probably a northern variant of FaAlC.
Mussel beds (open coast circalittoral rock/mixed substrata)
Modiolus modiolus beds with hydroids and red seaweeds on tide-swept circalittoral mixed substrata
Musculus discors beds on moderately exposed rock (with mucous-congealed mats of silt/pseudofaeces). Variety of sponges, hydroids and bryozoans typical of the open coast situation in the area also present such as Phorbas fictitius, Hemimycale columella, Polymastia boletiformis, Balanus crenatus, Urticina felina, Salmacina dysteri and Pentapora foliacea. Some of the sites with this biotope exposed to moderately strong tides such as found near Maen Mellt on the Lleyn Peninsula.
Musculus discors beds on moderately exposed circalittoral rock
Mytilus edulis beds with hydroids and ascidians on tide-swept moderately exposed circalittoral rock
Dense mussel Mytilus edulis beds occur in strong tides on a variety of substrata. Apart from a continuous bed of mussels species richness is not particularly high. Asterias are usually common, as are crabs such as Cancer pagurus, Carcinus maenas and Necora [Liocarcinus] puber. Hydroids such as Kirchenpaueria and those characteristic of strong tides and a little scour are also often present such as Sertularia argentea and Tubularia indivisa. Ascidians such as Molgula manhattensis and Polycarpa spp. and Flustra foliacea may be present, particularly in silty conditions, although not often on the mussels themselves.
Piddocks with a sparse associated fauna in upward-facing circalittoral very soft chalk or clay
Horizontal plains of soft chalk and firm clay bored by bivalves. Species vary with location but Pholas dactylus, Barnea candida and Zirfaea crispata are recorded regularly. Found mainly in south-east England (Sussex and Thanet) although some Irish records exist. Other species present include Polydora ciliata and Crepidula fornicata. The rock surface is very friable or erodes very quickly and therefore unsuitable for larger species to settle and attach.
Polydora sp. tubes on upward-facing circalittoral soft rock
Large patches of upward-facing chalk and soft limestone covered entirely by Polydora sp. tubes to the exclusion of almost all other species. Also with Cliona celata - boring form only. In a few cases this biotope occurs in small patches amongst other biotopes.
Mixed faunal turfs (moderately exposed rock)
Erect sponges, Eunicella verrucosa and Pentapora foliacea on slightly tide-swept moderately exposed circalittoral rock
Mainly found on exposed and moderately exposed rock, in slight tidal currents and often relatively silty, with a rich variety of species typically including branching and cup sponges, the seafan Eunicella verrucosa and the ross coral Pentapora foliacea. Typically a bryozoan turf of Cellaria spp. and Bugula spp. is present amongst the larger species (see Bug). The branching sponges Axinella dissimilis, Stelligera spp. and Raspailia spp. are typically present, with cup sponges Axinella infundibuliformis and Phakellia ventilabrum found in some cases. Alcyonium glomeratum and Parerythropodium coralloides may also be present and short vertical faces sometimes have the star anemone Parazoanthus axinellae and/or P. anguicomus. There are numerous examples of sites with lots of branching and cup sponges where seafans have not been found (but are often known to be present within the same geographical area); some of these are included in ErSPbolSH. Diazona violacea is also often recorded in this biotope although it occurs in ErSSwi also. There are a few instances of Swiftia pallida being found at the same sites (in SW Ireland) as Eunicella verrucosa. Where this biotope occurs on more open coast (e.g. SW Britain and W Ireland) the cotton spinner sea cucumber Holothuria forskali is often present.
Cushion sponges (Polymastia boletiformis, Tethya), stalked sponges, Nemertesia spp. and Pentapora foliacea on moderately exposed circalittoral rock
Bedrock, boulders and cobbles in a variety of wave exposures (usually exposed and moderately exposed), often with a light covering of silt. This biotope does not usually occur deeper than 15-20 m and therefore often borders the upper circalittoral and lower infralittoral. The sponge cover usually appears patchy with no one species obviously dominant although the yellow Polymastia spp. orange Esperiopsis fucorum and tufts of hydroids Nemertesia spp. on the tops of boulders and rocky ridges tend to stand out more clearly then the under-storey of finer hydroids and bryozoans. Polymastia boletiformis forms frequent cushions on the silty rock, often with Tethya, P. mamillaris, Hemimycale and Pentapora nearby at similar densities. Some branched sponges, particularly Raspailia ramosa and Stelligera stuposa are found in moderate abundance. Under-boulders may have sponge crusts such as Terpios fugax with the tubeworm Bispira volutacornis between the boulders. Candy-striped flatworm Prostheceraeus vittatus often found at sites with this biotope in Cardigan Bay as well Epizoanthus couchii and less often Isozoanthus sulcatus. The physical habitat in this biotope is somewhere between that described in the ErSEun and the less stable cobble and pebble plains in SNemAdia and is characterised by species typical of a moderate degree of stability although also contains some typical of the more ephemeral and/or scoured biotopes.
Erect sponges and Swiftia pallida on slightly tide-swept moderately exposed circalittoral rock
Circalittoral rock subject to slight tidal currents, with the seafan Swiftia pallida and various erect branching and cup sponges, including Axinella infundibuliformis, Stelligera spp. and Raspailia spp. The rocky surfaces usually have a sparse turf of hydroids including Aglaophenia tubulifera and Schizotricha frutescens, bryozoans Bugula spp., Caryophyllia smithii, Porella compressa and occasionally Alcyonium glomeratum and Diazona violacea. The feather stars Antedon bifida and Antedon petasus (the latter more numerous in deeper water than the former) and large solitary ascidians Ascidia mentula and Polycarpa pomaria (see AmenCio) are also characteristic of the less exposed sites with this biotope. Rock surfaces often with Neocrania anomala - found both in Irish and Scottish examples of this biotope. Short verticals and overhangs occasionally with Parazoanthus anguicomus. Mycale lingua recorded in deep water at some of the sites in Scottish sealochs. There are a few records from Kenmare River in SW Ireland which have Swiftia and Eunicella at the same sites. These records have been included in ErSEun although there were several other biotopes in Kenmare River which share close links with those from Scottish sealochs.
Phakellia ventilabrum and axinellid sponges on deep exposed circalittoral rock
In deep water (40-50m+) in exposed and very exposed conditions erect cup and branching sponges are found on bedrock and boulders. The sponge Phakellia ventilabrum tends to dominate, although Axinella infundibuliformis, Stelligera spp. and Axinella dissimilis are also characteristic. In deep water Axinella flustra may also be found. Other species included Porella compressa, large Cliona celata and Pachymatisma johnstonia. There are also instances of a variant of this biotope on similarly very exposed, upward- facing bedrock where Phakellia ventilabrum is in relatively high abundance with the ball-shaped sponges Tetilla zetlandica and Tetilla cranium amongst it. Most records of this biotope are from the west coast of Ireland. Nearest similar biotopes (species-wise) are ErSEun which has similar axinellid species, although mainly Axinella dissimilis, and CCParCar which has a few similar elements and might occur at the same sites although in shallower water within reach of wave action / mixing.
Brachiopod and solitary ascidian communities (sheltered rock)
Ascidiella aspersa on sheltered circalittoral rocks on muddy sediment
Sheltered bedrock and/or boulders on muddy sediment, sometimes subject to variable salinity, with high numbers of Ascidiella aspersa and a variety of other solitary ascidians capable of colonising small fragments of hard substrata (shells etc.). Dendrodoa grossularia usually present. Less species-rich than the other ascidian biotopes (AmenCio and SubSoAs). Sparse Antedon spp., Ophiothrix fragilis and hydroids such as Halecium halecinum and Kirchenpaueria pinnata. Liocarcinus depurator often present on the sediment. Similar epifaunal communities are found on Crepidula fornicata (CreTha) beds with shell debris, oyster beds (Ost), Modiolus beds (ModHAs) and on cobbles and stones - all in estuarine conditions.
Solitary ascidians, including Ascidia mentula and Ciona intestinalis, on very sheltered circalittoral rock
Upper circalittoral, often vertical, bedrock and steep boulder slopes in generally sheltered conditions with little tidal flow and typically with Ascidia mentula and Ciona intestinalis. Brachiopods and/or Protanthea simplex found at some sites (where this biotope may occur above NeoPro for example) and sponges include small amounts of Esperiopsis fucorum, Suberites carnosus, Polymastia mamillaris and barnacles often frequent. Hydroids such as Halecium halecinum often present. The large ascidian Phallusia mammillata seems to occasionally occur in this biotope. Some of the Irish examples of this biotope have Corynactis in shallow water. In extreme shelter, but with perhaps slightly more tidal flow, a more species-rich biotope with solitary ascidians and more sponge (SubSoAs) is found.
Large Metridium senile and solitary ascidians on grazed very sheltered circalittoral rock
Very sheltered circalittoral rock with very large Metridium senile (possibly where slight tidal streams pass over rocky ridges) and a variety of solitary ascidians including Ascidia mentula and Ciona intestinalis. Much of the rock surface appears Echinus-grazed and is covered in silt and coralline crusts with sparse Pomatoceros triqueter. Occasional Bolocera tuediae found at some sites in the north Clyde sealochs. Other species include Edwardsiella carnea, Sarcodictyon roseum and sparse Modiolus modiolus. Often found in shallow water above the Neocrania and Protanthea biotope (NeoPro) and just below Laminaria saccharina forest but has often been included as part of one of these biotopes. This biotope is distinct from other Metridium-dominated types (e.g. those which occur on strongly tide-swept and exposed circalittoral rock and steel wreckage) in that most of the associated fauna is characteristic of very sheltered conditions.
Antedon spp., solitary ascidians and fine hydroids on sheltered circalittoral rock
Typically found in sheltered parts of sealochs which might be subject to slight tidal currents. No one phyla or species dominates the rock but the most conspicuous comprise featherstars (Antedon bifida, Antedon petasus and more rarely Leptometra celtica), solitary ascidians (e.g. Ascidia mentula) and fine hydroids (Kirchenpaueria pinnata, Halecium halecinum and Bougainvillia ramosa). In the sealochs, where the three species of featherstar are found at the same site Antedon petasus is often the more abundant featherstar in deeper water whereas A. bifida tends to dominate the shallower regions. Leptometra celtica tends to occur in deep water and is also found on rocks on mud plains. Caryophyllia smithii, serpulid worms, Balanus balanus, Munida rugosa, brachiopods, some brittlestars, and algal crusts are all typically present. Crustose sponges such as Hymedesmia paupertas may occur on vertical faces. In deep water at some sites in sealochs Mycale lingua and Leptometra celtica are found on upward facing rock. This biotope has some overlaps with the solitary ascidian biotopes (As) although these tend to occur is slightly more sheltered conditions with little or no tidal flow.
Neocrania anomala and Protanthea simplex on very sheltered circalittoral rock
Deep rock (often vertical walls) in the landward basins of fjordic sealochs often have dense Protanthea simplex growing on rock and tubes of Chaetopterus sp. and amongst Sabella pavonina. The underlying rock surfaces are covered with Neocrania anomala and large solitary ascidians such as Corella parallelogramma, Polycarpa pomaria, Ascidia mentula and Ascidia virginea are often present amongst the worm tubes. ROV records in Loch Duich from 60-160 m show a gradual change from the above to a community dominated by white Sabella and large numbers of Protula tubularia.
Brachiopods, calcareous tubeworms (Placostegus tridentatus, Hydroides) and sponges on variable salinity circalittoral rock
Deep (20-30 m+) bedrock in fjordic sealochs where slight fluctuations in salinity might influence the biotope structure. Neocrania anomala, Pomatoceros triqueter and Placostegus tridentatus occur with large sponges Clathria barleei, Axinella infundibuliformis and the crustose Phakellia vermiculata. This biotope has some similarities with NeoPro.Den although occurs in more open lochs and tends to be more species-rich with erect sponges and solitary ascidians typical of the sheltered conditions.
Neocrania anomala, Dendrodoa grossularia and Sarcodictyon roseum on reduced or low salinity circalittoral rock
This biotope is a variant of the Neocrania biotopes which characterise steep circalittoral rock in the landward basins of fjordic sealochs, although in this case it is found only in Loch Etive. There is very little water movement and salinity fluctuates considerably through the year, even in deep (20 m +) water. The near-bare granite supports relatively few species with patches of dense Dendrodoa grossularia, small lines of Sarcodictyon roseum, sometimes abundant Neocrania anomala, a few Terebratulina retusa and Placostegus tridentatus (which broadly resemble Pomatoceros triqueter). The solitary ascidians Corella parallelogramma, Ascidiella scabra and Ascidia virginea are also associated with this biotope. Echinus-grazed 'barren' rock is found in other sealochs in Scotland and Ireland occasionally with a similar suite of encrusting fauna. However, Echinus were not present in Loch Etive and the bareness of the rock is almost certainly attributable to the variable/low salinity.
Suberites spp. and other sponges with solitary ascidians on very sheltered circalittoral rock
Silty very sheltered circalittoral rock, (often vertical surfaces) subject to only weak tidal streams with a rich mixture of sponges (Polymastia boletiformis, Suberites carnosus, occasionally Suberites ficus, Iophon hyndmanni, Dysidea fragilis, Raspailia ramosa and Stelligera rigida) and a variety of large solitary ascidians (Ascidia virginea, Ascidiella aspersa, Ascidia mentula and, more rarely, Phallusia mammillata and Styela clava).
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 sponges, hydroids and bryozoans, on soft shelly mud in areas of slight tidal currents. The clams Chlamys varia and Aequipecten opercularis are present in large numbers amongst the Modiolus shells. Sponges include Mycale rotalis, Mycale macilenta, Mycale similaris, Spanioplon armaturum, Iophon hyndmani and Haliclona spp. The holothurians Thyone fusus and Thyonidium drummondii and the ascidian Pyura microcosmus are also present. This biotope is found in Strangford Lough where the Modiolus beds are well developed. Similar communities have been found on cobble and pebble plains in stable, undisturbed conditions in other sealochs. However, 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. Large solitary ascidians (Ascidiella aspersa, Corella parallelogramma, Ciona intestinalis) and fine hydroids (Bougainvillia ramosa, Kirchenpaueria pinnata) present attached to the mussel shells. Decapods such as spider crabs and Munida rugosa typically present. Coralline algal crusts on the mussel shells, with some red seaweeds in shallower water. Aequipecten opercularis often present in moderate abundances. The much richer version of this biotope ModCvar has far more sponges and hydroids growing on and amongst the Modiolus and large numbers of Chlamys varia. Brittlestars Ophiothrix fragilis and Ophiocomina nigra, as well as Ophiopholis aculeata are often common, sometimes forming a dense bed as described in Oph. The biotope ModHo, characterised by Modiolus and holothurians occurs in similar physiographic features, although seems to be in softer sediment in some cases. There may some overlap in these two biotopes as several of the holothurians extend their tentacles above the surface of the sediment for only a limited amount of time during the year.
Infralittoral rock (and other hard substrata)
Kelp with cushion fauna, foliose red seaweeds or coralline crusts (exposed rock)
Alaria esculenta on sublittoral fringe bedrock
Alaria esculenta forest on exposed sublittoral fringe bedrock with an encrusting fauna of mussels and barnacles. The rock surface is covered with encrusting coralline red algae. Two variants of this biotope are described. The more wave exposed of the two lacks Laminaria digitata and is also characterised by patches of mussels (EIR.Ala.Myt). The other variant is slightly less exposed and is characterised by a mixture of A. esculenta and L. digitata (EIR.Ala.Ldig).
Alaria esculenta and Laminaria digitata on exposed sublittoral fringe bedrock
Exposed sublittoral fringe bedrock characterised by a mixture of Laminaria digitata and Alaria esculenta with anemones, mussels Mytilus edulis and barnacles growing over a coralline algal crust. The bryozoan crust Umbonula littoralis is typical of this zone on the shore and the barnacle Verruca stroemia may be present. This biotope also occurs on less exposed steep and vertical shores where a localised increase in wave action restricts the growth of L. digitata. As a result of this increased wave action the L. digitata plants are usually small and often show signs of damage. EIR.Ala.Ldig represents an intermediate on the wave exposure gradient, with pure stands of Alaria esculenta (EIR.Ala.Myt) being found on more exposed shores and pure Laminaria digitata (MIR.Ldig) on more sheltered shores. This biotope has a greater abundance of Mytilus edulis, limpets and coralline algae compared with MIR.Ldig. In contrast with the more exposed EIR.Ala.Myt, this biotope has a greater diversity of foliose red algae, including Cryptopleura ramosa, Osmundea (Laurencia) pinnatifida and Lomentaria articulata. This biotope usually occurs immediately above a sublittoral Laminaria hyperborea forest (EIR.LhypR or MIR.Lhyp), although a narrow band of L. digitata (MIR.Ldig) may occur between these two zones. On exposed shores in the north, Alaria alone tends to occupy the sublittoral fringe. A number of different biotopes may be found above EIR.Ala.Ldig; most commonly these are Himanthalia elongata (ELR.Him), a red algal turf (MLR.R) or a Fucus serratus-red algal mosaic (MLR.Fser.R).
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 Mytilus edulis, both of which grow over a dense cover of encrusting coralline algae. Foliose red algae may also be present, but the species composition and their abundance varies between sites. Species such as Corallina officinalis, Mastocarpus stellatus and Plocamium cartilagineum occur widely. Limpets and barnacles are often common. Patches of anemones (such as Sagartia elegans) and the hydroid Tubularia indivisa also occur in wave-surged areas. Laminaria digitata is usually absent, although stunted plants may be present at a few sites (typically greater than frequent). On very exposed shores this biotope is usually found beneath the Mytilus edulis-barnacle zone (ELR.MytB) and above the sublittoral Laminaria hyperborea forest (EIR.LhypR or EIR.LhypFa). In extremely exposed areas the Alaria zone may extend as deep at 15 m, where it generally has less Mytilus and greater densities of Tubularia (e.g. Barra and shallow areas of Rockall). This biotope is, however, distinguished from the deep Alaria forest (EIR.AlaAnSC) found on Rockall by its lack of short turf-forming hydroids. On less exposed shores an Alaria-dominated zone may, however, lie immediately above a narrow Laminaria digitata zone (MIR.Ldig). This biotope can also occur on exposed steep or vertical shores, where wave-crash restricts the growth of Laminaria digitata.
Alaria esculenta forest with dense anemones and sponge crusts on extremely exposed infralittoral bedrock
This biotope has only been recorded from Rockall, where Alaria appears to replace L. hyperborea as the dominant kelp forest species on the extremely wave exposed steep and vertical rock. Some Laminaria is reported to occur mixed with Alaria on the nearby Helen's reef. Beneath the Alaria, the rock surface is covered by a dense turf of anemones (such as Sagartia elegans, Phellia gausapata and Corynactis viridis) and encrusting sponges. Tubularia indivisa also occurs, but it does not form such a dense turf as in shallower waters. Cryptopleura ramosa is the dominant red seaweed on horizontal surfaces. This zone extends from 14 m - 35 m. Above this zone (about 5 m to 13 m) Alaria still dominates, but it more closely resembles the typical sublittoral fringe Alaria biotope (EIR.Ala.Myt), though it has a very dense turf of small hydroids and few foliose algae. Towards the lower part of this Alaria forest (30 m to 35 m) the Alaria thins and the rock surface is characterised by a dense turf of red algae.
Foliose red seaweeds on exposed or moderately exposed lower infralittoral rock
A dense turf of foliose red seaweeds (including Plocamium cartilagineum, Cryptopleura ramosa and Delesseria sanguinea) 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. The red seaweed species composition varies considerably and at some sites a single species may dominate (particularly Plocamium or Cryptopleura) 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. In some areas Dictyota may occur at high densities (see EIR.FoR.Dic). Other red seaweed-dominated biotopes occur in less wave-exposed areas (MIR.PolAhn), though they are affected by sand scour and are characterised by seaweeds that are resilient to the scouring.
Foliose red seaweeds with dense Dictyota dichotoma and/or Dictyopteris membranacea on exposed lower infralittoral rock
A dense turf of foliose red seaweeds (including Delesseria sanguinea, Plocamium cartilagineum and Callophyllis laciniata) mixed with a dense turf of the 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 may be subject to a moderate amount of scour from nearby sand. Dictyota is relatively tolerant of such scour and in such areas a zone may form with other tolerant seaweeds, such as Schottera nicaeensis and Desmarestia spp. Dictyopteris is confined to south-western coasts. Dictyota also occurs in the kelp park, and records should only be assigned to this biotope where kelp is sparse or absent (less than occasional) and a relatively high density of Dictyota and / or Dictyopteris (generally greater than common) is present.
Laminaria hyperborea forest with a faunal cushion (sponges and polyclinids) and foliose red seaweeds on very exposed 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, beneath which is a rich mixture of sponges, polyclinid ascidians, anemones and dense foliose red seaweeds. 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 shallowest kelp plants are often short or stunted, while deeper plants are taller with heavily epiphytised stipes. The faunal composition of this biotope varies markedly between sites, but commonly occurring animals are Alcyonium digitatum, Sagartia elegans, Corynactis viridis, the sponges Halichondria panicea and Pachymatisma johnstonia and polyclinid ascidians. Similarly the foliose seaweed turf may show considerable variation. At some sites it can be virtually mono-specific, comprising stands of Delesseria sanguinea, Ptilota plumosa, Cryptopleura ramosa or Plocamium cartilagineum or, in the north, Odonthalia dentata. Other sites may contain a dense mixed turf of these and other species. Beneath the under-storey the rock surface is generally covered with encrusting coralline algae. At sites where the rock is fissured and has many vertical and overhanging surfaces, the fauna is particularly diverse. Large areas of vertical rock are often dominated by Alcyonium digitatum with Metridium senile and or Corynactis viridis (IR.CorMetAlc) and encrusting red algae. This kelp forest most commonly occurs beneath a zone of Alaria/Mytilus (EIR.Ala.Myt) and may contain small patches of Alaria esculenta. At less wave surged sites, or in slightly deeper water beneath this biotope, the kelp forest or park generally lacks the dense faunal turf, and is characterised by kelp and dense red seaweeds (EIR.LhypR.Ft or EIR.LhypR.Pk). In some areas of Shetland the lower infralittoral zone is characterised by a park of L. saccharina and or Saccorhiza polyschides (EIR.LsacSac).
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 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 dense coralline algal crust, and occasional Laminaria hyperborea and Saccorhiza polyschides. The anemones 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.
Laminaria hyperborea with dense foliose red seaweeds on exposed infralittoral rock
Very exposed and exposed upper 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 (EIR.LhypR.Ft), the kelp park below (EIR.LhypR.Pk) and a third type of kelp forest that is characterised by a mixture of L. hyperborea and Laminaria ochroleuca (EIR.LhypR.Loch). The fauna of these biotopes is markedly less abundant than kelp forests in areas of greater wave surge (EIR.LhypFa); sponges, anemones and polyclinid ascidians may be present, though never at high abundance. Beneath the under-storey 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 and exposed upper infralittoral bedrock or large boulders characterised by a dense forest of the kelp Laminaria hyperborea, beneath which is a dense turf of foliose red seaweeds. The dense seaweed turf is due, in part, to the relatively low urchin-grazing pressure in such shallow exposed conditions. The shallowest kelp plants are often short or stunted, while deeper plants are taller with heavily epiphytised stipes. Amongst the red seaweeds, an often dense turf of the bryozoans Scrupocellaria spp. and Securiflustra securifrons may occur. The cushion fauna in this biotope is markedly less abundant than kelp forests in areas of greater wave surge (EIR.LhypFa) and whilst sponges, anemones and polyclinid ascidians may be present, they do not occur at high abundance. Beneath the under-storey the rock surface is generally covered with encrusting coralline algae. This kelp forest most commonly occurs beneath a zone of Alaria/Mytilus (EIR.Ala.Myt) and above a L. hyperborea park (EIR.LhypR.Pk) or a park of L. saccharina and/ or Saccorhiza polyschides (EIR.LsacSac).
Mixed Laminaria hyperborea and Laminaria ochroleuca forest on exposed infralittoral rock
Mixed Laminaria hyperborea and Laminaria ochroleuca forests on upper infralittoral exposed rock are restricted to the coast of Cornwall and the Isles of Scilly. Superficially, the L. ochroleuca biotope looks similar to the more widespread exposed Laminaria hyperborea forest (EIR.LhypR.Ft), containing a similar suite of foliose red algae (such as Phycodrys rubens, Plocamium cartilagineum, Callophyllis laciniata and Delesseria sanguinea) beneath the canopy. Unlike L. hyperborea, however, L. ochroleuca has a smooth stipe and so it lacks dense assemblages of epiphytic seaweeds, though some Palmaria palmata may occur. This biotope commonly occurs below EIR.LhypR.Ft, since L. ochroleuca is less tolerant of wave action than L. hyperborea. L. ochroleuca occurs at low abundances in other kelp biotopes (sheltered through to exposed) from Dorset to Lundy Island. In such cases, records should be treated as regional variations of the usual kelp biotope. Records should only be assigned to this 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 abundances). This biotope is similar to the mixed L. hyperborea and L. ochroleuca biotope found on moderate and sheltered coasts (MIR.Lhyp.Loch), though the latter generally occurs in shallower water and has a lower density of L. hyperborea, fewer foliose and more filamentous red algae. Both L. ochroleuca biotopes are common on the Brittany and Normandy coasts.
Laminaria hyperborea park with dense foliose red seaweeds on exposed lower infralittoral rock
Very exposed and exposed lower infralittoral bedrock or large boulders characterised by a park of the kelp Laminaria hyperborea with a dense turf of foliose red seaweeds. Dense foliose red seaweeds dominate the under-storey in a similar abundance to the upper infralittoral kelp forest. In addition, moderate to high abundances of foliose brown seaweeds, such as Dictyota dichotoma and / or Dictyopteris membranacea, are more common in this kelp park than the forest above. At some sites, a dense band of Dictyota may form a separate zone (see EIR.FoR.Dic). In the late summer both the kelp and the foliose seaweeds can become heavily encrusted with the bryozoan crusts Electra pilosa and Membranipora membranacea. This biotope usually occurs below the exposed kelp forests (EIR.LhypFa.Ft and EIR.LhypR.Ft) and all these biotopes have a similar species composition. This biotope does, however, have a much reduced density of large kelp plants.
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 or 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 may also develop on bedrock where it is affected by its close proximity to unstable substrata. Other fast-growing algae such as Ulva spp., Alaria esculenta, Desmarestia spp. and Chorda filum are often present. This biotope can be found below the L. hyperborea zone (EIR.LhypFa or EIR.LhypR), especially where close to a rock/ sand interface (subjected to sand scour in winter?). Some L. hyperborea plants may occur in this biotope, but they are typically small since the plants do not survive many years. In St Kilda this biotope is present on steep/vertical rock between the sublittoral fringe of Alaria esculenta and the Laminaria hyperborea forest below. In such places this biotope occurs because intense wave action in winter storms is too severe to allow L. hyperborea to develop and remain in shallow water.
Robust faunal cushions and crusts (surge gullies & caves)
Robust faunal cushions and crusts (surge gullies and caves)
Balanus crenatus and/or Pomatoceros triqueter with spirorbid worms and coralline crusts on severely scoured infralittoral rock (No description at this level)
Walls, or massive boulders, in caves or gullies that are subject to severe wave-surge may be characterised by extensive thin crusts of Halichondria panicea with smaller patches of other sponges including Clathrina coriacea and Leuconia nivea. Small turfs of robust hydroids such as Diphasia rosacea and Ventromma halecioides and patches of Balanus crenatus and coralline crusts may be present. This biotope is subject to a greater degree of wave surge and scour than either of sponge crust and ascidian biotopes (EIR.SCAs), or the sponge crust and anemone-dominated biotopes (EIR.SCAn).
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 look bare, but are characterised by a limited scour-tolerant fauna of Balanus crenatus and / or Pomatoceros triqueter with spirorbid polychaetes. In areas where sufficient light is available, the rock surface is covered by encrusting coralline algae and non-calcareous crusts, 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 may produce a narrow band of bare coralline algal crust at the very bottom of the walls, with a band of Pomatoceros 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, small Mytilus edulis and occasional Actinia equina, Urticina felina and Sagartia spp. 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 EIR.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 often appear bare. Where there is sufficient light, however, the boulders are encrusted by coralline algal crusts. Decapods such as Pagurus spp., Cancer pagurus and Carcinus maenas also occur, often beneath and between the rocks. The slightly less-scoured walls often found above this biotope in caves and gullies are generally characterised by a similar, but richer community of scour-tolerant Balanus crenatus, Pomatoceros triqueter, coralline crusts and spirorbid worms (EIR.CC.BalPom). This impoverished biotope may form an intermediate between barren gravel and slightly more stable larger pebbles and cobbles which are covered by algae that are often found in the mouths of caves (EIR.FoSwCC).
Foliose seaweeds and coralline crusts in surge gully entrances
This biotope is often found on steep wave-surged entrances to gullies and caves and on mobile boulders in the entrance to caves and gullies. The rock is abraded by the movement of the boulders and cobbles in heavy surge and is dominated by dense foliose seaweeds that grow rapidly in the calmer summer months. Beneath the foliose seaweeds the rock surface is 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 Plocamium cartilagineum, Kallymenia reniformis and Phyllophora crispa common. 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 may also arise in this biotope, though the mobility of the substratum prevents the kelp from forming a kelp forest. Dense swathes of very young kelp plants are, however, not uncommon and should be included in this biotope. This biotope may appear similar to EIR.LsacSac, though EIR.LsacSac, often occurs further away from the cave / gully entrance on larger boulders. As such, the greater (relative) stability of the boulders allows the opportunistic kelps to survive long enough to form a forest.
Sponge crusts on extremely wave-surged infralittoral cave or gully walls
Sponge crusts and anemones on 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, Leucosolenia botryoides and Halichondria panicea) and anemones, such as Sagartia elegans and dwarf Metridium senile generally dominate the area, the anemones often appearing to protrude through the sponge layer. This biotope is generally unaffected by sand scour (compare with those dominated by sponge crusts and ascidians (EIR.SCAs). A variant of this biotope has been identified from the very wave-surged sublittoral fringe with dense aggregations of the hydroid Tubularia (EIR.SCAn.Tub). Both of these biotopes may contain colonial ascidians, but never at high densities (compare with EIR.SCAs). Encrusting coralline algae and tufts of foliose red seaweeds may also occur on well-illuminated rock faces. Due to the wave-surged nature and vertical orientation of these biotopes, kelps are rare and certainly never dominate (compare with EIR.LhypFa and EIR.Ala.Myt). This biotope may also include a turf of Crisia or Scrupocellaria spp.
Sponge crusts, anemones and Tubularia indivisa in shallow infralittoral surge gullies
Shallow, vertical or overhanging very exposed and exposed bedrock gullies, tunnels and cave entrances that are subject to strong wave-surge and characterised by sponge crusts (such as Halichondria panicea, Myxilla incrustans and Leucosolenia botryoides), anemones (such as Sagartia elegans and dwarf Metridium senile), and often dense aggregations of Tubularia indivisa and patches of small mussels Mytilus edulis. Some patches of colonial ascidians may occur, but they never dominate the biotope (compare with EIR.SCAs). Corynactis viridis and Alcyonium digitatum may both occur, but only ever at low to moderate abundances (compare with IR.CorMetAlc) due to the high degree of wave-surge at such shallow depths.
Sponge crusts and colonial ascidians on wave-surged vertical infralittoral rock
Wave-surged, overhanging, vertical and steep infralittoral rock in caves tunnels and gullies subject to some sand-scour and characterised by sponge crusts and ascidians. This biotope is found in similar locations to the sponge crusts and anemones biotope (EIR.SCAn), but the latter are not subject to as much scour. Sponges include Clathrina coriacea, Leucosolenia botryoides, Esperiopsis fucorum and Halichondria panicea while the ascidians include mixtures of Polyclinum aurantium, Dendrodoa grossularia, Aplidium spp., Diplosoma spp. and other didemnids. On surfaces that receive sufficient illumination, a moderately dense turf of foliose red seaweeds may also occur. Crevices and other areas that offer some protection from sand scour may contain anemones, such as Sagartia elegans and Metridium senile, though they never dominate the biotope (compare with EIR.SCAn). On vertical walls towards the back of caves, the rock may be dominated by only Dendrodoa grossularia and Clathrina coriacea (see EIR.SCAs.DenCla). In deeper, though still scoured gullies, caves and tunnels the rock may be covered by sponge crusts, polyclinid ascidians and a bryozoan and hydroid turf (see EIR.SCAs.ByH).
Sponge crusts, colonial (polyclinid) ascidians and a bryozoan/hydroid turf on wave-surged vertical or overhanging infralittoral rock
Vertical and overhanging wave-surged rock, subject to some scour in caves gullies and tunnels, and dominated by sponge crusts, colonial ascidians and a short turf of bryozoans and hydroids. Like the other sponge crust and ascidian-dominated biotopes, this biotope is also subject to a degree of scouring. It is, however, generally found in slightly deeper water and is not subject to as much wave surge as the shallower biotopes (EIR.SCAs or EIR.SCAs.DenCla). This biotope may occur at a similar depth and in similar conditions to the biotope characterised by sponges, Corynactis, Metridium and Alcyonium biotope (IR.CorMetAlc), though the additional scouring in this biotope leads to dominance by ascidians rather than anemones. The sponge and ascidian composition of this biotope is similar to the others in this group, though this biotope is distinguished by the often dense short turf of bryozoans such as Crisia and Scrupocellaria. Hydroids, particularly Tubularia indivisa, may also occur, especially on protruding surfaces. Foliose red seaweeds may occur, though generally not in high abundances, since the biotope is usually (but not always) found where light levels are too low. As with the other sponge and ascidian- dominated biotopes, anemones may occur, although scouring prevents them dominating over the ascidians. Patches of rock that are protected from sand scour may also contain anemones, such as Sagartia elegans and Metridium senile, though they never dominate (compare with EIR.SCAn).
Dendrodoa grossularia and Clathrina coriacea on wave-surged vertical infralittoral rock
Vertical and overhanging wave-surged rock that is subject to some scour especially in the middle or back of caves but also in gullies and tunnels, are often dominated by dense sheets of Dendrodoa grossularia with the sponge Clathrina coriacea. At some sites Dendrodoa may form continuous sheets, with few other species present. Other sponges such as Esperiopsis fucorum, Pachymatisma johnstonia and Halichondria panicea regularly occur in this biotope, though generally at low abundance. Other ascidians, especially Polyclinum aurantium, Diplosoma and other didemnids may also occur, though only Polyclinum is ever as abundant as Dendrodoa. 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 in this biotope, though encrusting coralline algae are not uncommon. As with the other sponge and ascidian- dominated biotopes, anemones may occur, though scouring prevents them dominating over the ascidians. Micro-habitats protected from sand scour may also contain anemones, such as Sagartia elegans and Metridium senile, though they never dominate this biotope (compare with EIR.SCAn).
Fauna and seaweeds (shallow vertical rock)
Alcyonium digitatum and a bryozoan, hydroid and ascidian turf on moderately exposed vertical infralittoral rock
Vertical, shaded surfaces in the infralittoral zone tend to lack dense kelp and other red seaweeds and are instead dominated by Alcyonium digitatum with a turf of bryozoans such as Bugula flabellata and hydroids including Kirchenpaueria pinnata. Beneath this turf the rock is generally encrusted by coralline algae, encrusting bryozoans and Pomatoceros triqueter. Ascidians such as Botryllus schlosseri, Clavelina lepadiformis and Ciona intestinalis are also common. This biotope has a wide species composition, and warrants further data analysis.
Hiatella arctica, bryozoans and ascidians on vertical infralittoral soft rock
Vertical faces of soft rock (limestone, chalk, sandstone) bored by Hiatella arctica. Bored holes are occupied by brittlestars such as Ophiopholis aculeata and Ophiactis balli and small crustaceans such as Pisidia longicornis and Porcellana platycheles. Open rock surfaces are often colonised by tufted bryozoans Bugula spp. and Scrupocellaria spp., sponges, hydroids and ascidians including Polycarpa scuba, P. pomaria and Dendrodoa grossularia. This biotope is similar to IR.AlcByH, but this biotope additionally has rock-boring bivalves.
Corynactis viridis, Metridium senile and Alcyonium digitatum on exposed or moderately exposed vertical infralittoral rock
Vertical walls in exposed or moderately exposed, wave-surged or tide-swept areas with Corynactis viridis, dwarf Metridium senile and Alcyonium digitatum. This biotope may show a large variation in relative abundances of the characterising species, some appearing to be dominated by Corynactis or Alcyonium or Metridium alone. Beneath and between these species, sponge crusts and polyclinid ascidians may be present and where sufficient light is available, encrusting coralline algae and tufts of foliose red seaweeds. This biotope may be found in deeper gullies below the more wave-surged biotopes (see EIR.SCAs and EIR.SCAn), or on vertical cliffs found within the kelp zone (EIR.LhypFa or EIR.LhypR). When Alcyonium occurs at high abundance in this biotope, it may be confused with the more sheltered biotope in which Alcyonium also dominates (IR.AlcByH). The latter, deeper biotope, lacks the associated surge-tolerant species such as encrusting sponges and anemones (e.g. Corynactis and Sagartia elegans). As it is less wave-surged than EIR.SCAn.Tub, this biotope lacks such high densities of Tubularia and Mytilus, but contains a greater abundance of turf-forming bryozoans such as crisiids. This biotope occurs at a similar depth and in similar conditions to the sponge crust, polyclinid ascidian and bryozoan / hydroid biotope (EIR.SCAs.ByH), although the latter is more affected by sand scour, allowing the ascidians to dominate over the anemones.
Grazed Laminaria hyperborea with coralline crusts on infralittoral rock
Laminaria hyperborea forests and parks on bedrock and boulders, subject to intense grazing by Echinus esculentus, with rock surfaces dominated by encrusting algae (coralline or brown algae). Erect seaweeds are sparse or absent.
Grazed Laminaria hyperborea forest with coralline crusts on upper infralittoral rock
Exposed and moderately exposed kelp forest in some areas is intensely grazed by the urchin Echinus esculentus. The rock surface lacks any significant turf of foliose seaweeds and generally looks bare, though it is covered by coralline algal crusts. The kelp stipes may or may not be grazed; in the most extremely grazed areas, they too are devoid of epiphytic seaweeds. More usually, however, the stipes offer a refuge from grazing, and are characterised by dense turfs of red seaweeds, especially Phycodrys rubens, Palmaria palmata, Membranoptera alata and Delesseria sanguinea. The fauna within a grazed kelp forest is also relatively sparse, though some species will survive in cracks and crevices, or other areas that are protected from grazing. In wave-exposed steep rocky areas, the shallowest water may be characterised by a forest of kelp with red seaweeds (EIR.LhypR.Ft), with a grazed kelp forest beneath. This effect may be a result of the increased wave action in shallower water which regularly dislodges the urchins thereby reducing their impact. With increasing depth, the kelp forest grades into a grazed kelp park (MIR.LhypGz.Pk), the lower limit of which is often abrupt, which represents the balance point between urchin grazing pressure and algal growth capabilities.
Grazed Laminaria hyperborea park with coralline crusts on lower infralittoral rock
Exposed and moderately exposed kelp park in some areas is heavily grazed by the urchin Echinus esculentus. The rock surface lacks any significant turf of foliose seaweeds and generally looks bare, though it is covered by coralline algal crusts and some grazing-resistant species such as the keel worm Pomatoceros triqueter. The kelp stipes may or may not be grazed; in the most extremely grazed areas, they too are devoid of epiphytic seaweeds. More usually, however, the stipes offer a refuge from grazing, and are characterised by dense turfs of red seaweeds, especially Phycodrys rubens, Palmaria palmata, Membranoptera alata and Delesseria sanguinea. The fauna within a grazed kelp park is also relatively sparse, though some species will survive in cracks and crevices, or other areas that are protected from grazing. This biotope generally occurs below a grazed kelp forest (MIR.LhypGz.Ft).
Kelp with red seaweeds (moderately exposed rock)
Laminaria digitata on moderately exposed or tide-swept sublittoral fringe rock
Exposed to sheltered sublittoral fringe rock with a canopy of the kelp Laminaria digitata. Several variants of this biotope are described for moderately exposed, sheltered, tide-swept and boulder shores.
Laminaria digitata on moderately exposed sublittoral fringe rock
Moderately exposed to sheltered sublittoral fringe bedrock or boulders dominated by a dense canopy of Laminaria digitata often with a wide range of filamentous and foliose red seaweeds beneath. The rocky substratum is usually covered by encrusting coralline algae, on which occasional limpets Patella vulgata and topshells Gibbula spp. graze. A wide variety of fauna occurs, including the sponge Halichondria panicea, barnacles (Balanus crenatus and Semibalanus balanoides) and occasional small mussels Mytilus edulis. Kelp holdfasts provide a refuge for a varied assemblage of species including sponges (e.g. Leucosolenia spp.), anemones (Urticina felina), limpets (Helcion pellucidum), crustaceans, encrusting bryozoans and colonial ascidians. This biotope is usually found beneath the Fucus serratus zone (MLR.Fser) and above the truly sublittoral Laminaria hyperborea zone (MIR.Lhyp). Other canopy-forming kelps such as Alaria esculenta and Laminaria saccharina, may occur although never at high abundance (compare with EIR.Ala.Ldig and SIR.Lsac.Ldig respectively). In areas where tidal water movement is increased, a richer L. digitata-dominated biotope (MIR.Ldig.T) generally replaces the sheltered shore Laminaria saccharina (SIR.Lsac) biotope.
Laminaria digitata and under-boulder fauna on sublittoral fringe boulders
This Laminaria digitata biotope is found on moderately exposed to sheltered boulder shores. Upper surfaces of the boulders are similar to MIR.Ldig.Ldig and are colonised by dense Laminaria digitata, beneath which are a variety of red seaweeds including Mastocarpus stellatus, Lomentaria articulata, Osmundea (Laurencia) pinnatifida and Corallina officinalis. Where space is available beneath the boulders there may be a rich assemblage of animals. Characteristic species include the hairy porcelain crab Porcellana platycheles, the smooth porcelain crab Pisidia longicornis and juvenile edible crabs Cancer pagurus. Also present beneath the boulders are often high densities of the barnacle Balanus crenatus, the keel worm Pomatoceros spp., spirorbid worms, gammarid amphipods and a few small gastropods and mussels. The encrusting bryozoans Umbonula littoralis and Schizoporella unicornis and encrusting colonies of the sponges Hymeniacidon perleve and Halichondria panicea are also typical of this habitat. The richest examples also contain a variety of brittlestars, ascidians and small hydroids.
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, Pholas dactylus and Petricola pholadiformis), the bivalve Hiatella arctica and worms Polydora spp. Beneath the kelp forest, a wide variety of red seaweeds, including Corallina officinalis, Palmaria palmata, Chondrus crispus, Membranoptera alata and Halurus flosculosus, may occur. Empty piddock burrows are often colonised by the anemones Sagartia elegans or by the sand-tube building worm Sabellaria spinulosa. The undersides of small chalk boulders are colonised by encrusting bryozoans, colonial ascidians and the keel worm Pomatoceros lamarcki. The boulders and any crevices within the chalk provide a refuge for small crustaceans such as Carcinus maenas, young Cancer pagurus, Pagurus bernhardus and Porcellana platycheles. [Further data and analysis still required].
Laminaria digitata, ascidians and bryozoans on tide-swept sublittoral fringe rock
Very sheltered bedrock, boulders and cobbles that are subject to moderate to strong tidal water movement characterised by dense Laminaria digitata, ascidians and bryozoans. Species richness is generally greater than in the non tide-swept L. digitata biotope (MIR.Ldig.Ldig), with a greater abundance and wider range of foliose red seaweeds. The increased water movement encourages several filter-feeding faunal groups to occur. The sponges Leucosolenia spp., Halichondria panicea and Hymeniacidon perleve frequently occur on steep and overhanging faces. In addition, the ascidians Ascidia conchilega, Dendrodoa grossularia and colonial ascidians are also found. Areas where increased tidal movement influences such a community are in the narrows and/or intertidal sills of sealochs. This biotope may be found immediately below the tide-swept Fucus serratus biotope (SLR.Fserr.T). The sublittoral fringe of similarly sheltered shores that are not tide-swept are generally characterised by mixed L. saccharina and L. digitata (SIR.Lsac.Ldig) or L. saccharina (SIR.Lsac).
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. This suite of biotopes differ from the wave exposed Laminaria hyperborea biotopes by having a lower diversity of encrusting faunal species. The foliose red seaweed component of the two suites of biotopes may also differ in composition with a tendency for MIR.Lhyp to include some more delicate filamentous species. Several variants of this biotope are described: kelp forests, kelp parks, kelp park and two tide-swept kelp types.
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 (such as Plocamium cartilagineum, Cryptopleura ramosa and Delesseria sanguinea). The rock surface is generally covered by encrusting coralline algae, while cracks and crevices are filled with the sponge Halichondria panicea. Small vertical surfaces within the kelp forest generally lack kelp plants, instead being characterised by foliose red seaweeds, Alcyonium digitatum, Caryophyllia smithii and solitary and colonial ascidians. Kelp stipes are usually covered in a rich mixture of red seaweeds including Palmaria palmata, Phycodrys rubens and Membranoptera alata, and sometimes small kelp plants. This biotope generally occurs below the sublittoral fringe L. digitata zone (MIR.Ldig). Where urchins are present, the abundance of red seaweeds may be much reduced (though not the species richness?) (see MIR.LhypGz.Ft).
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. Superficially, the L. ochroleuca biotope looks similar to a moderately exposed Laminaria hyperborea forest (MIR.Lhyp.Ft), containing a similar suite of foliose and filamentous red algae beneath the canopy. Unlike L. hyperborea, however, L. ochroleuca has a smooth stipe and so it lacks dense assemblages of epiphytic seaweeds. 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 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). This biotope is similar to the mixed L. hyperborea and L. ochroleuca biotope found on exposed coasts (EIR.LhypR.Loch), though the latter generally occurs in slightly deeper water (often below pure L. hyperborea - EIR.LhypR.Ft) as L. ochroleuca is less tolerant of strong wave action at its northern distributional limit. Both L. ochroleuca biotopes are common on the Brittany and Normandy coasts.
Laminaria hyperborea park and foliose red seaweeds on moderately exposed lower infralittoral rock
Below the dense kelp forest (MIR.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. The faunal component of this biotope is similar to that found below the kelp in the upper circalittoral zone. Many species of foliose red seaweed found in this biotope, such as Membranoptera alata and Ptilota plumosa, occur in the shallower kelp forest at greater abundance. Other species such as Hypoglossum hypoglossoides, Pterothamnion plumula and Brongniartella byssoides are more abundant in this zone than the upper infralittoral.
Laminaria hyperborea forest, foliose red seaweeds and a diverse fauna on tide-swept upper infralittoral rock
Moderately exposed, tide-swept, rock with dense Laminaria hyperborea forest is characterised by a rich under-storey and stipe flora of foliose seaweeds such as Plocamium cartilagineum, Callophyllis laciniata, Heterosiphonia plumosa, Cryptopleura ramosa and Delesseria sanguinea and crustose algae. 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 sponges, anemones (such as Alcyonium digitatum, Sagartia elegans and Urticina felina), hydroids, colonial ascidians and bryozoans. At some sites, instead of being covered by red algae, the kelp stipes may be heavily epiphytised by the sponge Halichondria panicea or the bryozoan Alcyonidium diaphanum. From some areas (such as Orkney), particularly good examples of this biotope may contain maerl and / or rhodoliths, with associated fauna between boulders. Both the flora and fauna of this biotope can be similar to the wave-exposed kelp forest (EIR.LhypFa) and although MIR.Lhyp.TFt is likely to contain species that are unable to tolerate strong wave action, further data analysis is required to clarify the differences. An example of this biotope was found in Lashy Sound in Orkney where Laminaria digitata dominated the tide-swept rock due to the very strong tides and/or non-laminar flow of water.
Laminaria hyperborea park with hydroids, bryozoans and sponges on tide-swept lower infralittoral rock
Moderately exposed, 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, Callophyllis laciniata, Heterosiphonia plumosa, Cryptopleura ramosa and Delesseria sanguinea. Amongst the red seaweeds is a rich fauna comprising sponges, anemones (such as Alcyonium digitatum, Sagartia elegans and Urticina felina), hydroids, colonial ascidians and bryozoans. At some sites, instead of being covered by red seaweeds, the kelp stipes may be heavily epiphytised by the sponge Halichondria panicea or the bryozoan Alcyonidium diaphanum, with smaller quantities of hydroids such as Tubularia indivisa. Both the flora and fauna of this biotope are similar to the wave exposed kelp park (EIR.LhypR.Pk), but this MIR.Lhyp.TPk has a greater faunal component. Further data analysis is required to clarify the differences, however.
Sand or gravel-affected or disturbed kelp and seaweed communities
Sand and gravel-affected or distributed kelp and seaweed commmunities
Ephemeral red seaweeds and kelps on tide-swept mobile infralittoral cobbles
Tide-swept infralittoral cobbles and pebbles which are 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. Characteristic species include Schmitzia spp., Lomentaria orcadensis, Halarachnion ligulatum and Taonia atomaria. In addition, ephemeral algae grow rapidly in periods of relative stability. Scattered Laminaria and Desmarestia plants may also be present on the more stable substrata. Some areas of cobbles may be quite barren, dominated only by encrusting coralline algae and brittlestars. The faunal component of this biotope maybe relatively sparse. Turfs of hydroids (Nemertesia spp.) and bryozoans (Crisia spp. and Bugula spp.) are the major components.
Halidrys siliquosa and mixed kelps on tide-swept infralittoral rock with coarse sediment
This tide-swept biotope is characterised by Halidrys siliquosa, which is often dense and is typically mixed with other kelps including Laminaria saccharina, L. hyperborea and Saccorhiza polyschides. Below the canopy is an undergrowth of foliose red seaweeds which are tolerant of sand scour. There may be a rich epibiota on the Halidrys plants, including Aglaophenia pluma, ascidians including Botryllus schlosseri and sponges. This biotope may occur on the open coast or in rapids areas, and is distinguished from MIR.XKScrR by its greater scour.
Laminaria saccharina, Chorda filum and dense red seaweeds on shallow unstable infralittoral boulders and cobbles
Unstable boulders and cobbles in very shallow water may be seasonally disturbed which prevents a stable Laminaria hyperborea forest from developing. Seasonal movement of the substratum results in a community of the opportunistic kelp L. saccharina, Chorda filum and Desmarestia spp. with encrusting algae and sediment-tolerant seaweeds. The shallowest areas of the Sarns in Cardigan Bay are typical examples of this biotope.
Polyides rotundus, Ahnfeltia plicata and Chondrus crispus on sand-covered infralittoral rock
Similar to the Halidrys siliquosa biotope (MIR.HalXK) but lack of large boulders or more prominent bedrock prevents dominance by Halidrys or kelps. Rock which is surrounded by sand and often subject to burying by the sand with the red seaweeds Polyides rotundus, Furcellaria lumbricalis and Ahnfeltia plicata typically on the rock growing through the sand. Coralline crusts cover the rock, which is grazed by Tectura virginea and chitons.
Sabellaria spinulosa with kelp and red seaweeds on sand-influenced infralittoral rock
Sabellaria spinulosa, sediment-tolerant red seaweeds and occasional Laminaria hyperborea characterise this biotope. Some of the richer examples of this biotope (e.g. Luce Bay) also have a rich fauna of ascidians, sponges, hydroids and bryozoans. A similar biotope is also found in the circalittoral zone, where it lacks the algal component (MCR.Sspi).
Saccorhiza polyschides and other opportunistic kelps on disturbed upper infralittoral rock
The sublittoral fringe, mainly in the south-west and west, may be dominated by the kelp Saccorhiza polyschides. This opportunistic coloniser may replace Laminaria digitata or L. hyperborea as the dominant kelp, following disturbance of the canopy such as through storm losses or sand scour. Being essentially a summer annual (it occasionally lasts into a second year), S. polyschides is particularly common close to rock/sand interfaces which are too scoured during winter months to allow the longer-living kelps to survive. As a result of its transient nature, the composition of this biotope is varied and it may contain several other kelp species, including Laminaria digitata, Laminaria saccharina and Alaria esculenta, at varying abundances. Beneath the kelp, the under-storey seaweeds include Cladostephus spongiosus, Ceramium nodulosum, Dilsea carnosa and coralline algae, all of which are tolerant to sand scour. On some shores (for example in Cornwall and south-west Ireland), Saccorhiza polyschides may compete so effectively with the other laminarians that it forms a well-defined zone between the L. digitata and L. hyperborea zones. In addition, in wave exposed areas, it may also dominate the infralittoral zone (see EIR.LsacSac).
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 (including Laminaria saccharina, Laminaria hyperborea and Saccorhiza polyschides) and Desmarestia spp; there may also be an under-storey of foliose seaweeds that can withstand scour or burial. This biotope often occurs below a L. hyperborea forest, close to a rock-sediment boundary. Red seaweeds such as Calliblepharis ciliata are able to withstand the effects of scouring as they have tough fronds and a stoloniferous base from which new growth occurs. Other seaweeds are annuals growing rapidly in the spring, taking advantage of the calmer summer weather. At some times of the year, seaweeds may be sparse (due to urchin grazing?), leaving predominantly kelps and encrusting coralline algae.
Estuarine faunal communities (shallow rock/mixed substrata)
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.
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. 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.
Mytilus edulis beds on reduced salinity tide-swept infralittoral rock
This biotope is reported to occur in shallow tide-swept conditions and also in reduced salinity tide-swept conditions (may be 2 biotopes?). Some descriptions indicate a wide variety of epifaunal colonisers on the mussel valves, including seaweeds, hydroids and bryozoans. Predatory starfish Asterias rubens also occur in this biotope. This biotope generally appears to lack large kelp plants, although transitional examples containing mussels and kelps plants may also occur. [Further data and analysis required for this biotope]
Echinus, brittlestars and coralline crusts on grazed lower infralittoral rock
This biotope often looks bare, with few large species present. Laminaria saccharina may be present, but always at low abundance. The biotope is characterised by relatively high abundances of the urchin Echinus esculentus and/ or brittlestars (Ophiocomina nigra or Ophiothrix fragilis). As a result of the high grazing pressure the rock surfaces look bare, though they are usually covered by coralline algal crusts with scattered tufts of various red and filamentous brown algae. Grazing molluscs may also be abundant in this biotope.
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. Associated under-storey flora of both filamentous and foliose red seaweeds.
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 beneath which red seaweeds such as Plocamium cartilagineum, Bonnemaisonia asparagoides, Delesseria sanguinea and Cryptopleura ramosa occur on top of encrusting coralline algae. The stipes of L. hyperborea are generally densely covered with seaweeds such as Phycodrys rubens, Membranoptera alata and Plocamium cartilagineum, as well as solitary ascidians, while the fronds are often epiphytised by Obelia geniculata and Membranipora membranacea. Beneath the often cape-form kelp canopy, the faunal component is generally less diverse than the more exposed kelp forests.
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. Beneath the kelp canopy, foliose red algae such as Delesseria sanguinea and Callophyllis laciniata are often present at high densities. Other red algae such as encrusting coralline algae, Dilsea carnosa, Phycodrys rubens and Plocamium cartilagineum are also present. The animal component of this biotope is generally richer than the upper infralittoral mixed kelp forest (SIR.LhypLsac.Ft), with a variety of bryozoans, anemones and ascidians present.
Laminaria saccharina on very sheltered infralittoral rock
Very sheltered infralittoral rock dominated by Laminaria saccharina. Typically very silty and often with few associated seaweeds due to siltation, grazing or shading from the dense kelp canopy.
Sparse Laminaria saccharina with Codium spp. and sparse red seaweeds on heavily silted very sheltered infralittoral rock
This biotope has been recorded from below sublittoral fringe Laminaria saccharina. Shallow heavily silted rock is characterised by sparse Laminaria saccharina with often dense aggregations of Codium spp. and sparse silt-tolerant red algae.
Laminaria saccharina forest on very sheltered upper infralittoral rock
Very to extremely sheltered sublittoral fringe and infralittoral bedrock, boulders and cobbles may be characterised by a dense canopy of Laminaria saccharina. In such sheltered conditions a distinct sublittoral fringe is not always apparent and this biotope often extends from below the Fucus serratus zone (SLR.Fserr) into the upper infralittoral zone, though there may be a mixed Laminaria saccharina and Laminaria digitata (SIR.Lsac.Ldig) zone between. This biotope has a relatively low species richness due to heavy siltation of the habitat and the lack of light penetrating through the dense kelp canopy. Only a few species of red seaweed, such as Ceramium spp., Chondrus crispus and Palmaria palmata may be present (compare with SIR.Lsac.Ldig), whilst limpets, barnacles and littorinids are rare. Saddle oysters Pododesmus patelliformis and chitons may occur in high abundance at some sites. In very sheltered but tide-swept habitats, the L. saccharina tends to be replaced by L. digitata (MIR.Ldig.T) in the sublittoral fringe.
Laminaria saccharina and Laminaria digitata on sheltered sublittoral fringe rock
Sheltered bedrock and boulders in the sublittoral fringe may be characterised by a mixed canopy of the kelps Laminaria digitata (usually in its broad-fronded cape form) and Laminaria saccharina (both species generally frequent or greater). Beneath the canopy a wide variety of red seaweeds, including Palmaria palmata, Corallina officinalis, Mastocarpus stellatus, Chondrus crispus and Plocamium cartilagineum, may be present. The surface of the rock is usually covered with encrusting coralline algae; there may be patches of the sponge Halichondria panicea frequently occurs in cracks in the rock. Beneath and between boulders a variety of mobile crustaceans (Carcinus maenas, Cancer pagurus and Porcellana platycheles), spirorbid worms, starfish (Asterias rubens) and encrusting bryozoans are common. On such sheltered shores the transition between sublittoral fringe and the true sublittoral zone may not be distinct; this biotope therefore extends into the shallow sublittoral.
Laminaria saccharina park on very sheltered lower infralittoral rock
Silty rock with a Laminaria saccharina park (often the cape-form). Beneath the canopy, the bedrock and boulders are covered by coralline algal crusts and urchins such as Echinus esculentus and Psammechinus miliaris are present. Though present, foliose algae are less abundant than in the Laminaria hyperborea park (MIR.Lhyp.Pk) with the most common species being Phycodrys rubens and Delesseria sanguinea. The most conspicuous animals in this biotope are ascidians, particularly Ascidia mentula, Ciona intestinalis and Corella parallelogramma.
Laminaria saccharina, foliose red seaweeds, sponges & ascidians on tide-swept infralittoral rock
Sheltered, tide-swept, rock with dense Laminaria saccharina forest and an under-storey (sometimes sparse) of foliose seaweeds such as Plocamium cartilagineum, Brongniartella byssoides, Ceramium nodulosum, Lomentaria clavellosa and Cryptopleura ramosa. On the rock surface, a rich fauna comprising sponges (particularly Halichondria panicea) anemones (such as Urticina felina), colonial ascidians (Botryllus schlosseri) and the bryozoan Alcyonidium diaphanum. Areas that are scoured by sand or shell gravel may have a less rich fauna beneath the kelp, with the rock surface characterised by encrusting coralline algae, Balanus crenatus or Pomatoceros triqueter. Good examples of this biotope may have maerl gravel or rhodoliths between cobbles and boulders.
Laminaria saccharina on reduced or low salinity infralittoral rock
Infralittoral rock in areas of significantly reduced or low salinity with Laminaria saccharina and associated seaweeds tolerant of these salinity conditions (e.g. green seaweeds, Phyllophora spp.).
Sparse Laminaria saccharina with dense filamentous red seaweeds, sponges and Balanus crenatus on tide-swept variable salinity infralittoral rock
Tide-swept variable salinity infralittoral rock in turbid waters (such as rias or estuaries) characterised by sparse Laminaria saccharina and a dense covering of filamentous red algae (Callithamnion spp., Ceramium spp., Pterothamnion plumula, Polysiphonia spp.). The animal community is dominated by the sponges Halichondria panicea and Hymeniacidon perleve and the barnacle Balanus crenatus.
Laminaria saccharina with Phyllophora spp. and filamentous green seaweeds on reduced or low salinity infralittoral rock
Infralittoral bedrock or boulder slopes, in reduced or low salinity conditions, characterised by Laminaria saccharina and Phyllophora spp., with filamentous green seaweeds in low salinity areas. Solitary ascidians, such as Corella parallelogramma, Ciona intestinalis and Ascidiella scabra, dominate the animal community.
Laminaria saccharina and Psammechinus miliaris on slightly reduced salinity grazed infralittoral rock
Dense Laminaria saccharina, usually with coralline algal crusts but few foliose seaweeds present. Large numbers of the urchin Psammechinus miliaris are typically present, although where absent the brittlestar Ophiothrix fragilis may occur, giving a grazed appearance to the habitat.
Submerged fucoids, green and red seaweeds (lagoonal rock)
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.
Mixed fucoids, Chorda filum and green seaweeds on reduced salinity infralittoral rock
Permanently submerged mixed fucoids on rock in lagoons. Laminaria saccharina absent, possibly due to the low salinity conditions. The main species are Fucus vesiculosus and F. serratus, with Chorda filum and a variety of green seaweeds. Patches of dense Cladophora rupestris may occur on vertical rock faces.
Fucus ceranoides and Enteromorpha spp. on low salinity infralittoral rock
Permanently submerged lagoon fringes with dense Fucus ceranoides. There is typically a very limited associated biota due to low salinity conditions.
Polyides rotundus and/or Furcellaria lumbricalis on reduced salinity infralittoral rock
Bedrock and boulders characterised by a dense turf of Polyides rotundus and/or Furcellaria lumbricalis, often with a dense mat of filamentous seaweeds. Associated with these seaweeds are the ascidians Clavelina lepadiformis and Distaplia rosea.
Littoral rock (and other hard substrata)
Exposed littoral rock (mussel/barnacle shores)
Corallina officinalis on very exposed lower eulittoral rock
Very exposed lower eulittoral rock on some shores supports a band of dense Corallina officinalis with low abundances of other turf-forming red algae such as Lomentaria spp., Mastocarpus stellatus, Ceramium spp. and Osmundea (=Laurencia) pinnatifida, the red encrusting alga Callithamnion spp. and the brown alga Scytosiphon lomentaria. The coralline turf also creates a micro-habitat for small animals such as spirorbid worms. The brown alga Bifurcaria bifurcata and the barnacle Balanus perforatus may occur in the extreme south-west. This community usually forms a distinct band just above the kelp zone (Ala, Ala.Ldig or Ldig).
Fucus distichus subsp. anceps and Fucus spiralis f. nana on extremely exposed upper eulittoral rock
Extremely exposed gently or steeply sloping upper shore bedrock may support a mixture of Fucus distichus and Fucus spiralis f. nana, the latter often at the top of the zone. This biotope is rare and restricted to the far north and west coasts. This mixed band is generally found between the Verrucaria maura and Porphyra zone (Ver.Por) above, and the Mytilus edulis and barnacle zone below (MytB). Although it may occur above a red algal zone (Mas), as recorded on Barra or above a Porphyra and sparse barnacle zone (Ver.Por) as on St Kilda.
Himanthalia elongata and red seaweeds on exposed lower eulittoral rock
Exposed to moderately exposed lower eulittoral bedrock may be characterised by buttons and straps of the thong weed Himanthalia elongata (at least frequent) with a dense turf of red algae beneath. The predominant red algae are usually Mastocarpus stellatus, Laurencia pinnatifida, Corallina officinalis and Palmaria palmata which tend to grow over a crust of pink coralline algae. Any patches between the algal turf may be colonised by barnacles Semibalanus balanoides, or Balanus perforatus in the south-west, and limpets Patella vulgata. Pits and crevices in the rock often provide a refuge for anemones, gastropods (Nucella lapillus and Littorina neglecta) and small mussels Mytilus edulis. This biotope generally characterises those shores which are too exposed for Fucus serratus to form a dense canopy, often occurring as large patches within the F. serratus / red algal turf zone (Fser.R). Consequently, F. serratus plants frequently occur amongst the Himanthalia and red algae (F. serratus common or less). On some shores this biotope may occur as a distinct zone between the F. serratus / red algal turf (Fser.R) and the Alaria esculenta / Laminaria digitata zone (Ala.Ldig). In the south and south-west Bifurcaria bifurcata may replace Himanthalia, and can sometimes form a distinct band on the lower shore. Himanthalia may occur on tide-swept, sheltered shores in sealochs (e.g. Loch Maddy).
Barnacles and Patella spp. on exposed or moderately exposed, or vertical sheltered, eulittoral rock
Exposed or moderately exposed upper and mid eulittoral bedrock and boulders are characterised by dense barnacles Semibalanus balanoides and the limpet Patella vulgata. In the south-west Chthamalus spp. can be the dominant barnacle. Patella ulyssiponensis predominates in the south-west, but in the north is restricted to very exposed conditions. The barnacles may be covered by Porphyra on the upper shore of exposed sites. Patches of Lichina pygmaea may be prominent, especially in the south, where this may form a distinct Lichina zone (BPat.Lic). Cracks and crevices in the rock provide a refuge for small mussels Mytilus edulis, winkles Littorina saxatilis and the dog whelk Nucella lapillus. Damp crevices are also frequently occupied by red algae, particularly Osmundea pinnatifida, Mastocarpus stellatus and encrusting coralline algae. With decreasing wave exposure Fucus vesiculosus is able to survive, gradually replacing the Barnacles and Patella biotope (see FvesB). On such moderately exposed shores BPat may occur on steep and vertical faces, while fucoids dominate the flatter areas. It should not be confused with more exposed shores characterised by Fucus vesiculosus f. linearis and Chthamalus spp. (BPat.Fvesl). In areas of soft rock (e.g. shales), the barnacles may be scarce or absent and the rock dominated by Patella.
Catenella caespitosa on overhanging, or shaded vertical, upper eulittoral rock
Overhanging or shaded vertical littoral fringe and upper eulittoral bedrock may be characterised by the red alga Catenella caespitosa, together with littorinid molluscs, the anemone Actinia equina, ephemeral green algae Enteromorpha spp. and shade-tolerant red algae (e.g. Lomentaria articulata). Often at the same level on these shores, south-facing vertical rock is characterised by similar-looking patches of the lichen Lichina pygmaea (BPat.Lic). Where the turf of Catenella is well established, barnacles are rare or absent from the biotope. In the south-west, the red alga Bostrychia scorpioides is commonly found with Catenella and may co-dominate. B. scorpioides is also known to occur on the north and east coast of Scotland and the Outer Hebrides.
Chthamalus spp. on exposed upper eulittoral rock
Exposed to moderately exposed upper and mid eulittoral bedrock and boulders are characterised by dense barnacles, Chthamalus spp. and the limpet Patella vulgata. On the west coast Chthamalus spp. dominate the upper to mid eulittoral, often forming a distinct white band above a darker Semibalanus balanoides zone (BPat.Sem). This is because Chthamalus montagui is better adapted to resist desiccation and, therefore, extends further up the shore. There is much regional variation in the distribution and zonation of Chthamalus spp. In more northern latitudes, such as north-west Scotland, the abundance of Chthamalus is greater on more wave exposed shores. In the south-west Chthamalus spp. can be the dominant barnacle throughout the eulittoral zone. Patches of Lichina pygmaea may be prominent within the Chthamalus zone, especially in the south. Where this forms a distinct Lichina zone it should be recorded as BPat.Lic. Cracks and crevices in the rock provide a refuge for small mussels Mytilus edulis, winkles Littorina saxatilis and the dog whelk Nucella lapillus. Damp crevices are also frequently occupied by red algae, particularly Osmundea pinnatifida and encrusting coralline algae. With decreasing wave exposure Fucus vesiculosus is able to survive and this alga gradually replaces the barnacles and Patella biotope (see FvesB). On such moderately exposed shores BPat.Cht may occur on steep and vertical faces, while fucoids dominate the flatter areas. It should not be confused with more exposed shores characterised by Fucus vesiculosus f. linearis and Chthamalus spp. (BPat.Fvesl). In areas of soft rock (e.g. shales), the barnacles may be scarce or absent and the rock dominated by Patella. Chthamalus spp. are uncommonly abundant in the upper eulittoral zone in very sheltered sealochs in Argyll, West Scotland.
Barnacles, Patella spp. and Fucus vesiculosus f. linearis on exposed eulittoral rock
Very exposed and exposed upper and mid eulittoral bedrock characterised by dense barnacles, predominantly Chthamalus spp. (regionally abundant in the south and west) and the non- vesiculate form linearis of Fucus vesiculosus. This fucoid forms tufts on the bedrock (frequent or above) and may occupy up to 50% of the rock on some shores. With decreasing wave exposure the normal vesiculate form of Fucus vesiculosus is able to survive and this alga gradually replaces the Barnacle and Patella biotope (see FvesB). BPat.Fvesl is characterised by typically exposed-shore species such as the small littorinid Littorina neritoides, which frequently occurs in empty barnacle tests and a variety of sparse red algae, particularly Porphyra umbilicalis.
Barnacles and Lichina pygmaea on steep exposed upper eulittoral rock
Areas of steep and vertical rock in the upper eulittoral on exposed shores are often characterised by the lichen Lichina pygmaea. In some areas, a high abundance of this lichen results in a distinct Lichina zone, particularly in the south. On Chthamalus-dominated shores (south and west coasts) this band of Lichina lies within the barnacle zone, whereas on Semibalanus shores (north and east coasts) this biotope lies astride the upper limit of the barnacles. The band of Lichina, therefore, generally lies between the Verrucaria zone (Ver) above and the barnacle-Patella zone (BPat.Sem) below. Within the Lichina zone, the barnacles Chthamalus montagui and Chthamalus stellatus are common, although long-established patches of Lichina ultimately exclude barnacles. The rigid branching thallus of Lichina provides an ideal habitat for the molluscs Lasaea rubra and Littorina neritoides. Other upper shore biotopes (Ver.B, Ver.Por) may contain occasional patches of Lichina pygmaea, particularly on steep sunny faces, though not forming a distinct zone. L. pygmaea also occurs on less steeply sloping shores, provided they are in a sunny aspect.
Semibalanus balanoides on exposed or moderately exposed, or vertical sheltered, eulittoral rock
Exposed to moderately exposed eulittoral bedrock and boulders characterised by dense barnacles Semibalanus balanoides and the limpet Patella vulgata. In the north-west, where Chthamalus spp. also occur, Semibalanus balanoides may form a grey band below the distinct white band of Chthamalus spp. (BPat.Cht) in which patches of Lichina pygmaea may be prominent On some shores, particularly in the south, the Lichina may form a distinct zone (see BPat.Lic). On the east coast, where there is no Chthamalus spp. Lichina, if present, tends to form a band astride the upper limit of the barnacles (i.e. partly in BPat and partly in Ver.B). Cracks and crevices in the rock provide a refuge for small mussels Mytilus edulis, winkles Littorina neglecta and the dog whelk Nucella lapillus. Damp crevices are also frequently occupied by red algae, particularly Osmundea pinnatifida, Mastocarpus stellatus and encrusting coralline algae. With decreasing wave exposure Fucus vesiculosus is able to survive, gradually replacing the barnacles and Patella biotope (see FvesB). BPat.Sem may also occur on steep and vertical faces on sheltered shores, while fucoids dominate the flatter areas.
Mytilus edulis and barnacles on very exposed eulittoral rock
The eulittoral zone, particularly mid and lower shore zones, of very exposed rocky shores are typically characterised by patches of small mussels Mytilus edulis interspersed with patches of barnacles Semibalanus balanoides. Amongst the mussels small red algae including Ceramium shuttleworthianum, Corallina officinalis, Mastocarpus stellatus and Aglaothamnion spp. can be found. Two red algae in particular, Porphyra umbilicalis and Palmaria palmata, are commonly found on the Mytilus itself and can form luxuriant growths. The abundance of the red algae generally increases down the shore and in the lower eulittoral they may form a distinct zone in which mussels or barnacles are scarce (R, Him or Coff. Where Mytilus occurs on steep rock, red algae are scarce, and restricted to the lower levels. The dog whelk Nucella lapillus and a few littorinid molluscs occur where cracks and crevices provide a refuge in the rock. Fucoids are generally absent, although some Fucus vesiculosus f. linearis may occur where the shore slopes more gently. MytB is generally found above a zone of either mixed turf-forming red algae (R), Himanthalia elongata (Him) or above the sublittoral fringe kelp Alaria esculenta (Ala). Above MytB there may be a Porphyra zone (Ver.Por), a Verrucaria maura and sparse barnacle zone (Ver.B) or a denser barnacle and limpet zone (BPat), often with Porphyra. In addition, patches of Lichina pygmaea with barnacles (BPat.Lic) may also occur above this biotope, particularly on southern shores. This biotope also occurs on steep moderately exposed shores which experience increased wave crash.
Blidingia spp. on vertical littoral fringe soft rock
Vertical soft rock in the littoral fringe may be characterised by a green band of Blidingia minima. It is usually found below the Verrucaria zone (Ver.Ver) and above a band of the similar looking green alga Enteromorpha spp. (Eph). Other filamentous green algae, including Ulothrix spp. and Urospora spp., are found amongst the Blidingia. During low tide terrestrial mites, insects and centipedes migrate into this zone.
Prasiola stipitata on nitrate-enriched supralittoral or littoral fringe rock
Supralittoral and littoral fringe bedrock that receives nitrate enrichment from nearby roosting sea birds is frequently characterised by a band or patches of the ephemeral tufty green alga Prasiola stipitata, which grows over the black lichen Verrucaria maura in the littoral fringe or yellow and grey lichens in the supralittoral zone. The Prasiola reaches its maximum abundance during the winter months. It generally dies out during the summer in southern Britain but in northern areas some Prasiola may be present all year round.
Ulothrix flacca and Urospora spp. on freshwater-influenced vertical littoral fringe soft rock
An assemblage of algae occurring at High Water Spring Tide level on steep and vertical soft rock is visually recognised as closely adherent, often shiny, mats of filamentous growth. It comprises Ulothrix flacca, Urospora penicilliformis, Urospora wormskioldii and Bangia atropurpurea. In late winter B. atropurpurea may be predominant and the community appears as shiny blackish mats of filamentous growth. The community is more consistently present in areas of freshwater seepage. Associated species include Blidingia minima and Enteromorpha prolifera. On chalk coasts this community overlaps with and merges into the Enteromorpha community (Eph). Although this biotope is believed to occur on soft rock other than chalk, this description has been derived from chalk coast sites.
Verrucaria maura on littoral fringe rock
Bedrock or stable boulders and cobbles in the sublittoral fringe is typically covered by a band of the black lichen Verrucaria maura. It occurs below the yellow and grey lichen zone (YG) and above communities of barnacles and fucoid algae. This biotope occurs in a wide range of wave exposures. Several variants are defined. On exposed shores Verrucaria spp. may occur with sparse barnacles (Chthamalus spp. or Semibalanus balanoides) (Ver.B). Where the ephemeral red alga Porphyra umbilicalis occurs this should be recorded as Ver.Por. More sheltered shores tend to lack these species (Ver.Ver).
Verrucaria maura and sparse barnacles on exposed littoral fringe rock
Exposed rock in the littoral fringe with a sparse covering of barnacles over the black lichen Verrucaria maura. On south-west and western shores the barnacle is usually Chthamalus montagui which may extend over the whole of the zone. On north and east coast shores the barnacle is usually Semibalanus balanoides, and is usually restricted to the lower littoral fringe, with a band of V. maura only in the upper littoral fringe. Littorinid molluscs are usually present; Pelvetia canaliculata may be present, becoming increasingly more common with greater shelter (see PelB). Ver.B occurs on vertical faces of more sheltered shores with Pelvetia (PelB). Ver.B is usually found above Mytilus edulis and barnacles (MytB) or the Barnacle and Patella zone (BPat, BPat.Cht or BPat.Sem), both of which have much denser coverings of barnacles.
Verrucaria maura and Porphyra umbilicalis on very exposed littoral fringe rock
The littoral fringe of very exposed to exposed rocky shores may be dominated by tufts or sheets of the red alga Porphyra umbilicalis and microscopic blue-green algae (Myxophyceae) (the latter particularly in the north), which overlie the black lichen Verrucaria maura. During warm weather the Porphyra is often bleached light brown and sticks to the rock as it dries out. The abundance of Porphyra umbilicalis shows considerable seasonal and geographical variation. It may be absent in the south during the summer (reverting to Ver.B) on all but the most exposed shores. In the cooler north the Porphyra zone persists throughout the year, where during the late winter and spring it may also contain Porphyra linearis. Porphyra spp. may also occur on exposed shores in the upper eulittoral, generally growing on mussels (MytB) or barnacles (BPat).
Verrucaria maura on moderately exposed to very sheltered upper littoral fringe rock
Upper littoral fringe bedrock and stable boulders on very exposed to very sheltered shores are typically characterised by the black lichen Verrucaria maura and littorinid molluscs. Littorina saxatilis is most common, although Littorina neritoides may be found on more exposed shores. This black lichen zone is normally found below the yellow and grey lichen zone (YG), with yellow and grey lichens typically less than common in this biotope. In very sheltered areas there is not always a clear transition from one zone to the next and a mixed zone of YG and Ver.Ver is common. With increasing wave exposure the two lichen zones become wider and more distinct.
Yellow and grey lichens on supralittoral rock
Rock in the supralittoral is typically characterised by a maritime community of yellow and grey lichens, such as Xanthoria parietina and Caloplaca marina. This band of lichens is usually found immediately above a zone of Verrucaria maura (Ver), a black lichen which is also present in this zone, though typically less than common. Damp pits and crevices are occasionally occupied by littorinid molluscs and acarid mites. In sheltered areas the transition from this biotope to Verrucaria maura (Ver.Ver) is often indistinct and a mixed zone of YG and Ver.Ver may occur. With increasing wave exposure both zones become wider and more distinct. In estuaries this biotope is often restricted to artificial substrata such as sea defences.
Moderately exposed littoral rock (barnacle/fucoid shores)
Modereately exposed littoral rock (barnacle /fucoid shores)
Barnacles and fucoids (moderately exposed shores)
Barnacles or fucoids (moderately exposed shores)
Fucus serratus on moderately exposed lower eulittoral rock
Lower eulittoral bedrock and stable boulders with a canopy of the serrated wrack Fucus serratus. Several variants of this biotope are described. These are Fucus serratus with red seaweeds (Fser.R), dense F. serratus (Fser.Fser), F. serratus with under-boulder communities (Fser.Fser.Bo) and F. serratus and piddocks on soft rock (Fser.Pid). Dense Fucus serratus also occurs on more sheltered shores (Fserr).
Dense Fucus serratus on moderately exposed to very sheltered lower eulittoral rock
Moderately exposed to very sheltered lower eulittoral rock subject to fully marine conditions is typically characterised by a dense canopy of Fucus serratus (typically common - superabundant). There is a wide range of associated species, including barnacles, limpets Patella vulgata, littorinid molluscs, turf-forming red algae and the sponge Halichondria panicea. This biotope usually occurs immediately below a Fucus vesiculosus-barnacle mosaic (FvesB) on moderately exposed shores or a dense canopy of F. vesiculosus (Fves) or Ascophyllum nodosum (Asc) on sheltered shores; consequently low abundances of these species (typically less than frequent) may also occur in this biotope.
Fucus serratus and under-boulder fauna on lower eulittoral boulders
This variant of the Fucus serratus biotope is found on moderately exposed to sheltered boulder shores. While the upper surfaces of the boulders are colonised by a very similar fauna and flora to Fser.Fser, the presence of the boulders increases the micro-habitat diversity which often results in a greater species richness. The shaded sides of the boulders are often colonised by a variety of red algae, including Mastocarpus stellatus, Lomentaria articulata, Osmundea pinnatifida and Corallina officinalis. The species composition on the underside of the boulders varies considerably depending on the substratum underlying the boulders. On muddy shores the fauna living under the boulders may be limited to a few burrowing worms, such as Cirratulus cirratus. Where more space is available beneath the boulders there may be a rich assemblage of animals. Characteristic mobile species include the hairy porcelain crab Porcellana platycheles, the smooth porcelain crab Pisidia longicornis and juvenile edible crabs Cancer pagurus. Also present beneath the boulders are often high densities of the barnacle Balanus crenatus, the tubeworm Pomatoceros spp., spirorbid worms and gammarid amphipods, and a few small gastropods and mussels. Encrusting bryozoans (Umbonula littoralis and Schizoporella unicornis) and encrusting colonies of the sponges Hymeniacidon perleve and Halichondria panicea are also typical of the undersides of boulders. The richest examples 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) may be characterised by Fucus serratus beneath which are dense aggregations of rock-boring piddocks (such as Barnea spp. and Pholas dactylus) and Hiatella arctica. A dense red algal turf occurs beneath the F. serratus and includes Gelidium pusillum, Palmaria palmata, Corallina officinalis and Ceramium nodulosum. The top few centimetres of the soft rock may be bored by the worm Polydora ciliata, while empty piddock holes provide a refuge for species such as the hydroid Dynamena pumila and the anemone Actinia equina.
Fucus serratus and red seaweeds on moderately exposed lower eulittoral rock
Moderately exposed lower eulittoral bedrock and boulders may be characterised by mosaics of Fucus serratus and turf-forming red algae such as Osmundea (Laurencia) pinnatifida or Mastocarpus stellatus. The Fucus serratus canopy is generally less dense (frequent - abundant) than on more sheltered shores (common - super abundant), and contains a much greater number and abundance of red algae (compare with Fser.Fser). Other canopy algae such as Himanthalia elongata and Laminaria digitata may also occur, though never at high abundance (generally less than frequent). On boulder shores and uneven bedrock F. serratus and red algae often dominate the upper-facing surfaces, while steep or vertical rock is characterised by Semibalanus balanoides and Patella vulgata (BPat). In addition, such shores provide a greater number of permanently damp refuges between the stones. Within these micro-habitats, anemones (Actinia equina), crabs (Carcinus maenas), and gastropods (Gibbula cineraria and Littorina littorea) are found.
Fucus vesiculosus and barnacle mosaics on moderately exposed mid eulittoral rock
Moderately exposed mid eulittoral bedrock and boulders are frequently characterised by a mosaic of barnacles (mainly Semibalanus balanoides, but Chthamalus spp. in the south-west) and the bladder wrack Fucus vesiculosus. The limpet Patella vulgata is also typically present, with small Mytilus edulis confined to crevices. This biotope forms an intermediate along the wave exposure gradient between the exposed-shore barnacle-Patella biotope (BPat) and the sheltered shore Fucus vesiculosus biotope (Fves). It is distinguished from BPat by the presence of short, but vesiculate Fucus vesiculosus (typically frequent-common in this biotope) and its greater variety of red algae and from Fves by its greater abundance of barnacles and lower abundance of Fucus vesiculosus. Vertical surfaces tend to be dominated by the barnacle-Patella biotope (BPat). On some shores, particularly those which are moderately exposed to wave action, long-term changes in the abundance of limpets, barnacles and fucoid algae may occur. As a result, over a number of years, a single shore may cycle between the barnacle-Patella dominated biotope (BPat), through this mosaic (FvesB) to a F. vesiculosus-dominated biotope (Fves).
Pelvetia canaliculata and barnacles on moderately exposed littoral fringe rock
Moderately exposed, or sheltered steep, lower littoral fringe rock characterised by the upper shore fucoid Pelvetia canaliculata and barnacles (moderately exposed southern and western shores are typically characterised by Chthamalus spp., with Semibalanus balanoides on northern and eastern shores). The Pelvetia typically overgrows a crust of the black lichens Verrucaria maura and Verrucaria mucosa, in contrast to Hildenbrandia rubra on very sheltered shores (see Pel). This biotope differs from the sheltered shore Pelvetia biotope (Pel) by the presence of some typically exposed-shore species; these include the grazing molluscs Littorina neritoides and L. neglecta and the black lichen Lichina pygmaea. However, the striking difference exists in the greater number of barnacles by comparison to the sheltered shores.
Ephemeral green or red seaweeds (freshwater or sand-influenced)
Enteromorpha spp. on freshwater-influenced or unstable upper eulittoral rock
Upper shore hard substrata that is relatively unstable (e.g. soft rock) or subject to considerable freshwater runoff is typically characterised by a dense mat of the green filamentous algae Enteromorpha intestinalis and Enteromorpha prolifera, often together with the red alga Porphyra umbilicalis. This band of Enteromorpha spp. is usually found above the Fucus spiralis zone (Fspi) and may replace the Pelvetia canaliculata zone (PelB).
Porphyra purpurea or Enteromorpha spp. on sand-scoured mid or lower eulittoral rock
Moderately exposed mid-shore bedrock and boulders occurring adjacent to areas of sand which significantly affects the rock. As a consequence of sand-abrasion, fucoids are scarce and the community is typically dominated by ephemeral algae, particularly Porphyra purpurea and Enteromorpha spp. Under the blanket of ephemeral algae, barnacles and limpets occur in the less scoured areas. Few other species are present. In areas where sand abrasion is less severe, the sand-binding red alga Rhodothamniella floridula occurs with other sand-tolerant algae and fucoid algae (especially Fucus serratus) (Rho).
Rhodothamniella floridula on sand-scoured lower eulittoral rock
Lower eulittoral and sublittoral fringe sand-scoured bedrock and boulders are often characterised by canopy algae (usually Fucus serratus), beneath which a mat of the sand-binding red alga Rhodothamniella floridula occurs. These mats can also form distinct areas without F. serratus. The small hummocks of R. floridula also contain other small red and brown algae and species of worm and amphipod may burrow into the Rhodothamniella mat. Other sand-tolerant algae, such as Polyides rotundus, Furcellaria lumbricalis, Gracilaria verrucosa and Cladostephus spongiosus, may be present. Ephemeral algae such as Enteromorpha spp., Ulva spp. and Porphyra spp. may occur. Where sand scour is more severe, fucoids and Rhodothamniella may be rare or absent and these ephemeral algae dominate the substratum (EntPor).
Mytilus (mussels) and fucoids (moderately exposed shores)
Mytilus edulis and Fucus vesiculosus on moderately exposed mid eulittoral rock
Mid eulittoral exposed to moderately exposed bedrock, often with nearby sediment, may be covered by dense large Mytilus edulis which form a band or large patches and support scattered Fucus vesiculosus and occasional red algae. This differs from mussels in the lower eulittoral (MytFR) which occur with a wider range of red algae (often in higher abundance than the mid eulittoral). Ephemeral green algae such as Enteromorpha spp. 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 dog whelk Nucella lapillus and a range of littorinids also occur within the mussel bed.
Mytilus edulis, Fucus serratus and red seaweeds on moderately exposed lower eulittoral rock
Lower eulittoral moderately exposed bedrock, often with nearby sediment covered by dense, large Mytilus edulis with a covering of scattered Fucus serratus and red algae. The algae include Porphyra umbilicalis, Rhodothamniella floridula, Palmaria palmata, Mastocarpus stellatus and Ceramium nodulosum. Ephemeral green algae such as Enteromorpha spp. 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 dog whelk Nucella lapillus and a range of littorinids also occur within the mussel bed. This biotope differs from MytFves which has far fewer red algae present and scattered Fucus vesiculosus, indicative of the mid eulittoral zone.
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 spp. and the American piddock Petricola pholadiformis. The surface of the clay is characterised by small clumps of Mytilus edulis, with barnacles and the winkle Littorina littorea. Algae are generally sparse on the clay, although small patches of Corallina officinalis and Halurus flosculosus occur, usually attached to loose-lying cobbles or mussel shells. Species richness is generally low. [More data required for this biotope].
Red seaweeds (moderately exposed shores)
Mastocarpus stellatus and Chondrus crispus on very to moderately exposed lower eulittoral rock
Moderately exposed lower eulittoral bedrock on some shores is characterised by a dense turf of Mastocarpus stellatus and Chondrus crispus (either together or separately) which form a band above the main kelp zone, above Alaria (Ala) or Mytilus (MytB) or within a Fucus serratus-red algal mosaic (Fser.R). Mastocarpus is more resistant to wave action than Chondrus, and may therefore dominate much more exposed shores; it can dominate vertical rock at very exposed sites (e.g. Mingulay, Outer Hebrides). On more sheltered shores, especially in the south-west, Mastocarpus may give way to Chondrus which has a faster growth rate. Beneath these foliose algae the rock surface is covered by encrusting coralline algae. Although both Mastocarpus and Chondrus 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 the more general mixed red algal turf biotope (XR).
Osmundea (Laurencia) pinnatifida and Gelidium pusillum on moderately exposed mid eulittoral rock
Exposed to moderately exposed lower eulittoral rock may be characterised by extensive areas or a distinct band of Osmundea (Laurencia) 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 algae, such as Ceramium spp. and Callithamnion hookeri may be present, although Osmundea and/or Gelidium always dominate. On flatter, more sheltered shores, Laurencia hybrida may also occur. Small patches of bare rock amongst the algal turf are occupied by barnacles Semibalanus balanoides, the limpet Patella vulgata, dog whelks Nucella lapillus and small mussels Mytilus edulis. A variation of this biotope has been described for the chalk platforms in Kent where extensive turfs of Gelidium pusillum occur in the mid eulittoral above the main Osmundea zone.
Palmaria palmata on very to moderately exposed lower eulittoral rock
Moderately exposed lower eulittoral rock may support an often pure stand of dulse Palmaria palmata which forms a dense band or occurs in large patches above the main kelp zone (Ldig). It can also occur on very exposed shores (recorded from Orkney). Palmaria is a common component of adjacent biotopes; it should only be recorded as Pal where it forms a distinct band or occurs in large patches on the shore. Palmaria favours shaded or overhanging rock and often forms a band at the top of overhanging rock. Relatively low abundances of other red algae, such as Osmundea pinnatifida, Chondrus crispus and Corallina officinalis, may also occur in this biotope although Palmaria always dominates. It is likely that the Palmaria biotope represents an opportunistic assemblage of fast-growing species which occupy gaps within or between the canopies of longer-lived perennials such as Fucus serratus. Palmaria often forms a luxurious growth on Mytilus edulis on exposed shores in which case it should be recorded as MytB.
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 is characterised by a dense algal mat, predominantly Ceramium spp. but also with Ulva spp., Enteromorpha spp. and Polysiphonia spp. Damp areas amongst the algal mat are covered by aggregations of the sand mason worm Lanice conchilega and the fan worm Sabella pavonina. The anemone Sagartia troglodytes and 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 prawn Crangon crangon. [Description derived largely from sites in north Norfolk. Further records of this biotope required].
Mixed red seaweeds on moderately exposed lower eulittoral rock
Moderately exposed lower eulittoral bedrock and stable boulders may be characterised by a dense turf of red algae. Canopy-forming algae such as Fucus serratus and Himanthalia elongata are sparse (generally < frequent) in this community. The red algal turf is most frequently characterised by a mixture of species, including Mastocarpus stellatus, Chondrus crispus, Osmundea pinnatifida, Corallina officinalis and Palmaria palmata. Amongst these many other species, including Lomentaria articulata, Ceramium spp. and Gelidium pusillum, may also occur. Beneath the turf-forming algae, the rock surface is usually covered by coralline algal crusts. Gaps in the dense turf are frequently dominated by barnacles Semibalanus balanoides and limpets Patella vulgata, while pits and crevices in the rock often provide a refuge for small mussels and gastropods. On moderately exposed shores this biotope is often found in patches amongst the Himanthalia elongata zone (Him) or the F. serratus and red algal mosaics (Fser.R). It is also common on very steep or vertical faces where canopy algae are absent.
Littoral Sabellaria (honeycomb worm) reefs
Sabellaria alveolata reefs on sand-abraded eulittoral rock
Many wave-exposed boulder scar grounds in the eastern basin of the Irish Sea (and as far south as Cornwall), are characterised by reefs of Sabellaria alveolata which build tubes from the mobile sand surrounding the boulders and cobbles. The tubes formed by Sabellaria alveolata form large reef-like hummocks, which serve to further stabilise the boulders. Other species in this biotope include the barnacles Semibalanus balanoides, Balanus crenatus and Elminius modestus and the molluscs Patella vulgata, Littorina littorea, Nucella lapillus and Mytilus edulis. Low abundances of algae tend to occur in areas of eroded reef. The main algal species include Porphyra spp., Mastocarpus stellatus, Ceramium spp., Fucus vesiculosus, Fucus serratus, Enteromorpha spp. and Ulva spp. On exposed surf beaches in the south-west Sabellaria forms a crust on the rocks, rather than the classic honeycomb reef, and may be accompanied by the barnacle Balanus perforatus (typically common to abundant). On wave-exposed shores in Ireland, the brown alga Himanthalia elongata can also occur.
Rhodothamniella floridula in upper littoral fringe soft rock caves
The upper littoral fringe in the moist dark conditions inside caves on soft rock may be characterised by velvety bands of the red alga Rhodothamniella floridula. In chalk caves, on the east and south-east coast of England, a distinctive assemblage of species occurs, including the brown alga Pilinia maritima and the bright green alga Pseudendoclonium submarinum which often covers the roofs of chalk caves. Where the rock is sufficiently hard, the crustose red alga Hildenbrandia rubra may occurs on the cave roofs.
Sponges, bryozoans and ascidians on deeply overhanging lower shore bedrock
Overhanging, and shaded vertical, bedrock on the lower shore, which is not subject to appreciable wave-surge, is characterised by turfs of bryozoans (Umbonula littoralis and Scrupocellaria spp.), sponges (Grantia compressa, Halichondria panicea and Hymeniacidon perleve) and colonial ascidians (Botryllus schlosseri and Botrylloides leachi). The overhanging rock frequently supports the barnacles Balanus crenatus and Balanus perforatus (sometimes at high densities), and the calcareous-tubed polychaetes Spirorbis spp. and Pomatoceros triqueter. Some overhangs have a high abundance of the ascidian Dendrodoa grossularia.
Sponges and shade-tolerant red seaweeds on overhanging lower eulittoral bedrock
Overhanging bedrock on the lower shore characterised by shade-tolerant red algae (such as Lomentaria articulata, Plumaria elegans and Membranoptera alata) and sponges (e.g. Grantia compressa, Halichondria panicea and Hymeniacidon perleve). The rock surfaces often support dense populations of calcareous tube-worms Spirorbis spp. and Pomatoceros triqueter. In the south and west the barnacle Balanus perforatus may occur at high densities. The anemone Actinia equina thrives in the permanently damp conditions.
Corallina officinalis and coralline crusts in shallow eulittoral rockpools
Shallow rockpools throughout the eulittoral zone may be characterised by a covering of encrusting coralline algae on which Corallina officinalis often forms a dense turf. These 'coralline' pools have a striking appearance as they are dominated predominantly by red algae. Filamentous and foliose red algae found in these pools include Dumontia contorta, Mastocarpus stellatus and Ceramium rubrum. The green algae Cladophora rupestris and Enteromorpha spp. can also occur. The pools may hold large numbers of grazing molluscs, particularly Littorina littorea (which often occurs in exceptionally high densities in upper shore pools), Patella vulgata and Gibbula cineraria. Gastropods may graze these pools to such an extent that they are devoid of any foliose red algae, and are reduced to encrusting coralline algae and large numbers of gastropods. Large brown algae are generally absent (compare with FK), although small Halidrys siliquosa may be present. Within the pools, pits and crevices are often occupied by the anemone Actinia equina and small Mytilus edulis. Similar sized pools in the littoral fringe generally lack the encrusting coralline algae and are characterised by green algae (see G). In Ireland, the sea urchin Paracentrotus lividus can dominate these shallow coralline pools (see Cor.Par). In south-west Britain, the brown alga 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 dominated by the brown alga Bifurcaria bifurcata. Shallow coralline pools typically dominated by red algae (see Cor) can support dense growths of B. bifurcata with little else other than Corallina officinalis, encrusting coralline algae and some grazing gastropods and anemones. [B. bifurcata is at the edge of its range in Britain; in France it occurs in deeper lower shore pools where the alga forms a noticeable band in the mid pool level, below a band of Corallina officinalis and coralline crusts]. Cystoseira spp., another warm-water brown algae found in south-west Britain, often occurs in equal abundance in the shallow pools. B. bifurcata also occurs in deeper pools (see LR.FK) with the brown algae Halidrys siliquosa and Himanthalia elongata, below which Laminaria digitata may occur.
Cystoseira spp. in shallow eulittoral rockpools
Shallow eulittoral rockpools on exposed to moderately exposed south-western shores can be dominated by the brown alga Cystoseira spp. and coralline algae. These pools generally contain some sand and pebbles on the base and support dense red algal growth comprising: Ceramium spp., Calliblepharis jubata, Chondrus crispus and Gelidium latifolium.
Coralline crusts and Paracentrotus lividus in shallow eulittoral rockpools
In south and west Ireland shallow coralline pools may be dominated by the sea urchin Paracentrotus lividus. Soft bedrock, such as limestone, allows the urchin to bore into the rock. This biotope is a sub-type of the Coralline rockpool (Cor); the algal diversity is generally limited to coralline crusts and Corallina officinalis due to the Paracentrotus grazing. The gastropods Gibbula spp. and Littorina littorea may be numerous in such pools.
Fucoids and kelps in deep eulittoral rockpools
Deep rockpools in the mid to lower eulittoral zone often contain a community characterised by Fucus serratus and Laminaria digitata. Other large brown algae, including Laminaria saccharina, Himanthalia elongata and Halidrys siliquosa, may also occur. The rock surface is usually covered by encrusting coralline algae. A wide variety of filamentous and foliose algae, which are typical of lower shore and shallow sublittoral zones (e.g. Palmaria palmata, Chondrus crispus, Ceramium spp., Membranoptera alata and Gastroclonium ovatum) occur beneath the brown algal canopy. Algal-free vertical and overhanging faces often support the sponge Halichondria panicea and anemones Actinia equina. The abundance of grazing molluscs varies considerably. In some, large numbers of littorinids and limpets are probably responsible for the limited variety of red seaweeds present. In other pools, fewer grazers may result in an abundance of these algae. Where boulders occur in these pools they provide a greater variety of micro-habitats which support a variety of fauna. Mobile crustaceans (Pagurus bernhardus and Carcinus maenas), brittlestars (Ophiothrix fragilis and Amphipholis squamata), encrusting bryozoans and ascidians are typically found beneath and between boulders.
Sargassum muticum in eulittoral rockpools
The non-native brown alga Sargassum muticum has spread extensively around the south-west coast of Britain since its introduction to UK waters in the early 1970s. It is an opportunistic alga which can dominate rockpools in the south-west, often to the exclusion of other species which would otherwise occupy this niche (Laminaria spp. and fucoids). Where S. muticum dominates shallow to medium-depth pools, this biotope (FK.Sar) should be recorded. At low tide the swards of Sargassum thalli lie flat on the water surface, thereby reducing the illumination available to red algae (Gelidium spp., Dumontia contorta, and Corallina officinalis) which subsequently occur in low abundances. The fauna that occur are common to the eulittoral coralline pools (see Cor) and include littorinids, Patella and the anemone Actinia equina. Where sediment occurs in the pool the red algae Polyides rotundus and Furcellaria lumbricalis can also be found.
Green seaweeds (Enteromorpha spp. and Cladophora spp.) in upper shore rockpools
Rockpools in the supralittoral, littoral fringe or upper eulittoral which are subject to variable salinity and widely fluctuating temperatures are characterised by the ephemeral green alga Enteromorpha spp. or the filamentous green alga Cladophora spp. Due to the physical stress imposed on these upper shore pools, grazing molluscs are generally in lower abundance than eulittoral pools, allowing the green algae to proliferate under reduced grazing pressures. The rock surface is often covered by the black lichen Verrucaria maura. On more exposed shores crevices in the rock may contain small Mytilus edulis. The bright orange copepod Tigriopus fulvus is tolerant of large salinity fluctuations and may also occur in large numbers in these upper shore pools.
Hydroids, ephemeral seaweeds and Littorina littorea in shallow eulittoral mixed substrata pools
Shallow pools on mixed cobbles, pebbles, gravel and sand may be colonised by hydroids (Obelia longissima and Kirchenpaueria pinnata), ephemeral green algae (Enteromorpha spp. and Ulva sp.) and the winkle Littorina littorea. Within these 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 also present in the pools. Barnacles (Semibalanus balanoides and Elminius modestus) and the keel worm Pomatoceros triqueter may be attached to shells and small stones.
Seaweeds in sediment (sand or gravel)-floored eulittoral rockpools
Rockpools with sediment floors support distinct communities of scour-tolerant algae. Deep pools with sediment are similar to FK, and are typically dominated by fucoids and kelps (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 algae such as Furcellaria lumbricalis, Polyides rotundus, Ahnfeltia plicata and Rhodothamniella floridula (compare with FK). Chorda filum may occur attached to pebbles and shells embedded within the sediment. In pools with large areas of sand, infaunal species such as Arenicola marina and Lanice conchilega often occur. The sea-grass 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 (Mastocarpus stellatus mixed with Ceramium spp., Calliblepharis ciliata and Cystoclonium purpurea and green algae).
Ascophyllum nodosum on very sheltered mid eulittoral rock
Sheltered to very sheltered mid eulittoral rock with the knotted wrack Ascophyllum nodosum. Several variants of this biotope are described. These are: full salinity (Asc.Asc), tide-swept (Asc.T) and variable salinity (Asc.VS).
Ascophyllum nodosum on full salinity mid eulittoral rock
Bedrock, or stable boulders and cobbles, in the mid-eulittoral zone of sheltered to very sheltered shores, typically in fully marine or near fully marine conditions, are characterised by a dense canopy of Ascophyllum nodosum. Fucus vesiculosus also occurs and in some places may co-dominate the canopy. Such mixed canopies occur when clearings are formed in the Ascophyllum, since F. vesiculosus is able to colonise such clearings more rapidly. Ascophyllum (which may live for up to 25 years) will, however, eventually out-compete any F. vesiculosus. Such changes in the overlying canopy have little effect on the under-storey species. Beneath the canopy, filamentous and foliose red algae, including Mastocarpus stellatus and Chondrus crispus, and the green alga Cladophora rupestris, occur in moderate to low densities. The Ascophyllum is generally epiphytised by Polysiphonia lanosa (compare with Asc.VS). Very steep and vertical surfaces are often characterised by barnacles and limpets (BPat.Sem), but by small fucoids in areas of extreme shelter. Large numbers of the winkle Littorina obtusata may be present. This biotope usually lies between the Fucus spiralis (Fspi) and Fucus serratus (Fser) zones, although on some shores a narrow zone of Fucus vesiculosus (Fves) may occur immediately above the Ascophyllum. With increasing wave exposure the Ascophyllum canopy is replaced by F. vesiculosus (Fves). Asc.Asc may also occur on moderately exposed shores, where there is localised shelter.
Ascophyllum nodosum, sponges and ascidians on tide-swept mid eulittoral rock
Very sheltered areas of mid eulittoral rock that are subject to strong to moderate tidal streams, such as the narrows in sealochs, are characterised by Ascophyllum nodosum with a rich associated fauna of sponges and ascidians. Species richness is generally greater than in the non tide-swept Ascophyllum nodosum biotope (Asc.Asc), with a greater abundance and wider range of foliose and filamentous red algae such as Gelidium pusillum, Mastocarpus stellatus, Chondrus crispus, Lomentaria articulata and Membranoptera alata. The increased water movement encourages several filter-feeding groups to occur. The sponges Leucosolenia spp., Halichondria panicea and Hymeniacidon perleve frequently occur on steep and overhanging faces of boulders and bedrock. Large numbers of ascidians, especially Dendrodoa grossularia and Ascidiella scabra, also occur on steep surfaces and beneath boulders.
Ascophyllum nodosum and Fucus vesiculosus on variable salinity mid eulittoral rock
Very sheltered mid eulittoral bedrock, boulders or cobbles that are subject to variable salinity are characterised by an impoverished community dominated by a mixture of Ascophyllum nodosum and Fucus vesiculosus. Species richness is generally low compared with Asc.Asc and Asc.T. The epiphytic red alga Polysiphonia lanosa is less common on Ascophyllum in this biotope than it is in the other Ascophyllum-dominated biotopes. Sponges, hydroids and the polychaetes Pomatoceros triqueter and Spirorbis spp. are also typically absent. On some shores clumps of large Mytilus edulis may be found beneath the algal canopy.
Fucus ceranoides on reduced salinity eulittoral rock
Bedrock and stable boulders in the eulittoral zone that are subject to reduced salinity may be characterised by the horned wrack Fucus ceranoides. As this fucoid is more tolerant of reduced salinity than the other fucoids, F. ceranoides tends to replace Fucus spiralis, Fucus vesiculosus and Ascophyllum nodosum towards the upper reaches of estuaries and sealochs. This biotope may, however, still contain other fucoids, although Fucus ceranoides always dominates. Species richness is typically low in this biotope. Since areas of bedrock and stable boulder are generally scarce within estuarine systems, this community is more commonly encountered on stable mixed substrata (see FcerX).
Fucus serratus on sheltered lower eulittoral rock
Fucus serratus, sponges and ascidians on tide-swept lower eulittoral rock
Very sheltered lower eulittoral bedrock, boulders and cobbles that are subject to increased tidal water movement are characterised by Fucus serratus, sponges and ascidians. Species richness is generally greater than in the non tide-swept F. serratus biotope (Fser.Fser), with a greater abundance and wider range of foliose red seaweeds. The increased water movement encourages several filter-feeding faunal groups to occur. The sponges Grantia compressa, Leucosolenia spp., Halichondria panicea and Hymeniacidon perleve occur frequently on steep and overhanging faces. In addition, the ascidians Ascidiella scabra, Dendrodoa grossularia and colonial ascidians are also found in this biotope. Areas where increased tidal movement influences such a community are in the narrows and/or intertidal sills of Scottish sealochs and rias in south-west England. In the few cases where the rock is also subject to variable salinity, an impoverished community results and records should be classified as Fserr.VS rather than the present biotope.
Fucus serratus and large Mytilus edulis on variable salinity lower eulittoral rock
Areas of very sheltered lower eulittoral bedrock and stable boulders that are influenced by freshwater, such as towards the heads of sealochs and in estuaries, may support an impoverished community dominated by Fucus serratus and clumps of large Mytilus edulis. This biotope may be found below the variable salinity Ascophyllum nodosum biotope (Asc.VS), particularly in Scottish sealochs. The canopy of F. serratus is usually less dense (typically common) than in the other F. serratus biotopes (Fser.Fser and Fserr.T). Sponges, hydroids and the polychaetes Pomatoceros triqueter and Spirorbis spp. are generally rare or absent. In areas (such as the Scottish sealochs) where variable salinity water passes through tide-swept narrows and the associated biota is impoverished such records should be classified as Fserr.VS rather than Fserr.T.
Fucus spiralis on moderately exposed to very sheltered upper eulittoral rock
Moderately exposed to very sheltered upper eulittoral bedrock and boulders are typically characterised by a band of the spiral wrack Fucus spiralis overlying the black lichens Verrucaria maura and V. mucosa. Limpets Patella vulgata, winkles Littorina spp. and barnacles Semibalanus balanoides are usually present under the fucoid fronds and on open rock. During the summer months ephemeral green algae such as Enteromorpha spp. and Ulva lactuca may also be present. This zone usually lies below a Pelvetia canaliculata zone (Pel or PelB); occasional clumps of Pelvetia may be present (usually less than common) amongst the F. spiralis. In areas of extreme shelter, such as in Scottish sealochs, the Pelvetia and F. spiralis zones often merge together forming a very narrow band. Fspi occurs above the Ascophyllum nodosum (Asc) and/or Fucus vesiculosus (Fves) zones and these two fucoids may also occur, although Fucus spiralis always dominates. Vertical surfaces in this zone, especially on moderately exposed shores, often lack the fucoids and are characterised by a barnacle-Patella community (BPat.Sem).
Fucus vesiculosus on sheltered mid eulittoral rock
Moderately exposed to sheltered mid eulittoral rock characterised by a dense canopy of large Fucus vesiculosus plants (typically abundant to superabundant). Beneath the algal canopy the rock surface has a sparse covering of barnacles (typically rare-frequent) and limpets, with mussels confined to pits and crevices. Littorina littorea and Nucella lapillus are also found beneath the algae, whilst Littorina obtusata and Littorina mariae graze on the fucoid fronds. The fronds may be epiphytised by the filamentous brown alga Elachista fucicola and the small calcareous tubeworm Spirorbis spirorbis. In areas of localised shelter, Ascophyllum nodosum may also occur, though never at high abundance (typically rare to occasional) - (compare with Asc). Damp cracks and crevices often contain patches of the red seaweeds Osmundea (Laurencia) pinnatifida, Mastocarpus stellatus and encrusting coralline algae. This biotope usually occurs between the Fucus spiralis (Fspi) and the Fucus serratus (Fser) zones; both of these fucoids may be present in this biotope, though never at high abundance (typically less than frequent). In some sheltered areas Fucus vesiculosus forms a narrow zone above the A. nodosum zone (Asc). Where freshwater runoff occurs on more gradually sloping shores F. vesiculosus may be replaced by Fucus ceranoides (Fcer).
Pelvetia canaliculata on sheltered littoral fringe rock
Lower littoral fringe bedrock or stable boulders on sheltered shores are characterised by a dense cover of the fucoid Pelvetia canaliculata. The fucoid overgrows a crust of black lichens Verrucaria maura and Verrucaria mucosa, or Hildenbrandia rubra on very sheltered shores. This biotope lacks the density of barnacles found amongst the Pelvetia on more exposed shores (PelB). The littorinids Littorina littorea and L. saxatilis occur. The red alga Catenella caespitosa is characteristic of this biotope, as is the lichen Lichina confinis. Though not typical, this biotope may occur on moderately exposed shores where local topography provides shelter.
Fucoids, barnacles or ephemeral seaweeds (mixed substrata)
Ascophyllum nodosum on mid eulittoral mixed substrata
Very sheltered mixed substrata (cobbles, boulders and pebbles on sediment) in full or near fully marine conditions may be characterised by an Ascophyllum nodosum canopy. Like the Ascophyllum community that occurs on bedrock (Asc), Fucus vesiculosus may be co-dominant. In addition, however, this community also contains a selection of infaunal species, such as Arenicola marina, which occur in the sediment between the cobbles. Large mussels Mytilus edulis commonly occur in clumps, and provide further suitable substrata for the attachment of fucoids and barnacles. Littorina littorea is the most commonly occurring littorinid, and at some sites it may reach high densities. The spaces between cobbles and boulders provide a refuge for crustaceans, especially Carcinus maenas. On shores with a smaller proportion of cobbles and boulders, the large Ascophyllum nodosum plants become uncommon (presumably since they lack a suitable substrata for attachment) and Fucus vesiculosus dominates the canopy (FvesX). F. vesiculosus also tends to replace Ascophyllum in areas with greater freshwater influence.
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, may support beds of the free-living Ascophyllum nodosum ecad mackaii. Cobbles and other hard substrata are often characterised by the normal form of Ascophyllum nodosum and other fucoids such as Fucus serratus and Fucus vesiculosus. The loose mats of A. nodosum ecad mackaii provide a cryptic and humid habitat for mobile species such as gammarids, the shore crab Carcinus maenas, littorinid molluscs (especially Littorina littorea) and eels Anguilla anguilla. Semibalanus balanoides and Mytilus edulis are commonly attached to pebbles and cobbles on the sediment, while the infauna may contain Arenicola marina, Lanice conchilega and other polychaetes.
Barnacles and Littorina littorea on unstable eulittoral mixed substrata
Banks of cobbles and pebbles which are too unstable or too small to support fucoids are usually colonised by the barnacles Semibalanus balanoides (often with Elminius modestus) with Patella vulgata on larger rocks and often dense aggregations of Littorina littorea. Between the cobbles and pebbles Mytilus edulis often occurs, but always at low abundance (compare with MytX). Juvenile Carcinus maenas occur between pebbles, and where patches of sediment occur, infaunal species such as the lugworm Arenicola marina and cockle Cerastoderma edule may be present. Fucoids are rare in this biotope. This biotope covers a wide range of wave exposures from mobile exposed and unstable shores to more sheltered stony shores in which fucoids are unable to attach and Mytilus edulis is infrequent. [Further data required to split this biotope into two: open coast cobble sites and estuarine stony sediment sites].
Ephemeral green and red seaweeds on variable salinity or disturbed eulittoral mixed substrata
Eulittoral mixed substrata (pebbles and cobbles overlying sand or mud) that is subject to variations in salinity and / or siltation are often characterised during the summer months by dense blankets of ephemeral green and red algae. The main species present are Enteromorpha spp., Ulva lactuca and Porphyra spp. Although fucoid algae occur in these areas they are typically rare. Small numbers of other species such as barnacles Semibalanus balanoides and Elminius modestus and keel worms Pomatoceros spp. are confined to any larger cobbles and pebbles. This biotope may be a summer variation of BLlit, in which ephemeral algal growth has exceeded the capacity of the grazing molluscs. In common with the other biotopes found on mixed substrata, patches of sediment are typically characterised by infaunal species including bivalves (Cerastoderma edule and Macoma balthica) and polychaetes (Arenicola marina and Lanice conchilega). Occasional clumps of Mytilus edulis may also occur, although at considerably lower density than in MytX.
Fucus ceranoides on reduced salinity eulittoral mixed substrata
Boulders, cobbles and stones in the eulittoral zone that are subject to reduced salinity conditions may be covered by Fucus ceranoides. This biotope typically occurs where streams run across the shore, or towards the heads of marine inlets. Other fucoids may occur, but are generally scarce. Amongst the fucoid algae, opportunistic green algae such as Enteromorpha spp. and Ulva lactuca are frequently encountered. Littorinid molluscs and clumps of large Mytilus edulis may be present. Species diversity is generally low with red algae being rare or absent. Sediment, on which the cobbles and boulders frequently lie, often contains infaunal species such as the lugworm Arenicola marina and the ragworm Hediste diversicolor.
Fucus serratus on lower eulittoral mixed substrata
Sheltered and very sheltered lower eulittoral mixed substrata often supports Fucus serratus. This biotope differs from Fser.Fser in having a less dense canopy and reduced richness of epifaunal species, being subject to increased siltation and disturbance of unstable substrata. Amongst the pebbles and cobbles can be found shore crabs Carcinus maenas, numerous gastropods (Littorina littorea, Littorina obtusata/mariae and Gibbula cineraria) and large mussels Mytilus edulis, commonly occurring in clumps. Sediment in the spaces between the loose substrata may support infauna such as the lugworm Arenicola marina and the sand-mason Lanice conchilega. FserX occurs below mid eulittoral fucoids (FvesX or AscX) on mixed substrata shores, or on sediment shores where mixed substrata occurs in discrete patches on the lower shore. One variant of this biotope is described: tide-swept F. serratus (FserX.T).
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 may be characterised by a rich community of sponges (Halichondria panicea and Hymeniacidon perleve), hydroids (Dynamena pumila), bryozoans (Anguinella palmata and Walkeria uva), ascidians (Ascidiella aspera, Ascidiella scabra, Styela clava and Botryllus schlosseri) and red seaweed (Halurus flosculosus, Ceramium sp., Gracilaria verrucosa and Chondrus crispus). The brown algae Dictyota dichotoma, Fucus serratus and Ectocarpus sp. may be found on any more stable substrata. Patches of sand or mud are often characterised by the sand mason worm Lanice conchilega, the peacock worm Sabella pavonina and the anemone Sagartia troglodytes. Aggregations of the mussel Mytilus edulis and, in southern and eastern England, the slipper limpet Crepidula fornicata may also be found attached to cobbles and pebbles. Sites in Scottish sealochs may support maerl Lithothamnion corallioides and bivalves Venerupis senegalensis (see also IMX.VsenMtru).
Fucus vesiculosus on mid eulittoral mixed substrata
Sheltered and very sheltered mid eulittoral pebbles and cobbles lying on sediment are typically characterised by Fucus vesiculosus. FvesX is usually subject to some variability in salinity from riverine input or, in more marine conditions, the habitat consists predominantly of smaller stones which are too unstable for Ascophyllum nodosum to colonise to any great extent (compare with AscX). This biotope typically differs from Fves in having a less dense canopy and reduced richness of epifaunal species, presumably as a result of the increased siltation, variable salinity and lack of stable substrata. In addition, the sediment between patches of hard substrata often contains the lugworm Arenicola marina, cockles Cerastoderma edule or the ragworm Hediste diversicolor. Littorinids, particularly Littorina littorea, commonly graze on the algae. Ephemeral algae such as Enteromorpha spp. are often present, especially on any more mobile pebbles during the summer. Limpets are less common than in AscX, because of the limited availability of larger rocks.
Mytilus edulis beds on eulittoral mixed substrata
Moderately exposed to very sheltered mid and lower eulittoral mixed substrata (mainly cobbles and pebbles on muddy sediments) with dense aggregations of the mussel Mytilus edulis. In high densities the mussels bind the substratum and provide a habitat for many species more commonly found on rocky shores. Fucus vesiculosus is often found attached to either the mussels or the cobbles and it frequently occurs at high abundance. The mussels are usually encrusted with the barnacle Semibalanus balanoides (and/ or Elminius modestus in areas of reduced salinity). Littorina littorea and small Carcinus maenas are common amongst the mussels, whilst areas of sediment may contain Arenicola marina, Lanice conchilega, Cerastoderma edule and other infaunal species. In contrast with the mussel beds found on rocky shores (MLR.MF) this biotope contains few limpets or red algae. This biotope is also found in lower shore tide-swept areas, such as in the tidal narrows of Scottish sealochs.
Chrysophyceae on vertical upper littoral fringe soft rock
"Chrysophyceae" communities form orange, brownish or blackish gelatinous bands at high tide and supralittoral levels on open cliff faces and in caves and tunnels of soft rock. Open cliff-faces and entrances to chalk caves and tunnels at lower supralittoral levels bear a dark brown band comprising an assemblage dominated by Apistonema carterae. During summer this gelatinous growth dries and often peels off. The filamentous green alga Epicladia perforans is often associated with Apistonema, forming a green layer beneath the upper layer of Apistonema. Entodesmsis maritima and Thallochrysis litoralis are commonly associated with Apistonema. 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 Littorina neritoides.
Oligochaetes in reduced or low salinity gravel or coarse sand shores
Coarse sands and gravel are often associated with the lower shore river channel in estuaries where the sediment is coarse and mobile due to strong river flow and subject to a reduced salinity. There is usually very little mud in the sediment. Oligochaetes, including Heterochaeta costata and enchytraeid oligochaetes dominate the infaunal assemblage with a few polychaetes being recorded in most cases. Other species that may be found, but only sporadically include Bathyporeia spp., Hediste (Nereis) diversicolor, Nephtys hombergii, Scolelepis squamata, Corophium volutator and Hydrobia spp. Depending on the degree of mobility, any pebbles and small cobbles that are present may have Enteromorpha attached. This biotope is restricted in mid and upper estuary situations to areas where finer material is consistently washed out by draining water or river flow.
Burrowing amphipods and Eurydice pulchra in well-drained clean sand shores
Well-draining beaches of coarse- to medium-grained mobile sand, generally on exposed coasts, support populations of burrowing amphipods and the isopod Eurydice pulchra. The degree of drainage appears to be a critical factor in determining the presence of polychaetes; only Scolelepis squamata appears to be capable of tolerating the well-drained sediments of this biotope. In more exposed conditions this biotope may extend the full width of the shore or be restricted to the lower part of the shore with barren sands (LGS.BarSnd) higher up. This biotope has two facies; drying upper and mid shore sands, and highly mobile lower shore and shallow sublittoral sand bars. Burrowing amphipods found frequently include Bathyporeia pelagica, B. pilosa, Pontocrates arenarius and Haustorius arenarius. Scolelepis squamata, if present, occurs in only low densities. Oligochaetes may be present and are often common where there is freshwater influence. This community is distinguished from the Amphipod-polychaete communities (LGS.AP) by its impoverished polychaete fauna (only occasional Scolelepis squamata or other polychaetes) and its lack of bivalves.
Burrowing amphipods and polychaetes in clean sand shores
Mid and lower shore clean sandy shores on wave-exposed or moderately wave-exposed coasts support a community of burrowing amphipods and polychaetes, sometimes with bivalves such as Angulus tenuis. The medium to fine-grained sand remains damp throughout the tidal cycle. The community consists of burrowing amphipods (Pontocrates altamarinus, P. arenarius, Bathyporeia elegans, B. guilliamsoniana, B. pelagica, B. pilosa and B. sarsi), the isopod Eurydice pulchra, the cumacean Cumopsis goodsiri and polychaetes (including Nephtys cirrosa, Scolelepis squamata, Paraonis fulgens and Arenicola marina). The presence of polychaetes is seen as coloured burrows running down from the surface of the sediment. The sediment is often rippled and typically lacks an anoxic black sub-surface layer. This community differs from the community of burrowing amphipods (LGS.AEur) in its greater variety of polychaete species and the presence of bivalves. The two sub-types are LGS.AP.P and LGS.AP.Pon depending upon the proportion of amphipods and polychaetes and the specific species present in the sand. More stable sediment, such as is found in sandy inlets or extensive coastal sandflats are LMS.PCer or LMS.MacAre.
Burrowing amphipods and polychaetes (often with Arenicola marina) in clean sand shores
Mid and lower shore clean sand on wave-exposed or moderately wave-exposed coasts support a community of burrowing amphipods and polychaetes. Amphipods Bathyporeia pelagica, B. pilosa, B. sarsi, Pontocrates arenarius and the isopod Eurydice pulchra are typically present. Polychaetes make the greater part of the community in terms of species richness and are dominated by Nephtys cirrosa, Scolelepis squamata and Arenicola marina. The medium and fine sand remains damp throughout the tidal cycle and contains little organic matter. The lugworm Arenicola marina present are usually as a temporary recruitment that are likely to be washed out during storms. The presence of polychaetes may be seen as coloured burrows running down from the surface of the sediment. The sediment is often rippled and typically lacks an anoxic black sub-surface layer. LGS.AP.P is distinguished from LGS.AP.Pon in that it is more stable sediment with fewer amphipod species and greater density of polychaetes, particularly Arenicola marina and Capitella capitata. This community differs from the community of burrowing amphipods (LGS.AEur) in its variety of polychaete species. More stable sediment, found in sandy inlets or extensive coastal sandflats are considered to be LMS.PCer or LMS.MacAre, depending upon the community present.
Burrowing amphipods Pontocrates spp. and Bathyporeia spp. in lower shore clean sand
Lower shore clean sand on wave-exposed or moderately wave-exposed coasts support a community of burrowing amphipods and polychaetes. Amphipods make up the greater part of the community and are typically dominated by Pontocrates altamarinus, P. arenarius, Bathyporeia elegans, B. pelagica, B. pilosa the isopod Eurydice pulchra and the cumacean Cumopsis goodsiri. Polychaetes are dominated by Nephtys cirrosa, Paraonis fulgens and Scolelepis squamata. Angulus tenuis is also frequently found in this biotope. Although the characterising species are not found very frequently, they are faithful to this biotope. The medium and fine sand remains damp throughout the tidal cycle and contains little organic matter. The presence of polychaetes may be seen as coloured burrows running down from the surface of the sediment. The sediment is often rippled and typically lacks an anoxic black sub-surface layer. LGS.AP.Pon is distinguished from LGS.AP.P as being less stable sediment with a community dominated by amphipods, particularly Pontocrates altamarinus, Bathyporeia elegans and Cumopsis goodsiri or the bivalve Angulus tenuis. This community differs from the community of burrowing amphipods (LGS.AEur) in its greater variety of polychaete and amphipod species. More stable sediment, found in sandy inlets or extensive coastal sandflats are considered to be LMS.PCer or LMS.MacAre, depending upon the community present.
Freely-draining coarse sandy beaches, particularly on the upper 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. Burrowing amphipods Bathyporeia spp. or Pontocrates spp. and the isopod Eurydice pulchra may be found in extremely low abundances, but if present in any quantity should be classed as LGS.AEur. Other species that may be found in low abundance may be left behind by the ebbing tide.
Dense Lanice conchilega in tide-swept lower shore sand
Medium to fine sand, which is usually clean but may contain some fines and supports dense populations of Lanice conchilega, usually on the lower shore but also sometimes on water-logged mid shores. The biotope occurs under tide-swept conditions in sheltered straits, sounds and fully marine sealochs or on shores moderately exposed to wave action. The biotope is distinguished from others in sandy beaches by the presence of Lanice conchilega at levels of common and above or as the main polychaete component. Other polychaetes present are tolerant of sand scour or mobility of the surface levels of the sediment and include glycerid polychaetes, Anaitides mucosa, Nephtys cirrosa, Nephtys hombergii and Pygospio elegans. Few crustaceans are found regularly and the bivalve component is restricted to cockles Cerastoderma edule and more rarely Macoma balthica. Pebbles and cobbles may also be mixed in with lower shore tide-swept sand with dense Lanice conchilega between the cobbles, but the infaunal component is rarely sampled. The infaunal community under these circumstances, provided that the cobbles are not packed very close together, will be similar to that in areas of purer sand. Dense L. conchilega also occurs in shallow sublittoral sediments (IGS.Lcon).
Talitrid amphipods in decomposing seaweed on the strand-line
A community of talitrid amphipods may occur on any shore where decomposing seaweed accumulates on the extreme upper shore strand-line. The community occurs on a wide variety of sediment shores composed of shingle and mixed substrata through to fine sands, but may also occur on mixed and rocky shores in some circumstances. The decaying seaweed provides cover and humidity for Talitrus saltator and other components of the community. The amphipods Orchestia spp. are also often present, as well as enchytraeid oligochaetes. Polychaetes, molluscs and other crustaceans may be brought in on the tide, but are not necessarily associated with the infaunal community. Further analysis of the data may determine that Orchestia spp. are associated with a denser strand and that there are differences in the community dependant upon the substratum-type. Talitrus saltator may occur further down the shore, almost invariably accompanied by burrowing amphipods such as Bathyporeia spp. (LGS.AEur).
Shingle or gravel shores, typically with sediment particle size from 4-256 mm, are normally only found on exposed open coasts in fully marine conditions. Such shores tend to have little associated finer sediment and due to their high degree of mobility support virtually no macrofauna. Larger 'sediment' is considered to be boulders and is addressed in the mixed shores section of the classification. Coarse sand, the next grade of sediment smaller than this size range is also found on exposed open coasts and has no distinct macrofaunal community as described in LGS.BarSnd. The shingle shore and mobile littoral sand biotopes are therefore distinguished solely on the basis of their substratum (i.e. particle size). Macrofauna are absent or extremely sparse in this very mobile and freely draining substratum. Trial excavations are unlikely to reveal macroscopic infauna. However, the few species that may be found are those washed into the habitat by the ebbing tide, including the occasional amphipod or small polychaete. There may be a temporary cover of the green algae Enteromorpha or Ulva during periods of stability in the summer.
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 may support populations of the amphipod Pectenogammarus planicrurus. Material finer than 2 mm reduces the ability of the amphipod to survive. The biotope is often associated with the lee side (wind or ?tide) of obstacles such as rock outcrops and groynes; this may be due to the deposition of algal debris, shelter from wave action or degree of sorting due to localised tidal flow around the obstacle (most likely a combination of the first and last influences). The biotope is characterised by dense populations of the amphipod Pectenogammarus planicrurus, although the species is usually also present as patchy populations within the mid shore band of other moderately wave-exposed sandy shore biotopes (e.g. LGS.Tal, LGS.AP). 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 and may be a variant of LGS.Tal demonstrated by the similarity of species found and presence of strand material.
Bathyporeia spp. and Corophium spp. in upper shore slightly muddy fine sands
Wave-sheltered upper and mid shore sandflats containing a small amount of silt with the amphipods Bathyporeia pilosa, Corophium arenarium and Corophium volutator. This biotope is typically found higher up the shore than sandflats with the cockle Cerastoderma edule (LMS.PCer) in the large sandy estuaries of the west coast of England and Wales. The salinity, although predominantly recorded as variable probably varies little from fully marine on the upper shore of these broad estuaries. Polychaetes and bivalves (with the exception of Macoma balthica) are limited in their abundance and variety. Tidal streams may be strong during spring tides, accounting for the low mud fraction and the presence of amphipods Bathyporeia pilosa that are more commonly associated with open coast sandflats. Cerastoderma edule and numerous polychaetes are found in the neighbouring biotopes LMS.PCer and LMS.MacAre whilst the polychaetes Hediste (Nereis) diversicolor and Pygospio elegans and bivalves Macoma balthica, Scrobicularia plana and Mya spp. are associated with the muddier estuarine biotopes LMU.HedMac, LMU.HedStr, LMU.HedScr and LMU.HedOl.
Macoma balthica and Arenicola marina in muddy sand shores
Muddy sand and fine sand flats on the mid and lower shore tend to occur on extensive moderately exposed shores and sheltered shores, on open coasts and in marine inlets. The sediment generally remains water-saturated during low water and the habitat may be subject to variable salinity conditions in marine inlets. The lugworm Arenicola marina and Scoloplos armiger are typically common along with the Baltic tellin Macoma balthica and cockle Cerastoderma edule. Amphipods such as the mud burrowing-amphipod Corophium volutator can be common, as well as polychaetes Pygospio elegans and Nephtys hombergii. The lugworm Arenicola marina, due to the variable recruitment success, may be absent, but Scoloplos armiger and other components of this biotope are still to be found. A black layer of anoxia is usually present within 5 cm of the sediment surface can be seen in the worm casts on the surface. The presence of Hediste (Nereis) diversicolor and oligochaetes usually indicates the more sheltered and muddy biotope LMU.HedMac.Are. The presence of Mya arenaria in abundance is described in LMS.MacAre.Mare. The biotope LMS.PCer is similar to this biotope, but is generally less muddy and has a higher frequency of amphipods such as Bathyporeia spp. and Cerastoderma edule. Arenicola marina may be dense (usually due to temporary recruitment) on more wave-exposed sandy shores with Nephtys cirrosa and Bathyporeia spp., LGS.AP.P.
Arenicola marina, Macoma balthica and Mya arenaria in muddy sand shores
Sheltered muddy sand and fine sand on very and extremely sheltered shores of estuaries, lagoons and marine inlets with polychaetes and bivalves. The biotope is distinguishable from LMU.HedMac by the high abundance of Mya arenaria and other bivalves. The polychaetes Nephtys hombergii, Scoloplos armiger, Pygospio elegans and Arenicola marina and the bivalves Cerastoderma edule, Macoma balthica and Mya arenaria are characterising species. The substratum varies from fine sand to muddy sand, but the mud content is typically lower than that found in the biotopes LMU.HedMac, LMU.HedStr and LMU.HedScr and the frequency of Hediste (Nereis) diversicolor and oligochaetes is also lower. The presence of Mya arenaria is often very localised, such that specific estuaries or tributaries may show consistently high populations of the bivalve over many years e.g. River Orwell, Suffolk. Records of this biotope are currently limited; it is possible that this is a transition between the biotopes LMS.MacAre and LMU.HedMac.Mare. It is important to distinguish between the two species of Mya - M. arenaria and M. truncata.
Polychaetes and Cerastoderma edule in fine sand and muddy sand shores
Fine sand on extensive moderately wave-exposed and sheltered shores, where the sediment is sufficiently stable to accommodate populations of Cerastoderma edule (at least occasional) and other bivalves. The community is found mainly on the mid and lower shore where the sediment is water-saturated most of the time. Slightly muddy conditions at some sites are reflected in a reduced amphipod population and a wider range of polychaetes compared to Amphipod-polychaete biotopes (LGS.AP). The community consists of polychaetes Nephtys hombergii, Scoloplos armiger, Pygospio elegans, Spio filicornis and Capitella capitata, oligochaetes, the amphipod Bathyporeia sarsi, and the bivalves Cerastoderma edule and Macoma balthica. This biotope carries commercially viable stocks of cockles Cerastoderma edule. It is therefore possible to find areas of this habitat where the infauna may have been changed through recent cockle dredging. Higher on the shore, adjacent to this biotope, LMS.BatCor is found with fewer polychaete and bivalve species due to the drier sediment found on the upper shore. LMS.PCer has broad transition areas with LMS.MacAre, LMU.HedMac.Pyg and LMU.HedMac.Are. LMS.MacAre and LMU.HedMac.Are are indicated by the presence of Arenicola marina, the latter also having Hediste (Nereis) diversicolor, oligochaetes and other species that indicate a more sheltered, muddy sand biotope. LMU.HedMac.Pyg has a greater proportion of the polychaetes Hediste diversicolor, Pygospio elegans and Eteone longa, oligochaetes and the amphipod Corophium volutator. The species richness of LMS.PCer, particularly for polychaetes and bivalves, is greater than the more wave-exposed biotopes LGS.AP.
Zostera noltii beds in upper to mid shore 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. This is similar to polychaetes and Cerastoderma edule (LMS.PCer) since it is most frequently found on lower estuary and sheltered coastal muddy sands with a similar infauna. Exactly what determines the distribution of the Zostera noltii is, however, not entirely clear. Zostera noltii 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. A black layer is usually present below 5 cm sediment depth. The infaunal community is characterised by polychaetes Pygospio elegans and Arenicola marina, mud amphipods Corophium volutator and bivalves Cerastoderma edule, Macoma balthica and Scrobicularia plana. Typically an epifaunal community is found that includes the mud snail Hydrobia ulvae, shore crabs Carcinus maenas and the green alga Enteromorpha sp. This biotope should not be confused with IMS.Zmar which is a Zostera marina bed on the lower shore or shallow sublittoral clean or muddy sand.
Hediste diversicolor and oligochaetes in low salinity mud shores
A low species-rich community found in soft mud in low salinity conditions, typically at the head of estuaries. Oligochaete worms (Heterochaeta costata, Tubificoides benedii, T. pseudogaster and enchytraeids) are common or abundant together with the ragworm Hediste (Nereis) diversicolor and sometimes the mud amphipod Corophium volutator. This biotope is distinguishable from other reduced salinity muddy sand communities (LMU.HedMac.Pyg, LMU.HedMac.Mare) and mud communities (LMU.HedStr and LMU.HedScr) by the absence of bivalves (except possibly for a few Macoma balthica) and a generally reduced polychaete fauna. The polychaete Manayunkia aestuarina may be common in more saline conditions, whilst at the very upper limit of the estuary only oligochaetes would be expected. Corophium volutator can be present in firmer mud. Filamentous algae such as Enteromorpha spp. may form mats on the surface of the mud during the summer months. The mud is often very soft and fluid, with a 'wet' surface appearance. LMU.HedStr has a similar habitat but is not exposed to such low salinity levels.
Hediste diversicolor and Scrobicularia plana in reduced salinity mud shores
Mid and upper shore sandy mud and mud that is subject to variable and reduced salinity is typically colonised by the polychaete Hediste (Nereis) diversicolor and the bivalve Scrobicularia plana. The polychaetes Eteone longa, Pygospio elegans and Streblospio shrubsolii, oligochaetes, particularly Tubificoides benedii and the isopod Cyathura carinata are all characteristic of the infaunal assemblage. Other bivalves, such as the Baltic tellin Macoma balthica and cockle Cerastoderma edule, are also frequently recorded. The mud snail Hydrobia ulvae is usually common. The green alga Ulva lactuca may colonise the surface of the mud in the summer months or it may be covered by a mat of filamentous algae such as Enteromorpha spp. Typically, the sediment is wet in appearance and has an anoxic layer below 1 cm depth. The surface of the mud has the distinctive 'crows foot' pattern formed by Scrobicularia plana. The biotope LMU.HedStr is very similar, but with some differences in the polychaetes and bivalves recorded. In LMU.HedStr, the frequency and abundance of Eteone longa is lower, whilst the frequency of the polychaetes Nephtys hombergii, Streblospio shrubsolii, Aphelochaeta marioni and Melinna palmata is greater. The bivalve richness in LMU.HedScr is typically higher with a greater frequency of Cerastoderma edule, Macoma balthica, Scrobicularia plana and Abra tenuis. LMU.HedScr may be intermediate between LMU.HedStr and LMU.HedMac or LMU.HedMac.Mare. It is muddier and is subject to a lower salinity level than LMU.HedMac. The diversity of species recorded is much greater than in LMU.HedOl.
Hediste diversicolor and Streblospio shrubsolii in sandy mud or soft mud shores
Sandy mud and 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 the presence of sea defences, rocky outcrops, rubble training walls or shallow layers of cobbles and pebbles in the sediment in the upper and mid estuary. In addition, the presence of nearby sewage outfalls or a high organic content probably influences the infaunal community. Tidal streams can be strong, further supporting the possibility that this biotope has a disturbed habitat. The infaunal polychaete community includes species with a limited salinity range tolerance such as Streblospio shrubsolii, Tharyx killariensis and Manayunkia aestuarina. In addition to the mentioned polychaetes, Hediste (Nereis) diversicolor, Nephtys hombergii, Pygospio elegans, the burrowing amphipod Corophium volutator, the mud snail Hydrobia ulvae and the bivalves Macoma balthica and Abra tenuis are characterising species. In the absence of the more frequently encountered characterising species, the presence of the isopod Cyathura carinata or polychaetes Polydora spp., Heteromastus filiformis or Ampharete grubei are also indicative of this biotope. The sediment is anoxic and black close to the surface and remains water saturated throughout the tidal cycle. The frequency and abundance of oligochaetes, particularly Tubificoides benedii and Tubificoides pseudogaster, is greater than in LMU.HedMac, whilst the closely related LMU.HedMac.Pyg rarely has Streblospio shrubsolii or Manayunkia aestuarina and has a greater frequency and abundance of Cerastoderma edule and Eteone longa. LMU.HedScr is similar to this biotope, but is slightly less muddy, has a higher frequency and abundance of bivalve species and a less diverse range of polychaete species, reflecting the more stable habitat of LMU.HedScr. The polychaete species richness is greater than in LMU.HedOl. The number of species that may be present in this biotope and the number of transition areas along salinity, wave-exposure and sediment particle size continua make this biotope potentially very variable in species content.
Hediste diversicolor and Macoma balthica in sandy mud shores
Littoral sandy mud and mud in sheltered, often estuarine, conditions with a community of polychaetes together with the bivalve Macoma balthica. The most abundant large polychaete is typically Hediste (Nereis) diversicolor, which can be readily seen when digging over the sediment. Other smaller polychaetes include Eteone longa, Nephtys hombergii, Tharyx marioni, Pygospio elegans, Arenicola marina and Manayunkia aestuarina. Oligochaete worms (e.g. Tubificoides benedii, T. pseudogaster and enchytraeids) are common or abundant and the amphipod Corophium volutator may be abundant. The mud snail Hydrobia ulvae is often common, with individuals or their fine tracks visible on the mud surface. The bivalve Macoma balthica may be accompanied by Cerastoderma edule, Abra tenuis and Mya arenaria. The surface of the mud may be covered with green algae such as Enteromorpha spp. or Ulva lactuca. There is usually a black anoxic layer close to the sediment surface. LMU.HedStr is a similar biotope that is associated with muddier sediment in reduced salinity conditions with Streblospio shrubsolii, Manayunkia aestuarina or Tharyx killariensis and with fewer bivalves. Three variations of this biotope are recognised: HedMac.Are, HedMac.Pyg and HedMac.Mare.
Hediste diversicolor, Macoma balthica and Arenicola marina in muddy sand or sandy mud shores
Mid shore muddy sand in estuaries, sheltered bays and marine inlets. This is the least sheltered and least muddy sub-type of LMU.HedMac, with the lugworm Arenicola marina usually abundant or as the numerically dominant polychaete and Cerastoderma edule relatively frequent. The following characterising species are typically present Eteone longa, Hediste (Nereis) diversicolor, Pygospio elegans, oligochaetes, the mud-burrowing amphipod Corophium volutator, the mud snail Hydrobia ulvae and the Baltic tellin Macoma balthica. Typically a black anoxic layer is present below 5 cm and this can be seen in the Arenicola marina casts. The community differs from LMS.MacAre in the muddiness of the sand and the high abundance of certain species including Hediste diversicolor, oligochaetes and Corophium volutator. LMU.HedMac.Pyg is similar to this biotope, but does not have the significant numbers of Arenicola marina, whilst LMU.HedMac.Mare has a rich bivalve content including Mya arenaria. This biotope can be considered as intermediate between LMS.MacAre and LMU.HedMac.Pyg.
Hediste diversicolor, Macoma balthica and Mya arenaria in sandy mud shores
Mid and low shore sandy mud in fully marine and variable salinity, sheltered to extremely sheltered estuaries, bays and marine inlets. This sub-type biotope of LMU.HedMac is differentiated from other LMU.HedMac biotopes in having Mya arenaria in high densities in most cases. Polychaetes Eteone longa, Hediste (Nereis) diversicolor, Pygospio elegans, oligochaetes, the mud-burrowing amphipod Corophium volutator, the mud snail Hydrobia ulvae, the cockle Cerastoderma edule, the Baltic tellin Macoma balthica and the soft clam Mya arenaria are the most frequently recorded and characterising species. The sediment is typically anoxic below 1 cm. The presence of Mya is usually indicated by jets of water of up to 50 cm high over the sediment surface, but should be confirmed through digging up the bivalve. The species that are found in LMU.HedStr can sometimes be present in high abundance in this biotope, reflecting the similarity of LMU.HedStr to this biotope. The tolerance to reduced salinity and substratum type of Mya arenaria is such that this biotope overlaps with LMS.MacAre and with LMU.HedStr; the significance of Mya arenaria as a characterising species is therefore unclear, but the conspicuousness of this species makes it a useful indicator of this habitat type. LMU.HedMac.Pyg is similar to this biotope, but contains very few Mya arenaria. LMU.HedScr can have a similarly rich bivalve component, but is usually restricted to reduced salinity mud habitats. LMU.HedOl has a much reduced polychaete and bivalve fauna compared to LMU.HedMac.Mare. This biotope is more muddy and probably more influenced by variable salinity than LMS.MacAre.Mare. A similar biotope that has a substratum with more gravel and pebbles and is limited to the lower shore is LMX.Mare. Like LMS.MacAre.Mare, the high densities of Mya arenaria can be very localised and be specific to certain estuaries or tributaries within estuaries over long periods of time.
Hediste diversicolor, Macoma balthica and Pygospio elegans in sandy mud shores
Mid and lower shore muddy sand in estuaries, sheltered bays and marine inlets sometimes subject to variable salinity. This sub-type of LMU.HedMac is characterised by the polychaetes Eteone longa, Hediste (Nereis) diversicolor, Pygospio elegans, Capitella capitata, oligochaetes (particularly Tubificoides benedii), the mud-burrowing amphipod Corophium volutator, the mud snail Hydrobia ulvae and the Baltic tellin Macoma balthica. The polychaetes Mediomastus fragilis and Marenzelleria spp. are found predominantly in this biotope. None of the characterising species are especially faithful to this biotope, since they are found in most littoral muddy sediments. Bivalves other than Macoma balthica and the cockle Cerastoderma edule are typically only present in low abundance, as are the polychaetes Arenicola marina, Streblospio shrubsolii and Manayunkia aestuarina. The similar biotope LMU.HedMac.Are contains the polychaetes Arenicola marina and Scoloplos armiger in higher abundance than in this biotope, and Nephtys cirrosa is also usually found in LMU.HedMac.Are. LMU.HedMac.Pyg is typically muddier than LMU.HedMac.Are, but not as muddy as LMU.HedStr, whilst the similar biotope LMU.HedOl has a much reduced polychaete fauna.
Mya arenaria and polychaetes in muddy gravel shores
Lower shore mixed sediment subject to reduced salinity in very sheltered marine inlets with the clam Mya arenaria, polychaetes and amphipods. The substratum consists of sand, gravel, pebbles and cobbles in varying degrees, usually with a small amount of silt. The infauna are characterised by the polychaetes Eteone longa, Anaitides maculata, Hediste (Nereis) diversicolor, Scoloplos armiger, Pygospio elegans and Tharyx killariensis, oligochaetes, amphipods including Urothoe poseidonis, Bathyporeia pilosa and Gammarus locusta, the mud snail Hydrobia ulvae and the bivalves Cerastoderma edule and Mya arenaria. Due to the stony nature of the sediment it is often not particularly well sampled. The presence of larger stones and cobbles on the surface leads to the growth of fucoids and other seaweeds (see SLR.FserX.T). [Further records are required to substantiate this biotope].
Mytilus edulis and Fabricia sabella in poorly-sorted muddy sand or muddy gravel shores
Pebbles, gravel or sand with mud in sheltered Firths with strand of fucoid algae which has a limited infauna characterised by juvenile infaunal Mytilus edulis, often in very high numbers. Polychaetes such as Fabricia sabella, Scoloplos armiger, Pygospio elegans and Hediste (Nereis) diversicolor and bivalves Macoma balthica and Cerastoderma edule typical of muddy sediments characterise the community. Fabricia sabella is typically found amongst algal holdfasts and between cobbles on rocky shores. This biotope description is devised mainly from records from the Dornoch Firth and Moray Firth. [More records are needed to verify this biotope].
Venerid bivalves in circalittoral coarse sand or gravel
Circalittoral gravels, coarse sands and shell gravels, often in relatively deep water, may be characterised by the presence of conspicuous venerid bivalves such as Circomphalus casina, Clausinella fasciata, Timoclea ovata and other robust bivalve species such as Glycymeris glycymeris and Astarte sulcata. Spatangus purpureus may also be present especially where the interstices of the gravel are filled by finer particles, in which case, Gari tellinella and Timoclea ovata may also be prevalent (Glémarec 1973). Such communities in gravely sediments may be relatively species-rich as they may also contain epifauna such as Hydroides norvegicus and Pomatoceros lamarcki. In sand wave areas this biotope may contain elements of the IGS.Sell and IGS.FabMag biotopes. 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). CGS.Ven may contain more sub-biotopes than have yet been described in the present work: e.g. Ford (1923) describes a 'Series A' and a 'Series B' characterised by Echinocardium cordatum-Chamelea gallina and Spatangus purpurea-Clausinella fasciata. Collectively, the CGS.Ven biotope dominates the offshore Irish Sea benthos (Mackie, Oliver & Rees 1995).
Venerid bivalves and Branchiostoma lanceolatum in circalittoral coarse sand with shell gravel
Gravel and coarse sand with shell gravel often contains communities of robust venerupid bivalves (CGS.Ven). Shallower examples, such as the biotope presented here, may support a significant population of Branchiostoma lanceolatum. Other conspicuous infauna are Clausinella (Venus) fasciata, Spatangus purpureus, Echinocyamus pusillus, Glycymeris glycymeris, Nucula hanleyi, Spisula elliptica, Arcopagia crassa (especially in the south of UK), Laevicardium crassum, Ampelisca spinipes and Psammechinus miliaris. Sessile epifauna are typically a minor component of this community. Also present are: Ensis arcuatus, Asterias rubens and Ophiura albida. 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 (Glémarec 1973). Deeper examples of this biotope give way to other CGS.Ven types.
Neopentadactyla mixta and venerid bivalves in circalittoral shell gravel or coarse sand
Sublittoral plains of clean maerl gravels, shell gravels and stone gravels or sometimes coarse sands, with frequent Neopentadactyla mixta and robust bivalves such as Clausinella fasciata, Circomphalus casina, Lutraria lutraria and Ensis arcuatus. These sediments may be thrown into dunes by wave action or tidal streams. Widespread species such as Cerianthus lloydii, Chaetopterus variopedatus, Lanice conchilega and Gibbula magus 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. Epifaunal species may include Pecten maximus and Callionymus spp. This biotope may also occur adjacent to maerl beds and to some extent in the lower infralittoral where some seaweeds may occur in low abundances. It should be noted that Neopentadactyla may exhibit periodicity in its projection out of, and retraction into, the sediment (Picton 1993).
Abra alba, Nucula nitida and Corbula gibba in circalittoral muddy sand or slightly mixed sediment
Muddy sands or slightly mixed sediments in sheltered or slightly reduced salinity environments may be characterised by the presence of the bivalves Abra alba, Nucula nitidosa and Corbula gibba as well as N. nucleus, Lagis koreni and Nephtys sp. The echinoderms Echinocardium cordatum, Ophiura albida and Ophiura ophiura may also be present. Sandier habitats contain the CMS.AfilEcor biotope and increasing silt (and depth) gives rise to the CMU.BriAchi biotope. The relative density of the characterising species in this biotope is known to vary from year to year (Molander 1962); Nucula nitidosa can, in some cases, be at least if not more prevalent than Abra alba (Salzwedel, Rachor & Gerdes 1985).
Amphiura filiformis and Echinocardium cordatum in circalittoral clean or slightly muddy sand
Medium to fine clean / muddy (clayey) sand off shallow wave- exposed coasts can be characterised by Amphiura filiformis and Echinocardium cordatum. This community occurs in muddy sands and deeper water (Hiscock 1984; Picton et al. 1994) and may be related to the 'off-shore muddy sand association' described by other workers (Jones 1951; Mackie 1990). This community is also characterised by Pholoe sp., Nephtys hombergii, Nucula nitidosa, Callianassa subterranea and Eudorella truncatula (e.g. Künitzer et al. 1992). Virgularia mirabilis, Cerianthus lloydii and Chaetopterus variopedatus may be other conspicuous surface features but they do not occur in high numbers in this biotope. Deeper, more muddy sediments may give rise to CMS.AbrNucCor. In areas subject to benthic fisheries disturbance, Arctica islandica (if present) may show scars on their shells (Klein & Witbaard 1993).
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. A rich associated biota attached to the calcareous tube may include Esperiopsis fucorum, thin encrusting sponges, the ascidians Ascidiella aspersa, Pyura microcosmus and Diplosoma listerianum and fine hydroids such as Halopteris catharina. In shallow water dense Phycodrys rubens may grow on the 'reefs'. Reefs from Loch Creran have been recently studied (Moore 1996). The only other known site in UK for these reefs is Loch Sween, where they are reported to have deteriorated. Otherwise only known from Salt Lake, Cliffden and Killary Harbour, Co. Galway.
Virgularia mirabilis and Ophiura spp. on circalittoral sandy or shelly mud
Circalittoral fine sandy mud and shelly gravel may contain Virgularia mirabilis and Ophiura spp. Such sediments are very common in sealochs, often occurring shallower than the finest mud or in somewhat more exposed parts of the lochs. 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. Greater quantities of stones and shells on the surface may give rise to more sessile epibenthic species (CMS.VirOph.HAs). 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. Inachus dorsettensis, Aporrhais pespelecani, Pagurus prideaux and Astropecten irregularis, although less widespread, are typical species of this sediment type. Virgularia mirabilis is usually accompanied by Cerianthus lloydii, Chaetopterus variopedatus, terebellids, including Lanice conchilega and, less commonly, Arenicola marina and Myxicola infundibulum in this biotope. Amphiura chiajei and Amphiura filiformis occur in high densities in the sandier examples of this biotope but are uncommon in the more gravely muds. Polychaetes and bivalves are the main components of the infauna, although nemerteans, Edwardsia claparedii, Phoronis muelleri and Labidoplax buski are also widespread. Of the polychaetes Goniada maculata, Nephtys incisa, Minuspio cirrifera, Chaetozone setosa, Notomastus latericeus and Owenia fusiformis are the most widespread species. Myrtea spinifera, Lucinoma borealis, Mysella bidentata, Abra alba and Corbula gibba were common bivalves in this sediment type. Turritella communis may form dense aggregations at sandier sites.
Virgularia mirabilis and Ophiura spp. with hydroids and ascidians on circalittoral sandy or shelly mud with shells or stones
Circalittoral fine sandy mud with shell gravel and notable quantities of shells or small stones scattered over the sediment surface. These sediments, like CMS.VirOph, may contain Virgularia mirabilis 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, and the solitary ascidians Corella parallelogramma and Ascidia mentula are most common. The serpulids Protula tubularia, Serpula vermicularis and Pomatoceros triqueter and the barnacles Balanus balanus and Balanus crenatus are also often present. Munida rugosa are frequently found under larger stones. All these species are typical of more rocky habitats in such sheltered conditions.
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 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).
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. This community is very similar to CMS.AbrNucCor and CMS.AfilEcor but tends to occur in deeper and siltier muds. Transitional communities between the two may contain large numbers of Turritella. 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). 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, M. Costello pers. comm. 1997). This community is the 'Boreal Offshore Mud Association' and 'Brissopsis - Chiajei' communities described by other workers (Petersen 1918; Jones 1950).
Seapens and burrowing megafauna in circalittoral soft 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. These soft mud habitats occur extensively throughout the more sheltered basins of sealochs and voes and are present in quite shallow depths (as little as 15 m) in these areas probably because they are very sheltered from wave action. 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 crustaceans present may include Nephrops norvegicus, Calocaris macandreae or Callianassa subterranea. The former of these species is the only one frequently recorded from surface observations, whilst grab sampling may fail to sample any of these species. Indeed, some forms of sampling may fail to indicate seapens as characterising. The crab Goneplax rhomboides may sometimes be recorded, again rarely, in this habitat. Large mounds formed by the echiuran Maxmuelleria lankesteri are also present in some sealoch sites. It is unclear from the data examined whether differences in the balance of species composition from site to site represent additional biotopes within this assemblage. Pachycerianthus multiplicatus is quite specific to this habitat and is scarce in Great Britain (Plaza & Sanderson 1997). The ubiquitous epibenthic scavengers Asterias rubens, Pagurus bernhardus and Liocarcinus depurator are present in low numbers. The brittlestars Ophiura albida and Ophiura ophiura are sometimes present, but are much more common in slightly coarser sediments. In the deeper fiordic lochs which are protected by an entrance sill, the tall seapen Funiculina quadrangularis may also be present (CMU.SpMeg.Fun). The brittlestars Amphiura chiajei and Amphiura filiformis may be present in large numbers, although there may be some sites, where these species are absent. 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 , although the latter may not be frequently found in remote samples. Overall, CMU.SpMeg is closely allied to CMU.BriAchi and COS.ForThy and shows strong similarities in infaunal species composition. It may differ from these biotopes as a result of a lack of disturbance or linkage to productive overlying waters (?). IMU.PhiVir is superficially similar to CMU.SpMeg but is found in shallower, less thermally stable waters and lacks the large burrowing species.
Seapens, including Funiculina quadrangularis, and burrowing megafauna in undisturbed circalittoral soft mud
Deep muds, especially in sealochs, which support populations of seapens such as Virgularia mirabilis and Pennatula phosphorea, but sometimes also with forests of the nationally scarce Funiculina quadrangularis. The sediment is usually extensively burrowed by crustaceans, the most common of which is Nephrops norvegicus, but Callianassa subterranea may also be present (the latter is likely to be under-recorded by grab sampling because it is deep burrowing). Lesueurigobius friesii is present at many sites. Amphiura spp. are usually present in high densities.
Sparse Modiolus modiolus, dense Cerianthus lloydii and burrowing holothurians on sheltered circalittoral stones and mixed sediment
Pebbles and cobbles on muddy shell gravel in sealochs with dense Cerianthus lloydii and sparse Modiolus modiolus. Large burrowing holothurians (many only extend their tentacles above the sediment surface seasonally) include Psolus phantapus, Paracucumaria hyndmani, Thyonidium commune, Thyone fusus and Leptopentacta elongata. This biotope is well developed in the Clyde sealochs, although many examples are rather species-poor. Some examples in south-west Scotland sealochs have greater quantities of boulders and cobbles and therefore have a richer associated biota (compared with other sheltered Modiolus bed biotopes such as SCR.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 (see MCR.Oph.Oacu).
Modiolus modiolus beds on 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. Brittlestars such as Ophiothrix fragilis may also occur with this community. This biotope is very similar to the 'boreal off-shore gravel association' and the 'deep Venus community' described by previous workers (Ford 1923; Jones 1951). Similar Modiolus beds on open coast stable boulders, cobbles and sediment are described under MCR.ModT.
Sabellaria spinulosa and Polydora spp. on stable circalittoral mixed sediment
The tube-building polychaete Sabellaria spinulosa at high abundances on mixed sediment, with Polydora spp. tubes attached. Infauna comprise typical sublittoral polychaete species, together with the bivalves Abra alba and Nucula nitidosa. Epifauna comprise calcareous tubeworms, pycnogonids, hermit crabs and amphipods.
Sparse fauna in reduced salinity infralittoral mobile sand
Very mobile sand in areas of strong tidal currents and reduced 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 species, such as Bathyporeia spp. and Haustorius arenarius, 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. The biotope bears some similarity with IGS.NeoGam although no freshwater community will be present. IGS.MobRS is a reduced salinity version of IGS.Mob, distinguished from this by the absence of species not tolerant of reduced salinities.
Nephtys cirrosa and fluctuating salinity-tolerant fauna in reduced salinity infralittoral mobile sand
Mobile sand in reduced 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 spp. The biotope contains relatively few species each typically in low abundance. It is found in tidal channels with moderate to strong tidal streams. The habitat is more stable than IGS.MobRS and may contain a small percentage of silt/clay, especially when sampled on slack water when deposition of the finer sediment grades occurs. Care should be taken in identification of this biotope due to the presence juveniles and species washed in during slack water. The biotope is a reduced salinity version of IGS.NcirBat, distinguished from this by the absence of species not tolerant of reduced salinities, in particular the polychaete Chaetozone setosa.
Neomysis integer and Gammarus spp. in low salinity infralittoral mobile sand
Upper estuary mobile sands with very low fluctuating salinity characterised by the mysid shrimp Neomysis integer (see Arndt 1991) and amphipods of the genus Gammarus spp. 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. It may be found in conjunction with IMU.LimTtub, although it lacks appreciable numbers of oligochaetes. The biotope occurs in a similar habitat to IGS.MobRS although it is more affected by lower salinity.
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. This biotope may also be contain opportunistic red seaweeds such as Palmaria palmata, Associated species are often typical of a hydroid/bryozoan turf but with infauna such as Sabella pavonina and Megalomma vesiculosum. It should be noted that this habitat may show considerable variation in community composition.
Spisula elliptica and venerid bivalves in infralittoral clean sand or shell gravel
Coarse, loose sands subject to moderately strong water movement and containing Chamelea gallina may be characterised by a prevalence of Spisula elliptica. IGS.Sell differs from IGS.FabMag because it has generally coarser loose sands influenced by greater water movement and populations of the more robust Spisula elliptica rather than the brittle-shelled Fabulina fabula. The community is less stable in its species composition than IGS.FabMag to which it is closely allied and collectively considered to be 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 IGS.FabMag; 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 deep-burrowing and more dispersed species such as Paphia, Ensis and Spatangus. This biotope may give way to others characterised by Angulus tenuis, Donax vittatus and Nephtys caeca on exposed lower shore sands (LGS.AP.Pon) (Jones 1950). In southern regions of the UK, S. elliptica is replaced by S. subtruncata in this biotope. It is possible that Spisula solida may also be characteristic of this habitat (needs clarification) (see Kühne & Rachnor 1996) and it should be noted that for some workers the three species of Spisula commonly encountered in UK waters may present difficulties in identification.
Fabulina fabula and Magelona mirabilis with venerid bivalves in infralittoral compacted fine sand
In stable, fine, compacted sands in the infralittoral and littoral fringe, communities occur that are dominated by venerid bivalves such as Chamelea gallina. The biotope may be characterised by a prevalence of Fabulina fabula and Magelona mirabilis. Remote grab sampling is likely to under-estimate deep-burrowing species such as Ensis sp. (Warwick & Davis 1977). Slightly muddy examples may have low numbers of Mysella bidentata. The community is relatively stable in its species composition, unlike IGS.Sell, which is closely allied and collectively considered to be the 'shallow Venus community' or 'boreal off-shore sand association' of previous workers (see Petersen 1918; Jones 1950; Thorson 1957). IGS.FabMag differs from IGS.Sell because of the prevalence of the brittle-shelled F. fabula over the more robust Spisula elliptica and because it occurs in generally finer, more compacted sands. 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 (Künitzer et al. 1992). In very shallow water and eulittoral sands this biotope may give way to IMS.MacAbr. Sites with this biotope may undergo transitions in community composition e.g. IMS.SpiSpi may be a transitional community between IGS.FabMag and CMS.AfilEcor (see Salzwedel, Rachor & Gerdes 1985).
Dense Lanice conchilega and other polychaetes in tide-swept infralittoral sand
Where strong tidal streams or wave action and coarse sand occur in the shallow sublittoral, dense beds of Lanice conchilega may occur. Several other species of polychaete also occur as infauna e.g. Scoloplos armiger, Chaetozone setosa and Arenicola marina. The dense Lanice biotope (LGS.Lan) on certain lower shores may be a littoral extension of this biotope. This biotope also appears to have a limited occurrence in some Scottish lagoonal entrance channels and some sealochs. Overall, there may be more than one entity in this biotope.
Sparse fauna in marine infralittoral mobile clean sand
Coarse sandy sediment in shallow water, often duned, 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. Sand eels Ammodytes sp. may occasionally be observed in association with this biotope (and others). This biotope is more mobile than IGS.NcirBat and may be closely related to LGS.BarSnd 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. A similar biotope, IGS.MobRS, occurs in reduced salinities but differs in that the sparse fauna of IGS.Mob are not tolerant of reduced salinities.
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 strong tidal streams or wave action and may be closely allied to the intertidal biotopes LGS.AEur and LGS.AP.Pon and intermediate in the degree of disturbance between the subtidal biotopes IGS.Mob and IGS.Sell. The faunal diversity of this biotope is considerably reduced compared to less disturbed biotopes 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). The range in wave exposure and tidal streams within which this biotope occurs is indicative of the fact that either wave exposure or tidal streams are responsible for the level of physical disturbance that yields this biotope. This biotope is very similar to IGS.Ncir which occurs in reduced/variable salinities with additional reduced salinity fauna. Stochastic recruitment events in the Nephtys cirrosa populations may be very important to the population size of other polychaetes present and may therefore create a degree of variation in community composition (Bamber 1994).
Sertularia cupressina and Hydrallmania falcata on tide-swept sublittoral cobbles or pebbles in coarse sand
Shallow sands with cobbles and pebbles, exposed to strong tidal streams, with conspicuous colonies of hydroids, particularly Sertularia cupressina and Hydrallmania falcata. These hydroids are tolerant to periodic submergence and scour by sand. Both diving and dredge surveys will easily record this biotope. Flustra foliacea and Alcyonidium diaphanum may also occur on the more stable cobbles and pebbles, whereas Lagis koreni is often a common component of the infaunal sand community. The less scoured biotope MCR.Flu.SerHyd occurs where there is less sand. Infaunal elements of the 'Venus' associations may occur in this biotope; indeed, this biotope may be at one extreme of the spectrum of such associations (E.I.S. Rees pers. comm. 1997).
Lithothamnion glaciale maerl beds in tide-swept variable salinity infralittoral gravel
Upper infralittoral tide-swept channels of coarse sediment subject to variable or reduced salinity which support distinctive beds of Lithothamnion glaciale maerl 'rhodoliths'. Phymatolithon calcareum may also be present as a more minor maerl component. This biotope can often be found at the upper end of Scottish sealochs where the variable salinity of the habitat may not be immediately obvious. Associated fauna and flora may include species found in other types of maerl beds (and elsewhere), e.g. Chaetopterus variopedatus, Lanice conchilega, Mya truncata, Plocamium cartilagineum and Phycodrys rubens. IGS.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 and Henricia oculata are also fairly typically present at sites. In Scottish lagoons (obs) 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 include red algae such as Cryptopleura ramosa, Brongniartella byssoides and Plocamium cartilagineum with Desmarestia spp. and Dictyota dichotoma also very often present. Algal species may be anchored to the maerl or to dead bivalve shells amongst the maerl. Polychaetes, such as Chaetopterus variopedatus, and the gastropods Gibbula magus and Gibbula cineraria may 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 and Dosinia exoleta are more widespread than available data currently suggests. IGS.Phy contains two distinct entities depending on depth: a shallower type with red seaweeds (IGS.Phy.R) and a lower infralittoral entity with notably less epiphytic seaweeds (IGS.Phy.HEc). It seems likely that stable wave-sheltered maerl beds with low currents may be separable from IGS.Phy; 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). At some sites where IGS.Phy 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 IGS.Phy as well as IMX.Lcor, where it dominates.
Phymatolithon calcareum maerl beds with hydroids and 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 hydroids and echinoderms. Hydroids present are typically erect colonies such as Nemertesia spp. and often occur on the maerl or attached to dead shells within the maerl. Echinoderms such as Antedon bifida, Ophiothrix fragilis, Ophiocomina nigra, Ophiura albida and Neopentadactyla mixta are occasional or frequent in IGS.Phy.HEc but do not often occur in IGS.Phy.R. Other, more ubiquitous echinoderms such as Marthasterias glacialis are found throughout IGS.Phy 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 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 IGS.Phy.HEc. Anthozoans and echinoderms are much less common in this biotope than in IGS.Phy.HEc, which typically occurs deeper than IGS.Phy.R.
Capitella capitata in enriched sublittoral muddy sediments
The polychaete Capitella capitata is an opportunist especially associated with organically enriched and polluted sediments (Warren 1977; Pearson & Rosenberg 1978) where it may be superabundant. Although more widely occurring, when this species occurs in high numbers and the overall species richness is considerably reduced, the sediments are invariably anoxic and often have a very high organic load. Nematodes, Tubificoides, Pygospio elegans and Malacoceros fuliginosus may also survive in this habitat, but rarely in anything but comparatively low numbers. This biotope may also occur to some extent in the intertidal. IMS.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. C. capitata may also occur in high numbers in estuaries (see IMU.CapTub), but this may be a result of competitive refuge rather than organic enrichment (Wolff 1973).
Echinocardium cordatum and Ensis sp. in lower shore or shallow sublittoral 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 arcuatus. A rich variety of polychaetes, such as Notomastus latericeus, Mediomastus fragilis and Scoloplos armiger, may occur in abundance. Bivalves such as Mysella bidentata, Tellimya ferruginosa, Dosinia lupinus, Chamelea gallina and Gari fervensis are typical of this habitat (but may not be present all at once), as are the predatory worms Pholoe inornata and Harmothoe spp. Seagrass Zostera marina may occur in low density (see also IMS.Zmar). Amphiura brachiata is common in fine sandy sediments and Labidoplax media in slightly muddier sediments. This biotope is currently broadly defined and needs further consideration, especially in relation to IGS.FabMag and IMS.MacAbr.
Macoma balthica and Abra alba in infralittoral muddy sand or mud
Near-shore shallow muddy sands and muds, and sometimes mixed sediments, may be characterised by the presence of the bivalve Macoma balthica. Abra alba, Lagis koreni and Donax vittatus may also be significant components although they may not necessarily all occur simultaneously. Fabulina fabula, Nephtys cirrosa, Echinocardium cordatum and Crangon crangon may also be present. The community is especially stable (Dewarumez et al. 1992). The substratum is typically rich in organic content and the community may occur in small patches or swathes in shallow waters parallel to the shore (Jones 1950; Cabioch & Glaçon 1975). This biotope is known to occur in patches between Denmark and the western English Channel. 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 & Glaçon 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). Sites with IMS.MacAbr may give over to neighbouring Amphiura biotopes with time (E.I.S. Rees pers. comm. 1996).
Spio filicornis and Spiophanes bombyx infralittoral clean or muddy sand
Fine, clean or slightly muddy sands may support a community dominated by the polychaetes Spio filicornis, Spiophanes bombyx and Nephtys hombergii. This is a biotope that is known from varied sediment conditions and occasionally occurs in coarser sands. The biotope may be transitional or part of a succession / cycle between CMS.AfilEcor and IGS.FabMag (see Salzwedel, Rachor & Gerdes 1985). Elements of the communities of these two biotopes are evident in IMS.SpiSpi as well as similarities with IMS.MacAbr and CMS.AbrNucCor. Ophiura albida may be common (more than 100 m-2). However, community composition may also be quite varied and may also contain Fabulina fabula, Magelona mirabilis, and Lanice conchilega. Spio filicornis and Spiophanes bombyx occur in several other biotopes therefore records should only be assigned to this biotope if they clearly do not fit the more stable and widely-occurring biotopes listed above. [The validity of this biotope in Britain and Ireland is uncertain].
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 and Spinachia spinachia which are less common on filamentous algal-dominated sediments. Seaweeds such as Chaetomorpha spp., Enteromorpha spp., and Chorda filum are also often present. In some cases the stoneworts Chara aspera and Lamprothamnium papulosum occur.
Zostera marina/angustifolia beds in lower shore or infralittoral clean or muddy sand
Expanses of clean or muddy fine sand 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 IMS.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) and other bivalves listed below. It should be noted that sparse beds of Zostera marina may be more readily characterised by their infaunal community. 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. Some examples of Zostera marina beds have markedly anoxic sediments associated with them.
Consistently low salinity infralittoral mud with beds of Potamogeton pectinatus. This biotope appears to replace Ruppia beds where the salinity is consistently low as opposed to variable. Other associated species are broadly similar to that of IMS.Rup, with blankets of filamentous green algae such as Enteromorpha intestinalis, Cladophora liniformis and Rhizoclonium tortuosum. The grazing gastropods Hydrobia ulvae and Potamopyrgus jenkinsi are 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 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. This biotope is further described as NVC type A12 (Rodwell 1995).
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).
Aphelochaeta marioni and Tubificoides spp. in variable salinity infralittoral mud
Variable salinity cohesive muddy sediment dominated by the polychaete Aphelochaeta marioni and the oligochaetes Tubificoides spp. The polychaetes Polydora ciliata, Cossura longocirrata and Melinna palmata may also occur in high numbers. The cirratulid polychaete Caulleriella zetlandica may also occur (there is still inconsistency in the identification of the cirratulid group, 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. The biotope may be separated from similar biotopes such as IMU.NhomTub by the abundance of A. marioni, terebellids and an indication of the stability of the sediment. In areas of mixed sediment A. marioni may also occur in high numbers. In this case it may be difficult to separate IMU.AmpTub from IMX.PolMtru requiring classification on sediment characteristics and associated species such as the bivalve Mya truncata in addition to the abundance of A. marioni. It may be separated from IMX.CreAph by the relative abundances of the slipper limpet Crepidula fornicata in addition to A. marioni. This biotope may also be found in conjunction with IMS.MacAbr.
Capitella capitata and Tubificoides spp. in reduced salinity infralittoral muddy sediment
Reduced salinity muddy sediment dominated by the polychaete Capitella capitata with a very low species richness. Large numbers of the oligochaetes Tubificoides spp. may be found in conjunction with the C. capitata. The biotope is found in the muddier sediments, usually with a high organic content, away from tidal channels in estuaries. On occasion relatively large numbers of C. capitata can be found in sandier sediments within a more mobile habitat although these are thought largely to be imported by tidal streams from nearby populations a definition of a separate biotope may be appropriate. A similar biotope IMU.Tub can be separated from IMU.CapTub by a swap in the dominant species from C. capitata to Tubificoides spp and may occur in lower salinity. More mobile muds which occur in areas with an extremely high suspended particulate component to the water column, IMU.MobMud, may contain a similar suite of species to IMU.CapTub although in lower abundance. Only a description of the sediment consistency in the field would allow positive classification. 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). In estuaries the presence of this biotope 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 oligochaetes Limnodrilus hoffmeisteri and Tubifex tubifex. This biotope is found in the transitional zone between the freshwater and brackish environments where tidal currents are sufficiently reduced to allow the deposition of fine silt and the establishment of an infaunal community. The biotope contains elements of both freshwater and brackish communities and may be found adjacent to IGS.NeoGam away from the stronger tidal streams. It is similar to IMU.Tub although the latter lacks the freshwater element.
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. This biotope may be under-recorded due to sampling problems, and also where sediment descriptions are absent from field data. It may be found adjacent to; IMU.Tub, IMU.NhomTub and to some extent IMU.ThaTub.
Nephtys hombergii and Tubificoides spp. in variable salinity infralittoral soft mud
Variable salinity soft infralittoral mud and sandy mud characterised by the polychaete Nephtys cirrosa and oligochaetes of the genus Tubificoides. Also present are low numbers of the bivalves Macoma balthica, Abra alba and the polychaete Scoloplos armiger. The biotope is found in areas of silt deposition in soft and sandy muds but may not form a stable habitat. It may be found adjacent to IMU.ThaTub, separated by the abundance of Tharyx marioni and its more cohesive sediments. More mobile muds, IMU.MobMud, may contain a reduced element of this biotope in which case only sediment description will distinguish the two biotopes. This biotope may be in conjunction with IMS.MacAbr.
Polydora ciliata in variable salinity infralittoral firm mud or clay
Variable salinity clay and firm mud characterised by a turf of the polychaete Polydora ciliata. P. ciliata also occurs in high densities elsewhere - see MCR.Pol. (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.
Tubificoides spp. in reduced salinity infralittoral muddy sediment
Reduced salinity muddy sediments characterised by oligochaetes, particularly of the genus Tubificoides. The abundance of the oligochaetes may vary by several orders of magnitude but very few other species will be present. This biotope is found towards the edges of tidal channels in estuaries where current velocities allow deposition of silt and the establishment of an infaunal community. Organic loading and poor water-exchange within the sediment lead to anoxic conditions which may explain the low species richness within this biotope. The biotope may occur downstream of IMU.LimTtub, differentiated by the absence of the freshwater species, and adjacent to more mobile and sandier biotopes in the tidal channels. A similar biotope IMU.CapTub can be separated from IMU.Tub by the dominance of the polychaete Capitella capitata. More mobile muds which occur in areas with an extremely high suspended particulate component to the water column, IMU.MobMud, may contain a very similar suite of species to IMU.Tub and can only positively be separated by a description of the sediment characteristics in the field.
Arenicola marina and synaptid holothurians in extremely shallow soft mud
In very shallow extremely sheltered very soft muds Arenicola marina may form very conspicuous mounds and casts. At such sites, high densities of synaptid holothurians such as Labidoplax media and Leptosynapta bergensis occur. This biotope typically occurs in waters shallower than about 5 m in sheltered basins of sealochs and lagoons that may be partially separated from the open sea by tidal narrows or rapids. Sediment surfaces may become covered by a diatom film at certain times of the year.
Ocnus planci aggregations on sheltered sublittoral muddy sediment
Dense aggregations of Ocnus planci [?brunneus] on various substrata, typically muddy but sometimes with stones or shells, in sheltered conditions such as sealochs. Associated species vary but are typical of very sheltered muddy habitats. Melanella alba, which parasitises holothurians, is found in large numbers at one site.
Philine aperta and Virgularia mirabilis in soft stable infralittoral mud
Physically very stable muds with a high proportion of fine material (greater than 80 %) may contain the seapen Virgularia mirabilis. These muds typically occur in shallow water 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. The opisthobranch Philine aperta is the most characteristic species of this habitat, occurring in high densities at many sites. The seapen Virgularia mirabilis, a species found more widely in muddy sediments, appears to reach its highest densities in this shallow mud. Other conspicuous species found in this shallow muddy habitat include Cerianthus lloydii, Sagartiogeton spp., Ascidiella aspersa and Myxicola infundibulum. Amphiura chiajei and Amphiura filiformis may also be present at some sites. Burrowing crustacean megafauna, characteristic of deeper mud, are rare or absent from this shallow sediment. Of these burrowers Nephrops norvegicus may sometimes be recorded. The bivalves Nucula sp., Thyasira flexuosa and Corbula gibba may be other conspicuous infaunal species. The sediment may be covered by a diatom film. 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 (Glémarec 1973; Dauvin et al. 1994). Similar but deeper more stable muds to IMU.PhiVir are characterised by burrowing megafauna (CMU.SpMeg). IMU.PhiVir has a lot of similarity with CMU.BriAchi, possibly differing on account of low disturbance or linkage with enriched overlying waters, however, these hypotheses are untested. IMU.PhiVir may also be closely allied to CMS.AbrNucCor, showing some of the infaunal elements of this biotope.
Semi-permanent tube-building amphipods and polychaetes in sublittoral mud or muddy sand
Sublittoral stable mud and muddy sands occurring over a wide depth range may support large populations of semi-permanent tube-building amphipods and polychaetes. This community is poorly known and appears to occur in restricted patches. Amphipods such as Ampelisca spp., Corophium spp. and Haploops tubicola have been described as occurring in high densities in such habitats (see Petersen 1918; Thorson 1957) and polychaetes such as Spiophanes bombyx and Polydora ciliata may also be conspicuously numerous. It may be that this community develops as a result of moderate nutrient enrichment. It is possible that this biotope may contain more than one entity as all the characterising species listed need not occur simultaneously.
Crepidula fornicata and Aphelochaeta marioni in variable salinity infralittoral mixed sediment
Variable salinity mixed sediment characterised by the slipper limpet Crepidula fornicata and the polychaete Aphelochaeta marioni. 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). This biotope occurs in the lower estuary where currents allow a stable environment to develop. It is associated with oyster beds and relict oyster beds, (IMX.Ost), in southern England and Wales, separated from these by the superabundance of C. fornicata. It may be found adjacent to or in conjunction with IMU.AphTub, again separated by the abundance of C. fornicata and its sediment characteristics. It may be associated with IMX.VsenMtru and possibly form a component of SCR.Aasp.
Mytilus edulis beds in variable salinity infralittoral mixed sediment
Shallow sublittoral mixed sediment, often subject to variable salinity conditions, characterised by beds of the common mussel Mytilus edulis. Infaunal species include the polychaetes Heteromastus filiformis and Capitella capitata, the amphipod Gammarus salinus and oligochaetes of the genus Tubificoides. Epifaunal species in addition to the M. edulis include the whelks Nucella lapillus and Buccinum undatum and the common starfish Asterias rubens. This biotope may be an extension of littoral communities SLR.MytX. It is similar to IMX.PolMtru and may be separated by the dominance of M. edulis in 'beds' rather than scattered individuals. Care must be taken with data to ensure juvenile spat recruitments are not classified as mussel beds. (Description based on records from the Tay Estuary; this biotope will require further records to confirm description.)
Polydora ciliata, Mya truncata and solitary ascidians in variable salinity infralittoral mixed sediment
Variable salinity mixed muddy sediment characterised by the polychaetes Polydora ciliata, Aphelochaeta marioni, the bivalve molluscs Abra nitida and Mya truncata and the ascidians Ascidiella aspersa, Ascidiella scabra, Molgula sp. and Dendrodoa grossularia (the ascidians may not be recorded adequately by remote infaunal surveys). This biotope occurs in lower estuary mixed muddy sediments which are relatively stable, even though subject to moderate tidal streams. It may be found adjacent to IMU.AphTub, IMX.CreAph, IMX.Ost and IMX.MytV. It may also (as yet unproven) represent the infaunal component of SCR.Aasp. It is similar to IMU.AphTub, separated by a combination of sediment characteristics and the abundance of A. marioni. Some difficulty may arise in distinguishing this biotope from reduced versions of IMX.CreAph, IMX.Ost and IMX.MytV as it is unclear at what density the characterising molluscs have to occur to divide a 'bed' from shell debris. This biotope may be associated with IMX.VsenMtru.
Shallow mixed sediment faunal communities
Burrowing anemones in sublittoral muddy gravel
Sublittoral muddy gravel or shell gravel can contain conspicuous communities of burrowing anemones such as Mesacmaea mitchellii, Aureliania heterocera, Cereus pedunculatus and Cerianthus lloydii. Some ascidians such as Corella parallelogramma may also be present in the substratum if surface features such as shell material is large enough. There may be more than one variety of this biotope, influenced by the strength of the currents and the composition of the sediment.
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 'nest' 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 hydroids such as Kirchenpaueria pinnata, Nemertesia spp. and Plumularia setacea, mobile crustaceans (e.g. Hyas araneus) and echinoderms (Crossaster papposus, Ophiothrix fragilis and Ophiocomina nigra). Sometimes red seaweeds occur if the beds are in shallow enough water.
Venerupis senegalensis and Mya truncata in lower shore or infralittoral muddy gravel
Intertidal and shallow sublittoral muddy gravel in sheltered inlets that do not have a significantly reduced salinity (sea lochs) with Venerupis senegalensis and occasionally with Mya truncata. This biotope is perhaps best considered as an extension onto the extreme lower shore of a sublittoral biotope. Other typical components of the community include the polychaetes Notomastus latericeus, Aphelochaeta marioni and Tubificoides benedii.
Laminaria saccharina (sugar kelp) and filamentous seaweeds (mixed sediment)
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, 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 Derbesia marina. This biotope may also contain some red seaweeds, such as Furcellaria lumbricalis, but always at low abundance (compare with SIR.PolFur). Amongst the filamentous green algae, grazing molluscs and solitary ascidians may be present.
Laminaria saccharina, Chorda filum and filamentous red seaweeds on sheltered infralittoral sediment
Very sheltered infralittoral sandy and muddy mixed cobbles, pebbles and gravels with the cape form of Laminaria saccharina and Chorda filum. Beneath the kelp canopy, a variety of filamentous and foliose red algae are usually present, along with filamentous brown ectocarpoid algae. In the sandier sediments Cerianthus lloydii and terebellids such as Lanice conchilega are common. Where the cobbles, pebbles and gravels occur on muddier sediments, the infauna is characterised by a range of polychaetes and bivalves. This biotope is currently very broadly defined, and is likely to be further sub-divided following detailed data analysis, as the infauna and associated seaweeds appear to be distinctive depending on the specific sediment type.
Loose-lying mats of Phyllophora crispa on infralittoral muddy sediment
Infralittoral mud 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. IMX.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 and typically in fully saline waters. The seaweeds in this biotope may epiphytised by ascidians such as Ascidiella aspera and Ascidia mentula.
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 and species of Derbesia. Often the mud is gravely 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 IMX.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.
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, Gracilaria verrucosa and Ulva spp. are often present, although are not restricted to this biotope, whereas Dudresnaya verticillata and Cutleria multifida tend not to occur on other types of maerl beds. The anemones Anthopleura ballii, Anemonia viridis and Cereus pedunculatus and the fan worm Myxicola infundibulum are typically found in IMX.Lcor whereas Echinus esculentus tends to occur more in other types of maerl. IMX.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 IMX.Lcor (see IGS.Phy).
Lithothamnion dentatum maerl beds on infralittoral muddy sediment
Shallow, sheltered infralittoral mud with Lithophyllum dentatum maerl. This rarely recorded maerl species forms locally abundant balls, generally about three centimetres in diameter but as large as 15 cm (Irvine & Chamberlain 1994; H. Fazakerley pers. comm. 1997). IMX.Lden may be found on mud, muddy gravel and in association with small amounts of other maerl species such as Lithothamnion corallioides, Phymatolithon calcareum and Lithophyllum fasciculatum. Filamentous seaweeds such as Rhodothamniella floridula, Asparagopsis armata (Falkenbergia phase) and Sphacelaria cirrosa may occur in this biotope, as well as creeping plants of Gelidium latifolium, encrusting red and brown algae and small foliose red seaweeds. Faunal components of this biotope include Gibbula magus, sponges, burrowing worms, porcelain crabs, Galathea spp., amphipods and isopods. Knowledge of the community composition of this biotope is currently incomplete.
Lithothamnion fasciculatum maerl beds with Chlamys varia on infralittoral sandy mud or 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). IMX.Lfas may be found on mud and muddy gravel mixed with shell. Species of burrowing 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. Chlamys varia and Thyone fuscus are occasional in all records of this biotope and red seaweeds such as Plocamium cartilagineum, Calliblepharis jubata and Chylocladia verticillata are present.
Ostrea edulis beds on shallow sublittoral muddy sediment
Dense beds of the oyster Ostrea edulis can occur on muddy fine sand. 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. Several conspicuously large polychaetes may be present, such as Chaetopterus variopedatus and terebellids, as well as additional suspension-feeding polychaetes such as Myxicola infundibulum, Sabella pavonina and Lanice conchilega. 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.