Sponge crusts, colonial (polyclinid) ascidians and a bryozoan/hydroid turf on wave-surged vertical or overhanging infralittoral rock
|Within Vocab||Marine Habitat Classification for Britain and Ireland Version 97.06|
|Definition||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).|
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