Identity:

This biotope is found in variable salinity environments and tends to occur on the upper faces of circalittoral bedrock and boulders, in sheltered sites subject to moderately strong tidal streams. This biotope is characterised by aggregations of cushion sponges such as Hymeniacidon perleve, Halichondria panicea, Halichondria bowerbanki and Cliona celata, other sponges (Leucosolenia botryoides and Suberites ficus) along with occasional hydroid tufts of Nemertesia antennina, Nemertesia ramosa and Plumularia setacea. Other species that may be present include the colonial ascidians Clavelina lepadiformis and Morchellium argus, Dendrodoa grossularia, the anemones Metridium senile and Sagartia troglodytes, the barnacle Balanus crenatus, Asterias rubens, Carcinus maenas and Bugula plumosa. Two variants of this biotope have been recorded: units A4.2511 and A4.2512.