Cushion sponges, hydroids and ascidians on turbid tide-swept sheltered circalittoral rock

Description (English)

This sub-biotope typically occurs in a mixture of turbid, full and variable salinity water, on wave-sheltered and moderately exposed bedrock or boulders. Tidal streams are typically moderately strong but may vary considerably. This sub-biotope occurs in relatively shallow water (typically 5m to 11m water depth) and is dominated by cushion sponges, hydroids and ascidians. On the silty, rocky substrata, large growths of sponge are usually associated with this biotope (Suberites ficus, Hymeniacidon perleve, Cliona celata, Halichondria panicea, Raspailia ramosa). The tasselled form of Esperiopsis fucorum is also notably present. Other epifauna present includes silty hydroids such as Nemertesia antennina, Nemertesia ramosa, Plumularia setacea, Hydrallmania falcata and Halecium halecinum. Individual colonies of dead mans fingers Alcyonium digitatum and plumose anemones Metridium senile may be seen attached to the tops of boulders and ridges. At some sites, whole sides of rocks may be colonised by the anemones Sagartia elegans, Sagartia troglodytes and Actinothoe sphyrodeta. Within crevices in the rocky substratum and at the base of boulders Urticina felina and Cereus pedunculatus may be found. Ascidians such as Clavelina lepadiformis, Morchellium argus, Dendrodoa grossularia, Diplosoma listerianum and Distomus variolosus may all be observed. Other ubiquitous species which may be recorded include Polydora, terebellid worms, Balanus crenatus, Alcyonidium diaphanum and Asterias rubens.

Source: EUNIS habitat classification