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Marine Habitat Classification


1 result for 'CR.HCR.DpSp.PhaAxi'

   CR.HCR.DpSp.PhaAxi  Phakellia ventilabrum and Axinellid sponges on deep, wave- exposed circalittoral rock

This biotope typically occurs on the upper faces of deep (commonly below 30m depth), wave-exposed circalittoral rock subject to negligible tidal streams. Although it occurs in exposed and very exposed conditions, at such depth, the turbulent wave action appears to have a much-attenuated effect on the fauna compared with shallower depths. As the majority of records are from depths between 30-50+ m, slightly deeper than the depths of most surveys, it is possible that this biotope is more widespread than the available dataset indicates. The sponge component of this biotope is the most striking feature, with similar species to the bryozoan and erect sponge biotope complex (BrErSp) although in this case, the sponges Phakellia ventilabrum, Axinella infundibuliformis, Axinella dissimilis and Stelligera stuposa dominate. Other sponge species frequently found on exposed rocky coasts are also present in low to moderate abundance. These include Cliona celata, Polymastia boletiformis, Haliclona viscosa, Pachymatisma johnstonia, Dysidea fragilis, Suberites carnosus, Stelligera montagui, Hemimycale columella and Tethya aurantium. The cup coral Caryophyllia smithii and the anemone Corynactis virdis may be locally abundant in some areas, along with the holothurian Holothuria (Panningothuria) forskali. The soft corals Alcyonium digitatum and Alcyonium glomeratum are frequently observed. The bryozoans Pentapora foliacea and Porella compressa are also more frequently found in this deep-water biotope. Bryozoan crusts such as Parasmittina trispinosa are also occasionally recorded. Isolated clumps of large hydroids such as Nemertesia antennina, Nemertesia ramosa and Sertularella gayi may be seen on the tops of boulders and rocky outcrops. Large echinoderms such as Echinus esculentus, Luidia ciliaris, Marthasterias glacialis, Strichastrella rosea, Henricia oculata and Aslia lefevrei may also be present. The seafan Eunicella verucosa may be locally common but to a lesser extent than in ByErSp.Eun. The top shell Calliostoma zizyphinum is often recorded as present.
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