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  4. MC1-2162 - Flustra foliacea, petites ascidies solitaires et coloniales sur roche ou blocs du circalittoral soumis aux courants de marée en Atlantique
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MC1-2162 - Flustra foliacea, petites ascidies solitaires et coloniales sur roche ou blocs du circalittoral soumis aux courants de marée en Atlantique

Flustra foliacea, small solitary and colonial ascidians on tide-swept Atlantic circalittoral bedrock or boulders
MC1-2161 - Polyclinum aurantium et Flustra foliacea sur roche du circalittoral abrasée par le sable, soumise aux courants de marée et modérément exposée aux vagues en Atlantique
MC1-2163 - Flustra foliacea et ascidies coloniales sur substrat hétérogène du circalittoral exposé et soumis aux courants de marée en Atlantique

Classification des habitats EUNIS 2022

Descriptif de l'habitat

This sub-biotope is typically found on the upper faces of exposed to moderately exposed, tide-swept, scoured, circalittoral bedrock or boulders. It most frequently occurs between 10-20m water depth. The biotope is characteristically dominated by dense Flustra foliacea with a variety of slightly scour/silt-tolerant species forming a dense turf. This turf is primarily composed of bryozoans (Alcyonidium diaphanum, Bugula flabellata, Bugula plumosa, Bicellariella ciliata) and hydroids (Tubularia indivisa, Nemertesia antennina, Sertularia argentea, Hydrallmania falcata, Abietinaria abietina). Where space permits, barnacles such as Balanus crenatus may be found encrusting on the rock surface. There may also be occasional crusts formed by the polychaete Sabellaria spinulosa, especially where the rock is most influenced by sand. Anthozoans which may be observed include Urticina felina, Sagartia elegans, whilst the soft coral Alcyonium digitatum may be recorded on the tops of boulders and bedrock ridges. A range of small solitary and colonial ascidians may be seen, including Polycarpa scuba, Dendrodoa grossularia, Molgula manhattensis, Botryllus schlosseri, Clavelina lepadiformis and polyclinids. Sponges found include Scypha ciliata, Cliona celata, Esperiopsis fucorum and Dysidea fragilis. Echinoderms such as Asterias rubens, Henricia oculata and Crossaster papposus may be seen on the rock surface. Other species found include the top shell Calliostoma zizyphinum, the crabs Cancer pagurus and Necora puber.
Situation: Above this variant, exposed kelp forest supporting Laminaria hyperborea is commonly found (unit MB1-213). At locations where wave-exposure and/or tidal streams are less, this biotope may be replaced by Alcyonium digitatum and Securiflustra securifrons (unit MC1-2243). Where the substrata changes to a less stable mixed substrata, then this biotope will be replaced by the sub-biotope MC1-2163, with more `sediment' species such as Cerianthus lloydii and Chaetopterus variopedatus.

Bibliography

European Topic Centre on Biological Diversity 2022. EUNIS marine habitat classification 2022 including crosswalks. Table Excel. (Source)