Description of Sponges, shade-tolerant red seaweeds and [Dendrodoa grossularia] on wave-surged overhanging lower eulittoral bedrock and caves
Overhanging bedrock on the lower shore, at cave entrances, to and on inner walls of caves, subject to wave surge and low light levels, and characterised by a high density of small groups of the solitary ascidian Dendrodoa grossularia. The sponges Grantia compressa, Halichondria panicea and Hymeniacidon perleve are common on the rock surface, while the hydroid Dynamena pumila (normally found on fucoids) hangs in distinct form from overhanging rock. Found on the rock surface are the calcareous tube-forming polychaetes Spirorbis spp. and Pomatoceros spp. along with the barnacles Semibalanus balanoides. The anemone Actinia equina thrives in the permanently damp pits and crevices. Where sufficient light is available a sparse community of shade-tolerant red seaweeds. These include Membranoptera alata, Lomentaria articulata, Audouinella spp. and coralline crusts. Situation: This biotope is found on lower shore overhangs and on the entrances and inner walls of lower shore caves, and usually dominates the available habitat. It is generally found above the A1.44A biotope and may extend to the upper walls of caves. Temporal variation: Some variation in the species composition of the individual caves must be expected depending on local conditions.