Mussel and/or barnacle communities with seaweeds on Atlantic littoral rock

Description (English)

Moderately exposed rocky shores characterised by a mosaic of fucoids and barnacles on bedrock and boulders, where the extent of the fucoid cover is typically less than the blanket cover associated with sheltered shores. Other species are normally present as well in this habitat including the winkle Littorina littorea, the whelk Nucella lapillus and the red seaweed Mastocarpus stellatus. Beneath the band of yellow and grey lichens at the top of the shore is a zone dominated by the wrack Pelvetia canaliculata, scattered barnacles, while the black lichen Verrucaria maura covers the rock surface (MA1-241). Below, on the mid shore the wrack Fucus vesiculosus generally forms a mosaic with the barnacle Semibalanus balanoides and the limpet Patella vulgata (MA1-243). Finally, the wrack Fucus serratus, dominates the lower shore, while a variety of red seaweeds can be found underneath the F. serratus canopy (MA1-244). A number of variants have been described: lower shore bedrock and boulders characterised by mosaics of F. serratus and turf-forming red seaweeds (MA1-2441); where the density of F. serratus is greater (typically Common - Superabundant) and the abundance of red seaweeds less MA1-23F1 should be recorded. The presence of boulders and cobbles on the shore can increase the micro-habitat diversity, which often results in a greater species richness. Although the upper surface of the boulders may bear very similar communities to MA1-23F1 there is often an increase in fauna (crabs, tube-forming polychaetes, sponges and bryozoans) and MA1-2442 should be recorded. Sand-influenced exposed to moderately exposed lower shore rock can be characterised by dense mats of Rhodothamniella floridula (MA1-245).
Situation: Mid and lower eulittoral moderately exposed bedrock with a lichen zone above and a kelp dominated community below in the sublittoral zone.
Mid and lower eulittoral exposed to moderately exposed bedrock, often with nearby sediment, may be densely covered by large individuals of the mussel Mytilus edulis. Three biotopes have been described: In the mid eulittoral, the mussels may form a band or large patches with scattered bladder wrack Fucus vesiculosus (MA1-246). In the lower eulittoral a range of red seaweeds including Mastocarpus stellatus and Palmaria palmata occur amongst the mussels (in higher abundance than the mid eulittoral) (MA1-247). Clay outcrops in the mid to lower eulittoral may be bored by a variety of piddocks including Pholas dactylus, Barnea candida and Petricola pholadiformis, while the surface is characterised by small clumps of the mussel M. edulis, the barnacle Elminius modestus and the winkle Littorina littorea (MA1-248). Ephemeral green seaweeds such as Enteromorpha intestinalis and Ulva lactuca commonly occur on the shells of the mussels. Barnacles are common on both the mussel valves and on patches of bare rock, where the limpet Patella vulgata is found as well, often at high abundance. The whelk Nucella lapillus and a range of littorinids also occur within the mussel bed. A dense M. edulis community may be found on more sheltered coasts on mixed substrata (MA2-271).
Situation: Above this habitat type is a M. edulis and S. balanoides dominated zone or a F. vesiculosus dominated biotope (MA1-243). In the lower eulittoral zone below is a zone dominated by the wrack Fucus serratus, M. edulis and a variety of red seaweeds (MA1-24) while kelp dominate the sublittoral fringe.

Source: EUNIS habitat classification