Description of [Fucus vesiculosus] on variable salinity mid eulittoral boulders and stable mixed substrata
Sheltered to extremely sheltered mid eulittoral pebbles and cobbles lying on sediment subject to variable salinity and characterised by the wrack Fucus vesiculosus. The wrack Ascophyllum nodosum can occasionally be found on larger boulders, while the barnacles Semibalanus balanoides and Elminius modestus and the mussel Mytilus edulis can be present on cobbles. Winkles, particularly Littorina littorea, commonly graze on the seaweeds, while Littorina saxatilis can be found in crevices. Ephemeral seaweeds such as Enteromorpha intestinalis can occupy available space. Patches of sediment found between the hard substrata often contains the lugworm Arenicola marina or the sand mason Lanice conchilega, while the crab Carcinus maenas, gammarids and amphipods occur on and under cobbles. Situation: This unit can be found below the biotope dominated by the wracks Fucus spiralis or Fucus ceranoides (units A1.3122; A1.327) or a community dominated by S. balanoides, P. vulgata and L. littorea (A2.431). It is found above a community dominated by M. edulis (A1.111) or the wrack Fucus serratus (A1.326). Temporal variation: Some variation in the ephemeral seaweeds and their abundance depending on the season is likely.