Biodiversity & Conservation

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Exposed or moderately exposed upper and mid eulittoral bedrock and boulders are characterized by dense barnacles Semibalanus balanoides and the limpet Patella vulgata. In the south-west Chthamalus spp. can be the dominant barnacle. Patella ulyssiponensis predominates in the south-west, but in the north is restricted to very exposed conditions. The barnacles may be covered by Porphyra on the upper shore of exposed sites. Patches of Lichina pygmaea may be prominent, especially in the south, where this may form a distinct Lichina zone (ELR.BPat.Lic). Cracks and crevices in the rock provide a refuge for small mussels Mytilus edulis, winkles Littorina saxatilis and the dog whelk Nucella lapillus. Damp crevices are also frequently occupied by red algae, particularly Osmundea pinnatifida, Mastocarpus stellatus and encrusting coralline algae. With decreasing wave exposure Fucus vesiculosus is able to survive, gradually replacing the barnacles and Patella biotope (see MLR.FvesB). On such moderately exposed shores ELR.BPat may occur on steep and vertical faces, while fucoids dominate the flatter areas. It should not be confused with more exposed shores characterized by Fucus vesiculosus f. linearis and Chthamalus spp. (ELR.BPat.Fvesl). In areas of soft rock (e.g. shales), the barnacles may be scarce or absent and the rock dominated by Patella. (Information taken from the Marine Biotope Classification for Britain and Ireland, Version 97.06: Connor et al., 1997a, b).