Mytilus edulis and fucoids on moderately wave-exposed Atlantic littoral rock

Mid- and lower eulittoral bedrock exposed or moderately exposed to wave action, often with nearby sediment, and which may be densely covered by large individuals of the mussel Mytilus edulis. Three biotopes have been described associated with this habitat: In the mid eulittoral, the mussels may form a band or large patches with scattered bladder wrack Fucus vesiculosus. 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). 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. Ephemeral green seaweeds such as Ulva intestinalis and U. 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 

Indicators of quality:

Both biotic and abiotic indicators have been used to describe marine habitat quality. These include: the presence of characteristic species as well as those which are sensitive to the pressures the habitat may face; water quality parameters; levels of exposure to particular pressure, and more integrated indices which describe habitat structure and function, such as trophic index, or successional stages of development in habitats that have a natural cycle of change over time.

There are no commonly agreed indicators of quality for this habitat, although particular parameters may have been set in certain situations e.g. protected features within Natura 2000 sites, where reference values have been determined and applied on a location-specific basis. Indicators which have been developed for the assessment of ecological quality of coastal water bodies for the Water Framework Directive (WFD) that are relevant to this habitat include a consideration of macroalgae species richness, proportions of different taxa of algae present, and the abundance and coverage of the rocky surfaces by typical species. The density and abundance of Mytilus edulis is also a potential indicator of habitat quality.

Synthesis of Red List assessment

Confidence in the assessment

Pressures and threats