Faunal communities on variable salinity Atlantic circalittoral rock

This habitat type occurs on wave-sheltered, variable/reduced salinity bedrock and boulders, subject to moderately strong to weak tidal streams. There may be large growths of the brackish-tolerant sponge Halichondria bowerbanki. It is characterised by sponges tolerant of variable salinity, barnacles and a sparse hydroid and bryozoan turf. Especially where low salinity is frequently present, ‘groves’ of the peacock worm Sabella pavonina may be present. Beds of mussels, Mytilus edulis, may also be present but may be ephemeral.

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.

Synthesis of Red List assessment

Confidence in the assessment

Pressures and threats