Echinoderms and crustose communities on moderate energy Atlantic upper circalittoral rock

This habitat occurs on wave-exposed, moderately strong to weakly tide-swept, circalittoral bedrock and boulders. Echinoderms, faunal and algal crusts (red encrusting algae) dominate, giving a sparse appearance. It occurs from depths, where the light becomes insufficient for macroalgae down to about 100 meters although occasionally also encountered in deeper water.

On vertical faces there may be dense aggregations of the cup coral Caryophyllia smithii, large expanses of encrusting red algae or, in conditions of moderate exposure, the soft coral Alcyonium digitatum. The sea fan Swiftia pallida can be present on silty substratum and the anemone Urticina feline and the sponge Ciocalypta penicillus at the sand-rock interface. The polychaete Pomatoceros triqueter can be locally abundant, and may in some cases cover far more rock surface than A. digitatum, especially on vertical faces. Clumps of robust hydroids such as Abietinaria abietina and Nemertesia antennina occur occasionally.

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