Mixed faunal turf communities on high energy Atlantic upper circalittoral rock

This habitat type occurs on wave-exposed circalittoral bedrock and boulders, sometimes on vertical or steep slopes, subject to tidal streams ranging from strong (3-6 kn) to moderately strong (1-3 kn). The rocky outcrops may be surrounded by coarse sediment, for example shelly gravel or muddy gravel. The majority of the organisms are filter feeders, depending on suspended material in the water column and providing important water quality regulation and nutrient cycling services. Amongst others, sponges, bryozoans, hydroids, ascidians and sea-anemones, whose functional roles are of high importance, form these communities. Slow-growing complex biogenic structures created by hydroids, bryozoans and sponges modify the flow of currents, consolidate sediments and provide a three-dimensional habitat to a multitude of associated species.

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