Kelp with cushion fauna and/or foliose red seaweeds on wave-exposed Atlantic infralittoral rock

This is a rocky habitat occurring in the infralittoral zone in areas exposed or extremely exposed wave action and/or strong tidal streams. It typically occurs from low water to depths of up to 45m. The rock supports a community of kelp Laminaria hyperborea or further south Laminaria ochroleuca, with foliose seaweeds and animals, the latter tending to become more prominent in areas of strongest water movement. In extremely wave exposed conditions, the sublitttoral fringe is characterised by dabberlocks Alaria esculenta  which, may extends from 5 to 10 m depth, or even replace L. hyperborea as the dominant kelp in the infralittoral zone. The depth to which the kelp extends varies according to water clarity, exceptionally (e.g. St Kilda, Scotland) reaching 45 m. The shallowest kelp plants are often short or stunted, while deeper plants are taller with heavily epiphytised stipes with foliose red seaweeds. At some sites the red seaweeds can be virtually mono-specific, while at other sites show considerable variation, containing a dense mixed turf of a large variety of species. 

The faunal and floral understorey is generally rich in species due, in part, to the relatively low urchin-grazing pressure in such shallow exposed conditions. As the exposure increases the rock surface is covered by a dense turf of anthozoans such as Sagartia elegans, Phellia gausapata and Corynactis viridis, encrusting sponges and coralline algae. The gastropod Margarites helicinus can be found grazing on the kelp fronds, whereas the crab Cancer pagurus can be found among the kelp stipes. The bryozoan Tubularia indivisa also occurs, but it does not form such a dense turf as in more shallow waters, while the ascidian Botryllus leachi is found encrusting the large brown seaweeds. Cryptopleura ramosa is the dominant red seaweed on horizontal surfaces. Winter storms may remove patches of kelp, and fast-growing annuals may form a temporary forest

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