Robust fucoid and/or red seaweed communities on wave-exposed Atlantic littoral rock

This habitat occurs on extremely exposed to moderately exposed upper to lower shores with seaweeds that are able to tolerate the extreme conditions of exposure. The physical stresses caused by wave action often results in dwarf forms of the individual seaweeds. The strong holdfasts and short tufts structure of the wracks Fucus distichus and Fucus spiralis f. nana allow these fucoids to survive on extremely exposed shores. Another seaweed able to tolerate the wave-wash is the red seaweed Corallina officinalis, which can form a dense turf on the mid- to lower shore. The olive brown wrack Pelvetia canaliculata positioned at the highest points of the intertidal shore, can withstand long periods of exposure. The wrack Himanthalia elongata occurs on the lower shore and can extend on to moderately exposed shores. The red seaweed Mastocarpus stellatus is common on both exposed and moderately exposed shores, where it may form a dense turf (particularly on vertical or overhanging rock faces. Very exposed to moderately exposed lower eulittoral rock can support a pure stand of the red seaweed Palmaria palmata. It is found either as a dense band or in large patches above the main sublittoral fringe.

Two biotopes associated with this habitat are characterised by extensive areas or a distinct band of Osmundea pinnatifida in areas exposed to moderately exposed lower eulittoral rock, and outcrops of fossilised peat in the eulittoral that are soft enough to allow a variety of piddocks, such as Barnea candida and Petricola pholadiformis, to bore into them.

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. Long term loss of the characteristic fucoids and/or red algae would indicate a deterioration in quality. 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. 

Synthesis of Red List assessment

Confidence in the assessment

Pressures and threats