Seaweeds on moderately exposed shores

This habitat is a calcareous turf on areas of intertidal rock exposed to wave action. It includes the biotope characterised by Chondracanthus acicularis which occurs on horizontal and vertical surfaces where it forms an extremely dense herbaceous stratum together with other species such as Chondracanthus teedei, Gelidium spinosum, Pterosiphonia complanata, Plocamium cartilagineum and Corallina elongata.These help prevent desiccation during the emersion periods. The fronds of the algae also provide habitat for several polychaetes, amphipods and molluscs.

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.  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