Submerged fucoids, green or red seaweeds on low salinity Atlantic infralittoral rock

Very shallow submerged rocky habitats in bays, inlets or estuaries subject to permanently reduced salinity conditions. These particular conditions lead to a variety of seaweed-dominated communities, which include fucoids, green and red macroalgae species. The fucoids, more typical of intertidal Atlantic habitats, penetrate into the subtidal under the reduced salinity conditions which are not tolerated by kelps. This habitat may also includes dense stands of Ascophyllum nodosum if salinities are high enough (>20psu).

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. Dominance of fucoids (cover or biomass ratios of fucoids to other macroalgae) or penetration of fucoids along the salinity gradient is used in some countries as a Water Framework Directive parameter for assessing ecological status.

Synthesis of Red List assessment

Confidence in the assessment

Pressures and threats