Perennial algal communities (excluding kelp) on Baltic infralittoral rock and mixed substrata (predominantly hard)

This is a Baltic Sea benthic habitat in the photic zone where at least 90% of the substrate is rock, boulders or stones and mixed (predominantly hard) substrates according to the HELCOM HUB classification. Perennial attached algae such as Fucus spp., or perennial red algae cover at least 10% of the seabed and more than other perennial attached erect groups. It is most common in areas exposed to wave action and typically occurs to depths of around 0.5 m.

Eight associated biotopes with different dominant species of algae have been described by HELCOM. ‘Baltic photic rock and boulders/mixed substrata dominated by Fucus spp.’ (AA.A1C1/AAM1C1) such as Fucus radicans, F. serratus or F. vesiculosus, is found in depths of 0.5–5m and in salinities over 4 psu. ‘Baltic photic rock and boulders/mixed substrata dominated by perennial non-filamentous corticated red algae’ (AA.A1C2/AA.M1C2) such as Furcellaria lumbricalis occurs at a depths of 2–10 m in similar salinities. These four biotopes are present in all the Baltic Sea sub-basins and are widely distributed, although not Bothnian Bay nor the most eastern part of the Gulf of Finland. ‘Baltic photic rock and boulders/mixed substrata dominated by perennial foliose red algae’ (AA.A1C3/AA.M1C3) such as Coccotylus spp., Phyllophora spp. and Delesseria spp. is typically found in depths of 2–10 m and in salinities over 4 psu. They are present in all the Baltic Sea sub-basins and are also widely distributed although also not in the Bothnian Bay nor the eastern half of the Gulf of Finland. ‘Baltic photic rock and boulders/mixed substrata dominated by perennial filamentous algae’ (AA.A1C5/AA.M1C5) such as Polysiphonia spp, Aegagrophila linnaei, Cladophora rupestris is found at depths of 0.5–10 m, in all the Baltic Sea sub-basins.

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

The lower depth limit of algae, especially Fucus spp. where applicable, and the amount of epiphytic algae are potential indicators of quality of this habitat. 

Synthesis of Red List assessment

Confidence in the assessment

Pressures and threats