Annual algal communities on Baltic infralittoral sand

This benthic Baltic Sea habitat occurs in the photic zone with at least 90% coverage of sand according to the HELCOM HUB classification. Annual algae cover at least 10%, while all other epibenthic biotic structures like rooted plants, unattached perennial algae or blue mussels cover less than 10%. The habitat occurs in the full salinity range of the Baltic Sea and is more common in moderate to sheltered, very shallow areas.

Two associated biotopes with different dominant species of algae (at least 50% of the biovolume of the annual algae) have been identified. ‘Baltic photic sand dominated by Chorda filum and/or Halosiphon tomentosus’ (AA.J1S2) usually down to a depth of 4 meters, in areas moderately exposed to wave action. These species give the appearance of growing on the sand but attach to small fractions of stable substrate like small stones, shell fragments or gravel buried in the sand. It is distributed in the whole Baltic Sea except in the most northern part of the Bothnian Bay.  A second associated biotope, ‘Baltic photic sand dominated by Vaucheria spp.’ (AA.J1S3), is usually present down to a depths of 7 meters, in areas more sheltered areas and in salinities less than 7 psu. It is distributed in the whole Baltic Sea except for the Belt Sea and the Sound.

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