Emergent vegetation communities on Baltic infralittoral sand

This is a Baltic Sea benthic habitat in the photic zone where at least 90% of the substrate is sand according to the HELCOM HUB classification. Emergent vegetation covers at least 10% of the seabed and exceeds that of other perennial attached erect groups. The habitat occurs in areas of low to moderate exposure to wave action, typically to depths of about about 3 meters. Two asociated biotopes with different dominant plant species (at least 50% of the biovolume of the emergent vegetation)  have been described. These are ‘Baltic photic sand dominated by common reed (Phragmites australis)’ (AA.J1A1) which is found in shallow water, down to a depth of 3 m and in moderate exposure, and ‘Baltic photic sand dominated by sedges (Cyperaseae)’ (AA.J1A2) where sedges such as Schoenoplectus spp. and Bolbaschoenus maritimus dominate. The latter is found in shallow water, down to a depth of 1m and in areas of moderate exposure to wave action. Nutrient levels play a part in affecting the balance between the two biotopes with reed dominated areas favoured by conditions of eutrophication.

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 overall quality and continued occurrence of this habitat is, however, largely dependent on the presence of the emergent plant species which create the biogenic structural complexity on which the characteristic associated communities depend. The density and the maintenance of a viable population of these species is a key indicator of habitat quality, together with the visual evidence of presence or absence of physical damage. In the case of this habitat the situation is further complicated because the reed dominated biotope is favoured by the deterioration of the sedge dominated biotope under conditions of eutrophication.

Synthesis of Red List assessment

Confidence in the assessment

Pressures and threats