Submerged rooted plant 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. Submerged rooted plants, including plants with rhizoids (i.e. Charales) cover at least 10% of the seabed and more than other perennial attached erect groups. The habitat is present across the full salinity range of the Baltic, in locations that are moderately to very sheltered from wave action and in depths of up to 6m. 

Eight associated biotopes with different dominant (>50% of the biovolume) macrophyte taxa (spiny naiad, spikerush, pondweed, watermilfoil, Ranunculus spp. Charales, and seagrass.) have been described.  They differ in their distribution along gradients in salinity, depth and wave exposure with the biotope dominated by the common eelgrass (Zostera marina)’ (AA.J1B7) differing most strongly from the others in distribution. This occurs mainly under conditions of moderate exposure to wave action and in salinities of 5 psu or higher. It is also typically found deeper than the other biotopes (1-6 m) and often marks the lower depth limit distribution of soft bottom vegetation. This biotope is absent from areas with low salinity in the inner part of Gulf of Finland and Gulf of Bothnia. 

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 vertical depth limit of submerged rooted plants is used in several countries as a Water Framework Directive parameter for assessing ecological status. The overall quality and continued occurrence of this habitat is, however, largely dependent on the presence of the rooted plant communities 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.

Synthesis of Red List assessment

Confidence in the assessment

Pressures and threats