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Bundesamt für Naturschutz

The Adler Ground HD site – Area II

The 234 km² encompassing Area II corresponds to the Adler Ground HD site and is located in the sea area between Rügen and Bornholm at the eastern edge of the Arkona Basin. The area is formed by several end moraines and consists of a large sand plate with centrally placed flat elevations of till that are often covered by gravel and rich with boulders. This interlocking of the habitat types sandbanks with reefs of rampart-like boulders, blue mussel banks on large boulders and on the sand areas, as well as strong macrophyte growth are characteristic for this unique protected area in the Baltic Sea and provide for a high species diversity.

Facts Adler Ground (HD site) – Area II of the complex area

Fact sheet

HD site
Adler Ground
EU Code: 1251-301


Habitat types


approx. 87 km²



approx. 110 km²


Harbour porpoise (Phocoena phocoena)

> 10


Grey seal (Halichoerus grypus)



Diversity in the food web

The bottom fauna with its abundance of individuals provides a rich food source for fish. The interlocking of the various habitat types offers retreat and hiding places for many different fish species. This species-rich fish fauna serves, in turn, as a food source for harbour porpoises, seabirds and grey seals. Especially in the winter months, marine mammals and resting birds migrate from ice-covered regions of the Baltic Sea into the ice-free and food-rich areas at Adler Ground.

The bivalve communities of the reefs and sandbanks constitute an important food source for sea ducks, e.g. long-tailed ducks. Due to the low salinity, the bivalves at Adler Ground can only form very thin calcium carbonate shells and are therefore a relatively convenient and energy-rich food for sea ducks.

Long-tailed ducks (Clangula hyemalis)
In the winter months, long-tailed ducks (Clangula hyemalis) feed primarily on bivalves.
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