AA.A1E2 Baltic photic rock and boulders dominated by Zebra mussel (Dreissena polymorpha)


HELCOM RED LIST Biotope Expert Team

Textual description            

Baltic bottoms in the photic zone with at least 90 % coverage of rock, boulders or stones of more than 63 mm in diameter. Epibenthic bivalves cover at least 10%of the seabed and more than other perennial attached erect groups. Out of the epibenthic bivalves Dreissena polymorpha constitutes at least 50 % of the biomass.

Physical environment       

Substrate is rock and/or boulders. Depth is typically from 2 to 10 meters. Appears in sheltered to moderately exposed areas. Salinity must be less than 5 psu.

Characteristic species        

Dreissena polymorpha

Quality descriptors             

Amount of sediment and epiphytic annual algae. Diversity, abundance and biomass of fauna.

Geographic range               

Estonian west coast and eastern Gulf of Finland

Correspondence with other classification systems               

HELCOM 1998: Sublittoral level soft rock bottoms with little or no macrophyte vegetation Sublittoral level stony bottoms with little or no macrophyte vegetation

EUNIS 2012:
A3.4 : Baltic exposed infralittoral rock
A3.5 : Baltic moderately exposed infralittoral rock
A3.6 : Baltic sheltered infralittoral rock