AB.A1G1 Baltic aphotic rock and boulders dominated hydroids (Hydrozoa)


HELCOM RED LIST Biotope Expert Team

Textual description 

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

Physical environment       

Substrate is rock and/or boulders.

Characteristic species        

Laomedea spp., Cordylophora caspia

Quality descriptors

Diversity, abundance and biomass of fauna.


Known from Russian waters

Correspondence with other classification systems    

HELCOM 1998:
2.1 Rocky bottoms

2.1.1 Soft rock Aphotic zone

2.1.2 Solid rock Aphotic zone

2.2 Stony bottoms

2.2.1 Aphotic zone