AA.M1G1 Baltic photic mixed substrate dominated hydroids (Hydrozoa)


HELCOM RED LIST Biotope Expert Team

Textual description 

Baltic photic bottoms with 10- 90 % coverage of hard (rock/boulders/stone) and 10-90 % soft substrata (e.g. muddy/coarse sediment/sand). Epibenthic cnidarians cover at least 10%of the seabed and more than other perennial attached erect groups. Out of the epibenthic nidarians,  Ascidiacea constitutes at least 50 % of the biomass.

Physical environment       

Substrate is soft or crystalline rock, boulders or stones mixed with mobile substrates such as sand or coarse substrate.

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:

2.8 Mixed sediment bottoms

2.8.2 Sublittoral photic zone With little or no macrophyte vegetation


EUNIS 2012:

A5 Sublittoral sediment

A5.4 : Sublittoral mixed sediments

A5.41 Sublittoral mixed sediment in low or reduced salinity

A5.411 Baltic level mixed sediment bottoms of the infralittoral photic zone with little or no macrophyte vegetation