AA.M1F1 Baltic photic mixed substrate dominated by sea squirts (Ascidiacea)


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 chordates cover at least 10%of the seabed and more than other perennial attached erect groups. Out of the epibenthic chordates 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  

 Ascidiacea, Dendrodoa grossulariaMolgula ssp     

Quality descriptors

Diversity, abundance and biomass of fauna.


Kattegat and Belt Sea

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