AB.A1F1 Baltic aphotic rock and boulders dominated by sea squirts (Ascidiacea)


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 chordates cover at least 10%of the seabed and more than other perennial attached erect groups. Out of the epibenthic chordates, sea squirts constitute at least 50 % of the biomass.

Physical environment       

Substrate is rock and/or boulders.

Characteristic species        

Ascidiacea: Dendrodoa grossularia, Modiolus spp.

Quality Descriptors

Diversity, abundance and biomass of fauna


Kattegat and Belt Sea

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

 related information

This biotope has been listed as Near Threatened (NT) in the HELCOM Red List of Baltic Sea biotopes and habitats.

See the Biotope Information Sheet of AB.A1F1