AA.M1S2 Baltic photic mixed substrate dominated by Chorda filum and/or Halosiphon tomentosus algae


HELCOM RED LIST Biotope Expert Team

Textual description            

Baltic bottoms in the photic zone with more than 10 %, but less than 90 % coverage of both hard and soft substrata. Annual algae cover at least 10 % of the seabed, while all other vegetation covers less than 10 %. Out of the annual algae, Chorda filum and/or Halosiphon tomentosus algae constitute at least 50 % of the biovolume.

Physical environment       

Exposure range: sheltered to moderate; Depth range: photic zone from about 0.5 to 4 meters.

Characteristic species        

Chorda filum, Halosiphon tomentosus


Must be mapped during the growth season.

Geographic range               

Whole Baltic Sea

Correspondence with other classification systems               

HELCOM 1998:

2.8 Mixed sediment bottoms

2.8.2 Sublittoral photic zone Dominated by macrophyte vegetation

EUNIS 2012:

A5 Sublittoral sediment

A5.5 Sublittoral macrophyte-dominated sediment