AA.J1S2 Baltic photic sand dominated by Chorda filum and/or Halosiphon tomentosus


HELCOM RED LIST Biotope Expert Team

Textual description 

Baltic bottoms in the photic zone with at least 90 % coverage of sand. Sand has less than 20 % of mud/silt/clay fraction (<63 µm), and the proportion of sand (grain size 0.063–2 mm) exceeds 70% of the combined gravel and sand fraction.  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 Halisiphon tomentosus constitutes at least 50 % of the biovolume.     

Physical environment       

Salinity range: <4.5 psu; Exposure range: moderate; Depth range: down to about 4 meters

Characteristic species        

Chorda filum, Halosiphon tomentosus

Quality descriptors

density of Fucus spp., amount of epiphytes


Baltic Sea up to the Quark

Anthropogenic threats


Correspondence with other classification systems               

HELCOM 1998:

2.5 Sandy bottoms

2.5.2 Sublittoral photic zone Level bottoms dominated by macrophyte vegetation

EUNIS 2012:

A5 Sublittoral sediment

A5.5 Sublittoral macrophyte-dominated sediment