AA.H1B4 Baltic photic muddy sediment dominated by Charales


HELCOM RED LIST Biotope Expert Team

Textual description            

Baltic bottoms in the photic zone with at least 90 % coverage of muddy sediment. The sediment must contain at least 20 % of mud, silt or clay (grain size less than 63 ┬Ám). Submerged rooted plants cover at least 10 % of the seabed and more than other perennial attached erect groups. Of the submerged rooted plants, Charales constitutes at least 50 % of the biovolume

Physical environment       

Salinity range: <6 psu; Exposure range: low; Depth range: photic zone from about 0.2 to 7 meters.

Characteristic species        

Chara aspera, Chara tomentosa, Tolypella nidifica, Chara horrida

Geographic range               

Whole Baltic Sea

Anthropogenic threats     


Correspondence with other classification systems               

HELCOM 1998:

2.7 Muddy bottoms

2.7.2 Sublittoral photic zone Dominated by macrophyte vegetation

EUNIS 2012:

A5 Sublittoral sediment

A5.5 Sublittoral macrophyte-dominated sediment


 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 AA.H1B4