AA.H1Q2 Baltic muddy sediment dominated by stable aggregations of unattached Fucus spp. (dwarf form)


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 µm). No perennial attached erect group has a coverage ≥ 10%. Stable aggregations of unattached perennial vegetation cover at least 10 % of the seabed. Out of the unattached perennial vegetation Fucus spp. (dwarf form) constitutes at least 50 % of the biovolume.

Physical environment       

Salinity range: >4.5 psu; Exposure range: low to moderately high; Depth range: photic zone from about 2 to 5 meters and deeper in clear waters.

Characteristic species        

Fucus vesiculosus dwarf form (synonyme f.pygmaea)

Quality descriptors             

density of unattached Fucus spp. (dwarf form)

Geographic range               

Known along the coast of Sweden and Germany

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 Endangered (EN) in the HELCOM Red List of Baltic Sea biotopes and habitats.

See the Biotope Information Sheet of AA.H1Q2