AB.H3 Baltic aphotic muddy sediment characterized by macroscopic infaunal biotic structures


HELCOM RED LIST Biotope Expert Team

Textual description             

Baltic bottoms in the aphotic 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). Macroscopic infauna present, no epibenthic macrofauna.

Physical environment        

Salinity range: All; Exposure range: All; Depth range: Below photic zone ‑ more common in deeper areas.                    

Mapping advise (habitat delineation, identification, similar types)             

Muddy sediment bottoms in the aphotic zone. Macroscopic infauna present, no epibenthic macrofauna.

Geographic range               

Whole Baltic Sea

Anthropogenic threats     

Dredging, dredge spoil dumping, poisonous substances

Correspondence with other classification systems               

HELCOM 1998:

2.7 Muddy bottoms

2.7.1 Aphotic zone

EUNIS 2012:

A5 Sublittoral sediment

A5.3 Sublittoral mud

A5.37 Deep circalittoral mud

A5.378 Baltic muddy bottoms of the aphotic zone