AB.H4U2 Baltic aphotic muddy sediment dominated by anaerobic organisms


HELCOM RED LIST Biotope Expert Team

Textual description 

Baltic aphotic zone bottoms 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). Macrocommunities are not present. Anaerobic organisms constitute at least 50% of the present biomass.

Physical environment       

Substrate is muddy sediment. Depth is typically from 50 to 250 meters. Appears in all wave exposure classes. No O2.

Characteristic species        


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