AA. H4U1 Baltic photic muddy sediment dominated by meiofauna


HELCOM RED LIST Biotope Expert Team

Textual description            

Baltic photic 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 µm). Macrovegetation or – fauna is not present. Meiofauna constitute at least 50% of the biomass.

Physical environment       

Substrate is muddy sediment. Appears in all wave exposure classes.

Characteristic species        

Oligochaeta, Ostracoda, Nematoda

Quality descriptors             

Diversity, abundance and biomass of meiofauna

Anthropogenic threats   


Correspondence with other classification systems               

HELCOM 1998:

2.7 Muddy bottoms

2.7.2 Sublittoral photic zone With little or no macrophyte vegetation

EUNIS 2012:

A5 Sublittoral sediment

A5.3 Sublittoral mud

A5.31 Sublittoral mud in low or reduced salinity

A5.311 Baltic brackish water sublittoral muddy biocenoses influenced by varying salinity