AA.H3M3 Baltic photic muddy sediment dominated by Marenzelleria spp.


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 ┬Ám). Biomass of infaunal polychaetes dominates and is highest in the group that includes infaunal bivalves/polychaetes/crustaceans/echinoderms/insect larvae. Out of the infaunal polychaetes Marenzelleria spp. constitutes at least 50 % of the biomass.

Physical environment       

Substrate is muddy sediment. Appears in low to moderate energy exposure classes.

Characteristic species        

Marenzelleria arctia, Marenzelleria viridis, Marenzelleria neglecta

Quality descriptors             

Diversity, abundance and biomass of fauna.

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