AB.I1E1 Baltic aphotic coarse sediment dominated by Mytilidae


HELCOM RED LIST Biotope Expert Team

Textual description 

Baltic aphotic zone bottoms with at least 90 % coverage of coarse sediment. Coarse sediment has less than 20 % of mud/silt/clay fraction (<63 µm), and the proportion of gravel and pebbles (grain size 2–63 mm) exceeds 30% of the combined gravel and sand fraction .Epibenthic bivalves cover at least 10 % of the seabed, and more than other Perennial attached erect groups. Out of the epibenthic bivalves, Mytilidae constitute at least 50 % of the biomass.

Physical environment       

Substrate is coarse sediment. Appears in high energy exposure areas. Salinity >5.

Characteristic species        

Mytilus spp., Hediste diversicolor

Quality descriptors

Diversity, abundance and biomass of fauna

Correspondence with other classification systems               

HELCOM 1998:

2.4 Gravel bottoms

2.4.1 Aphotic zone

EUNIS 2012:

A5 Sublittoral sediment

A5.1 Sublittoral coarse sediment

A5.11 Infralittoral coarse sediment in low or reduced salinity

A5.114 : Baltic gravel bottoms of the aphotic zone