AB.J3M4 Baltic aphotic sand dominated by multiple infaunal polychaete species: Pygospio elegans, Marenzelleria spp. and Hediste diversicolor


HELCOM RED LIST Biotope Expert Team

Textual description 

Baltic aphotic zone bottoms with at least 90 % coverage of sand. Sand has less than 20 % of mud/silt/clay fraction (<63 µm), and the proportion of sand (grain size 0.063–2 mm) exceeds 70% of the combined gravel and sand fraction. 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, Pygiospio elegans, Marenzelleria spp. and Hediste diversicolor constitutes at least 50 % of the biomass.


Substrate is sand. Appears in moderate to high exposure classes.

Characteristic species        

Pygospio elegans, Marenzelleria spp. and Hediste diversicolor.

Quality descriptors

Diversity, abundance and biomass of fauna

Correspondence with other classification systems               

HELCOM 1998:

2.5 Sandy bottoms

2.5.1 Aphotic zone

EUNIS 2012:

A5 Sublittoral sediment

A5.2 Sublittoral sand

A5.27 Deep circalittoral sand

A5.273 Baltic sandy bottoms of the aphotic zone