AB.I3L Baltic aphotic coarse sediment characterized by infaunal bivalves


HELCOM RED LIST Biotope Expert Team

Textual description

Baltica photic 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 . Sessile/semi-sessile epibenthic macrofauna is not present. Biomass of infaunal bivalves dominates and is the highest in the group that includes infaunal bivalves/polychaetes/crustaceans.

Physical environment

Substrate is coarse sediment. Depth below approximately 30 m. Appears in high energy exposure areas.

Characteristic species

Mytilus spp.

Quality descriptors

Diversity, abundance and biomass of fauna.

Geographic range

Whole Baltic Sea

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