AB.I4 Baltic aphotic coarse sediment characterized by no macroscopic biotic structures


HELCOM RED LIST Biotope Expert Team

Textual description            

Baltic bottoms in the aphotic zone 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. No macro- epi- or infauna

Physical environment       

Salinity range: all; Exposure range: moderate to high; Depth range: aphotic zone

Mapping advise (habitat delineation, identification, similar types)             

Aphotic zone areas with coarse sediment such as gravel. Coarse sediment has less than 20 % of mud/silt/clay fraction (<63 µm), and at least 30 % of grain size 2–63 mm. No macro- epi- or infauna

Quality descriptors             

Soft sediment covering the coarse sediment will decrease the quality.

Geographic range               

Whole Baltic Sea

Anthropogenic threats     

Silting caused by eutrophication, dredging spoil deposition etc.

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