AB.I4U1 Baltic aphotic coarse sediment dominated by meiofauna


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 .No macrocommunity present. Meiofauna constitutes at least 50% of the present biomass.

Physical environment       

Substrate is coarse sediment. Appears in all wave exposure classes.

Characteristic species        

Oligochaeta, Ostracoda, Nematoda

Quality descriptors

Diversity, abundance and biomass of meiofauna.

Anthropogenic threats


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