AA.I2W Baltic photic coarse sediment characterized by microphytobenthic organisms and grazing snails


HELCOM RED LIST Biotope Expert Team

Textual description            

Baltic photic 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. Less than 10 % of the seabed is covered by perennial vegetation or attached epifauna. Microphytobenthic organisms and grazing snails dominates. Grazing snails (e.g. Hydrobiidae, Theodoxus, Bithynia, Radix) constitute 50 % in biomass or volume

Physical environment       

Substrate is muddy sediment. Most common in low salinity

Characteristic species        

Hydrobiidae, Theodoxus spp, Bithynia spp, Radix spp.

Quality descriptors             

Diversity, abundance and biomass of fauna.

Correspondence with other classification systems               

HELCOM 1998:

2.4 Gravel bottoms

2.4.2 Sublittoral photic zone Level bottoms with little or no macrophyte vegetation

EUNIS 2012:

A5 Sublittoral sediment

A5.1 Sublittoral coarse sediment

A5.11 Infralittoral coarse sediment in low or reduced salinity

A5.111 : Baltic level gravel bottoms of the infralittoral photic zone with little or no macrophyte vegetation