AA.I1B7 Baltic photic coarse sediment dominated by common eelgrass (Zostera marina)


HELCOM RED LIST Biotope Expert Team

Textual description            

Baltic bottoms in the photic 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. Submerged rooted plants cover at least 10 % of the seabed and more than other perennial attached erect groups. Of the submerged rooted plants, common eelgrass constitutes at least 50 % of the biovolume.

Physical environment       

Salinity range: >6 psu; Exposure range: moderate to high; Depth range: photic zone from about 1 to 7 meters.

Characteristic species        

Zostera marina

Quality Descriptors

Lower limit of vegetation, amount of epiphytic algae


Whole Baltic Sea

Anthropogenic threats   


Correspondence with other classification systems               

HELCOM 1998:

2.4 Gravel bottoms

2.4.2 Sublittoral photic zone Level bottoms dominated by macrophyte vegetation

HELCOM 2007:

Seagrass beds

  • habitat under threat and/or in decline in all areas of occurrence

The Bothnian Sea, Åland Sea, Archipelago Sea, Gulf of Finland, Gulf ot Riga, The Northern Baltic Proper, Western Gotland Basin, Eastern Gotland Sea, The Southern Baltic Proper, The Gulf of Gdansk, Bay of Mecklenburg, Kiel Bay, Little Belt, Great Belt, The Sound, Kattegat

EUNIS 2012:

A5 Sublittoral sediment

A5.5 Sublittoral macrophyte-dominated sediment

A5.54 Angiosperm communities in reduced salinity

A5.545 [Zostera] beds in reduced salinity infralittoral sediments


OSPAR list of threathened biotopes:

Zostera beds

Habitat occurs in the OSPAR Region II (including Kattegat) and is listed threatened and/or in decline in this region

 related information

This biotope has been listed as Near Threatened (NT) in the HELCOM Red List of Baltic Sea biotopes and habitats.

See the Biotope Information Sheet of AA.I1B7