AA.I1C5 Baltic photic coarse sediment dominated by perennial filamentous algae


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 . Perennial attached algae cover at least 10 % of the seabed and more than other perennial attached erect groups. Out of the perennial attached algae perennial filamentous algae constitute at least 50 % of the biovolume.

Physical environment       

Salinity range: all; Exposure range: all; Depth range: photic zone

Characteristic species        

Polysiphonia spp.


Whole Baltic Sea

Anthropogenic threats   

Decreased light penetration depth and increased sedimentation caused by eutrophication

Correspondence with other classification systems               

HELCOM 1998:

2.4 Gravel bottoms

2.4.2 Sublittoral photic zone Level bottoms dominated by macrophyte vegetation

EUNIS 2012:

A5 Sublittoral sediment

A5.5 Sublittoral macrophyte-dominated sediment