AA.I1C3 Baltic photic coarse sediment dominated by perennial foliose red 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 foliose red algae constitute at least 50 % of the biovolume.

Physical environment       

Salinity range: >4.5 psu; Exposure range: Sheltered; Depth range: photic zone from about 2 to 10 meters

Characteristic species        

Coccotylus truncatus, Phyllophora spp.


Up to the Quark in the north and central Gulf of Finland in the east

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