AA.H1Q4  Baltic muddy sediment dominated by stable aggregations of unattached hornwort (Ceratophyllum demersum)


HELCOM RED LIST Biotope Expert Team

Textual description            

Baltic bottoms in the photic zone with at least 90 % coverage of muddy sediment. The sediment must contain at least 20 % of mud, silt or clay (grain size less than 63 µm). No perennial attached erect group has a coverage ≥ 10%. Stable aggregations of unattached perennial vegetation cover at least 10 % of the seabed. Out of the unattached perennial vegetation Ceratophyllum demersum constitutes at least 50 % of the biovolume.

Physical environment       

Exposure range: extremely sheltered; Depth range: photic zone to about 2 meters.

Characteristic species        

Ceratophyllum demersum

Mapping advise

Found in sheltered bays that can be affected by eutrophication

Correspondence with other classification systems               

HELCOM 1998:
2.7 Muddy bottoms
2.7.2 Sublittoral photic zone Dominated by macrophyte vegetation
EUNIS 2012:
A5 Sublittoral sediment
A5.5 Sublittoral macrophyte-dominated sediment
A5.54 Angiosperm communities in reduced salinity