AA.A1S Baltic photic rock and boulders characterized by annual algae


HELCOM RED LIST Biotope Expert Team

Textual description            

Baltic bottoms in the photic zone with at least 90 % coverage of rock, boulders or stones of more than 63 mm in diameter. Annual algae cover at least 10 % of the seabed, while all other epibenthic biotic structures cover less than 10 %.

Physical environment       

Salinity range: All; Exposure range: all, more common in exposed areas; Depth range: photic zone – usually in the most shallow part.

Characteristic species        

Cladophora glomerata, Ceramium tenuicorne, Pilayella littoralis, Ulva spp. Dictypsiphon spp.

Mapping advise (habitat delineation, identification, similar types)             

Mapping should take place during the months when the vegetation is fully developed. Annual algae can live as epiphytes (e.g. Pilayella/Ectocarpus on Fucus spp.). In the BSEUNIS classification epiphytes are considered to be quality descriptors, not habitat forming. Thus this biotope only occurs when annual algae dominate the substrate and not when they grow on perennial biotic structures.

Geographic range               

Whole Baltic Sea

Correspondence with other classification systems               

HELCOM 1998:

2.1 Rocky bottoms

2.1.1 Soft rock Sublittoral photic zone Level bottoms dominated by macrophytevegetation

2.1.2 Solid rock (bedrock) Sublittoral photic zone Level bottoms dominated by macrophytevegetation

2.2 Stony bottoms

2.2.2 Sublittoral photic zone Level bottoms dominated by macrophyte


EUNIS 2012:
A3.4 : Baltic exposed infralittoral rock
A3.5 : Baltic moderately exposed infralittoral rock
A3.6 : Baltic sheltered infralittoral rock