Infralittoral Benthic Biocoenoses from Northern Ría de Muros, Atlantic Coast of Northwest Spain

Infralittoral benthic biocoenoses and their patterns of zonation on exposed shores north of the Ria de Muros (northwest Spain) were studied. A total of 84 surveys allowed the characterisation of 11 main communities, which differ mainly due to depth and substrate. These communities develop in broad belts, with a well marked zonation: communities of Cystoseiraceae at the infralittoral fringe, communities of Laminariales down to 15 m deep, sciophilous communities at deeper levels, and infralittoral communities on sandy bottoms. Although variations with depth were noted, the main number of species is rather similar in all communities except for those on sandy bottoms. Numbers of Rhodophyta stand out in all communities except for that of Halidrys siliquosa. The number of animals is high in all communities, but animal cover is only high in this last community. Cover of Phaeophyceae stands out among the algal cover, except for communities of sandy bottoms. Hemiphanerophyceae are the algae with highest cover on rocky bottoms, and cover is more variable on sandy bottoms. The presence of upwelling in this area explains the presence of 9 of the 11 communities characterised as being typical of northwestern Europe, while only 2 (Phyllariopsis purpurascens and Cystoseira usneoides communities) show meridional affinities.