Infauna from Zostera marina L. meadows in Norway. Differences in vegetated and unvegetated areas

To investigate the importance of benthic vegetation for shallow infaunal assemblages, macroinvertebrates were sampled in Zostera marina meadows and in adjacent bare sand at three sites in the Skagerrak region and one in the Western part of Norway. A total of 3777 individuals were encountered, representing mainly the faunal groups Annelida, Nemertea, Echinodermata, Crustacea and Mollusca. Twice as many individuals were found in the Z. marina meadows compared to the bare sand. Oligochaetes were the most abundant group (29% of total number of individuals), followed by crustaceans (24%), polychaetes (18.5%) and molluscs (16%). Polychaetes showed the highest species number (42), followed by molluscs (30) and crustaceans (26). Multivariate cluster technique showed the highest similarities within sites and thereafter grouping according to the two different habitats; Zostera and sand. No regional differences were evident between the Skagerrak sites and the site in Western Norway, as the site from Western Norway grouped together with one of the Skagerrak sites. The high biodiversity in Zostera marina beds should have implications for the management of such areas.