Soft bottom species richness and diversity as a function of depth and iceberg scour in Arctic glacial Kongsfjorden (Svalbard)

摘要

Macrozoobenthic soft-sediment communities inhabiting six depth zones of central Arctic Kongsfjorden were analysed comparatively using SCUBA-diving. 63 taxa were found, 30 of which had not been reported for Kongsfjorden and seven for Svalbard. Suspensivorous or surface and sub-surface detritivorous polychaetes and deposit-feeding amphipods were dominant. Only eleven taxa of 45 species and additional 18 families identified inhabited the complete depth range. Biomass ranged from 3.5 to 25.0 g ash free dry mass m-2 and mean Shannon diversity (Log e) was 2.06. Similarity clustering from abun-dance and biomass data showed a significant difference between the shal-low station (5m) and the rest. The latter formed two subgroups (10-20m, 25-30m). These differences together with information on ice-scouring support the intermediate disturbance hypothesis indicating that habitats impacted by moderate iceberg scouring enable higher diversity. In contrast, biotopes frequently affected only host pioneer communities, while mature, less diverse assemblages dominate depths of low impact.