Macrobenthic species composition and diversity in the Godthaabsfjord system, SW Greenland

The southwest Greenland coast is made up of large and deep sill fjords. On the shelf, a number of shallow banks separated by deep troughs are located 20–50 km from the coast. We collected three 0.1-m² van Veen grabs at nine stations along a transect spanning from the inner Godthaabsfjord influenced by glaciers, across the shallow Fyllas Bank and out to the slope of the continental shelf at approximately 1,000 m depth. Along this transect, we explored patterns of macrobenthic diversity, species composition, abundance and biomass. The sampled stations were very different in terms of environmental variables, resulting in large differences in species composition primarily related to differences in depth, silt–clay fraction and chl a content of the sediment (BIO-ENV analysis). Habitat differences also reduced species spatial ranges and the majority of species were found at only one (49%) or two (20%) stations and, consequently, species turnover or beta diversity was high and correlated to differences in depth, silt–clay fraction and median sediment grain size. Species richness and diversity were lowest in sites exposed to sediment disturbance: near the glaciers in the inner fjord (physical disturbance by mineral sedimentation) and at selected stations on the shelf (bioturbation by burrowing sand eel). Alpha diversity and richness were only weakly correlated to environmental parameters, indicating that alpha richness and diversity are influenced by several factors or that relationships are non-linear as was found for species richness and silt–clay fraction.