Compositional patterns of benthic assemblages on the northwestern Ross Sea shelf, Antarctica: interacting environmental drivers operating at multiple spatial scales

Abstract

A comprehensive study of mega- and macro-invertebrate benthic assemblages was conduct- ed on the northwestern Ross Sea shelf in 2004 in order to examine concurrently the energy-, disturbance-, and habitat heterogeneity-diversity hypotheses, and their relevance for identifying the environmental drivers that structure benthic assemblages in Antarctica. Five transects were sampled, each of which was divided into 3 depth strata (50-250, 250-500, 500-750 m), running perpendicular to the Victoria Land coast between Cape Adare in the north and Cape Hallett in the south. The influence of environmental variables acting on different spatial scales on benthic assem- blages was assessed, including primary productivity (large-scale), iceberg scouring (quantified on different spatial scales), and habitat heterogeneity (small- scale). Clear geographic gradients could not be established for the environmental variables or for the invertebrate assemblages, but there were strong depth- related differences in the composition of assemblages. Overall, the results suggest that a combination, and interaction, of large-scale oceanographic (i.e. surface chlorophyll a, seasonal ice cover) and local habitat (e.g. sediment sponge spicule content) variables are responsible for the patterns of benthic invertebrate assemblage composition observed in the northwestern