Dynamic sedimentary environments of an Arctic glacier-fed river estuary (Adventfjorden, Svalbard). II: Meio- and macrobenthic fauna

The paper examines the meio- and macrobenthic responses to physical disturbance and sediment instabilities in a small Arctic glacier-fed river estuary. Zajiczkowski and Włodarska-Kowalczuk [Zajiczkowski, M., Włodarska-Kowalczuk, M., 2007. Dynamic sedimentary environments of Arctic glacier-fed river estuary (Adventfjorden, Svalbard). I. Flux, deposition, and sediment dynamics. Estuarine, Coastal and Shelf Science 74(1–2), 285–296] distinguished three zones in Adventfjorden (west Spitsbergen) estuary: the tidal flat, the slope (high sedimentation, frequent sediment slides), the central basin (low sedimentation, stable sediments). The numbers of individuals and species of meio- and macrofauna were very low on the tidal flat. The total densities of meio- and macrofauna were significantly lower on the slope of the glacio-fluvial delta than in the central basin. Only the macrofauna responded to sediment instabilities on the slope by a significant decrease in total biomass. Nematodes inhabiting the slope sediments were larger than those in the central basin, although there was no significant difference in the size of harpacticoids in the two zones. The frequently disturbed, resuspended, and redeposited slope sediments were colonized by the opportunistic polychaete Capitella capitata agg. and by the high sedimentation resistant polychaetes Chaetozone setosa agg. and Cossura longocirrata. Tube-dwelling, sedentary, or suspension-feeding fauna only occurred at the central basin stations. The species richness and ratio of surface-dwelling to burrowing deposit-feeders in the macrobenthic communities decreased towards the river mouths. The differences in the taxonomic composition of communities inhabiting the sediments of the slope and the central basin were less pronounced in meiofauna (studied at a higher taxonomic level) than in the macrofauna (identified to the species level). Nevertheless, the differences were significant for both benthic compartments (ANOSIM test, P < 0.05). The simultaneous survey of meio- and macrobenthic communities in an Arctic glacier-fed river estuary shows that both benthic compartments are sensitive to sediment instabilities and physical disturbance caused by high sedimentation and frequent sediment gravity flows.