Macrozooplankton of the Arctic - The Kara Sea in relation to environmental conditions

- Multivariate analysis identified a clear macrozooplankton division between the deepwater, shelf and estuarine zones.
- Macrozooplankton was concentrated mainly in the northwestern part of the sea.
- The common large zooplankton taxa was dominated by small-sized individuals.
- CCA showed great importance of hydrological factors and geographical variables in macrozooplankton variations.

The distribution, abundance, biomass and diversity of macrozooplankton were studied in relation to hydrological conditions in the Kara Sea during July-September 2012. Multivariate analysis of macrozooplankton density data identified a clear division between the community structure of the deepwater, shelf and estuarine zones. The first assemblage along the Novaya Zemlya Archipelago in the western part of the Kara Sea was characterized by high total abundance/biomass (80,450 ind. m−2/16.9 g dry mass m−2) and was dominated by Calanus glacialis, C. hyperboreus, C. finmarchicus and Metridia longa. The second assemblage in the central part of the Kara Sea was similar in species composition but differed in term of abundance and biomass (15,300 ind. m−2/2.7 g DM m−2). The lowest abundance/biomass (2130 ind. m−2/0.3 g DM m−2) was measured in the third assemblage, the Ob Shallow region, which was characterized by the presence of estuarine taxa and was heavily influenced by freshwater discharge. Parasagitta elegans, Mertensia ovum, Aglantha digitale, Aeginopsis laurentii, Dimophyes arctica and Clione limacina were present mainly as young stages suggesting reproduction of these species in July-August. Canonical correspondence analysis revealed that hydrological factors (salinity and temperature) and geographical variables (latitude, longitude and depth) were the main predictors of macrozooplankton community structures in the Kara Sea. Comparison of our data with other regions in the Arctic demonstrated similarity in the taxonomic composition and density of major large-bodied groups (i.e. amphipods, krill, medusae, pteropods, chaetognaths).