LAUSR

Analysis of zooplankton collected on five cruises (2007–2016) in the Kara and Laptev seas has revealed considerable heterogeneity in the spatial distribution of the biomass of the pteropod Limacina helicina, one of the important components of the Arctic zooplankton. The biomass and abundance of mollusks in 2014–2016 were significantly lower than in the previous period, in 2007 and 2011. The existence of persistent aggregations of L. helicina in the area of the continental slope of the Kara Sea (St. Anna Trough) with a biomass an order of magnitude higher than in the adjacent areas has been shown. Such aggregations of L. helicina were related to a combination of favorable factors: high salinity (≥33 psu), optimal temperature range (1–5°C), and local hydrophysical processes associated with the slope frontal zone. Results of the General Linear Mixed Model (GLMM) have shown that the biomass of pteropods is primarily related to salinity and temperature. No relationship between the biomass of pteropods and the average chlorophyll concentration in the upper layer has been found. However, within L. helicina aggregations, the biomass of mollusks correlated with the concentration of chlorophyll a in the layer of its maximum.