Regional differences of mesozooplankton communities in the Kara Sea

The Kara Sea is a little studied high Arctic region located between the Barents Sea, the Arctic Ocean and the Laptev Sea. The aim of this study was to reveal the spatial distribution of mesozooplankton community in relation to hydrographic conditions. Our survey was the first study covering most of the sea, excluding the eastern part. Zooplankton samples were collected at 47 stations using a Juday net (168 μm, 0.1 m2) in August 2012. Copepods dominated the total mesozooplankton abundance and biomass, with Calanus spp. being the most numerous in the western part and Pseudocalanus spp. in the eastern area. Cluster analyses revealed four groups of stations differing in terms of composition, abundance, biomass, species richness and diversity. The regional distribution of mesozooplankton communities was clearly associated with hydrographic habitats defined by their physical (temperature, salinity and main currents) and biological characteristics (food conditions). The domination of copepod populations by young copepodite stages and nauplii suggests early summer-like conditions in the mesozooplankton community although a high abundance of meroplankton suggests spring-like conditions in the mesozooplankton. Principal components analysis showed that temperature determined variations in the biomass of major taxa in the west, while the salinity was the main factor in the east. Phytoplankton concentrations also have measurable effect on the mesozooplankton community. The total mesozooplankton average biomass (6±1 g dry mass m-2) was higher than in adjacent waters, suggesting a high reproductive potential of zooplankton populations in the summer season.