Zooplankton productivity in the coastal area of the southern Barents Sea in spring

The results of the analysis of zooplankton assemblage state of the southern Barents Sea are presented. Zooplankton samples were collected during the cruise of the RV “Dalnie Zelentsy” in May 2016. Hydrological conditions were typical for Murmansk coastal water this season. A total of 47 zooplankton taxa were identified. Taxa number varied between stations, ranging 18–29, with copepods being a dominant group in zooplankton. The most frequent ones were Calanus finmarchicus, Metridia longa, Metridia lucens, Microcalanus spp., Oithona atlantica, Oithona similis, Pseudocalanus spp., copepod nauplii and ova, as well as cladoceran Evadne nordmanni, larvae of Echinodermata and Polychaeta, chaetognath Parasagitta elegans, and early stages of the euphausiids of the genus Thysanoessa. In populations of common copepod species Pseudocalanus spp. and Oithona similis, early age stages dominated, which indicated their continued reproduction. Total zooplankton abundance ranged from 748 to 6576 ind.·m−3, averaging 3012. Total zooplankton biomass varied from 17 to 157 mg of dry mass per m³, with a mean value of 83. The data obtained were comparable to those registered in Murmansk coastal water in July 2008 and were higher than those in August 2007. The authors suggest that it might be related to the differences in sampling seasons and hydrological conditions. Daily zooplankton production was estimated to be 0.49–4.04 mg of dry mass per m³, averaging (2.17 ± 0.17). These estimates were about twice as high as mean values, registered in Murmansk coastal water during summer period. This seems to be due to higher phytoplankton concentrations in spring. Total zooplankton stock for water area studied (25.8 thousand km²) was estimated to be 425,000 thousand tons of dry mass. Cluster analysis revealed four groups of stations that differ in relative abundance of Calanus finmarchicus, Copepoda nauplii, Oithona similis, larvae of Echinodermata, and appendicularian Fritillaria borealis. Spatial variation of zooplankton abundance was closely related to station location (latitude, longitude, and sampling depth), as well as bottom layer temperature and mean salinity at the station.