Variability of spatial Zooplankton distribution affected by the water dynamics in the northeastern part of the Black Sea

The effect of the meso- and basin-scale circulation on the spatial distribution of zooplankton was studied in the northeastern part of the Black Sea. The study was carried out during six cruises of RN Akvanavt in the falls of 1999-2001. The basin scale circulation and mesoscale dynamics were quite different in these periods. In 1999 and 2001, the mesoscale eddy dynamics prevailed in the eastern part of the sea, while the Caucasian part of the Rim Current was slow, wide, and unstable. During these years, a marked heterogeneity in the spatial distribution of the zooplankton populations was observed throughout the research area. There was no pronounced difference in the total mesozooplankton biomass between the 20-mile-wide coastal area and the deep-water parts of the sea. In 2000, the Rim Current jet was fast and narrow and flew close to the continental slope. The mesoscale circulation was weak, and no long-lived eddies were observed. Zooplankton was concentrated on the shelf and in the slope areas. Near the coast,, the mesozooplankton biomass was significantly higher than in the central parts of the sea. The live species inhabiting the thermocline were affected by hydrophysics and dynamics much stronger than those living under the thermocline. The state of the Rim Current and the mesoscale eddy dynamics had a great influence on the cross-shelf exchange and offshore transport of zooplankton.