Seasonal Changes in Abundance, Biomass, and Species Composition of Zooplankton Communities in the Open Sea near the Crimean Coast of the Black Sea and Sea of Azov

Data on seasonal changes in the abundance, biomass, and species composition of zooplankton communities and of copepods have been obtained at the shelf of the Crimean Peninsula and in deep-water areas of the Black Sea. Warm-water invasive copepod species Acartia (Acantacartia) tonsa and Oithona davisae are present at the shelf in summer and autumn, which affects the Copepoda taxocene structure. Cold-water native species dominate in deep-water areas, so the Copepoda taxocene structure during these seasons is more stable than those at the shelf. The quantitative indicators of copepods and fodder zooplankton in 2016 are higher compared to the 2010s and 1990s. The data allow a conclusion on the transition of the Black Sea pelagic ecosystem to a new, relatively stable state. The Black Sea species, including invaders, penetrate the Sea of Azov due to the increased salinity of the latter; currently, this predetermines the biodiversity of zooplankton in the region.