Variability of mesozooplankton, abiotic factors and ecological status of marine environment in the north-eastern part of the Black Sea

Seasonal and interannual dynamics of mesozooplankton abundance, biodiversity, ecological status of the marine environment and concurrent variability of abiotic forcings in the north-eastern part of the Black Sea in 2016–2023 were discussed. Mesozooplankton biomass, total biomass (mesozooplankton plus Noctiluca scintillans), biomass of Copepoda and Parasagitta setosa and harmful heterotrophic dinoflagellate Noctiluca scintillans have been considered along with the water temperature, wind, precipitation and salinity. Natural seasonal dynamic of mesozooplankton, disrupted by the invasion of M. leidyi in 1980s was found to be restored to some extent. General tendencies of interannual variability of mesozooplankton parameters and abiotic factors were documented: biomass exhibited maximums in 2017 and 2022, coincided with negative anomalies of SST and along-coast wind (upwelling conditions) and increased/decreased precipitation/salinity. Steady increase of Shannon index during considered period from 1.5-2 to 2.2–2.6 indicates growing biodiversity in the area. Marine environment had BAD ecological status in 2016–2018 and in 2022–2023 and GOOD one in 2019–2021. Ecological hazard of N. scintillans extensive development have been noticed.