2018-01-312018-01-311965https://repository.marine-research.ru/handle/299011/132The investigation was carried out to find out how spatial distribution of phytoplankton depends on season of a year and the abundance – on some variable abiotic factors, and to learn about ecological features inherent to some mass species. Material for the study were samples of phytoplankton collected during a series of surveys conducted over the northwestern Black Sea during 1951 – 1956. Unlike other regions of the Black Sea, its northwestern part is characterized by a highly variable hydrological regime due to which taxonomic composition and abundance of phytoplankton drastically differ in different seasons and years. Wind-induced upwellings, cyclonic and anticyclonic eddies typical of this area generate large-scale transfer of water masses over the Black Sea. During the period of our observations, in deep-water locations of the sea phytoplankton abundance largely depended on the currents; the major factor influencing distribution of phytoplankton within water column was vertical circulation of water masses.ruArticle