Study of Phytoplankton Within the Coastal Waters of Zmiinyi Island in 2016−2017

Purpose. To reveal seasonal changes in phytoplankton quantitative characteristics including biodiversity and species composition of potentially dangerous (toxic) species. Methods. Phytoplankton sampling in Odessa bay coastal waters and sample analyses were carried out using standard methodologies. The samples were preserved using formalin. Microscopes HUND−H600 and OLYMPUS−BH2 have been used for sample analyses. Classification of microalgae and Cyanobacteria was done according to the standards of the international database. Results. Analysis of the main abiotic factors influencing the state of phytocene has been carried out. In the species composition, 238 species of phytoplankton belonging to 11 classes have been registered: diatoms − Bacillariophyceae, dinophytes − Dinophyceae, green − Chlorophyceae, Cyanobacteria, Prymnesiophyceae, Euglenoidea, Chrysophyceae, Cryptophyceae, Dictyochophyceae, Choanoflagellatea. It was shown that the dominant phytoplankton species were Bacillariophyceae, Dinophyceae, Chlorophyceae and Cyanobacteria. For the first time, 11 freshwater species of dinophytes were registered in the Zmiinyi Island area. Statistical interconnections between phytoplankton metrics and abiotic characteristics were analysed. Development of 54 phytoplankton species, which refer to the group of potentially harmful (toxic) was registered; out of this number, 21 reached blooming level. Conclusions. The main abiotic factors determining the state of phytoplankton and its seasonal changes are salinity and transparency. During 2016−2017, 4 seasonal maximums of microalgae development were registered in the photic layer of the Zmiinyi Island coastal waters (in spring, summer, autumn and winter), which corresponded to the terms of the normal periodicity of the normal periodicity of the Black Sea phytoplankton vegetation. Comparison of modern maximum values with similar data obtained in previous years, allows us to conclude that a significant increase in the quantitative characteristics of phytoplankton took place in 2016−2017. The quality of water in the surface layers in the Zmiinyi Island area assessed using the main metrics of phytoplankton was much lower than that in the bottom water layers, which was caused by the Danube River discharge impact, first of all, observed in the surface layers of water.Black Sea phytoplankton vegetation. Comparison of modern maximum values with similar data obtained in previous years, allows us to conclude that a significant increase in the quantitative characteris-tics of phytoplankton took place in 2016−2017. The quality of water in the surface layers in the Zmiinyi Island area assessed using the main metrics of phytoplankton was much lower than that in the bottom water layers, which was caused by the Danube River discharge impact, first of all, observed in the surface layers of water.