Phytoplankton of the Kuyalnik estuary in 2015 – 2017

The sharp change in the salinity of the Kuyalnitsky estuary in the second half of the twentieth century. Caused a significant reorganization of its ecosystem, which led to loss of fishing, deterioration of the quality of water. At the beginning of the XXI century the study of the Kuyalnitsky estuary biota, which exists in hypergalian conditions, was unsystematic, so information on the quantitative characteristics of phytoplankton and its distribution in the estuary is extremely limited. Purpose. To obtaining detailed information about current composition and quantitative characteristics of phytoplankton species in the estuary during the period from March 2015 to March 2017, i.e. when influenced by the transfer of sea water from the Odessa Bay. Methods. Concentration of the collected samples was done by sedimentation method. The samples collected during microalgal blooms have not been concentrated. Results. The phytoplankton was monodominant all over the estuary in 2015 – 2017 due to development of Dunaliella salina (Dunal) Teodor., which was presented by two different life forms. Some water samples contained benthoplankton species of diatomic algae, as well as Chlorophyta and Cyanobacteria. During the period of study algae blooms of D. salina was registered in 36 water samples; some cases of Bacillariophyta and Chlorophyta blooming were observed as well. During the period 2015-2017 the total number of phytoplankton species in the northern and central part of the estuary reached 23; in the southern part 69 species were registered. Conclusions. It has been established that phytoplankton of Kuyalnik Estuary can quickly adapt to salinity reduction caused by the filling of the estuary with sea water, which is one of the reasons of frequent algal blooms in 2015-2017.