PHYTOPLANKTON STATE AND CYANOTOXINS IN THE SVYATOZERO LAKE BLOOM SPOT (ONEGA LAKE BASIN, RUSSIA)
Authors:   Northern Water Problems Institute, Karelian Research Center of the Russian Academy of Sciences, Smirnova V. S. ,   Federal Research Center “Karelian Research Center of the Russian Academy of Sciences”, Petrozavodsk, Russia, Tekanova E. V. ,   Northern Water Problems Institute, Karelian Research Center of the Russian Academy of Sciences; Federal Research Center “Karelian Research Center of the Russian Academy of Sciences”, Petrozavodsk, Russia, Kalinkina N. M. ,   Northern Water Problems Institute, Karelian Research Center of the Russian Academy of Sciences; Federal Research Center “Karelian Research Center of the Russian Academy of Sciences”, Petrozavodsk, Russia, Chernova E. N. ,   St. Petersburg Federal Research Center of the Russian Academy of Sciences; St. Petersburg Scientific Research Center for Ecological Safety of the Russian Academy of Sciences, St. Petersburg, Russia
Published: April 2021

Introduction. This paper is the first to address the state of phytoplankton in eutrophic Svyatozero Lake (61о32´ N, 33о35´ E.), used for trout farming in the Republic of Karelia, in the North-Western Region of Russia, during the period of water bloom. For northern reservoirs, water bloom is not a typical phenomenon. However, due to climate warming and the large-scale development of trout breeding in the region, it becomes more urgent to study blooming reservoirs and related consequences for northern aquatic ecosystems and humans. Methods. We processed phytoplankton samples and measured photosynthesis using conventional methods. The concentration of chlorophyll a in water was determined spectrophotometrically, and the content of cyanotoxins was estimated by liquid chromatography-mass spectrometry. Results. In September 2019, we studied the structural, quantitative and functional characteristics of phytoplankton in the bloom spot. The phytoplankton abundance was 198.712 mln cells/l, the biomass was 14.945 mg/l, and the concentration of chlorophyll a reached 215.3 μg/l, which corresponded to the β-eutrophic state of the ecosystem in the study area. It was revealed that cyanobacteria corresponded to 99.8% of the biomass and 96.7% of the abundance. The species of the genus Microcystis were dominant (42%). They are well-known potential producers of cyanobacterial hepatotoxins, in particular, microcystins. We established the presence of microcystins. Their intracellular and extracellular concentrations were equal and in total amounted to 12.56 μg/l. We also identified eight structural variants of microcystins; among those, [D-Asp3] MC-RR accounted for up to 90% of the total content. The most toxic MC-LR variant was present in trace amounts only in biomass. According to the WHO standards, the content of microcystins and the number of cyanobacterial cells in the Svyatozero Lake bloom spot corresponds to average danger in the case of recreational use and can pose a threat to human health. Conclusion. It is necessary to monitor the phytoplankton composition, the presence of potentially toxic cyanobacterial species and cyanotoxins, as well as the state of trout farmed in the waters of Svyatozero Lake, since cyanotoxins can accumulate in fish tissues.