Spatial distribution of cyanotoxins and ratios of microcystin to biomass indicators in the reservoirs of the Volga, Kama and Don Rivers, the European part of Russia

• Published in: Limnologica Vol. 84; p. 125819
• Main Authors: Chernova, Ekaterina, Sidelev, Sergey, Russkikh, Iana, Korneva, Ludmila, Solovyova, Vera, Mineeva, Natalia, Stepanova, Irina, Zhakovskaya, Zoya
• Format: Journal Article
• Language: English
• Published: Elsevier GmbH 01.09.2020
• Subjects: Anatoxin-a; Cyanobacteria; Drinking water reservoirs; European Russia; Microcystins; Anatoxin-a; Drinking water reservoirs; Cyanobacteria; Microcystins; European Russia
• ISSN: 0075-9511; 1873-5851
• DOI: 10.1016/j.limno.2020.125819

•Microcystin concentrations (MC) exceeding 1 μg L−1 were recorded in 25 % of the samples.•Anatoxin-a (0.01 μg L−1) was detected once.•MC reached 0.88 μg per μg Chl-a and 5.6 μg per mm³ producers biovolume (based on PCR).•Microcystis and Dolichospermum were the key microcystin producers.•Cuspidothrix issatschenkoi cf. Raphidiopsis mediterranea – possible anatoxin-producers. We studied the distribution of cyanotoxins and potential producers, as well as the variability of microcystin to biomass parameters (chlorophyll-a; MC/Chl-a; and biovolume; MC/BV) in 12 drinking water reservoirs of the world’s largest reservoir system, the Volga-Kama-Don cascade (European part of Russia) during the summers of 2016 and 2018. MC concentrations varied from below 0.1 μg L−1 in June up to 16.4 μg L−1 in August and exceeded 1 μg L-1 in 25 % of the samples. This MC variability was associated to changes in the abundance of widespread bloom formers such as Microcystis spp., Dolichospermum spp. and Planktothrix agardhii. Ratios of MC/Chl-a and MC/BVcyano ranged up to 0.88 μg μg−1 and 4.5 μg mm−³, respectively. Together with microcystin profiles MC/BVcyano ratios characterized cyanobacterial populations along the reservoir cascade and they indicated a potential toxin hazard better than MC/Chl-a. The neurotoxin anatoxin-a was observed only in the most southern and hypereutrophic Tsimlyansk Reservoir (maximum 0.01 μg L−1). Toxin gene analysis revealed that MC mostly originated from Microcystis and Dolichospermum. During their co-existence up to 14 MC congeners co-occurred. Cuspidothrix issatschenkoi cf. Raphidiopsis mediterranea was identified as possible neurotoxin producers.