Limnological characterization and the first data on occurrence of toxigenic cyanobacteria and cyanotoxins in the plankton of some lakes in the permafrost zone (Yakutia, Russia)
V. A. Gabyshev1, S. I. Sidelev2,3, E. N. Chernova4, O. I. Gabysheva1, I. V. Voronov1, Z. A. Zhakovskaya4
1Institute for Biological Problems of Cryolithozone SB RAS, Yakutsk, Russia
2Yaroslavl State University, Yaroslavl, Russia
3Papanin Institute for Biology of Inland Waters RAS, Borok, Russia
4St. Petersburg Federal Research Center of the Russian Academy of Sciences (SPC RAS), Scientific Research Centre for Ecological Safety of the Russian Academy of Sciences, Saint Petersburg, Russia
Keywords: toxigenic cyanobacteria, cyanotoxins, microcystins, plankton, lakes, permafrost zone
Abstract
In the study, the first data on the distribution of cyanobacterial toxins were obtained and, for the first time, a molecular genetic determination of cyanotoxin producers in the plankton of some lakes in the permafrost zone in Yakutia was carried out. Most of the lakes were characterized by high concentrations of nitrogen, phosphorus, chlorophyll a and an increased content of organic matter, which could be associated with a high anthropogenic load. During the summer period, water blooms were visually observed in three of the six studied lakes. The abundance and biomass of cyanobacteria in the lakes varied within 13.7-676.3 million cells/l and 0.6-4.8 mg/l, respectively. Eight species of potentially toxigenic cyanobacteria were found in phytoplankton using light microscopy. In environmental DNA isolated from planktonic samples, regions of the mcyE gene involved in the biosynthesis of microcystin were amplified using the polymerase chain reaction method. During the study period, cyanobacteria capable of producing neurotoxic anatoxin-a, saxitoxins, and hepatotoxic nodularins were absent in the lakes. Using genus-specific primers to the mcyE gene, it was found that species of the genus Microcystis were the main producers of microcystins in most of the lakes; and species of Dolichospermum - only in one of the lakes. Up to 8 structural variants of microcystins, in general arginine-containing isoforms MC-LR, MC-RR, MC-YR, MC-LY, MC-HIlR, [Asp3]MC-LR, [Asp3]MC-RR, [Asp3]MC-YR, were identified in lake plankton using liquid chromatography-mass spectrometry. The maximum concentration of microcystins in plankton (intracellular fraction, 803 ng/l) was recorded in a sample from Lake Ytyk-Kel. The calculated content of microcystins per unit biomass of producing cyanobacteria (toxin quota) was low (0.005-0.069 µg/mg). In order to assess the potential hazard of toxigenic species of cyanobacteria to human health, the distribution of cyanotoxins and their producers should be further studied in water bodies of the region.
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