Year-Round Presence of Microcystins and Toxin-Producing Microcystis in the Water Column and Ice Cover of a Eutrophic Lake Located in the Continuous Permafrost Zone (Yakutia, Russia).

This study aimed to test the hypothesis of the year-round presence of toxigenic Microcystis and cyanotoxins in the water and ice of the shallow eutrophic Lake Ytyk-Kyuyol located in the continuous permafrost zone. Three independent approaches-mass-spectrometry, molecular methods and light microscopy-were applied in the study. The cyanobacterial biomass ranged from 1.0 × 10-4 to 4.8 mg L-1. Microcystis flos-aquae and M. aeruginosa were the dominant morphospecies in plankton throughout the observation. In environmental DNA, the presence of M. aeruginosa was supported and mcy gene regions responsible for microcystin biosynthesis were detected through a BLAST (Basic Local Alignment Search Tool) search and phylogenetic estimation based on newly obtained 16S rRNA, 16S-23S ITS rRNA, mcyA and mcyE nucleotide sequences. The intracellular microcystin concentration ranged from <0.1 to 803 ng L-1, and the microcystin quota in the Microcystis biomass was extremely low. For the first time, it was shown that Microcystis cells containing mcy genes and microcystins presented permanently in the water column, both during the ice-free period and under ice, as well as inside thick ice covers within 7 months of severe winter. We hypothesized that minor pelagic and ice populations of Microcystis could participate in increasing cell density in the spring. However, further studies are needed to confirm the viability of the overwintering Microcystis colonies in the water and inside the ice of Lake Ytyk-Kyuyol.

A database of water chemistry in eastern Siberian rivers.

Permafrost degradation leads to considerable changes in river ecosystems. The Eastern Siberian River Chemistry (ESRC) database was constructed to create a spatially extensive river chemistry database to assess climate warming-induced changes in freshwater systems in permafrost-dominated eastern Siberia. The database includes 9487 major ion (Na+, K+, Ca2+, Mg2+, Cl-, SO42- and HCO3-) data of chemical results from 1434 water samples collected mainly in six large river basins in eastern Siberia spanning 1940-2019. Data were obtained from public databases, scientific literature in English and Russian, and researchers and were formatted with a consistent table structure. The database is transparent and reproducible. Climate variable (air temperature and precipitation) data, discharge data, trace element concentration data, and isotope data at the basin and subbasin scales are also provided. This database enhances knowledge about the water chemistry of the permafrost region, especially in eastern Siberia, where data are scarce. The database will be useful to those assessing spatiotemporal changes in river water chemistry associated with permafrost degradation or other environmental stressors in a warmer climate.