Data on cyanobacterial toxins and the genes of their biosynthesis in the phytoplankton of the mesotrophic Lake Pleshcheyevo (Yaroslavl oblast) during the blooming period of cyanobacterium Gloeotrichia echinulata (Smith et Sowebry) Richter are given for the first time. In the phytoplankton of the lake, the presence of hepatotoxins of microcystins (MC) was recorded using chromatography–mass spectrometry; in DNA isolated from plankton, the mcyE gene for the biosynthesis of these cyanotoxins was detected using PCR. No other types of cyanotoxins (cylindrospermopsin, anatoxin-a, and saxitoxins) or the presence of genes for their synthesis in the phytoplankton are identified during the study period. MC biosynthesis genes mcyA and mcyE were absent in thirty colonies of Gloeotrichia echinulata isolated from the lake, which is consistent with their inability to produce cyanotoxin. Using molecular methods, the potential ability to biosynthesize MC in Microcystis aeruginosa and species of the genus Dolichospermum inhabiting in the lake is demonstrated. This paper discusses the toxicity of Gloeotrichia echinulata and the need for the further long-term monitoring of toxigenic cyanobacteria in Lake Pleshcheyevo.

The article presents for the first time the data on cyanobacterial toxins and the genes of their biosynthesis in the phytoplankton of the mesotrophic Lake Pleshcheyevo Yaroslavl Region, during the period of cyanobacterium Gloeotrichia echinulata (Smith et Sowebry) Richter – bloom. In the phytoplankton of the lake, the presence of hepatotoxins microcystins was recorded using chromatography – mass spectrometry; in DNA isolated from plankton, the mcyE gene for the biosynthesis of these cyanotoxins was detected using PCR. During the study period, other types of cyanotoxins (cylindrospermopsin, anatoxin – a, saxitoxins) and the presence of genes for their synthesis in the phytoplankton were not identified. In thirty colonies of G. echinulata isolated from the lake, the microcystin biosynthesis genes mcyA and mcyE were absent, which is consistent with their inability to produce cyanotoxin. Using molecular methods, the potential ability to biosynthesize microcystins in Microcystis aeruginosa and species of the genus Dolichospermum inhabiting in the lake was demonstrated. The paper discusses the toxicity of Gloeotrichia echinulata and the need for further long-term monitoring of toxigenic cyanobacteria in Lake Pleshcheyevo.

Toxigenic cyanobacteria and microcystins in the oligotrophic pelagic zone and mesotrophic bay of Lake Onego—the second largest lake in Europe—were found for the first time. Microscopic analysis revealed that Dolichospermum lemmermannii, D. circinale and D. spiroides dominated in bloom spots in the oligotrophic zone of the lake and D. flos-aquae and Microcystis aeruginosa OKin the eutrophic bay. The abundance of cyanobacteria in bloom spots is potentially hazardous for humans and animals. PCR-analysis showed that mcyA gene involved in microcystin biosynthesis was found in cyanobacteria of the genera Dolichospermum and Microcystis. Five structural variants of intracellular microcystins were detected in a trace amount using high-performance liquid chromatography–mass-spectrometry of high resolution. The most hazardous hepatotoxin, MC-LR, was found only in the eutrophic bay. In the present study, the reasons for the low cyanotoxin content in the phytoplankton dominated by Dolichospermum are discussed. The findings of our study make a significant contribution to the accumulation of facts which state that toxigenic cyanobacterial blooms can occur in large oligotrophic lakes.

The first data on the distribution of cyanobacterial toxins have been obtained and a molecular genetic determination of cyanotoxin producers in the plankton of some lakes in the permafrost zone in Yakutia have been performed for the first time. Most of the lakes are characterized by high concentrations of nitrogen, phosphorus, and chlorophyll a and by an increased content of organic matter, which could be associated with a high anthropogenic load. Water blooms were visually observed in three of the six studied lakes during the summer period. 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. Regions of the mcyE gene involved in the biosynthesis of microcystin were amplified using the polymerase chain reaction method in environmental DNA isolated from planktonic samples. Cyanobacteria capable of producing neurotoxic anatoxin-a, saxitoxins, and hepatotoxic nodularins were absent in the lakes during the study period. The use of genus-specific primers to the mcyE gene enables us to find that the main producers of microcystins were represented by species of the genus Microcystis in most of the lakes and by species of Dolichospermum only in one of the lakes. Up to eight 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, and [Asp3]MC-YR, were identified in lake plankton using liquid chromatography–mass spectrometry. The maximal concentration of microcystins in plankton (intracellular fraction 803 ng/L) was recorded in a sample from Ytyk-Kyuyol Lake. 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.

As global climate change continues and the vegetation period lengthens, the importance of research into cyanobacterial recruitment biomass and associated toxin risks is growing. While most studies focus on planktonic cyanobacteria causing blooms, benthic cyanobacteria have been less explored. This study reports for the first time on the mass proliferation of benthic epilithic macrocolonies of cyanobacteria, Gloeotrichia cf. natans, in water bodies located in a region with continuous permafrost in Yakutia, North-East Russia. The study characterizes the environmental conditions of its habitat, including the chemical composition of the water, which expands our understanding of this species’ ecology. Cyanotoxins (microcystins, cylindrospermopsin, saxitoxins, and anatoxin-a) were not detected in the biomass of Gloeotrichia cf. natans using liquid chromatography–mass spectrometry and PCR methods.

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 multiprimer PCR-based technique for the joint molecular detection of microcystin-producing planktonic cyanobacteria of the genera Microcystis , Planktothrix and Dolichospermum was developed. To amplify the mcy genes of microcystin biosynthesis, three pairs of genus-specific primers were selected, while the fourth pair was used to amplify the inter-gene spacer (IGS) cpcBA acting as an inner positive control for the presence of cyanobacterial DNA in the analyzed samples. Four PCR products of predicted size were successfully amplified using a mixture of DNA templates isolated from microсystin-producing strains of M. aeruginosa , Planktothrix agardhii , and field colonies of Dolichospermum lemmermannii retrieved from the environment, as well as the environmental DNA template from lake plankton. The proposed multiprimer PCR-based approach may be used to design convenient test systems for monitoring aquatic ecosystems to prevent and/or assess the risk of accumulation of harmful cyanobacterial toxins.

A comparative of the species composition and ecological-geographical characteristics of cyanobacteria plankton of 13 reservoirs of the Volga-Kama cascade and the Don (Sheksna, Ivankovo, Uglich, Rybinsk, Gorky, Cheboksary, Kuibyshev, Saratov, Volgograd, Kama, Votkinsk, Nizhnekamsk and Tsimlyansk reservoirs) is analysed. An assessment of the change in the distribution of cyanobacteria biomass in a latitudinal gradient along the Volga cascade is presented. The seasonal and long-term (1954–2016) dynamics of the abundance, biomass and the ratio of functional groups of cyanobacteria in the Rybinsk Reservoir, the second largest in the cascade of Volga reservoirs, are analyzed. A positive long-term trend of abundance and diversity of cyanobacteria and the leveling of their biomass between reservoirs along a cascade in recent years has been established. An increase in the abundance and diversity of nonheterocystous species was established in the direction from the Upper to the Lower Volga and during the long-term succession of phytoplankton of the Rybinsk Reservoir. This is associated with an increase of water mineralization. Based on current research in the 2010s of the Volga, Kama and Don cascade reservoirs, 14 variants of microcystin structures were identified, the diversity of which depended on the composition of the producing species. Using PCR analysis, the main producers of microcystins (Microcystis and Dolichospermum) were identified. Cyanobacteria Cuspidothrix issatschenkoi and/or Raphidiopsis mediterranea have been identified as possible producers of neurotoxic anatoxin-a in the Tsimlyansk Reservoir. It was shown that water temperature and nitrogen were the greatest importance for development of microcystin-producing species of cyanobacteria.

Raphidiopsis raciborskii is a freshwater, potentially toxigenic cyanobacterium, originally described as a tropical species that is spreading to northern regions over several decades. The ability of R. raciborskii to produce cyanotoxins - in particular the alkaloid cylindrospermopsin (CYN), which is toxic to humans and animals - is of serious concern. The first appearance of R. raciborskii in Russia was noted in Lake Nero in the summer of 2010. This is the northernmost (57 degrees N) recorded case of the simultaneous presence of R. raciborskii and detection of CYN. In this study, the data from long-term monitoring of the R. raciborskii population, temperature and light conditions in Lake Nero were explored. CYN and cyr/aoa genes present in environmental samples were examined using HPLC/MS-MS and PCR analysis. A R. raciborskii strain (R104) was isolated and its morphology, toxigenicity and phylogeography were studied. It is supposed that the trigger factor for the strong development of R. raciborskii in Lake Nero in summer 2010 may have been the relatively high water temperature, reaching 29-30 degrees C. Strain R. raciborskii R104 has straight trichomes and can produce akinetes, making it morphologically similar to European strains. Phylogeographic analysis based on nifH gene and 16S-23S rRNA ITS1 sequences showed that the Russian strain R104 grouped together with R. raciborskii strains isolated from Portugal, France, Germany and Hungary. The Russian strain R104 does not contain cyrA and cyrB genes, meaning that it - like all European strains - cannot produce CYN. Thus, while recent invasion of R. raciborskii into Lake Nero has occurred, morphological, genetic, and toxicological data supported the spreading of this cyanobacterium from other European lakes. Detection of CYN and cyr/aoa genes in environmental samples indicated the cyanobacterium Aphanizomenon gracile as a likely producer of CYN in Lake Nero. The article also discusses data on the global biogeography of R. raciborskii. Genetic similarity between R. raciborskii strains isolated from very remote continents might be related to the ancient origin of the cyanobacterium inhabiting the united continents of Laurasia and Gondwana, rather than comparably recent transoceanic exchange between R. raciborskii populations.

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 mu g L-1 in June up to 16.4 mu g L-1 in August and exceeded 1 mu g 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 mu g mu g(-1) and 4.5 mu g mm(-3), respectively. Together with microcystin profiles MC/BV eya ,, o 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 mu g L-1). Toxin gene analysis revealed that MC mostly originated from Microcystis and Dolichospermum. During their co-existence up to 14 MC congeners cooccurred. Cuspidothrix issatschenkoi cf. Rcuphidiopsis mediterranea was identified as possible neurotoxin producers.

Four species of Gomphonema described by Hustedt with fusiform valve shape are studied for the first time using SEM. G. longissimum Hustedt, G. angustissimum Hustedt, G. woltereckii Hustedt and G. subtiliforme Hustedt were described, and are known only, from the ancient Malili lake system in Indonesia. Molecular investigations of two cultured strains of G. longissimum, using 18S rDNA and rbcL, are presented. In terms of morphology, these four species have unusually long valves and a fusiform shape otherwise unknown in Gomphonema, yet morphological similarities with other species include C-shaped or semi-circular areolae, uniseriate striae, pseudosepta, apical pore fields, a straight raphe with hooked internal proximal ends and a typical stigma in G. longissimum and G. angustissimum. Results of the molecular study support placement of G. longissimum with other 'typical' Gomphonema species. G. subtiliforme and G. woltereckii both lack a stigma. G. subtiliforme is similar in shape and morphology to members of the group G. subtile Ehrenberg, which all bear stigmata. G. woltereckii differs from G. longissimum and G. angustissimum by having areolae that are semi-circular, not C-shaped, and by the absence of a stigma. Therefore, based on morphology, we conclude these extraordinarily large Gomphonema taxa are similar to each other and generally resemble other species of the genus, yet there is enough variation in presence/absence of stigmata and structure of the areolae that they do not necessarily form a distinct group. Thus, despite their large size, and presence in the same lake system, we cannot conclude they form a species flock. Less than two dozen Gomphonema species are present in Malili lakes whereas some other ancient lakes, such as Lake Baikal, have many more species and exhibit species flocks.

For the first time, data are given on cyanobacterial toxins entering tap water, supplied to the population of some cities in Yaroslavl oblast. The detection of microcystins with their concentrations in tap water in different parts of Yaroslavl in 2013 far in excess of their safe levels in such water is due to the seasonal development dynamics of toxigenic cyanobacteria in the source of water supply, i.e., the Gorky Reservoir. The molecular-genetic analysis revealed Microcystis species as the main microcystin producers. The efficiency of some methods for removal of different types of cyanotoxins from water is estimated.

The first data on the distribution of microcystin genes among natural populations of different species of Microcystis from Russian reservoirs were obtained. It was statistically established that the occurrence of mcy gene-containing colonies of M. aeruginosa, M. viridis, and M. novacekii was significantly higher than that of M. wesenbergii and M. flos-aquae. It has been shown that M. wesenbergii from the water bodies in Russia and Eurasia is not capable of producing microcystins. These results are discussed with respect to various mechanisms that could explain the distribution of microcystin genes among the various Microcystis morphospecies, such as the compensation of microcystin functions by the synthesis of other secondary oligopeptides and the presence of dense mucilaginous envelopes surrounding the colonies of M. wesenbergii. No correlation was found between colony size and the frequency of mcy genes for individual morphospecies M. aeruginosa and M. flos-aquae.

Long-term dynamics of water level in Lake Nero (1930–2011) has been analyzed. Pronounced trends, determined by the climate and anthropogenic components have been identified. Up to the 1970s, at a drop in lake water level, the ecosystem still showed the main features of a shallow water body overgrown with macrophytes. Water level rise caused a more intense development of phytoplankton, an increase in biogenic element concentrations, a decrease in water transparency and the contribution of cyanobacteria of S 1 codon; pondweed disappeared almost completely. Step-by-step regression analysis of phytoplankton development indices and hydrological characteristics showed that water transparency in Lake Nero depends by 80% directly on water exchange and inversely on the concentration of chlorophyll a in seston. The main hypothesis of the study was confirmed: the key trigger in phytoplankton–macrophytes competition is water level rise.

The aim of this study was to obtain the first data on the occurrence and distribution of potentially toxic cyanobacteria and cyanotoxins in the Russian Easternmost part of the Gulf of Finland of the Baltic Sea. Studied samples were collected from 2012 to 2017 and three independent approaches - HPLC-HRMS, PCR and light microscopy were applied for cyanotoxins analysis and detection of toxigenic cyanobacteria. Aphanizomenon flos-aquae Ralfs ex Born. et Flah., Planktothrix agardhii (Gom.) Anag. et Kom., Microcystis aeruginosa (Kütz.) Kütz. and Dolichospermum spp. dominated among cyanobacteria in collected samples. In 2012-2013 during research cruises, microcystins concentrations varied from below detection levels to low (0.01-0.6 μg L-1) values. In the autumn of 2015 and 2017, during cyanobacterial bloom events very high concentrations of microcystins (dissolved up to 49 μg L-1, intracellular up to 466 μg g-1) and dissolved anatoxin-a (1.4 μg L-1) were detected. The evaluated toxin profile was represented by most common arginine-containing variants of microcystins (MC-LR, MC-RR, MC-YR) and their desmethylated forms. Leucine-containing congeners (MC-LF; MC-LY; MC-LW for the biomass sample from the coast of Komarovo, 2015) were found at low concentrations. In environmental DNA from bloom samples, we identified mcy genes regions responsible for MC biosynthesis that are specific for Dolichospermum, Microcystis, and Planktothrix. This study is the first molecular evidence the ability of Microcystis aeruginosa and Planktothrix agardhii from the Gulf of Finland to produce microcystins. On the basis of the obtained data of genus-specific PCR and microscopy, we suppose the presence of anatoxin-a-producing Apanizomenon flos-aquae population in the phytoplankton of Russian part of the Gulf of Finland.

The results of laboratory experiments on studying the characteristics of feeding of natural populations of Daphnia galeata from the freshwater Curonian Lagoon on cyanobacteria using the counting and radioisotope methods are discussed. The consumption and assimilation of the cyanobacterium Aphanizomenon flos-aquae by Daphnia have been revealed, as has the inhibition of feeding in Daphnia by species of the genus Microcystis. The results of PCR analysis of the total DNA of plankton from the Curonian Lagoon and enzyme-linked immunosorbent assay have proved the ability of Microcystis populations to produce microcystins, while no genes involved in the synthesis of cyanotoxins have been found in A. flos-aquae.