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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. [ABSTRACT FROM AUTHOR]

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 −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.

One of the most severe problems associated with eutrophication of urban freshwater ecosystems is the occurrence of increasingly frequent blooms of toxic cyanobacteria. Cyanotoxins might accumulate in the trophic web, producing diverse intoxication symptoms and chronic effects that are difficult to diagnose and prevent. High mortality of domestic animals and fish has been reported previously under these prevailing conditions. This study investigates the taxonomic composition of phytoplankton assemblages in Sheldon Lake during the summer of 2004, a year after the completion of a restoration project on the lake. The study analysed the physical and chemical changes caused by urban run-off and artificial mixing, as well as the usefulness of microcystin molecular markers derived from the mcy gene cluster for the detection of toxic cyanobacterial strains in environmental samples from Sheldon Lake. This study clearly demonstrates that the artificial mixing rate alone was insufficient to cause a transition to a well-mixed aquatic system, and that cyanobacteria remained dominant throughout the summer months. The presence of toxic cyanobacterial strains was confirmed with the use of molecular markers that detected the presence of the mcy gene cluster responsible for the production of toxin by Microcystis spp. This approach might have a great potential use in the routine analyses of urban aquatic ecosystems. It also might make toxicity monitoring more feasible, allowing for the early application of corrective actions, especially for cases such as Sheldon Lake, which is a public recreational focal point. [ABSTRACT FROM AUTHOR]

Benthic stages of the annual life cycle of the meroplanktonic cyanobacteriumMicrocystisspp. in relation to microcystin (MCYST) dynamics in sediments of a shallow lake (Quitzdorf Reservoir, Germany) were investigated. Based on changes in the absolute abundance of benthicMicrocystis, the annual life cycle was subdivided into four phenological stages: reinvasion, pelagic growth, sedimentation, and overwintering. Habitat-coupling processes, such as reinvasion of the pelagic zone in spring as well as autumnal sedimentation, were particularly triggered by changes in water temperature. During reinvasion substantial losses ofMicrocystiswere detected. Only a minor part of benthicMicrocystis(about 3%) formed the inoculum for pelagic growth. Between 65% and 85% of the benthicMicrocystisstock disappeared during the reinvasion phase. Because these colonies were neither detected within the sediments nor in the pelagic inoculum, it was concluded that they were subjected to decay. The occurrence of extracellular MCYSTs in the pelagic zone during this period, which cannot solely originate from the pelagicMicrocystispopulation, supports this conclusion. Dynamics of benthicMicrocystisand MCYSTs were characterized by almost identical successions with a decrease during reinvasion, an increase during sedimentation, and remarkable invariability throughout pelagic growth and overwintering. It can be deduced that MCYSTs are preserved within benthic resting stages ofMicrocystisbecause they could play a role during overwintering or reinvasion. [ABSTRACT FROM AUTHOR]