The current study focuses on the diversity, distribution and toxic potential of cyanobacteria in the waterbodies of Moscow, Russia. The research involves the sampling of natural and artificial water environments situated within the Moscow city agglomeration, including the waterbodies of recreational importance. A total of 20 strains of cyanobacteria, namely representatives of Anabaena, Aphanizomenon, Argonema, Dolichospermum, Microcystis and Woronichinia, are isolated from the collected samples. The morphology of the newly obtained strains is analyzed through light microscopy. The results of morphological identification are compared to the molecular data. The molecular phylogeny of the cyanobacterial strains is assessed on the basis of 16S rRNA sequencing. The detection of cyanotoxin-producing genes through PCR reveals two strains of Microcystis aeruginosa capable of microcystin synthesis. Further analysis using HPLC-HRMS demonstrates that microcystin production includes a high proportion (20–28%) of exceptionally toxic microcystin–leucine arginine compounds. Hereby, we discuss the morphology and phylogeny of the analyzed strains and provide comments on the toxic potential of cyanobacteria within the waterbodies of Moscow.

The paper presents long-term material on the succession of species Gonyostomum semen (Ehr.) Diesing collected on the lakes of the Valaam archipelago. The work was carried out on 10 small lakes about Valaam archipelago, maintaining a natural mode of functioning. The lakes differed in the shape of the basin, depth, and features of the hydrochemical regime. For lakes, a wide range of limnological parameters was revealed, such as transparency (0,3–4,6 m), active reaction of the environment (4,0–8,6), water color (27–296° according to Pt–Co scale), the content of total organic matter (10,8–63,8 mgO/dm3) and mineral phosphorus (0,001–0,646 mg/dm3). The phytoplankton structure varied significantly from lake to lake. In terms of abundance in most small lakes in biomass rafidophyte algae dominated. G. semen biomass varied from 1,1 to 82,3 mg/dm3. In the seasonal dynamics of phytoplankton, one or two peaks were noted, which occurred in different years in different months, most often in June or September.

The paper presents long-term material on the succession of phytoplankton collected on the lakes of the Valaam archipelago. The work was carried out on 11 lakes about Valaam archipelago, maintaining a natural mode of functioning. The lakes differed in the shape of the basin, depth, and features of the hydrochemical regime. Phytoplankton samples were taken once a month from May to October 1998–2019. In parallel with sampling, studies of the main limnological parameters were carried out. For lakes, a wide range of limnological parameters was revealed, such as transparency (0,3–4,6 m), active reaction of the environment (4,0–8,6), water color (27–296о according to Pt-Co scale), the content of total organic matter (10,8–63,8 mgO/dm3) and mineral phosphorus (0,001–0,646 mg/dm3). The phytoplankton structure varied significantly from lake to lake. In terms of abundance in most small lakes, cyanobacteria (in abundance) and rafidophyte (in biomass) algae dominated. Abundance of phytoplankton and biomass varied from 0.1 to 676.6 million cells/dm3 and from 0.1 to 105.2 mg/dm3, accordingly. In acidic polyhumous lakes, a simplification of the phytoplankton structure was noted. Representatives of the department of green algae (chlorococcal, volvox, ulotrix) dominated in these lakes throughout the season. In the seasonal dynamics of phytoplankton, one or two peaks were noted, which occurred in different years in different months, most often in June or September. It was shown that the variation in the structural parameters of the phytoplankton of lakes was determined by the specific catchment area, the depth of the reservoir, water transparency, color, electrical conductivity and nutrient content. To a large extent, the level of phytoplankton vegetation was also determined by the active reaction of the environment.

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.

Last decades, cyanobacterial blooms have been commonly reported in Russia. Among the boom-forming species, potential toxin producers have been identified. The aim of this paper was to study the presence of neurotoxic compounds - saxitoxins and anatoxin-a - in water bodies from different regions of Russia. We also made attempts to identify the neurotoxin-producing genera. The good convergence of the results obtained by light microscopy, PCR and LC-MS/MS analyses indicated the presence of active neurotoxin producing species in all investigated water bodies. Saxitoxin was detected in phytoplankton from 4 water bodies in Central European Russia and West Siberia, including lake and reservoirs used as a source for potable water. The water bodies differed with the respect of saxitoxin producers which belonged to Aphanizomenon and/or Dolichospermum genera. For the first time, we obtained quantitative data on the intracellular saxitoxin concentration in Russian freshwaters using LC-MS/MS. Anatoxin-a was detected only in lakes of Northwestern Russia. In the eutrophic shallow Lower Suzdal Lake, Aphanizomenon was the stated anatoxin-a-producing genus. In the large shallow artificial hypertrophic Sestroretskij Razliv Lake, it was very likely that both dominant species - Aphanizomenon flos-aquae and Dolichospermum planctonicum - were anatoxin-a producers.

Cyanobacteria are natural components of many freshwater bodies worldwide. In Russian lakes, the presence of potentially toxic cyanobacteria was also frequently observed. Our study was conducted in Sestroretskij Razliv Lake (Razliv) and Lower Suzdal Lake (Suzdal) in Saint Petersburg region, Northwestern Russia, which differ from one another in eutrophic status and composition of the phytoplankton community. In large, shallow, artificial and hypertrophic Razliv, Aphanizomenon flos-aquae and Microcystis spp. dominated. Fourteen microcystin variants were identified in this lake. The maximum concentration of extracellular microcystins was 41.37 mu g l(-1). In eutrophic and shallow Suzdal, dominated by Planktothrix agardhii, nine microcystin variants and anatoxin-a (<0.54 mu g l(-1)) were found. The maximum total concentration of extracellular MCs in this lake was 2.89 mu g l(-1). Regular studies into the production of cyanotoxins in these water bodies were carried out for the first time. The analyses performed with the application of high-resolution tandem mass spectrometry revealed the presence of microcystins in 59% of the samples collected during a 3-year study. Since both lakes are used for recreational purposes, the regular monitoring program should be implemented to protect water users from a potential risk that was identified in our study.