Occurrence of microcystins and anatoxin-a in eutrophic lakes of Saint Petersburg, Northwestern Russia

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 μg l⁻¹. In eutrophic and shallow Suzdal, dominated by Planktothrix agardhii, nine microcystin variants and anatoxin-a (<0.54 μg l⁻¹) were found. The maximum total concentration of extracellular MCs in this lake was 2.89 μg 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.