The presence of toxic cyanobacteria in water bodies is a growing concern due to their potential adverse effects on public health and the environment. Microcystis aeruginosa and M. wesenbergii are known to be key microcystin producers in Bulgarian waterbodies. In this study, water samples were collected from various Bulgarian waterbodies during the summer months of 2021, and the presence and abundance of Microcystis species were analyzed using microscopy and PCR-based methods. The microcystin concentration in the water samples was measured using high-performance liquid chromatography (HPLC). The results showed that Microcystis aeruginosa and M. wesenbergii were the dominant species of cyanobacteria in the waterbodies sampled, with high microcystin concentration above the recommended safe limit for human consumption.

Microcystis aeruginosa, microcystin, cyanobacteria

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