Cylindrospermopsin- and deoxycylindrospermopsin-producing Raphidiopsis raciborskii and microcystin-producing Microcystis spp. in Meiktila lake, Myanmar

Meiktila Lake is a shallow reservoir located close to Meiktila city in central Myanmar. Its waterisusedforirrigation,domesticpurposesanddrinkingwater. Nodetailedstudyofthepresence of cyanobacteria and their potential toxin production has been conducted so far. To ascertain thecyanobacterialcompositionandpresenceofcyanobacterialtoxinsinMeiktilaLake,watersamples were collected in March and November 2017 and investigated for physico-chemical and biological parameters. Phytoplanktoncompositionandbiomassdeterminationrevealedthatmostofthesamples were dominated by the cyanobacterium Raphidiopsis raciborskii. In a polyphasic approach, seven isolated cyanobacterial strains were classified morphologically and phylogenetically as R. raciborskii, and Microcystis spp. and tested for microcystins (MCs), cylindrospermopsins (CYNs), saxitoxins and anatoxins by enzyme-linked immunosorbent assay (ELISA) and liquid chromatography–mass spectrometry (LC–MS). ELISA and LC–MS analyses confirmed CYNs in three of the five Raphidiopsis strains between 1.8 and 9.8 µg mg−1 fresh weight. Both Microcystis strains produced MCs, one strain 52 congeners and the other strain 20 congeners, including 22 previously unreported variants. Due to the presence of CYN- and MC-producing cyanobacteria, harmful effects on humans, domestic and wild animals cannot be excluded in Meiktila Lake.