Stability of cyanotoxins, microcystin-LR, microcystin-RR and nodularin in seawater and BG-11 medium of different salinity

Microcystins and nodularin are potent hepatotoxins produced by fresh and seawater cyanobacteria. The persistence of three hepatotoxins – microcystin-LR, microcystin-RR and nodularin – was investigated in sterile BG-11 medium of different salinity and in water collected from the Gulf of Gdańsk. After 21 days of incubation at 17± 1◦C and constant illumination of about 40 μmol photon m−2 s−1 the concentration of toxins decreased by about 30–37%. No significant changes in toxin concentration in the BG-11 media of different salinity were observed. When toxins were incubated in non-sterile seawater, their concentrations decreased markedly. It is likely that some strains of bacteria are responsible for the breakdown of the toxins. Nodularin turned out to be more resistant to biodegradation than the two microcystins. The influence of certain components of cyanobacteria cells on the accelerated rate of toxin degradation was also considered.