Microcystis aeruginosa bloom and the occurrence of microcystins (heptapeptides hepatotoxins) from an aquaculture pond in Gazipur, Bangladesh

Bangladesh is a tropical country of large alluvial plain with 1.3 million freshwater ponds and lakes and has a proper environment for luxuriant growth of cyanobacteria. Algal bloom of Microcystis aeruginosa occurred in an aquaculture pond in Gazipur, Dhaka. Bloom sample was collected and filtered through a glass fiber filter. Methanol-water extract of filtered cells was analyzed by high performance liquid chromatography (HPLC) with UV, MS and MS-MS detection, detected three types of microcystins viz., Microcystinn-RR, Microcystin-YR and Microcystin-LR and those were confirmed by HPLC-MS. The amount of MC-LR was the highest (33.2 mu g L-1) followed by MC-RR (9.03 mu g L-1) and MC-YR (5.23 mu g L-1). The concentration of microcystins was well above the WHO provisional guideline value of 1 mu g L-1 MC-LR. Further investigations need to characterize other types of microcystins froth bloom forming cyanobacteria and their effect on human health and cultured fish in Bangladesh.