Quantification of potentially toxic cyanobacteria and microcystins in the Dau Tieng Reservoir, Vietnam

The present study examined the spatial and temporal variations in cyanobacterial and microcystin (MC) concentrations in the Dau Tieng Reservoir (DTR), Vietnam, using quantitative real-time polymerase chain reaction (Q-PCR) and high-performance liquid chromatography (HPLC). The results of Q-PCR showed Microcystis spp. to be the dominant group and the primary MC producer in DTR. The mean proportion of potentially toxic Microcystis accounted for 3.7%-91.2 % of the total toxic cyanobacterial concentration and 12.5 %-98.3 % of the total Microcystis concentration. MC concentrations in raw water ranged from 1.49 to 7.48 mu g L-1 and often peaked during April to July. Pearson correlation analysis revealed that the water temperature and nutrient showed a significant positive correlation with cyanobacterial concentration, potentially toxic Microcystis genotypes, and MC concentrations, suggesting that favoring cyanobacterial proliferation allowed the growth of a higher number of cells belonging to toxic genotypes and the accumulation of higher concentrations of MC. The concentrations of potentially toxic cyanobacteria and toxic Microcystis showed a positive correlation with MC concentrations. Our findings reconfirmed Q-PCR and HPLC to be reliable tools for monitoring toxic cyanobacteria in drinking water supplies.