Influence of Environmental Factors on Occurrence of Cyanobacteria and Abundance of Saxitoxin-Producing Cyanobacteria in a Subtropical Drinking Water Reservoir in Brazil

Blooms of cyanobacteria are frequent in Brazilian water reservoirs used for drinking water. The warning the presence potential toxin-producing is typically based on time-consuming microscopy, rather than specific molecular detection toxic genes cyanobacteria. In this study, we developed a quantitative PCR assay producing neurotoxin saxitoxin (STX). targets sxtA gene sxt cluster. Potential and dominant STX-producers Itupararanga reservoir were genera Raphidiopsis, Aphanizomenon Geitlerinema. Numbers varied from 6.76 × 103 to 7.33 105 cells mL−1 correlated positively with SXT concentrations Concentrations STX also TN:TP ratio pH, but negatively inorganic nutrients turbidity, confirming that regulation production was impacted by environmental variables. contrast, occurrence another cyanotoxin, microcystin, did not correlate any qPCR found be rapid robust approach quantification STX-producing should considered future investigations provide an early toxin episodes.