Prediction of Cyanotoxin Episodes in Freshwater: A Case Study on Microcystin and Saxitoxin in the Lobo Reservoir, São Paulo State, Brazil

Freshwater reservoirs constitute an important source of drinking water, but eutrophication and higher temperatures increase the risk more frequent blooms cyanobacteria, including species that produce toxins. To improve prediction cyanotoxin episodes, we studied annual occurrence potential microcystin (MC) saxitoxin (STX)-producing cyanobacteria in Lobo reservoir, São Paulo State, Brazil. Relationships among environmental variables, cyanobacterial biomass, numbers mcyE sxtA genotypes (genes encoding production MC STX, respectively), concentrations STX were determined to address variables applicable for monitoring predicting dynamics cyanotoxins reservoir. Microscopy confirmed presence potentially toxin-producing at all sampling times, qPCR detection showed both most samples. Concentrations generally low (MC 0–1.54 µg L−1; 0.03–0.21 L−1). The highest level exceeded recommended limit human intake 1 L−1. abundance genes, as well toxin concentrations, positively correlated with biomass Phormidium Raphidiopsis. Among toxic was mainly affected by P limitation (high TN:TP ratios). Our data show serves a useful reliable predictor episodes might be combined chemical form toolbox monitoring.