water Article Influence of Environmental Factors on Occurrence of Cyanobacteria and Abundance of Saxitoxin-Producing Cyanobacteria in a Subtropical Drinking Water Reservoir in Brazil Munique A. B. Moraes 1 , Raphaella A. M. Rodrigues 1 , Louise Schlüter 2, Raju Podduturi 3, Niels O. G. Jørgensen 3,* and Maria C. Calijuri 1 1 Department of Hydraulics and Sanitation, São Carlos School of Engineering, University of São Paulo, 400 Trabalhador São Carlense Avenue, São Carlos 13566-590, Brazil;
[email protected] (M.A.B.M.);
[email protected] (R.A.M.R.);
[email protected] (M.C.C.) 2 Environment and Toxicology, DHI, Agern Alle 5, 2970 Hørsholm, Denmark;
[email protected] 3 Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871 Frederiksberg, Denmark;
[email protected] * Correspondence:
[email protected] Abstract: Blooms of cyanobacteria are frequent in Brazilian water reservoirs used for drinking water. The warning for the presence of potential toxin-producing cyanobacteria is typically based on time- consuming microscopy, rather than specific molecular detection of toxic genes in cyanobacteria. In Citation: Moraes, M.A.B.; Rodrigues, this study, we developed a quantitative PCR assay for the detection of cyanobacteria producing the R.A.M.; Schlüter, L.; Podduturi, R.; neurotoxin saxitoxin (STX). The assay targets the sxtA gene in the sxt gene cluster. Potential and Jørgensen, N.O.G.; Calijuri, M.C. dominant STX-producers in the Itupararanga reservoir were the genera Raphidiopsis, Aphanizomenon Influence of Environmental Factors and Geitlerinema. Numbers of the sxtA gene varied from 6.76 × 103 to 7.33 × 105 cells mL−1 and on Occurrence of Cyanobacteria and correlated positively with SXT concentrations in the water.