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

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

Research Characteristics on Cyanotoxins in Inland Water: Insights from Bibliometrics

“…In Brazil, cyanobacteria blooms frequently occur in drinking water reservoirs. Brazilian researchers have developed a quantitative Polymerase Chain Reaction (PCR) method to provide early warning of possible cyanotoxin contamination of water bodies [46]. China, the United States, Germany, Canada, and Australia were the five countries with the largest numbers of published articles.…”

Estudo de cenários baseados em projeções de mudanças climáticas e de uso do solo para o reservatório de Itupararanga (SP): >i<open acess tools>/i< no gerenciamento da qualidade das águas

“…A comunidade fitoplanctônica tem sido dominada por cianobactérias, em particular a espécie Raphidiopsis raciborskii, que tem provado ser tóxica no reservatório dos Santos Machado et al, 2021;Moraes et al, 2021) e pode causar impacto nas comunidades aquáticas e cadeias alimentares ou até mesmo no abastecimento de água potável à população no futuro.…”