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

Author(s)

Moraes, Munique A. B. ^[1] ; Rodrigues, Raphaella A. M. ^[1] ; Schluter, Louise ^[2] ; Podduturi, Raju ^[3] ; Jorgensen, Niels O. G. ^[3] ; Calijuri, Maria C. ^[1]

Affiliation

^[1] Univ Sao Paulo, Sao Carlos Sch Engn, Dept Hydraul & Sanitat, 400 Trabalhador Sao Carlense Ave, BR-13566590 Sao Carlos - Brazil

^[2] DHI, Environm & Toxicol, Agern Alle 5, DK-2970 Horsholm - Denmark

^[3] Univ Copenhagen, Dept Plant & Environm Sci, Thorvaldsensvej 40, DK-1871 Frederiksberg - Denmark

• Document type: Journal article
• Source: WATER; v. 13, n. 12 JUN 2021.
• Web of Science Citations: 0

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 x 10(3) to 7.33 x 10(5) 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. (AU)

• FAPESP's process: 15/21191-4 - Spatio-temporal variability of cyanobacteria in Lobo Reservoir (Itirapina, SP): community composition, molecular and toxins analysis
• Grantee: Munique de Almeida Bispo Moraes
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 16/09405-1 - Spatio-temporal heterogeneity of the microbial community in subtropical reservoirs with different trophic status
• Grantee: Maria do Carmo Calijuri
• Support Opportunities: Regular Research Grants
• FAPESP's process: 18/00394-2 - Monitoring of cyanobacteria and cyanotoxins in two subtropical reservoirs by real-time quantitative PCR
• Grantee: Munique de Almeida Bispo Moraes
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate