Toxic Cyanobacteria in Four Brazilian Water Supply Reservoirs

Abstract

Cyanobacterial blooms have become a worldwide concern due to the production of toxins harmful to humans and animals. In Brazil and worldwide, microcystins are the most frequently found cyanotoxin in water bodies. Four important reservoirs in Brazil's Southeast and Northeast regions were sampled to identify the cyanobacteria community and the occurrence of potential toxin-producing species in the country's public supply reservoirs. A total of 14 taxa were identified, 11 of which are known as potential toxin producers. Potentially toxic cyanobacteria were recorded at concentrations above 20,000 cells·mL -1 in all samples from all four reservoirs, thus requiring microcystin monitoring in drinking water according to Brazilian legislation. Although the sample from Mundaú reservoir showed the highest concentration of microcystins in water, it had one of the lowest values of cells·mL -1 , which demonstrates the non-correspondence between these two parameters. This calls into question the existence of a minimum level of potentially toxic cyanobacteria cells to merit the monitoring of microcystins in the treated water from these sources.

Occurrence of Harmful Cyanobacteria in Drinking Water from a Severely Drought-Impacted Semi-arid Region

“…Araçagi had the highest toxin concentration (0.5 ± 0.2 μg l -1 microcystins/nodularins and 0.08 μg l -1 for cylindrospermopsin). Toxin levels were similar to those obtained in previous studies conducted in Rio Grande do Norte ( Fonseca et al, 2015 ), and in Pernambuco ( Piccin-Santos and Bittencourt-Oliveira, 2012 ). These levels were below the threshold for human consumption (<1 μg l -1 ), proposed by the World Health Organization ( Chorus and Bartram, 1999 ), and followed by the Brazilian Ministry of Health (Ordinance 2914/2011) ( Brazil Ministry of Health/Ministério da Saúde, 2011 ).…”

Detection of Cyanotoxin-Producing Genes in a Eutrophic Reservoir (Billings Reservoir, São Paulo, Brazil)

“…Billings Reservoir, the largest water resource of São Paulo Metropolitan Region (RMSP) in Brazil, has been monitored for the presence of cyanobacteria and cyanotoxins [36][37][38][39][40][41] by CETESB (Companhia Ambiental do Estado de São Paulo), an agency of the state government of São Paulo responsible for control, supervision, monitoring and licensing of pollution-generating activities. In the last available monitoring report [42], cyanobacteria were dominant in all points on the reservoir, with concomitant presence of microcystin.…”

Ecological and toxicological responses in a multistressor scenario: Are monitoring programs showing the stressors or just showing stress? A case study in Brazil

“…Due to eutrophy, cyanobacterial blooms are common in South America reservoirs and are becoming a problem in many countries in the world (Dörr et al, 2010;Sukenik et al, 2012). Cyanobacterial blooms constitute a potential risk to human and environmental health (Soares et al, 2013;Piccin-Santos and Bittencourt-Oliveira, 2012;Moschini-Carlos et al, 2009). However, despite the high number of noncompliances, and the relationships observed in other studies between cyanobacterial blooms and toxic responses (Chorus, 2001;Sotero-Santos et al, 2006), this variable did not show any explicative value in the chemometric analysis for responses on C. dubia.…”

“…Although not all species produce cyanotoxins and cause the risk of toxic effects, generally freshwater blooms of cyanobacteria produce toxic secondary metabolites (Chorus, 2001). Toxic cyanobacteria, and their respective cyanotoxins, have been detected in São Paulo State, and toxic effects in freshwater organisms have been described (Sotero-Santos et al, 2006;Moschini-Carlos et al, 2009;Piccin-Santos and Bittencourt-Oliveira, 2012).…”