Water quality monitoring of the Sinos River Basin, Southern Brazil, using physicochemical and microbiological analysis and biomarkers in laboratory-exposed fish

Abstract

The aim of this study was to monitor the water quality of three rivers of the Sinos River Basin (SRB), southern Brazil. Five sites were selected to evaluate physicochemical and microbiological parameters and genotoxic and histopathological effects in the fish species Astyanax jacuhiensis. Eight water samples were collected from March 2012 to May 2013 at sites located in the upper, middle and lower sections of the SRB. After collection, 35 water quality parameters were analyzed and fish were exposed to water samples under laboratory conditions. Five-day biochemical oxygen demand (BOD5), thermotolerant coliforms, ammoniacal nitrogen, dissolved oxygen, aluminum, iron and manganese values exceeded the permissible limits in some samples of the three sections and the cluster analysis showed three distinct groups composed by sites located in the same section of SRB. The micronuclei (MN) and other nuclear abnormalities (NA) frequencies did not differ from the control group in any sample. Higher frequencies of lamellae with alterations, such as hypertrophy and hyperplasia of epithelial cells, epithelial lifting, aneurysm, edema and necrosis were observed in fish exposed to some water samples of the five sites. The most frequent histopathological alteration was hypertrophy of epithelial cells. Therefore, in this study, the analysis of gill histopathological alterations showed higher sensitivity than the MN test under the conditions studied. The physicochemical and microbiological parameters and histopathological analysis indicate deterioration of water quality at sites located in the three sections of the Sinos River Basin.