Anthropogenic actions alter the aquatic environment quality: biomonitoring study of a river in Southern Brazil

The aim of the current study is to investigate urban region’s influence on the incidence of pesticides, and on physical, chemical and microbiological variables in the Potiribu River, in order to analyze their association with biochemical biomarkers in the Neotropical fish Astyanax spp. Water, sediment and fish samples were collected in both an upstream (S1) and downstream (S2) located in a city in Southern Brazil, at three different periods of the year (summer, autumn, and winter). Four pesticide active ingredients were detected in the Potiribu River: one fungicide, two herbicides and one insecticide (two of them recorded higher concentration in S2). Based on redundancy analyses results, pH, electrical conductivity, oxidation/reduction potential, turbidity and temperature were the water quality variables mostly contributing to biomarker responses in Astyanax spp. Pearson’s correlation analysis has shown that pesticides have both positive and negative correlation to biomarkers. In addition, physicochemical variables have overall shown positive correlation to lipid peroxidation and non-protein thiols levels, mainly in fish liver; as well as negative correlation to protein carbonylation levels in fish brain, gill, liver and muscle tissues. These results demonstrate the importance of evaluating physicochemical variables together with biomarkers, since the correlation of these variables demonstrated that fish already have damage in their tissues (lipid peroxidation and protein carbonylation) and that can compromise the fitness of the species in the long term. Water quality results indicated that Potiribu River is contaminated by agricultural and urban sources. Finally, both the water physicochemical variables and the pesticides are related to the biomarker responses in Astyanax spp.