Biomarkers’ Responses in Neotropical Freshwater Fish Living in Southern Brazil: Agricultural Activity or Seasonal Interference?

Brazil has been leading the consumer market for pesticides, mainly due to greater flexibility in registration for agricultural use. The constant application of chemicals increases the likelihood of contaminating adjacent aquatic environments. Furthermore, fluctuations in abiotic variables, especially in subtropical countries, can enhance the effects of pesticides on the aquatic community. The aims of the current study are to investigate the incidence of pesticides in a river in southern Brazil and to evaluate the water quality and toxicity biomarkers on fish species Astyanax jacuhiensis (Cope, 1894), in different crop seasons. Water, sediment, and fish samples were collected in the summer, autumn, and winter of 2019. The herbicides atrazine and clomazone and insecticide imidacloprid were identified in water throughout the sampling period—only atrazine has the maximum concentration established for surface water by Brazilian legislation. Redundancy analysis (RDA) mainly showed the effects of seasonality on biochemical responses such as pH and water temperature. Also, most A. jacuhiensis biomarkers alterations were associated with winter and autumn periods. Furthermore, it was possible to verify the relationship between non-enzymatic antioxidants (non-protein thiols) and oxidative damage (lipid peroxidation and protein carbonylation). Therefore, the results of pesticides detected in water emphasize the need to update Brazilian legislation for compounds registered in the country. Changes in the physicochemical variables of water can influence the responses of biomarkers in addition to pesticides. Finally, biomonitoring studies are important and necessary mainly in subtropical regions where there is variation in climatic conditions between periods of the year.