de Oliveira_2025_Environ.Res__123028

This study evaluated the effects of contaminants, particularly metals and pesticides, in three rivers in Southern Brazil - Sao Camilo, Santa Fe, and Pioneiro - using the catfish Hypostomus ancistroides as a bioindicator. Biomarkers of oxidative stress, neurotoxicity, and genotoxicity were employed and integrated into an Integrated Biomarker Response (IBR) index, spatial analysis conducted using Geographic Information Systems (GIS). Sampling occurred during two seasons, winter (2022) and summer (2023), with sediments and fish collected from three sites per river. Detected concentrations of metals, including Cu, Zn, K, and Mn, were below Brazilian regulatory thresholds. Biomarker responses revealed significant biological effects associated with oxidative stress, particularly at intermediate and downstream sites. These included acetylcholinesterase inhibition, increased activity of superoxide dismutase (SOD) and catalase (CAT), elevated levels of metallothionein's (MET) and lipid peroxidation (LPO), indicating neurotoxicity and oxidative damage. Site SF2 (Santa Fe River) exhibited the greatest impact, likely due to the urban and industrial influences. Nuclear morphological alterations revealed localized genotoxic effects. Despite the low contaminant levels, the results highlight notable sublethal effects on fish health and ecological integrity. The integration of biomarkers proved effective in identifying critical areas and informing environmental management strategies.