Chronic in-situ exposure to pesticide-contaminated water bodies impairs the metabolism, growth, and performance of the freshwater fish Prochilodus lineatus

Abstract

Anthropogenic contamination of freshwater ecosystems by complex pesticide mixtures is a growing concern, particularly in agricultural regions such as Southern Brazil. This study evaluated biomarker responses in juvenile Prochilodus lineatus under chronic in situ exposure to water bodies impacted by agricultural runoff. Fish were caged for 120 days at two sites with contrasting contamination levels and sampled at six time points (5, 15, 30, 60, 90, and 120 days). The reference site (RFS) had minimal anthropogenic influence, while the agricultural site (AGS), located in an area of intensive farming, presented elevated levels of pesticides and metals. A multidisciplinary approach was used to assess hematological, metabolic, neurotoxic, and histopathological biomarkers, along with ecologically relevant endpoints including somatic growth, Fulton's condition factor, hepatosomatic index, and swimming endurance. Principal Component Analysis revealed site- and time-dependent physiological responses. Energy metabolism markers—liver and muscle glycogen, plasma glucose, and hepatosomatic index—were key in differentiating site effects. The Integrated Biomarker Response (IBR) index was consistently higher in fish at the AGS site, with peaks at 15, 30, 90, and 120 days, suggesting sustained physiological stress. In contrast, fish at the RFS site exhibited a moderate IBR increase at 30 and 60 days, followed by recovery. Findings indicate that chronic exposure to agricultural contaminants induces adaptive and compensatory responses that elevate energy demands to maintain homeostasis. This energetic trade-off may impair growth and overall organic fitness, potentially affecting population dynamics of the fish in impacted freshwater environments.