Abstract

Chemical pollution poses a significant threat to freshwater ecosystems, yet sublethal biomarkers are often underestimated in risk assessments. 2,4-dichlorophenol (2,4-DCP) is a pollutant commonly detected in aquatic environments as a byproduct of industrial processes, herbicides and biocides. This study evaluated the effects of 2,4-DCP on native fish Galaxias maculatus using behavioral and exposure biomarkers. Fish were exposed to environmentally relevant concentrations (5 and 100 µg/L) of 2,4-DCP. Ethoxyresorufin-O-deethylase (EROD) and acetylcholinesterase (AChE) activities were assessed alongside swimming performance, schooling cohesion, exploration, and foraging. Exposure to 2,4-DCP induced neurotoxicity, evidenced by AChE inhibition, and activated detoxification pathways, indicated by increased EROD activity. These responses were associated with reduced swimming performance, exploration, and complete suppression of schooling cohesion at the highest concentration. The Integrated Biomarker Response index indicated elevated stress levels at both concentrations, suggesting a saturated response. The results highlight the sensitivity of sublethal biomarkers and support their inclusion in environmental risk assessments and aquatic biodiversity protection.