Combined effects of environmentally relevant glyphosate concentration and elevated temperature on zebrafish...

Climate change and chemical pollution are two major environmental stressors threatening aquatic ecosystems. Among pesticides, glyphosate is the most widely used herbicide worldwide and frequently detected in water bodies at environmentally relevant concentrations. This study investigated the combined effects of elevated temperature and glyphosate exposure on the embryonic development of Danio rerio. Embryos were exposed for 96 h to 0 or 65 μg/L of glyphosate at 28 °C, 30 °C, or 32 °C, simulating projected global warming scenarios for 2100. Developmental, cardiac, behavioral, and molecular endpoints were evaluated. Results showed that temperature increase and exposure to glyphosate synergistically reduced embryo survival and altered hatching rates. The combined stressors also potentiated cardiac hypofunction. Behavioral analyses revealed consistent impairments in optomotor and avoidance responses under higher temperatures and glyphosate exposure, in a synergistic way, as also observed for gene expression of oxidative stress markers (cat, sod1, sod2, gpx1a) that were downregulated in all glyphosate-temperature exposed groups, suggesting redox imbalance. Overall, the findings demonstrate that elevated temperature can affect glyphosate toxicity, highlighting the importance of considering multiple stressors and their interactions when assessing ecological risks under climate change scenarios.