Temperature-Dependent Biochemical Alterations in Oreochromis niloticus exposed to Pendimethalin and Fluometuron

Pesticides contamination and global warming are significant environmental challenges that threaten aquatic ecosystems. Aquatic organisms are often exposed to pesticide mixtures rather than individual compounds, leading to complex toxicological interactions that may enhance adverse effects. Additionally, temperature increase due to climate change can influence pesticide persistence and toxicity. This study aimed to investigate the combined biochemical effects of pendimethalin and fluometuron mixtures under different temperature conditions in the blood of Oreochromis niloticus. Fish were exposed to environmentally relevant low (0.1 ppb) and high concentrations (1 ppb) of herbicide mixtures for 96 hours at 220C and 280C. Results demonstrated significant interactions between pesticide concentration and temperature for all measured parameters. Cortisol level increased at 220C in both pesticide-exposed groups compared to control, while it decreased at 280C. Estradiol and testosterone levels were reduced 280C in both exposure concentrations. Thyroid hormones (triiodothyronine (T3) and thyroxine (T4)) were reduced in the high concentration group at both temperatures. Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) enzyme activities were decreased across both pesticide concentrations at both temperatures, except in the low concentration group at 280C. Ion levels were also reduced in the high pesticide concentration at 280C. Principal component analysis (PCA) confirmed that the most pronounced biochemical alterations were observed in the high concentration group at 280C, reflecting the synergistic effect of both stressors. These findings suggest that elevated temperature exacerbates the toxic effect of pesticide mixtures, emphasizing the need to examine interactive stressors to better predict the impacts of climate change on non-target organisms