Elevated temperature alleviates benzophenone-3 toxicity in Daphnia magna

Water temperature rises due to thermal discharge and global warming and the potential resulting impacts on the ecotoxicity of emerging chemicals are a growing concern. Benzophenone-3 (BP-3) is an ultraviolet filter added to personal care and plastic products, which is detected at highest concentrations during the hot summer season. This study aimed to investigate the effect of elevated temperature on acute (48 h) and chronic (21 d) BP-3 toxicity in Daphnia magna. Neonates (<24 h) acclimated at 28 °C showed much lower acute toxicity (EC₅₀ = 3.91 and 2.69 mg L⁻¹ at 20 and 28 °C, respectively) than those acclimated at 20 °C (EC₅₀ = 2.96 and 2.04 mg L⁻¹ at 20 and 28 °C, respectively). The body length, embryonic development, and the number of offspring in D. magna offspring exposed to BP-3 for 21 d were significantly decreased after exposure to 0.8 mg L⁻¹ BP-3 at 20 °C. However, these adverse effects of BP-3 in D. magna were significantly ameliorated at 28 °C. Under these conditions, stress response genes such as Hb (hemoglobin), Hsp70 (heat shock protein), Cyp4 (cytochrome P450), and GST (glutathione-S-transferase) were significantly upregulated. These findings suggest that elevated temperature activated stress responses in D. magna, leading to enhanced protection against BP-3 toxicity. This study will contribute to a better understanding of the ecotoxicological impacts of toxic chemicals on aquatic organisms at elevated temperature.