Oxidative stress status and antioxidative responses in neonate versus adult Daphnia magna exposed to polystyrene leachate

Abstract

Objective: Plastic pollution, particularly polystyrene, significantly threatens aquatic ecosystems worldwide. Furthermore, plastic leachates have been documented to be detrimental to some aquatic organisms; however, understanding the toxicity mechanism remains limited. This study aimed to investigate the ecotoxicological effects of polystyrene leachate on neonate and adult Daphnia magna, a keystone species in freshwater ecosystems. Methods: The effects of the leachate were studied by employing the novel technique of separating daphnids from the polystyrene microplastic fragments via dialysis tubing, which was prepared 24 and 72 h before organism exposure. Acute toxicity was assessed as effects on organism mobility, oxidative stress (reactive oxygen species), antioxidative enzyme responses (superoxide dismutase and catalase), as well as the effects on the biotransformation enzyme glutathione S-transferase’s activity. Results: Under the experimental conditions, the mobility and oxidative status of the daphnids were unaffected, irrespective of the organisms’ age or leaching time. In adults exposed for 24 h, the antioxidant defense enzyme activities were elevated, contributing to cellular homeostasis maintenance. However, the catalase activity was reduced for neonates and adults exposed to the prolonged pre-leached treatment, thus making them less capable of retaining homeostasis when exposed to toxicant mixtures. Conclusion: This study highlights the vulnerability of D. magna to polystyrene leachate and underscores the need for continued research on the ecotoxicological effects of plastic pollution in aquatic ecosystems. Findings from this investigation contribute to understanding the ecological consequences of plastic pollution, which can inform mitigation strategies and policy decisions to preserve the health and integrity of freshwater ecosystems.