Toxic Effects of Polyethylene and Polyvinyl Chloride Microplastics on Daphnia Magna and the Mechanisms Involved

Abstract

Microplastics (MPs) have been detected in aquatic environments around the world, and concern about these environmental pollutants is increasing. MPs are small, and some MPs can readily pass through cell membranes and accumulate in the tissues of exposed organisms, where they can cause physiological, metabolic, and growth disorders, decrease reproductive fitness, and even cause early mortality. The scientific community and the general public are concerned about the toxic effects of MPs in aquatic organisms. This study was focused on polyethylene (PE) and polyvinyl chloride (PVC) MPs. Daphnia magna , a primary consumer in aquatic environments, was used as a model organism. The toxic effects of PE and PVC MPs on D. magna growth, reproduction, and antioxidant defense responses were assessed, and the mechanisms involved were identified. The LC 50-96H values for PE and PVC MPs with a diameter of 5 μm on D. magna were 199.99 mg . L -1 and 48.19 mg·L -1 , respectively. D. magna growth and reproduction were strongly affected by 21 d exposure to PE and PVC MPs, and the intestines became swollen, blocked, and darkened. The shapes ofeggs were altered and the number of eggs decreased. Catalase activity in D. magna increased as the PE and PVC MPs concentration increased, but the reduced glutathione content did not change significantly. Metabonomic analysis indicated that the main metabolic pathways affected by PE were amino acid biosynthesis and metabolism. Lipid and pyrimidine metabolism were the main metabolic pathways involved in metabolite changes in D.magna exposed to PVC MPs. MPs ingested by D. magna may affect growth, reproduction, and population changes by affecting physiological reactions such as material and energy metabolism and antioxidant defenses.

Keywords: microplastics, daphnia magna, toxic effect, metabonomics, mechanism