Chronic toxicity of biodegradable microplastic (Polylactic acid) to Daphnia magna: A comparison with polyethylene terephthalate

The increase in the usage of biodegradable microplastics (MPs) as an alternative to conventional plastics has necessitated comprehensive ecotoxicity assessments of biodegradable MPs alongside conventional MPs. This study aimed to assess ecotoxicity of biodegradable polylactic acid (PLA) MPs at concentration of 1 and 5 mgL⁻¹ including a genetic analysis of Daphnia magna, and compared to effects of conventional polyethylene terephthalate (PET) MPs. The survival rate for D. magna exposed to 5 mg L⁻¹ of PLA-MPs declined to 52.4 %, signifying a higher rate of mortality when contrasted with PET-MPs, which exhibited 85.7 % survival rate. Chronic exposure to 1 and 5 mgL⁻¹ PLA-MPs resulted in a decrease of offspring, while increasing the sex ratio and deformed embryo. Interestingly, down-regulation of the SOD and AK genes was observed in D. magna after exposure to 5 mgL⁻¹ of PLA-MPs, while 1 mgL⁻¹ of PLA-MPs up-regulated. These results means that 5 mgL⁻¹ PLA-MP could not produce energy and cope with oxidative stress, resulting in high mortality, and 1 mgL⁻¹ of MP was maintained survival due to energy production and antioxidant action. This study contributes to our understanding of biodegradable microplastics (BMPs) toxic effects on D. magna which could be similar to conventional MPs and provide the importance of ecotoxicological data for risk assessment of BMPs in aquatic organisms.