Subchronic exposure to pristine and aged microplastics causes no impairment of survival or growth in a marine mysid (Americamysis bahia)

There are increasing concerns that µicroplastics (MPs) will be ingested by marine organisms that feed on small prey, such as plankton. In this study, we examined the biological effects (survival and growth) of exposure to pristine polyethylene MP and aged MP (aMP; length ≤ 53 µm) prepared by maintaining the MP under laboratory conditions at 20°C for 28 days to create biofouling that closely resembles that found in the natural environment. To determine the type of biofilm formed during the aging process, microbial community analysis of aMP was conducted. Rhodobacteraceae and Flavobacteriaceae were detected from the aMP, and these same bacterial members were associated with MP collected from actual marine environments, suggesting that we successfully produced aMP under conditions that simulated those in the field. We then evaluated the subchronic toxicity (7 d) of MP by using marine mysid ( Americamysis bahia ) larvae. After 10 mg/L pristine and aMP exposure, no significant differences in survival rate or body weight were observed between the solvent control group and MP exposure groups ( p  > 0.05), though aMP exposure slightly increased total length ( p  = 0.02). Overall, no remarkable adverse effects on marine mysid larvae were observed after pristine MP and aMP exposure at the tested sizes, materials, and concentrations. This suggests that the biological impact of aMP on marine planktonic crustaceans will be minimal at current levels of MP contamination, and that the small impact will make detection difficult in subchronic toxicity tests.