Impact of micro- and nano-plastics on marine organisms under environmentally relevant conditions

Micro- and nano-plastics (MNPs) pollution is a major issue of global concern, and the impacts of MNPs to marine organisms under environmentally relevant conditions were reviewed. Occurrence and distribution of both microplastics (MPs) and nanoplastics (NPs) in different marine environments were summarized based on current literature, showing that the maximal concentrations were 24.29 particles/L (Sanggou Bay) and 0.067 mg/L (polyethylene (PE), polyethylene terephthalate (PET), polystyrene (PS) in Antarctica sea ice), respectively. Impact of MNPs to different species of marine organisms (microalgae, crustaceans, gastropods and fish) at environmental concentrations were discussed. For microalgae, MPs at environmental concentrations (≤ 2 mg/L) showed two different short-term performances: no significant effect (52%) or significant inhibition (48%) on growth, while the long-term MPs stress could be alleviated through microalgae adaptation. Notably, the promotion of microalgae growth was observed after both short-term and long-term exposures of NPs. For high-trophic organisms (crustaceans, gastropods and fish), MNPs could induce physiological damage, and even cause reproductive toxicity. Environmental factors (e.g., dissolved organic matter, salinity and temperature) could alter the bioavailability and toxicity of MNPs, which were systematically introduced. Additionally, the impact of MNPs on the composition and diversity of marine communities were emphasized. Knowledge gaps were finally pointed out for better understanding the impact of MNPs under environmentally relevant conditions. This review provides useful information on the impact and risk of MNPs to marine organisms and the entire ecosystem.