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Microplastics: A Small but Not Negligible for Health of the Ecosystem

Professor Mei Li, School of the Environment, SKLPCRR

Plastics products are becoming widely used in agriculture, animal husbandry, industry and daily life. They have replaced glass, wood and other materials with its advantages of lightness, convenience and low cost. However, plastics can fragment leading to the formation of small plastics particles, known as microplastics (MPs), which has become a serious threat to the environment and ecosystem health. Therefore, to explore the potential toxicity of microplastics on model organisms, our research interests center around the behavior, transformation, and effects of microplastics in the ecosystem, with a view to improve ecological risk assessment of microplastics.

Firstly, we focused on the effects of polystyrene microplastics (PS-MPs) on E. gracilis, a freshwater microalgae. Our findings showed that PS-MPs do have adverse effects on microalgae, inhibiting growth, reducing pigment contents and increasing activities of antioxidant enzymes, inducing vacuoles increasing, chloroplast deformation and algae homo-aggregation. Secondly, laser confocal scanning microscopy observations confirmed that nano- PS-MPs entered V. faba roots and probably blocked cell connections or cell wall pores and disrupted the nutrients transport causing the observed toxic effects. These findings indicated that PS-MPs can be toxic to V. faba, what should be considered in future ecological risk assessment of interaction between microplastics and higher plants. Finally, to bridge the knowledge gaps between MPs and soil organisms, studies focusing on the effect of MPs on terrestrial ecosystems and on soil organisms, especially in earthworms, are important. Data on uptake or accumulation of PS-MPs in earthworm intestines, histopathological changes, oxidative stress, and DNA damage demonstrated that the toxicological effects of low concentrations of PS-MPs (≤ 1 mg/kg of soil) on earthworms (Eisenia fetida) were also occurred. These findings provide new insights regarding the toxicological effects of low concentrations of microplastics on earthworms and on the ecological risks of microplastics to soil animals.