Soil algae as a potential carrier for nanoplastics: Adsorption and internalization of nanoplastics in algal cells

Although plastics are widely distributed in soil environments, few studies have assessed their effects on different test species. In this study, the responses (adsorption or internalization) of two green algal species (Chlorococcum infusionum and Chlamydomonas reinhardtii) to nanoplastics in soil were evaluated via microscopic analysis for nine weeks; additionally, the effects of polystyrene (PS) nanoplastics on their photosynthetic activity and growth were assessed. The results showed that PS nanoplastics and C. infusionum or C. reinhardtii cells were aggregated with the formation of palmelloid colonies; additionally, internalization of PS nanoplastics to C. reinhardtii cells was verified. However, no significant effects of PS nanoplastics on photosynthetic activity and growth of soil algae were observed. Algae were more likely to be threatened by plastic aggregation in the soil environment than in the aquatic environment due to the formation of a mucilaginous sheath on their cell. Our results highlighted that soil algae are a potential carrier of nanoplastics to other organisms in the food chain due to plastic aggregation through adsorption or internalization. This study will enhance our understanding of nanoplastic distribution in soil algae.