Mechanism of the inhibition and detoxification effects of the interaction between nanoplastics and microalgae Chlorella pyrenoidosa

Most previous studies have focused on the toxicity of microplastics on aquatic organisms. However, research on nanoplastics is still limited and poses significant threat to aquatic organisms than microplastics. Therefore, this study investigated the effects of nanoplastics (80 nm) on the microalgae Chlorella pyrenoidosa. One unanticipated finding was that inhibition and detoxification effects existed in the interaction between nanoplastics and C. pyrenoidosa. Nanoplastics contributed the maximum inhibition rates of 27.73%, 29.64%, and 11.76% on algal growth, chlorophyll a, and Fv/Fm, respectively, which were much higher than those of microplastics. However, the inhibitory effect of nanoplastics gradually decreased with prolonged exposure time after reaching a maximum. The transcriptomic analysis explained that the inhibition effect of nanoplastics was due to the blockage of the gene expression of aminoacyl tRNA synthetase and the synthesis of related enzymes and proteins at low concentrations (10 mg·L). Moreover, it affected DNA damage repair and hindered photosynthesis at high concentrations (50 mg·L). The detoxification phenomenon is attributed to the promotion of cell proliferation, the acceleration of the degradation of damaged proteins and organs, and the regulation of intracellular osmotic pressure in algae. The results of this study provide an understanding of the mechanism underlying the interaction between nanoplastics and microalgae.