Species-specific susceptibility of green algae Raphidocelis subcapitata and Chlorella vulgaris to the exposure of microplastic leachates.

Microplastics are ubiquitous in aquatic environments, and their additives can leach into surrounding water. This study investigated the toxic effects of polyvinyl chloride (PVC) and polyisocyanurate (PIR) leachates on two freshwater microalgae, Chlorella vulgaris and Raphidocelis subcapitata, at concentrations corresponding to 1, 2, 5 and 15 g/L PVC or PIR for 14 days. A growth inhibition was observed in R. subcapitata exposed to the PVC leachate, while the 72 and 96 h EC50 values were estimated at 7.2 g/L. No growth inhibition was observed among the other tests. The effects of the leachates on chlorophyll a, b, total chlorophyll and carotenoids levels, as well as the chlorophyll a/b and carotenoids/total chlorophyll ratio were determined. In both algae exposed to the PVC leachate, photopigments exhibited patterns of stress response. Furthermore, activities of antioxidant enzymes (catalase, superoxide dismutase, glutathione S-transferase, glutathione reductase) and lipid peroxidation as response to oxidative stress were significantly affected in algae exposed to both PVC and PIR leachates. Based on the integrated biomarker response of photosynthesis (IBRv2photo), C. vulgaris exhibited a higher sensitivity of the photopigments to both leachates compared to R. subcapitata. However, the integrated biomarker response to oxidative stress (IBRv2bio) indicated a similar general oxidative and enzymatic stress response in both species exposed to the leachates. In conclusion, these results broaden our understanding of species-specific responses to microplastic leachates and their potential implications for species composition in aquatic environments.