Physiological, morphological, and growth effects of microplastics on freshwater alga Chlorella vulgaris

It is doubted that large numbers of microplastics (MPs) are present in aquatic environment and their concentrations are expected to rise in the foreseeable future. Interactions, uptake, excretion rates, and the effects of microplastics on biota remain largely unrevealed. This study investigated how microplastics impact algal growth, physiological response, and the antioxidant system (superoxide dismutase "SOD", peroxidase "POD", catalase "CA" and glutathione reductase "GR" enzymes) using the green freshwater alga Chlorella vulgaris as the test species. MPs significantly (P < 0.05) reduced chlorophyll content, photosynthetic efficiency, photosynthetic rates, and the activities of POD, and GR. Moreover, SOD activity was significantly (P < 0.05) induced in MP-treated algae, indicating that oxidative stress was induced after exposure to MPs. Algal growth decreased with the increase in MPs, which showed that algal growth inhibition was found to be MPs' concentration-dependent. C. vulgaris could be used as a bioindicator or a natural biomarker of contaminations in aquatic environments as it showed a range of physiological responses under MPs' stress.