Effects of Polystyrene Microparticles on Growth and Physiological Metabolism of Microalgae Scendesmus obliquus

Plastic products are widely used due to their lightness, durability, low cost, and malleability, and their threat to the environment is becoming increasingly apparent. However, the detailed mechanism of such an effect is unclear. Due to improper treatment, microplastic contamination is very much studied in the areas around sewage outfalls or some plastic manufacturers, and its content is high. To investigate the ecological impact of microplastics in this particular area, we evaluated the toxic effect of polystyrene microplastics (PS-MPs) on the microalgae Scenedesmus obliquus (S. obliquus). In particular, the cell growth, photosynthesis, antioxidant enzyme activity, membrane permeability, and morphology of the microalgae in the presence of different PS-MP concentrations were monitored. These new data revealed an increase in microalgae cell growth as an early response to low-dose PS-MP exposure with a maximum inhabitation rate of -3.33%. In contrast, a higher concentration of PS-MP solution leads to a significant inhibition within the test concentration, with a maximum inhabitation rate of 43.62%. Meanwhile, a decreased photosynthesis activity of S. obliquus was observed during the exposure. Moreover, PS-MPs induced oxidative damage to the algae cells, exhibiting decreased antioxidant activities and enhanced lipid peroxidation reactions, as evidenced by the reduction in the superoxide dismutase (SOD) level and increased malondialdehyde (MDA) content, as well as damaged cell membrane and soluble protein. Collectively, our study systematically investigates the toxicity of microplastics on microalgae, providing a deep insight into the possible influences of plastic pollution on the whole food web in the aquatic ecosystem.