Role of uniform 1 μm polystyrene microplastics in inducing oxidative damage and transcriptome alterations in Tetradesmus obliquus

The increasing prevalence of microplastics (MPs) in the aquatic environment poses a significant threat to aquatic organisms. However, research on their specific toxicological mechanisms remains limited. This study investigated the growth inhibition toxicity of 1 μm-sized polystyrene microplastics (PSMPs) at environmentally relevant concentrations (1.33 × 10 4 , 7.67 × 10 4 , 4.87 × 10 5 , and 2.78 × 10 6 particles/mL) to the microalga Tetradesmus obliquus and explored the physiological and transcriptional responses induced by PSMPs in the algae. Exposure to PSMPs did not significantly inhibit algal growth across all the concentrations. PSMPs at the highest concentration induced intracellular oxidative stress, leading to a statistically significant increase in reactive oxygen species levels, as well as elevated levels of superoxide dismutase and malondialdehyde. The decrease in mitochondrial membrane potential may serve as a signal for cell apoptosis triggered by oxidative damage caused by PSMPs. Exposure to PSMPs significantly altered the gene expression profile of T. obliquus , affecting biological processes such as cell differentiation, membrane integrity, material transport and ion regulation. Furthermore, PSMPs disrupted the sphingolipid metabolism pathway in T. obliquus , causing abnormal expression of key synthetic and degradative enzymes, which affected the structure and function of cellular membrane. Overall, these findings demonstrated that PSMPs not only induced oxidative stress responses in T. obliquus but also exerted adverse effects on the algae by disrupting their metabolic pathways and gene expression. This study provides novel molecular insights and ecological evidence regarding the impacts of MPs on aquatic organisms.