Abstract: This study focuses on the effects of engineered nanomaterials (ENMs) on marine ecosystems, specifically examining the impact of common and elemental ENMs with beneficial properties on primary marine producers, such as green microalgae cells. Dunaliella salina was selected as the experimental organism to investigate the influences of polystyrene nanoplastics (PS NPs) and elemental silicon nanoparticles (Si NPs) . The ENMs were introduced to the algal cultures during their logarithmic growth phase. Initially, both materials promoted cell growth, with intracellular photosynthetic pigment content increasing by 1.6% to 13.3% and betaine content rising by 2.7% to 45.23%. However, in the later stages of exposure, algal cells exhibited increased antioxidant enzyme activity, leading to oxidative stress responses and morphological fragmentation observed under transmission electron microscopy (TEM) . In the transcriptome analysis, the upregulation of photosynthesis-related genes further demonstrated the enhancement of cellular photosynthetic capacity. In this study, while ENMs can initially enhance cell growth and improve photosynthetic performance, changes in the cellular environment can trigger oxidative stress responses that may ultimately harm the cells. These findings hold significant implications for the effective application of ENMs in marine algal cell research.