Microplastics reduce trace metal bioavailability in Thalassiosira weissflogii by impairing physiological functions

Microplastics (MPs) have been recognized globally as a new environmental pollutant and can be transported in water environments all over the world. Diatoms contribute about 20% of marine primary productivity and play an important role in global carbon sequestration, climate regulation, and the biogeochemical cycling of biogenic elements. Understanding the impact of MPs on the primary biomass productivity of phytoplankton is crucial for assessing ecosystem resilience and maintaining essential ecosystem services. Here the relationships between phytoplankton physiological indicators and trace metal uptake were investigated to delineate how polystyrene microplastics (PS-MPs) affect the primary biomass productivity and alter the dynamics of trace metal sinks in marine ecosystems. We innovatively proposed that the influence of MPs on phytoplankton was not only shading effects on algae and causing oxidative damage, but also limiting the accumulation of trace metals in algae. The accumulation of Mn, Fe and Ni in algae is positively correlated with the content of chlorophyll a (Mn: r = 0.824; Fe: r = 0.697; Ni: r = 0.822), photosynthetic activity (Mn: r = 0.631; Fe: r = 0.467; Ni: r = 0.816) and β-carotene (Mn: r = 0.773; Fe: r = 0.307; Ni: r = 0.786), but negatively correlated with superoxide dismutase activity (Mn: r = −0.714; Fe: r = −0.730; Ni: r = −0.908). This provides a new perspective to reveal the influence mechanisms of MPs on primary biomass and trace metal sinks.