Combined effect of microplastics and copper complex on phytoplankton photosynthetic carbon sequestration: Intelligent sensing and multi-perspective analysis of copper bioavailability

The amount of carbon sequestration by phytoplankton accounts for about 50% of the total carbon sequestration on Earth. Microplastics are one of the new pollutants, and the ecological effects of microplastics-trace metals coupling on phytoplankton have attracted much attention. Copper is an important cofactor in the photosynthesis and respiration of phytoplankton, and its bioavailability is closely related to its speciation distribution and environmental factors. Here, we studied the effect of microplastics on copper bioavailability through intelligent sensing speciation and multi-perspective analysis and then how it affects the carbon sequestration of phytoplankton. Under the addition of PS, copper ligands, and PS‑copper ligands, when the concentration of copper absorption increased by 1 pg/cell, the carbon sequestration increased by 106.25, 406.43, and 2.47 μmol/min, respectively. We found that copper ligands could enhance carbon sequestration to varying degrees due to the influence of copper bioavailability, while PS had an inhibitory effect. Especially, the inhibitory effect was more pronounced under the addition of PS-copper ligands, showing an antagonistic effect. The study revealed the antagonistic mechanism of microplastic‑copper complexes from the perspective of the relationship between copper bioavailability and carbon sequestration for the first time. Thereby, it provided a new scientific basis for assessing the ecological risks of microplastics. It also offered a new perspective for elucidating the mechanism by which microplastic‑copper complexes influence the relationship between copper bioavailability and carbon sequestration.