Influence of Mesoscale Eddies on the Three-Dimensional Distribution of Microplastics in the Western North Pacific

Despite growing concern over marine microplastic pollution, the mechanistic understanding of what governs their three-dimensional distribution in the ocean remains critically limited. Here, we characterize the three-dimensional distribution of seawater microplastics in the Western North Pacific Ocean. We find mesoscale eddies, including anticyclonic and cyclonic eddies, are directly related to the distribution and characteristics of seawater microplastics. Compared with cyclonic eddies, anticyclonic eddies tend to host higher microplastic abundance and diversity in the upper ocean, extending to at least 600 m depth. Sea level anomaly (SLA) seems to be the dominant driver of this phenomenon, as confirmed by redundancy analysis. Moreover, higher positive SLA values are associated with greater diversity in microplastic characteristics. Exceptions are observed at the surface and at 50 m depth, where complex hydrodynamic conditions occur. Overall, our study establishes a link between mesoscale eddies and the three-dimensional distribution of microplastics. This improves our understanding of the environmental behaviors of oceanic microplastics and offers scientific guidance for better assessing their environmental and ecological impacts.