Submesoscale cyclone in the Mediterranean Sea concentrates anthropogenic microfibers

Cyclonic eddies are ubiquitous in the upper ocean, linking large-scale balanced dynamics and smaller-scale unbalanced turbulence. While their role in enhancing primary productivity through nutrient upwelling is well-documented, their impact on the transport and accumulation of anthropogenic pollutants remains poorly understood. Using high-resolution data collected across a submesoscale cyclone in the Western Mediterranean Sea, we reveal that such eddies are fundamentally important in shaping the distribution of man-made contaminants. Our results show a substantial subsurface accumulation of textile microfibers within the cyclone (0.34 MF l⁻¹) compared to surrounding waters (0.09 MF l⁻¹), with this accumulation persisting even after eddysplitting. Concurrently, nutrient upwelling within the cyclone drives a marked increase in chlorophyll-a concentrations in the upper 40 m (0.44 and 0.15 mg m-3 inside and outside, respectively), indicating a coupling between physical and biogeochemical processes. We discuss potential mechanisms, including vertical circulation and mixing dynamics, that may explain the observed patterns. This study highlights the importance of submesoscale processes in shaping the distribution of anthropogenic pollutants, with significant implications for marine ecosystem healthand survey designs.