Microfibers Accumulation within a Mediterranean Submesoscale Cyclone.

Cyclonic eddies are widespread upper ocean features known to enhance primary productivity via nutrient upwelling; yet, their role in the transport and retention of anthropogenic contaminants remains poorly understood. Here, we present high-resolution oceanographic measurements from a submesoscale cyclone in the Western Mediterranean Sea, revealing a pronounced subsurface accumulation of textile microfibers (MFs) within the eddy core (0.34 MF l) relative to surrounding waters (0.09 MF l). This enrichment persisted in a secondary, smaller cyclone that detaches following the main cyclone's fragmentation. Elevated chlorophyll-a concentrations in the upper 40 m, driven by isopycnal uplift, point to a coupled biological response to physical forcing. Spatial heterogeneity in pollution sources, vertical circulation, and mixing likely explains the observed microfiber distribution. Our findings demonstrate that submesoscale cyclones can function as transient yet efficient reservoirs of man-made contaminants, with potential consequences for pollutant exposure pathways and trophic transfer in marine ecosystems.