High nanoplastic concentrations across the North Atlantic - data code

Plastic pollution of the marine realm is widespread, with most scientific attention given to macro and microplastics. Ocean nanoplastics (1 μm), in contrast, remain largely unquantified, leaving gaps in our understanding of the mass budget of this plastic size class. Here we measure nanoplastic concentrations on an ocean basin scale along a transect crossing the North Atlantic from the subtropical gyre to the northern European shelf. Our findings reveal substantial amounts of polyethylene terephthalate (PET), polystyrene (PS) and polyvinyl chloride (PVC) nanoplastics (~ 1.5 - 32 mg m-3) throughout the entire water column. On average, we observed 1.4-fold higher concentrations of nanoplastics in the mixed layer when compared to intermediate water depth, with highest mixed layer nanoplastic concentrations near the European continent. Nanoplastic concentrations at intermediate water depth were 1.8-fold higher in the subtropical gyre compared to the open North Atlantic outside the gyre. The lowest nanoplastic concentrations (~5.5 mg m-3 on average), predominantly composed of PET, were found in bottom waters. For the mixed layer of the temperate to subtropical North Atlantic, we estimate that the mass of nanoplastic amounts to 27 million tonnes (Mt); This is in the same range or exceeds previous budget estimates of macro/microplastic for the entire Atlantic or the global ocean. Our findings suggest that nanoplastics comprise the dominant fraction of marine plastic pollution.