Abundance, size and polymer composition of marine microplastics ≥ 10 μm in the Atlantic Ocean and their modelled vertical distribution

We studied abundance, size and polymer type of microplastic down to 10 μm along a transect from the European Coast to the North Atlantic Subtropical Gyre (NASG) using an underway intake filtration technique and Raman micro-spectrometry. Concentrations ranged from 13 to 501 items m− 3. Highest concentrations were observed at the European coast, decreasing towards mid-Atlantic waters but elevated in the western NASG. We observed highest numbers among particles in the 10-20 μm size fraction, whereas the total volume was highest in the 50-80 μm range. Based on a numerical model size-dependent depth profiles of polyethylene microspheres in a range from 10-1000 μm were calculated and show a strong dispersal throughout the surface mixed layer for sizes smaller than 200 μm. From model and field study results we conclude that small microplastic is ubiquitously distributed over the ocean surface layer and has a lower residence time than larger plastic debris in this compartment.