Sources and distribution of microlitter in the tropical and temperate Atlantic Ocean

Marine microlitter is widespread in the ocean and known for accumulating in the North and South Atlantic Gyres. However, studies sampling continuous transects and providing a high spatial resolution are mainly descriptive and very scarce. The aim of this study was to assess the microlitter distribution from tropical to temperate regions of the Atlantic Ocean using the pump-underway ship intake system. A total of 52 samples collected from Brazil (Salvador) to the Strait of Gibraltar allowed us to identify its accumulation zones. The OpenDrift dispersion model was used to determine the potential pathways and sources of microlitter, based on the ocean currents' speed and direction from the GLORYS ocean model. The large fraction (≥315 μm) had an average abundance of 1.49 ± 1.11 items/m³ and was dominated by cellulosic fibers (90.46%) and the smaller-sized fraction (10-315 μm) had an average abundance of 20.63 ± 18.76 items/m³ and was dominated by fragments (95.57%). The Northern Hemisphere was shown to contain a greater cellulosic fiber abundance than the Southern Hemisphere, probably due to their greater population and industrial activity, combined with the accumulation mechanisms of the North Atlantic Gyre. The greatest microlitter abundances were found near the Equator, Brazil and around 10°N along our transect. The dispersion model determined that most particles originated from West Africa, mainly following the different branches of the Equatorial Current, with additional contributions from Northern Brazil and the Iberian Peninsula.