[M-IS09] Ocean Plastics, an earth science perspective

[MIS09-P11] Pelagic microplastics in the North Pacific Subtropical Gyre

*Shiye Zhao¹, Tracy Mincer², Laurent Lebreton³, Matthias Egger³ (1.Japan Agency for Marine-Earth Science and Technology, 2.Florida Atlantic University, 3.The Ocean Cleanup)

Keywords:microplastic, North Pacific Garbage Patch, Vertical transport, Biological carbon pump

Due to its ever-increasing ocean inputs, fossil-based microplastics (MP) comprise a considerable constituent in the particulate organic carbon (POC) pool, which is instrumental in ocean biogeochemical cycling. Their distribution within the oceanic water column and the underpinning processes, however, remain unclear. Here we show that MP prevails throughout the water column of the eastern North Pacific Subtropical Gyre, with exponential relationships between concentrations and water depth in the upper 500-m layer and marked accumulation below this layer. Our results suggest that the biological carbon pump (BCP) strongly contributes to the water column MP redistribution in terms of polymer type, material density, and particle size, which could influence the efficiency of organic matter export to the deep sea. We further show that dead carbon depleted plastic particles predictably are an emerging nonneglectable perturbation to radiocarbon signatures in the deep ocean. Our data provide insight into vertical MP flux and highlight the potential role of MP in alternating the marine particulate pool and interactions with the BCP.