Coastal ocean dynamics reduce the export of microplastics to the open ocean

Huge amounts of plastic waste are dumped into the ocean every year, forming large Garbage Patches. Countless microplastics, originating from fragmentation, weathering of larger objects or primary sources, pose a widespread ecological risk. In this study, the dispersion of suspended and floating microplastic particles in the East China Seas (ECSs) and adjacent seas was investigated via a coupled numerical model that included a Lagrangian particle tracking module. The role of tidal dynamics was considered in transporting the microplastic particles in the ECSs and adjacent seas. The results highlighted significant differences between the transport of suspended and floating microplastic particles. Although microplastic particles originating from different source areas followed different pathways, the Taiwan Strait, the Tokara Strait and the Tsushima Strait were identified as the major delivery channels. Of these, the Taiwan Strait played the most important role in the export of near-surface floating microplastic particles from the ECSs. The results showed that only a small fraction of the microplastic particles produced from the coastal waters of China (~18%) and Korea (~14%) entered the Pacific Ocean. However, nearly all of the microplastic particles originating from the west and south coasts of Kyushu Island entered the Pacific Ocean.