Distribution and composition of floating litter in coastal and offshore waters surrounding South Korea

Plastic pollution and its impacts on marine environments are increasing, yet data on the status and characteristics of floating macroplastics remain limited in East Asian waters, particularly around the Korean Peninsula. This study investigated floating litter in three marginal seas-the Yellow Sea, the northern part of the East China Sea, and the East Sea-using visual observations from ships. The mean density of floating litter across the study area was 181 ± 176 n/km². The offshore Yellow Sea exhibited the highest density (256 ± 150 n/km²), whereas the offshore East Sea had the lowest (48 ± 30 n/km²). Plastics (92%) were the dominant material type, with expanded polystyrene fragments (27%) and film-type fragments (16%) being the most abundant. Litter measuring 2.5-20 cm (72%) and white in color (59%) consistently predominated across all regions. Aquaculture activity and river discharge exhibited positive correlations with coastal pollution levels. These findings fill existing knowledge gaps on marine plastic pollution around the Korean Peninsula and provide insights into the distribution and characteristics of floating litter, thereby contributing to mitigation strategies in East Asian seas.