An integrated assessment of microplastic pollution in coastal surface water and sediment of Japan

The ubiquity of microplastics in the marine environment has been highlighted in recent years, yet the extent of microplastics pollution in coastal areas, especially off the coast of Japan, remains unclear. Here we provide a comprehensive dataset of microplastic pollution in surface water and sediment around coastal Japan. The survey encompasses 14 locations along Japanese coasts from the northernmost in Hokkaido to the southern archipelago of Okinawa. The overall microplastic concentration was 288.7 ± 651.6 g km2 and 1,185 ± 3,829 kg km2 for surface water and sediment, respectively. A total of 53,674 particles were extracted from both sediment and surface water as suspected microplastics using a series of sieving, density separation and digestions. Using Fourier Transform Infrared Spectroscopy, 85% of particles from surface water were identified as plastics and 70% in sediment. The main polymers found were the widely used polyethylene, polypropylene, and polystyrene. Analysis of sources and pathways of microplastics revealed that rainfall, population, aquaculture and fisheries were major driver of microplastic concentrations. This comprehensive survey highlights the rapid sinking of microplastic in coastal areas and the urgent need for better waste management associated with marine activities especially in rural areas.