Microplastic contamination is considered a major threat to the marine environment. Although microplastic pollution in the Pacific Ocean has been studied, its abundance, distribution, composition, and origin in the Western Pacific Ocean remain unclear. Here, we investigated the abundance and distribution characteristics of microplastics in surface waters of the Western Pacific Ocean and analyzed their potential sources. Results showed that microplastics were widespread in the Western Pacific Ocean, with abundance ranging from 0.03 to 2.36 particles/m³ (average 0.37 ± 0.47 particles/m³). Fibers/filaments and fragments were the main shapes of microplastics (71.6%) and the most abundant microplastic size class was <1.0 mm (42.4%). Significant differences in microplastic abundance were observed in different regions, with the lowest abundance in the South China Sea (0.03 particles/m³) and highest abundance in the seamount area in the Western Pacific Ocean (0.58 particles/m³), which may be due to the influence of monsoon and ocean currents. This study should provide baseline data and insights into the fate and transportation of microplastics in the Western Pacific region.

microplastics; Western Pacific; surface water; distribution characteristics; seamount area