Accumulation of Microplastics in the Freshwater Shrimp, Macrobrachium lanchesteri, from Khwae Noi Watershed in Western Thailand

Microplastics (MPs) have been considered as an environmental pollutant, which disperses and accumulates in the environment, including in aquatic organisms. In this study, MPs accumulation in the freshwater shrimp, Macrobrachuim lanchesteri, sampled from headstream, midstream and downstream of the Khwae Noi watershed in western Thailand was investigated. A total of 300 individuals from 30 sites were sampled with dip nets. MPs accumulation in the shrimp was found to be only the filamentous type in approximately 19.0% of frequency occurrence, with the lengths varying from > 50 to 300 µm and an average of 0.46 ± 1.64 piece/individual (n = 300). Sorensen Distance of 70% similar index was classified into three groups of MPs accumulation in the shrimp. The first was no MPs accumulation, the second showed an average of 0.32 ± 1.2 piece/individual (n = 100), and the third exhibited an average of 0.72 ± 0.4 piece/individual (n = 100). Fourier-transform infrared analysis illustrated four types of MPs accumulation: polydimethylsiloxane, polyamide, polyester and polymethyl methacrylate. All MPs types found in the shrimp were linked with those found in water and sediment, indicating that MPs were in the food chain in the freshwater ecosystem. Principal Correspondence Analysis demonstrated the MPs accumulation correlated with eight environmental factors.