Microplastics in commercial fish digestive tracts from freshwater habitats in Northern Thailand

Abstract

Microplastics (MPs) contamination in fish species was one of the emerging environmental issues as a result of the widespread presence of plastic pollution in the environment. The presence of MPs in Thailand's freshwater was scant, and in contrast to other countries, little was known about the presence of this contaminant in freshwater fish. Hence, the purpose of this study was to examine the abundance, characteristics, and variation of MPs in various Thai commercial freshwater fish species. In order to compare the differences in MP ingestion rates across different feeding zones, 166 fish representing 24 species from various feeding zones were collected. MPs were found in the gastrointestinal tracts (GIT) of all fish samples tested, which was a substantially larger number than previously reported in other locations. Of all the fish species, Anabas testudineus, Labeo rohita, and Oreochromis mossambicus had the highest concentration of MPs (34.90 ± 21.43, 34.50 ± 7.78, 34.10 ± 11.15 items/individuals). Microscopical examinations showed that the majority of MPs were fiber-shaped and blue in color. Fourier transform infrared analysis (FTIR) showed that the polymers found in fish GIT were polyethylene, polypropylene, polyethylene terephthalate, polyvinyl acetate, poly (methyl vinyl ether), poly (methyl vinyl ether), polybutadiene, poly (ethylene-co-propylene), poly (ethylene glycol) tetrahydrofurfuryl ether, poly (methyl phenyl siloxane), poly (styrene-co-divinylbenzene), and polyvinylidene fluoride. The results of this study demonstrate that demersal fish had a higher concentration of MPs than benthopelagic and pelagic fish, indicating that plastic ingestion in fish may be related to the feeding habitat. However, it was not discovered that differences in the fish's body weight and length affected the MPs' ingestion. Our findings will help people in Thailand understand which freshwater fish and fish from which feeding zones are more contaminated with MPs for human consumption.