Microplastic accumulation in the golden apple snail Pomacea canaliculata serves as a bioindicator in the urban lowlands of Nakhon Pathom Province, central Thailand

Bioindicators are useful for assessing pollution levels, bioavailability, and the ecological effects of pollutants. Several bioindicators have been proposed for monitoring microplastics (MPs) in the marine environment. There is no known bioindicator for MPs in freshwater. This was the first study to discover and quantify microplastic contamination in the golden apple snail Pomacea caaliculata and its surroundings in Nakhon Pathom Province, central Thailand's urban lowlands. The average MP concentration in snail of small, medium, and large sizes was 4.47 ± 3.37 items/individual, 3.40 ± 1.71 items/individual, and 9.21 ± 8.97 items/individual. Additionally, the snail egg mass had an average MP abundance of 3.03 ± 1.51 items/mass. The regression analysis revealed a significant variation in MP abundance between snail size and egg mass (p < 0.01). MPs in water and sediment had average concentrations of 5.0 ± 1.89 items/L and 140.67 ± 9.29 items/kg. Fibers accounted for 56–83% of particles in all snail sizes, while fragments made up 58% of the egg mass. Snail samples had microplastics ranging in size from <100 to >500 µm, with the most common size being <100 to 250 µm. The egg mass typically ranged in size from <100 to 250 µm. Blue and transparent particles made up more than 74% of all particles and were more prevalent than other colors. The most prevalent polymer was polyethylene terephthalate (PET), followed by polyvinyl acetate (PVAc), cellulose acetate butyrate (CAB), polypropylene (PP), and polyethylene (PE). Because microplastic contamination in the snail reflected the fluctuation of microplastic pollution in freshwater ecosystems, we established the snail as a bioindicator of microplastic pollution in freshwater systems, particularly sediments.