Occurrence of microplastics in freshwater gastropods from a tropical river U-Taphao, southern Thailand.

BACKGROUND

Microplastics (MPs) are pollutants in rivers and marine environments. Rivers can be sources and sinks of MPs that enter the biota. Previous studies focusing on freshwater species are quite limited, especially for gastropods. Freshwater gastropods are essential to aquatic ecosystems because they are food to other aquatic animals, such as fish, shrimp, and crabs. They are a crucial link in the food chain between water resources and human food. Therefore, this study aimed to investigate MP accumulation in freshwater gastropods, commonly known as snails ( and ), in a river flowing into a shallow coastal lagoon.

METHOD

In this study, snail tissue samples were digested with 30% hydrogen peroxide. The mixture was heated at 60 °C for 24 h. MP particles were identified, counted, and characterized (shape, size, and color) by visual identification under a stereomicroscope. Furthermore, polymer-type identification was performed using Fourier transform infrared spectroscopy (FTIR). Analysis of variance (ANOVA) was applied for the statistical analysis.

RESULTS

The MPs found were as follows: 4.76 particles/individual were found in upstream, 5.20 particles/individual were found in downstream, 7.28 particles/individual were found in upstream, and 4.00 particles/individual were found in downstream. It was found in the two-way ANOVA that the accumulation of MPs in gastropods was affected by species and study sites (upstream and downstream). There was a significant difference in the amount of MPs in between upstream and downstream sites ( = 0.003). Fibers were the most common MPs in both species. Moreover, upstream had the most significant amount of MPs. The smallest amount of MPs was recorded for downstream, but there was great diversity in shape, size, and polymer type. MPs sized 500 μm mm were the most common in both species. Fourier transform infrared spectroscopy revealed six polymers: poly (ethylene terephthalate), polypropylene, rayon, polyethyleneimine, polyamine, and poly propylene: ethylene). The occurrence of MPs in gastropods is alarming for food security in Thailand. The results of this study can be used to support baseline data on MP accumulation among freshwater gastropods.