Microplastics in Terrestrial Snails

Microplastics (MPs) have become a growing concern surrounding the unknown fates, toxicological effects, and transportation mechanisms in aquatic and terrestrial environments. However, there is little research on the flow and accumulation of MPs in terrestrial organisms, especially in lesser-studied organisms such as snails. To address this, we collected and examined land snails for MP content in shell and tissue. From September 11, 2020 to October 25, 2021 cover boards were placed (n=30) along relatively undisturbed sites in hardwood, forested areas, and tall grasses in Oak Ridge Tennessee. A total of 400 individuals and 16 snail species were collected. Snails were placed in 70% ethanol for analysis and each snail was digested for 24 hours using a 1:1 ratio of potassium hydroxide pellets (280g/250ml) and sodium hypochlorite (14% active chlorine) to reduce the amount of organic matter. Samples were vacuum filtered (0.47 μm), allowed to air dry for 1 week and then examined under a stereomicroscope. Shape, color, and number were recorded, and samples were examined twice independent of one another to ensure accurate MP counts. Two tests were performed as needed if MPs could not be distinguished from organic matter. The “hot needle test” whereas plastics deform and melt when exposed to heat, and the “spring test” to examine the physical characteristics of the MP. MP abundance was relatively consistent, ranging from 2-5 particles per snail and there seems to be no correlation between type of species and MP concentration. Previous studies have shown a significant increase in microplastic concentrations in highly disturbed areas, resulting in further pathways of digestion within snails. This study confirms the accumulation of MP’s in land snails. Future research will expand to examine MPs in snails in more urbanized and disturbed habitats.