MICROPLASTIC ACCUMULATION IN TERRESTRIAL GASTROPODS AND SOILS

Microplastics (MPs) have become an emerging threat to ecosystems across the world. Transport, impacts, and fates are grossly understudied, especially in terrestrial environments. Current research on MP bioaccumulation has focused mainly on aquatic organisms with little study of terrestrial organisms, including snails where data are nearly nonexistent. To address this, we collected and examined land snails and their surrounding soil 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 a Wildlife Management Area (WMA) in Oak Ridge Tennessee. A total of 150 individuals were collected and 2.2 lbs of soil per site was taken directly underneath coverboards. For comparison with a more disturbed habitat, 150 snails and soil were also collected on the University of Tennessee campus from March 1, 2022, to July 10, 2022. Snails were placed in 70% ethanol for analysis and digested for 24 hours using a 1:1 ratio of potassium hydroxide pellets and sodium hypochlorite for organic matter removal. Samples were vacuum filtered, air dried for 1 week and then examined via stereomicroscope. MP shape, color, and number were recorded, and samples were examined twice, independent of one another to ensure accurate MP counts. Two tests were performed if MPs could not be determined. The “hot needle test” causes plastics to deform and melt when exposed to heat, and the “spring test” to examine the physical characteristics of the MP. Results for the less disturbed WMA (Oak Ridge) showed total MP abundance at 214 particles in snails and 478 for soils. MP counts ranged from 0 to 6 per snail and 5 to 33 per soil sample. For campus (Knoxville), MP counts were higher, with a total of 270 particles in snails and 540 particles in soils. MP counts ranged from 0 to 8 per snail and 7 to 35 particles per soil sample. This study confirms the accumulation of MPs in land snails and indicates that higher human activity is associated with higher densities of MPs in both snails and soils.