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Microplastics in Snails from an Urbanized Creek
Summary
Aquatic snails collected from an urbanized creek in Knoxville, Tennessee were found to contain an average of more than 12 microplastic particles each, with microfibers comprising 92% of the 212 total particles recovered from just 10 specimens. This study demonstrates that urban freshwater invertebrates are heavily exposed to microplastics, with clothing-derived microfibers as the dominant source, raising concerns about contamination moving up the food chain.
Microplastics (MPs) have been identified on every continent and in many different ecological systems. MPs in urban ecosystems are especially abundant. This study aims to address the paucity of data surrounding MP uptake in aquatic snails ( Physella ). These were chosen as good bioindicators because of their high pollution tolerance and wholly aquatic life cycle. The specimens were collected alive, using an active capture technique from First Creek, in a heavily urbanized area of central Knoxville, Tennessee. Ten specimens were dissected, separating the shell from the tissue. After thorough rinsing with dionized water, the snail shells were digested in a solution of nitric acid (60% HNO 3 ) for 48 hours and snail tissues were digested in a solution of potassium hydroxide and sodium hypochlorite (15% KOH, 15%NaClO) for 48 hours. Each sample was passed through a filter (0.47 μm), dried, and observed under a stereomicroscope. Quantity, type (e.g., fiber, fragment, pellet), and color were recorded. Preliminary results of this study found that aquatic snails from urban stream are exposed to and contain a substantial abundance of MPs in both their shell and soft tissue. A total of 212 separate MPs were recorded in these 10 snail specimens. As with previous studies, the most common type of MP were microfibers (92%), followed by microfragments (8%). A common source of such microfibers is clothing and washing machine effluent. On average, more than 12 MPs (±3) were observed in the soft tissue and an average of 6 MPs (±4) were observed in the shells. This suggests that, in agreement with initial studies of most other freshwater organisms, available MPs are readily absorbed by aquatic snails. Much further study is needed to determine the impact of MPs on these snails and urban aquatic ecosystems in general.