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Increase in Microplastic Concentrations in Golden Clams (Corbicula fluminea) Between 2018 and 2025 in freshwater systems of the Southern Appalachian Mountains
Summary
Scientists studying rivers in the Southern Appalachian Mountains found that tiny plastic particles (mostly plastic fibers, likely from clothing and textiles) have increased dramatically in freshwater clams between 2018 and 2025, by nearly 74% per gram of tissue. Even remote, pristine-seeming streams that are home to rare fish and clams showed high microplastic levels, suggesting these particles are spreading everywhere, not just near cities or pollution sources. Since these clams are part of the food chain and similar to shellfish people eat, this rising contamination raises concerns about how much plastic may be
Global plastic production continues to increase by ~8% annually despite the growing concern over its environmental and human health impacts. Recent studies have demonstrated that forested headwater streams in the Southern Appalachian Mountains of western North Carolina contain some of the highest concentrations of microplastics (MPs) ever recorded in freshwater systems; however, concentrations of MPs in rivers within this region and across different years have not been examined. We used Golden Clams (Corbicula fluminea) as biological indicators to assess changes in MP concentrations from 2018 to 2025 at six sites in the Little Tennessee River basin in western North Carolina. For a more complete understanding of MPs in the whole freshwater system, atmospheric deposition and stream water samples were also collected and analyzed. Overall, from 2018 to 2025, we found a 54.5% increase in the total number of MPs in our clam samples and a 73.9% increase in MPs per gram of clam tissue, although those results varied among the six sites. Consistent with 2018 observations, fibers were the most prevalent type of MP, accounting for >90% of particles found in the atmosphere, stream water samples, and clams. Our findings on counts and concentrations of MPs in Golden Clams are among the highest ever recorded from bivalves. Interestingly, counts and concentrations of MPs were high even in remote sections of the Little Tennessee River, which is considered a biodiversity hotspot for rare fish and freshwater clams. Our findings support the need for further research into the pervasive nature and effects of microplastics on freshwater systems.