Freshwater Mussel Shells as a Proxy for Stream Salinization from Road Salt

Because high conductivity adversely affects many freshwater organisms, road salt contamination continues to threaten river and stream ecosystems. Despite knowledge of road salt pollution, records of stream salt concentrations are largely unavailable. To address this issue, this study assesses the utility of freshwater mussel shells (Epilito complanata) as archives of road salt contamination. Four streams were surveyed in Dutchess County, NY (Casperkill, Fallkill, Crum Elbow, and Sawkill); and at least three E. complanata individuals were collected from each stream. Water samples collected during the winter indicate that salt content varies from stream to stream: the Casperkill has nearly five times as much salt as the others streams (~5000 µM Na²⁺ vs. ~1000 µM Na²⁺). However, road salt also adds other minor elements into the environment as well. For example, considering an estimated 1500 metric tons of road salt are added annually to a neighboring watershed, this would also add 5000 kg of sulfur and 300 kg of strontium (based on the analysis of freshly applied road salt). Interestingly, the Casperkill also has elevated concentrations of these elements. Therefore, in addition to Na, other elements may be a proxy of road salt contamination. Ongoing investigation of shells of the E. complanata collected from these streams will provide data on Na, Sr, Mg, Ba and a suite of other elements to determine if they correlate with stream ion concentrations. The records potentially archived in these bivalve shells may be important new sources of information on environmental degradation in freshwater ecosystems