EVALUATING FRESHWATER MUSSELS SHELLS AS A PROXY OF ROAD-SALT RUNOFF INTO STREAMS

Bivalves have the ability to record past environmental information in the isotopic ratios as well as concentrations of elements archived in their shells. Bivalve shells allow us to investigate past environmental conditions and may give us insight on how ecosystems could respond to environmental change in the future. Most of the work that has been previously done has focused on marine bivalves, but freshwater mussels also can act as environmental proxies as well. This study utilized the freshwater mussel Elliptio complanata for a proxy of road salt pollution in freshwater streams. Due to the large amount of ice and snow that the Northeastern United States receives during the winter, road salt is applied and eventually is carried to streams via surface run-off and groundwater seepage. This salt that infiltrates into the streams is an important environmental concern because it greatly affects the water chemistry of the stream and can have deleterious effects on the flora and fauna that reside in the stream. The specimens of Elliptio complanata that we sampled came from four streams in Dutchess County, New York (Casperkill, Sawkill, Crum Elbow, and Fallkill) in May 2008 as well as two specimens that were collected from the Casperkill stream at Vassar College in 1877. Today, the stream that contains the highest amount of road salt pollution is the Casperkill. Trace element analyses were completed using laser ablation ICP-MS on shell cross sections. We found that [Na/Ca]_shell is higher in the modern shells from the Casperkill suggesting that [Na/Ca]_shell serves as a proxy for road salt pollution in freshwater ecosystems and that the salt pollution is indeed a modern pollutant in that stream.