Mussels could help researchers monitor road salt dissolved in streams
Road salt used in the winter to clear icy highways is
tainting many waterways in the Northeast (SN:
9/24/05, p. 195). The vast majority of such streams don’t have instruments
in place to monitor that pollution, says Matthew Winnick, a geophysicist at
For their study, the researchers collected water samples and living E. complanata mussels from four streams that flow into the Hudson River near Poughkeepsie, about 100 kilometers north of Manhattan. Then, the team used a dental drill to collect a 1.5- to 4-milligram sample of each mussel’s shell. Although mussel shells are primarily made of calcium carbonate, the shells also include trace elements from the water where the mussels lived, says Winnick.
In water samples taken from the Sawkill, Fallkill and Crum Elbow creeks — all of which run through watersheds with relatively few roads — concentrations of sodium ions ranged between 15 and 20 milligrams per liter of water. However, in the sample taken from the Casperkill Creek, which runs through a relatively developed area with many streets and roads, sodium levels were about 120 milligrams per liter of water. Similarly, the concentrations of other trace elements found in road salt, such as manganese and barium, were much higher in water from Casperkill Creek than they were in the other streams.
Those differences showed up in the mussel shells, the researchers found. In general, the higher an element’s concentration in the water was, the higher the element’s concentration in the mussel shells. Because freshwater mussels can live as long as a decade, their shells — which sport growth rings that record changes over time just as trees do — could serve as long-term monitors of road salt pollution, the researchers contend.