METALS FROM LEGACY SEDIMENTS AND THEIR IMPACT ON MACROINVERTEBRATES IN YELLOW BREECHES CREEK WATERSHED, CUMBERLAND COUNTY, PA

Over the last 250 years, thousands of mill dams in the Middle Atlantic States have accumulated sediment with included nutrients, trace metals, and organics from natural and synthetic fertilizers, urban runoff, and pesticide/herbicide application due to land-use change over time. These so-called “legacy sediments” (LS) (Walter and Merritts, 2008) are remobilized into streams by the breaching or removal of these dams. Previous work (Haynes and Niemitz, 2009) has found elevated levels of the trace metals and phosphorus over background at LS sites in the Yellow Breeches Creek watershed. We present preliminary dissolved and suspended load nutrient and bioavailable trace metal data from three LS sites within the watershed and assess the implications for uptake in macroinvertebrates from each site. An upper reach, forested (Eaton-Dikeman dam (ED)) site is the control for background levels of components. Site two is dominantly within the agricultural land use middle reach (Wittlinger dam (WD)). Site three collects runoff from an urbanized sub-watershed (Green Lane dam (GL)) in the lower reach. Samples were taken above and below dam sites. Samples and other chemical parameters were collected biweekly from July 2009 through February 2010. Filtered water and sediment samples were analyzed by ICP-MS for Cd, Cu, Fe, Pb, and Zn. Macroinvertebrates were digested and analyzed for metals by Flame AAS. Discharge below each site and rainfall in the watershed were monitored continuously. Preliminary results show low dissolved nutrient and trace metal concentrations from Eaton-Dikeman LS consistent with its land-use. Nutrients increase downstream with changing land-use in both the sediment and dissolved load relative to seasonal discharge e.g. WD dissolved metal load is four times ED. Macroinvertebrate metal concentrations are at least 10-fold higher compared to dissolved loads and at least 2-3 fold higher than suspended loads. Zn appears to be the most bioavailable trace element.