Metal Fate and Effects in Intertidal Food Webs at the Callahan Superfund site
Understanding the fate and effects of toxic metals found at Superfund sites in the U.S. is one of the main missions of the Superfund Research Program. Investigating impacts of specific Superfund sites on environmental and human health provides direct benefit to site managers, USEPA, and the public. Estuaries are the repositories of often high concentrations of metal contaminants from nearby mining activities, discharges of industrial complexes, and runoff from upland watersheds and there are numerous Superfund sites in estuaries.
The Callahan Mine in Brooksville Maine is an EPA Superfund (MED980524128) site that includes a large estuary, Goose Cove, which contains elevated levels of copper, lead and zinc due to the open pit mine that was dug and has since been abandoned. The original pit is now part of the estuary that experiences tidal cycles and inflow of freshwater from the nearby watershed.
This pilot project initiated an investigation of intertidal food webs and local killifish populations at this Superfund site. The two broad goals of the research were: 1) to characterize and compare the bioaccumulation and trophic transfer of metals in the resident food web of five sub-sites within the Callahan mine site and a nearby reference site at Horseshoe Cove, and 2) to characterize the genetic history of killifish at the mine site and across adjacent locations. Studies in 2010-2011 revealed strong gradients of metal concentrations closest to the mine tailings and waste rock piles in sediments, water, and fish. The elevated concentrations in water and fish suggest that there is rapid leaching of metals from the sediments or tailings that results in local bioaccumulation despite the constant mixing of the tidal cycle.