Regional Estimates of Contaminant Deposition in Aquatic

Frank H. McCormick, Ph.D.
US Forest Service, Environmental Sciences Research
Olympia Forestry Sciences Laboratory
3625 93rd Ave. SW, Olympia, WA 98512

We evaluated the extent of contamination of fish in the Mid-Atlantic Region as part of the U.S. Environmental Protection Agency’s Monitoring and Assessment Program’s regional assessment in 1993 through 1998 and in the Western United States in 2000 to 2004. Fish assemblages from wadeable streams were dominated by small, short-lived fishes (e.g., minnows, darters, and sculpins) that were more widely distributed and abundant than large fishes typically chosen for tissue contaminant studies (e.g., trout, black bass, sunfish, common carp). Chemical concentrations in whole-fish homogenates exceeded detection limits for mercury, DDT, and polychlorinated biphenyls (PCBs) in 75 to 100% of the stream length assessed using small fishes and 84 to 100% of the stream length assessed using large fishes. We developed wildlife values (WVs) representing a threshold for toxic effects to allow examination of the spatial extent of potential risk to piscivorous wildlife. For mercury, DDT, dieldrin, and chlordane, estimates of the regional extent of streams where fish contaminant concentrations exceeded the WVs were greater when based on small fishes than on large fishes.

Using stable isotope analysis, we are investigating pathways of contaminant deposition and incorporation into aquatic ecosystems.