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U.S. Fish and Wildlife Service, 1500 Capitol Avenue, Bismarck, ND 58501

In 1986, the U.S. Fish and Wildlife Service (Service) began a nationwide effort to determine baseline concentrations of potential environmental contaminants in fish, wildlife, and their habitats on National Wildlife Refuges. The impetus for this program was the discovery of severe selenium-induced reproductive impairment of aquatic birds at Kesterson National Wildlife Refuge in California. Selenium, mercury, and other toxic elements were the focus of contaminants studies on Service lands in North Dakota.

The Service owns or has easements on 533,350 ha in North Dakota, and manages them primarily for waterfowl production. These lands include 19 fee-title refuges, 44 easement refuges, approximately 1,000 Waterfowl Production Areas, and over 11,000 wetland and grassland easements. Fee-title refuges were the highest priority in the contaminants studies, but other Service and non-Service lands were sampled to meet objectives of individual studies. Eight fee-title refuges and 16 other areas were sampled for contaminants from 1986 through 1991. Sampling sites were distributed among the four major ecoregions and most major river drainages in North Dakota.

Livers from American coots (Fulica americana) (n = 263) and ducks (n = 160) were analyzed for selenium, mercury, and other elements. Specimens were mainly flightless juveniles; therefore, they were representative of conditions at collection sites. Median concentrations (and interquartile ranges) of selenium and mercury in livers of American coots were 2.7 (1.8 to 4.0) and 0.67 (0.40 to 1.30) µg/g dry-weight, respectively. Median concentrations (and interquartile ranges) of selenium and mercury in livers of dabbling ducks were 5.7 (3.6 to 11.0) and 0.48 (0.30 to 1.05) µg/g dry-weight, respectively.

These medians and associated measures of variability represent the best available estimates of baseline contaminant conditions in waterfowl from North Dakota. Two sites with unusually high selenium levels were discovered during these studies. Knowledge of baseline conditions is useful for screening new sites for potential contaminants. Sites where median concentrations of an element exceed the baseline range can be targeted for detailed studies and possible remediation. Use of this method for screening new sites will be demonstrated with data from refuges sampled in 1992.