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Wetland Symposium

Selenium Levels in Fish and Wildlife at Oakes Test Area, A Garrison Diversion Unit Project


U.S. Fish and Wildlife Service, Ecological Services, 1500 Capitol Avenue, Bismarck, ND 58501; U.S. Bureau of Reclamation, Missouri-Souris Projects Office, P.O. Box 1017, Bismarck, ND 58501; U.S. Fish and Wildlife Service, Ecological Services, 500 Capitol Avenue, Bismarck, ND 58501

The Garrison Diversion Unit proposes to divert water from the Missouri River to the James River for agricultural, municipal, and industrial use in eastern North Dakota. Potential selenium contamination of National Wildlife Refuges along the James River is of concern to the U.S. Fish and Wildlife Service (Service) and the U.S. Bureau of Reclamation (Reclamation) due to links between irrigation return flows and selenium-induced wildlife toxicity at several locations in the western United States. Baseline studies of the James River from 1986 through 1989 showed selenium concentrations in waterfowl livers were elevated at some sites during the drought years of 1988 and 1989. Studies of selenium bioaccumulation in aquatic systems that receive irrigation return flows were recommended.

Oakes Test Area is a 3,885-ha irrigation test area located along the James River. River water is used for irrigation of the test area and is returned through surface and subsurface drains. In 1991 and 1992, the Service and Reclamation studied accumulation of selenium and other elements in biota, sediments, and water in a marsh which receives drainwater from the test area. Results were compared to water quality criteria, national baseline levels, and toxicity thresholds established in other studies.

Median selenium concentrations in water were 2.0 µg/l in 1991 and <1.0 µg/l in 1992. These concentrations were below 5.0 µg/l, the water quality criterion for protection of aquatic life from chronic adverse effects of selenium. Selenium concentrations in sediments were at the high end of the normal range for soils of the western United States (0.039-1.4 µg/g), but were below the 4 µg/g concern level for potential toxic effects of selenium on reproduction of fish and waterfowl. Mean selenium concentrations in leopard frogs, small fish, and aquatic invertebrates were below concern levels (5 µg/g) for dietary toxicity to fish. Selenium concentrations in whole small fish, and in livers and gonads of larger fish, were below concern levels for adverse effects on fish reproduction.

Concern levels for selenium in waterfowl food (3 µg/g) were not exceeded in duckweed (Lemna spp.) samples either year; however, levels in aquatic invertebrates were slightly above this criterion in 1991. Selenium concentrations in duck livers averaged 8.4 and 10.1 µg/g in 1991 and 1992, respectively. Average selenium concentrations in livers of freshwater birds from uncontaminated sites range between 4 and 10 µg/g. Therefore, average concentrations in livers from Oakes Test Area were at the high end of the normal range for uncontaminated populations. These levels of selenium were below those (30 µg/g) associated with a high risk of adverse biological effects. Waterfowl eggs were not collected, but selenium concentrations in eggs of cliff swallows (Hirundo pyrrhonota) and yellow-headed blackbirds (Xanthocephalus xanthocephalus) averaged less (2.3 and 3.1 µg/g, respectively) than the 8 µg/g lower boundary for mean egg selenium in eggs of aquatic birds from populations with impaired hatchability.

Selenium concentrations were slightly elevated in most types of samples. However, concentrations of selenium in tissues and food items of fish and birds were generally below toxic concern levels. Based on these data, drainwater from irrigated soils in the Oakes Test Area is unlikely to result in selenium-induced fish and wildlife toxicity.

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