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The 866-acre Loch Katrine wetland complex in Park County, Wyoming provides habitat for many species of aquatic birds. However, the complex is sustained primarily by oil field produced waters. This study was designed to determine if constituents in oil field produced waters discharged into Loch Katrine pose a risk to aquatic birds inhabiting the wetlands. Trace elements, hydrocarbons and radium-226 concentrations were analyzed in water, sediment and biota collected from the complex during 1992. Boron and radium-226 were present in the produced water discharge and are bioaccumulating in the food chain. Although not present in acute concentrations, elevated boron in aquatic vegetation may cause chronic effects to aquatic birds such as reduced growth in ducklings or altered metabolism. The 93.7 pCi/l radium-226 concentration recorded at the Sidney Battery Discharge in July exceeded the Wyoming Department of Environmental Quality's (WDEQ) 60 pCi/l standard for the protection of aquatic life (WDEQ 1990). The radium-226 concentration in aquatic vegetation from Custer Lake, 29.5 pCi/g, exceeded the 2.9 pCi/g average concentration found in plants growing in uranium mill tailings in South Dakota (Rumble and Bjugstad 1986). The presence of radium-226 in aquatic vegetation suggests that this radionuclide is available to aquatic birds. The water quality criterion for the protection of aquatic organisms from acute effects was exceeded for arsenic at Custer Lake in July and for zinc at the Sidney Battery Discharge in April. Arsenic and zinc concentrations were also elevated in sediment but not in aquatic vegetation and invertebrates. Oil and grease concentrations in water from Sidney Battery Discharge exceeded the maximum 10 mg/l permitted by the WDEQ (1990). Total aliphatic and aromatic hydrocarbon concentrations in sediments were highest at the Sidney Battery Discharge, 6.376 μg/g, followed by Custer Lake, 1.104 μg/g. The higher levels of hydrocarbons found at Custer Lake, compared to Loch Katrine, may be explained by Custer Lake's closer proximity to the Sidney Battery Discharge. Benzo(a)pyrene was not detected in bile from gadwalls collected at Loch Katrine but was detected in bile from northern shovelers collected at Custer Lake. Benzo(a)pyrene concentrations in northern shoveler bile ranged from 500 to 960 ng/g (ppb) wet weight. The presence of benzo(a)pyrene in the shovelers indicates exposure to petroleum hydrocarbons. Nesting failure in aquatic birds was attributed to flooding and predation rather than contaminants. Contaminants from oil field produced water discharge are
probably not affecting nesting success because trace element concentrations in bird eggs were not present in levels known to cause embryo mortality and because no oil was observed on the egg shells. The risk to peregrine falcons and bald eagles feeding on aquatic birds from the Loch Katrine wetland complex is minimal because trace element and hydrocarbon concentrations in aquatic birds were low. Periodic monitoring of Loch Katrine for radium-226, arsenic, zinc and metabolized polycyclic aromatic hydrocarbons is warranted to determine trends and effects in the aquatic bird food chain.