Blood Lead Concentrations in Waterfowl Utilizing Lake Coeur d’Alene, Idaho

Abstract

The Coeur d'Alene River Basin, Lake Coeur d'Alene, and the Spokane River contain elevated heavy metal concentrations in sediment and water from historical mining and ore processing operations in the Coeur d'Alene Basin. Lead poisoning has been identified as the cause of death in hundreds of waterfowl utilizing wetlands in the floodplain of the Coeur d'Alene River, but little was known about hazards to waterfowl from heavy metal contamination in shallow bays and wetlands of Lake Coeur d'Alene. We examined lake sediment and blood lead concentrations in waterfowl utilizing Lake Coeur d'Alene, Idaho, to evaluate potential lead contamination of waterfowl utilizing the lake. We collected 56 palustrine and 102 lacustrine sediment samples and 61 mallard and 8 wood duck blood samples. Mean lead concentrations from palustrine and lacustrine sediment samples ranged from 14 to 3508 mg/kg dry weight (dw) and from 19 to 5009 mg/kg (dw), respectively. Lead concentrations in palustrine and lacustrine sediment from several Lake Coeur d'Alene bays were higher than those in lake reference areas and were higher than Bunker Hill Superfund Site target cleanup levels and suggested site-specific toxicity thresholds for swans. Mean blood lead from mallard and wood ducks sampled from Lake Coeur d'Alene bays were within lead toxicity ranges for waterfowl associated with clinical and severe clinical lead poisoning. We also collected 19 Canada goose and 3 mallard fecal samples to evaluate exposure through sediment ingestion. Waterfowl using Lake Coeur d'Alene appear to be exposed to lead by ingesting contaminated lake sediment. Our model predicts a sediment lead effects range of 147-944 mg/kg (dw) and mortality effects level of 1652 mg/kg (dw) for mallards utilizing Lake Coeur d'Alene. The locations of Harrison Slough, Powderhorn Bay, and Cottonwood Bay at the mouth of the Coeur d'Alene River and Blackwell Island and Cougar Bay near the Spokane River outflow of Lake Coeur d'Alene were the areas of greatest concern for waterfowl exposure to lead contaminated sediment.