Relating the ability of mallards to ingest high levels of sediment to potential contaminant exposure in waterfowl.

When waterfowl feed from the bottom of bodies of water, they sometimes ingest sediments along with their food, and this sediment can be a major source of contaminants. Learning how much sediment waterfowl can consume in their diet and still maintain their health would be helpful in assessing potential threats from contaminants in sediment. In a controlled laboratory study the maximum tolerated percentage of sediment in the diet of mallards (Anas platyrhynchos) was measured. When fed a well-balanced commercial avian diet, 50, 60, or 70% sediment in the diet on a dry-weight basis did not cause weight loss over a two-week period. Ducks fed this same commercial diet, but containing 80 or 90% sediment, lost 8.6 and 15.6% of their body weight, respectively, in the first week on those diets. After factoring in the ability of the mallards to sieve out some of the sediment from their diet before swallowing it, we concluded that the mallards could maintain their health even when approximately half of what they swallowed, on a dry-weight basis, was sediment.

Blood lead concentrations in waterfowl utilizing Lake Coeur d'Alene, Idaho.

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.

Phosphorus amendment reduces hepatic and renal oxidative stress in mallards ingesting lead-contaminated sediments.

Lead poisoning of waterfowl has been reported for decades in the Coeur d'Alene River Basin (CDARB) in Idaho as a result of the ingestion of lead-contaminated sediments. This study was conducted to determine whether the addition of phosphoric acid to CDARB sediments would reduce the bioavailability and toxicity of lead to the liver and kidney of mallards (Anas platyrhynchos). Mallards received diets containing 12% clean sediment (controls) or 12% sediment from three different CDARB sites containing 4520, 5390, or 6990 microg/g lead (dry weight) with or without phosphoric acid amendment. Liver and kidney lead concentrations were significantly higher in all CDARB treatment groups and ranged from geometric mean values of 18.2 (liver) and 28.7 (kidney) for the first 2 sites to 22.5 (liver) and 45.6 (kidney) microg/g (wet weight) for the third site. With amendments all liver lead concentrations were reduced 36 to 55%, and all kidney lead concentrations were lowered 54 to 73%. Unamended CDARB sediment from the third site resulted in the following hepatic effects: over 1.6-fold elevation of liver glutathione (reduced form; GSH) concentration, higher GSH S-transferase and oxidized glutathione (GSSG) reductase activities, and lower protein-bound thiols (PBSH) concentration. Renal effects included higher kidney GSH concentrations for all CDARB sites, with over 2.1-fold higher for the third site. Resulting kidney GSSG to GSH ratios were lower at two sites. At the third site, gamma-glutamyl transferase (GGT) activity was elevated, and lipid peroxidation as thiobarbituric acid-reactive substances (TBARS) was 1.7-fold greater. Amendment restored all hepatic variables as well as the renal variables TBARS and GGT so they did not differ from controls. Although amendments of phosphorus substantially reduced the bioavailability of lead and some of the adverse effects, lead concentrations in the tissues of mallards fed the amended sediments were still above those considered to be harmful to waterfowl under the present conditions.

Phosphorus amendment reduces hematological effects of lead in mallards ingesting contaminated sediments.

Lead poisoning of waterfowl has been reported for decades in the Coeur d'Alene River Basin (CDARB) in Idaho as a result of the ingestion of lead-contaminated sediments. This study was conducted to determine whether the addition of phosphoric acid to sediments would reduce the bioavailability and toxicity of lead to mallards (Anas platyrhynchos) as related to adverse hematological effects and altered plasma chemistries. Mallards received diets containing 12% clean sediment (controls) or 12% sediment from three different CDARB sites containing 4520, 5390, or 6990 microg/g lead (dw) with or without phosphoric acid amendment. Blood lead concentrations were significantly higher in all CDARB treatment groups and ranged from geometric mean values of 5.0 microg/g for the first two sites to 6.2 microg/g for the third site. With amendments, all blood lead concentrations became 41% to 64% lower. Red blood cell ALAD activity was depressed by 90% or more with lead-contaminated sediment from all sites and did not differ with amended diets. Free erythrocyte protoporphyrin (FEP) concentrations were elevated by contaminated sediment from all sites. Amendment decreased the elevations in FEP by as much as 80%. Hematocrit values and hemoglobin concentrations were lower for all lead site sediments by as much as 30% for site 3. Plasma enzyme activities for ALT, CK, and LDH-L were elevated by as much as 2.2-fold, and plasma creatinine concentration was 1.7-fold higher for site 3 sediment. Amendments restored hematocrit, hemoglobin, and plasma enzyme activities so that they did not differ from controls. Although amendments of phosphorus substantially reduced the bioavailability of lead and alleviated many of the adverse hematological effects, lead concentrations in the blood of mallards fed the amended sediments were still above those believed to be harmful to waterfowl under the present conditions.

Phosphorus amendment reduces bioavailability of lead to mallards ingesting contaminated sediments.

Lead poisoning of waterfowl has been reported for decades in the Coeur d'Alene River Basin in Idaho as a result of the ingestion of lead-contaminated sediments. We conducted a study to determine whether the addition of phosphoric acid to sediments would reduce the bioavailability of lead to mallards (Anas platyrhynchos). When sediments were amended with 1% phosphorus under laboratory conditions, and diets containing 12% amended sediment were fed to mallards, reductions in tissue lead were 43% in blood, 41% in liver, and 59% in kidney with sediment containing about 4,520 microg/g lead on a dry-weight basis and 41, 30, and 57% with sediment containing about 6,990 microg/g lead. When sediments were treated with phosphorus and left to age for about 5 months in the field, reductions in lead were 56% in blood, 54% in liver, and 66% in kidney at one site with about 5,390 microg/g lead and 64, 57, and 77% at a second site with about 6,990 microg/g lead. In the field, the inability to mix the phosphoric acid uniformly and deeply enough into the sediment may have resulted in more than 1% phosphorus being added to the sediment. Although both lab and field amendments of phosphorus substantially reduced the bioavailability of lead, lead concentrations in the tissues of mallards fed the amended sediments were still above those believed to be harmful to waterfowl. Based on earlier studies of sediment toxicity to waterfowl in the Coeur d'Alene River Basin, combined with the results of our amendment study, the addition of phosphoric acid as we used it might only significantly benefit waterfowl where sediments or soils contain less than 1,000-2,000 microg/g lead.