The biological and physiological effects of excess copper in juvenile mallards (Anas platyrhynchos): an investigation of the toxicity of acid mine drainage in waterfowl
Date
1999
Authors
Foster, Stiven Daniel, author
Ramsdell, Howard, advisor
Tessari, John D. (John Domenic), committee member
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Journal ISSN
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Abstract
In the early 1990's, concentrations of copper in the Alamosa River were increased by the release of acid mine drainage from the Summitville Mine site. Concern about the potential impact to resident waterfowl led to an investigation of copper toxicity in juvenile mallards. The investigation described in this thesis included a small field survey and six laboratory studies. The field survey provided an indication of potential exposure concentrations and a relative measurement of copper exposures in mallards from the Alamosa River. The laboratory studies examined the biological and physiological effects of excess copper in juvenile mallards and the relationship between copper exposure and tissue copper accumulation. Acute copper toxicity produced mortality in juvenile mallards that received a drinking water dose of 800 milligrams of copper per kilogram body weight per day (mg Cu/kg BW/d). Sublethal copper toxicity was quantified by decreased weight gain. Mallards experienced minor reductions in weight gain (10-20%) with exposures ranging from 70-210 mg Cu/kg BW/d. Weight gain was substantially decreased, by more than 50% compared with control birds, in mallards that received larger doses of copper(≥250 mg Cu/kg BW/d). Based on decreased weight gain, a dose of 20 mg Cu/kg BW/d was determined to be a No Observed Adverse Effect Level (NOAEL) for copper in juvenile mallards. Tissue copper concentrations were measured by flame atomic absorption spectrophotometry. Untreated mallards accumulated substantial concentrations of copper in their livers, up to 700 μg Cu/g on a dry weight basis. Hepatic copper increased significantly in mallards that received a dose greater than or equal to 160 mg Cu/kg BW/d. Feather copper concentrations were significantly correlated with both dietary (R2 = 0.99, p < 0.001) and drinking water exposure (R2 = 0.76, p < 0.001). Analysis of feather tissue was determined to be the most sensitive method for evaluating copper exposure. Feather copper concentrations were significantly increased in mallards that received a dose greater than or equal to 70 mg Cu/kg BW/d. Concentrations of copper in both liver and feather tissue reached their peak at a dose below the highest treatment level. Copper accumulation appears to be diminished in birds that received doses greater than or equal to 340 mg Cu/kg BW/d. Drinking water pH was investigated for its ability to influence copper absorption. Copper accumulation in feather tissue was significantly reduced when exposure pH was decreased. In addition to influencing tissue copper accumulation, acidic water (pH≤3.5) produced signs of direct toxicity in juvenile mallards. Weight gain was significantly reduced in mallards exposed to drinking water at pH 3.5. Drinking water at pH 3.0 exceeded the LC50 for very young mallards (< 5 days old). Evaluation of liver tissue from mallards that were collected on the Alamosa River indicated that these birds had increased exposure when compared to mallards from uncontaminated areas. Vegetation collected from the Alamosa River below the Wightman Fork contained a substantial concentration of copper, 463 mg Cu/kg. A diet that consisted solely of this copper-rich vegetation would provide mallards with approximately 88 mg Cu/kg BW/d. A similar dose of copper significantly reduced weight gain in laboratory mallards.
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Covers not scanned.
Print version deaccessioned 2019.
Print version deaccessioned 2019.
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Subject
Mallard
Copper -- Physiological effect
Acid mine drainage -- Environmental aspects -- Colorado -- Alamosa River