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Mercury accumulation and loss in mallard eggs
Gary H Heinz1, David J Hoffman
1U.S. Geological Survey, Patuxent Wildlife Research Center, 11510 American Holly Drive, Laurel, Maryland 20708-4017, USA. gary_heinz@usgs.gov
Environmental Toxicology and Chemistry
|February 11, 2004
Summary
Female mallards exposed to methylmercury chloride accumulated significant mercury in their eggs. Egg mercury levels decreased after birds were switched to uncontaminated diets, indicating mercury elimination.
Area of Science:
- Environmental Toxicology
- Avian Biology
- Biogeochemistry
Background:
- Methylmercury is a potent neurotoxin.
- Avian species are susceptible to mercury contamination.
- Egg composition can influence mercury bioaccumulation.
Purpose of the Study:
- To quantify methylmercury accumulation and depuration in mallard eggs.
- To determine the distribution of mercury within egg components (albumen and yolk).
- To assess the percentage of mercury present as methylmercury in eggs.
Main Methods:
- Female mallards were fed diets with 5, 10, or 20 ppm methylmercury chloride.
- Eggs were collected before, during, and after mercury exposure.
- Mercury concentrations in eggs, albumen, and yolk were analyzed.
Main Results:
- Egg mercury levels increased with dietary exposure, reaching 7, 18, and 35 ppm (wet-weight) for 5, 10, and 20 ppm diets, respectively.
- Post-exposure, egg mercury levels decreased significantly, with final levels of 0.16, 0.80, and 1.7 ppm.
- Mercury concentrations were higher in albumen than yolk.
- 95-100% of egg mercury was in the methylmercury form.
Conclusions:
- Mallard eggs bioaccumulate methylmercury in a dose-dependent manner.
- Significant depuration of methylmercury occurs after exposure cessation.
- Methylmercury is the predominant form in contaminated mallard eggs, with higher concentrations in albumen.