Mercury Effects on Avian Embryos

The following is a brief section from my senior seminar paper on an extremely interesting and insightful article. I promise I'll get to newer articles soon, but I wanted to give this a shot and I just loved this paper.

Mercury can limit avian productivity by impairing the development of the embryo, which are especially sensitive to environmental toxins such as mercury. Heinz et al. (2008) compared embryo sensitivity of wild bird species by injecting eggs with methylmercury chloride. The response to mercury was measured using the median lethal concentration (LC₅₀), or the concentration at which the embryo mortality rate was 50%. The results show that the embryos fall largely within three sensitivity groups. At low sensitivity (LC₅₀s > 1 μg g^-1 mercury) were the Mallard, Hooded Merganser, Lesser Scaup, Canada Goose, and Laughing Gull. At medium sensitivity (LC₅₀s > 0.25 μg g^-1 mercury) were the Clapper Rail, Sandhill Crane, Ring-necked Pheasant, Common Grackle, Domestic Chicken, Tree Swallow, Herring Gull, Common Tern, Royal Tern, Caspian Tern, Great Egret, Brown Pelican, and Anhinga. At high sensitivity (LC₅₀s < 0.25 μg g^-1 mercury) were the American Kestrel, Osprey, White Ibis, Snowy Egret, and Tri-colored Heron. The rank order of embryo mercury sensitivity was also found to mirror mercury levels deposited naturally by the mother (Heinz et. al., 2008).

This research provides an invaluable means to evaluate whether mercury concentration poses a threat to specific wild species and points in the direction of which species may be at most risk. I believe this may have profound implications for conservation and management of ecotoxins. It also allows for more precise targeting for species as bioindicators.

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Heinz, G. H., D. J. Hoffman, J. D. Klimstra, K. R. Stebbins, S. L. Kondrad, C. A. Erwin. 2008. Species differences in the sensitivity of avian embryos. Archives Environmental Contamination Toxicology 56: 129-138.