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Patterns and Consequences of in ovo Exposure to Methylmercury in Common Loons, poster presentation
Citation:
KENOW, K., M. W. MEYER, AND R. ROSSMANN. Patterns and Consequences of in ovo Exposure to Methylmercury in Common Loons, poster presentation. Presented at Midwest Chapter of Society of Environmental Toxicology and Chemistry, La Cross, WI, March 30 - April 01, 2009.
Impact/Purpose:
We conducted a field study to (1) characterize in ovo methylmercury (MeHg) exposure in Wisconsin common loons and (2) determine the level of in ovo MeHg exposure that results in detrimental effects on fitness and survival of loon embryos and hatched chicks by manipulating MeHg exposure via egg injection.
Description:
A critical component of a common loon/mercury (Hg) risk assessment model under development is the determination of the concentration of Hg in eggs that poses a population level risk. We conducted a field study to (1) characterize in ovo methylmercury (MeHg) exposure in Wisconsin common loons and (2) determine the level of in ovo MeHg exposure that results in detrimental effects on fitness and survival of loon embryos and hatched chicks by manipulating MeHg exposure via egg injection. Mercury concentrations ranged from 0.17 to 1.23 ppm in eggs collected from nests on lakes representing a wide range of pH (5.02 - 8.10) and were modeled as a function of adult female mercury exposure (which was negatively correlated with lake pH) and egg laying order. Blood Hg concentrations in a sample of loon chicks ranged from 0.84 to 3.86 ppm at hatch, indicating exposure in some chicks rivals that of adult birds during the breeding season. Blood Hg concentrations rapidly declined in growing chicks, likely the result of rapid elimination (feather sequestration important) and growth dilution relative to dietary intake. By six weeks of age, blood Hg concentrations were about 5% of the concentration at hatch. Survival of common loon embryos through hatch was assessed in untreated eggs and in eggs injected with varying amounts of mercury. Reduced embryo survival was evident in eggs injected at a rate of =1.3 ppm Hg wet-mass. When maternally deposited Hg and injected Hg were considered together, the median lethal concentration of Hg (LC50) was estimated to be 1.8 ppm Hg wet-mass.