Abstract
BackgroundMercury (Hg) and methylmercury are widely considered significant issues for wildlife, and in particular, piscivorous birds due to their widespread availability and neurotoxic properties. Whereas a substantial number of studies of Hg contamination of Bald Eagles (Haliaeetus leucocephalus) have been conducted throughout the east coast of the United States, little has been done that directly addresses Hg contamination in Bald Eagles in Virginia, particularly the inland population.MethodsWe collected blood and feather samples from nestling Bald Eagles in the coastal plain, piedmont, and western regions of Virginia in an effort to determine which areas of the state were more likely to contain populations showing evidence of Hg toxicity. We analyzed the samples for total Hg using a Milestone DMA-80.ResultsSamples collected from individuals located in the coastal region exhibited low concentrations of Hg compared to those further inland located on freshwater rivers and reservoirs. Samples collected from the inland population exhibited levels in some areas that are approaching what may be considered to be sub-lethal to avian health (blood: mean 0.324 mg/kg, SE = 0.13, range = 0.06‒0.97 mg/kg; feather: mean = 8.433 mg/kg, SE = 0.3, range = 3.811‒21.14 mg/kg).ConclusionsEven after accounting for known point-sources of Hg, the inland eagle population in Virginia is susceptible to concentrations of Hg that are significantly higher than their coastal counterparts. Moreover, several locations besides those currently known to be impacted by point-sources are exhibiting concentrations that are approaching a sub-lethal level.
Highlights
Mercury (Hg) and methylmercury are widely considered significant issues for wildlife, and in particular, piscivorous birds due to their widespread availability and neurotoxic properties
It is well known that the neurotoxic properties of mercury (Hg) and methylmercury (MeHg) represent a substantial risk to wildlife, in particular, higher trophic level species (Scheuhammer 1987; Yates et al 2004, 2005; Evers et al 2005; Hopkins et al 2013)
Our objectives were to establish reference levels for Hg contaminants in Bald Eagles in coastal Virginia based on previous work (Cristol et al 2012) and from collection and analysis of new tissue samples from nestling Bald Eagles
Summary
Mercury (Hg) and methylmercury are widely considered significant issues for wildlife, and in particular, piscivorous birds due to their widespread availability and neurotoxic properties. Whereas a substantial number of studies of Hg contamination of Bald Eagles (Haliaeetus leucocephalus) have been conducted throughout the east coast of the United States, little has been done that directly addresses Hg contamination in Bald Eagles in Virginia, the inland population. It is well known that the neurotoxic properties of mercury (Hg) and methylmercury (MeHg) represent a substantial risk to wildlife, in particular, higher trophic level species (Scheuhammer 1987; Yates et al 2004, 2005; Evers et al 2005; Hopkins et al 2013). In contrast to the Chesapeake Bay, several inland areas in the state have been identified as hotspots for Hg exposure to other avian species, including the Shenandoah River (Jackson et al 2011; Cristol et al 2012; Hopkins et al 2013) and the North Fork of the Holsten River (Echols et al 2009). Jackson et al (2011) noted that forest songbirds were exhibiting elevated Hg concentrations over 130 km downstream of the known point source on the Shenandoah River, with Hg distributed in downstream habitat features such as flood plain areas
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