Assessing the Impacts of Methylmercury on Piscivorous Wildlife as Indicated by the Common Loon, 1998-2000

Evers, David; De Sorbo, Chris; Savoy, Lucas

'Anthropogenic inputs of mercury (Hg) into the environment have significantly increased in the past few decades. In conjunction, the current availability of methylmercury (MeHg) in aquatic systems has increased to levels posing risks to human and ecological health. Risk levels vary considerably in topography, and proximity to airborne sources. We selected the Common Loon as the most suitable bioindicator of aquatic Hg toxicity, based on ecological, logistical, and other criteria, including public valuations of natural resources.' '...Based on risk categories developed from the literature an in situ studies by BioDiversity Research Institute and their collaborators, 28% of the breeding loon population in Maine is estimated to be at risk, while 40% of the eggs laid are potentially impacted. Because the results from national sampling indicated loons were at most risk from Hg in New England (particularly Maine), we identified several individual- and population-level parameters to better understand the extent of mercury toxicity across Maine. Between 1994-1999, we collected 80 abondoned eggs and blood and feather samples from 159 adult and 78 juvenile wild loons monitored and captured in Maine. The Hg concentraion in these samples were used to analyze potential subtle impacts of Hg on egg development, behavior, development stability, immunosuppression, individual survival, and overall reporductive success. A total of 108 loon territories were monitored on 29 lakes during 1998-1999, and behavioral studies were conducted on 6 lakes with 10 loon territories in 1999....When combined with exposure levels in three matrices (n-431) our documented impacts provide strong evidence that individual loons and potentially Maine's breeding populations are at significant risk to Hg toxicity. Continued research will refine these risk assesments of regional and national interest. Use of the loon as a biosentinel has contributed immensly to our understanding of mercury's impacts on Maine's ecological health. We now recommend investigations into other high-risk species to measure the extent of MeHg toxicity and how it may be impacting other wildlife populations in Maine.' /STUDY LOCATIONS:/ /MOUNT DESERT ISLAND/Seal Cove Pond/Echo Lake/

Assessing the Impacts of Methylmercury on Piscivorous Wildlife as Indicated by the Common Loon, 1998-2000

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