Bi-phasic trends in mercury concentrations in blood of Wisconsin common loons during 1992–2010

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Wisconsin Department of Natural Resources (WDNR) assessed the ecological risk of mercury (Hg) in aquatic systems by monitoring common loon (Gavia immer) population dynamics and blood Hg concentrations. We report temporal trends in blood Hg concentrations based on 334 samples collected from adults recaptured in subsequent years (resampled 2-9 times) and from 421 blood samples of chicks collected at lakes resampled 2-8 times 1992-2010.. Temporal trends were identified with generalized additive mixed effects models (GAMMs) and mixed effects models to account for the potential lack of independence among observations from the same loon or same lake. Trend analyses indicated that Hg concentrations in the blood of Wisconsin loons declined over the period 1992-2000, and increased during 2002-2010, but not to the level observed in the early 1990s. The best fitting linear mixed effects model included separate trends for the two time periods. The estimated trend in Hg concentration among the adult loon population during 1992-2000 was -2.6% per year and the estimated trend during 2002-2010 was +1.8% per year; chick blood Hg concentrations decreased by -6.5% per year during 1992-2000, but increased 1.8% per year during 2002-2010. This bi-phasic pattern is similar to trends observed for concentrations of methylmercury (meHg) and SO4 in lake water of a well studied seepage lake (Little Rock Lake, Vilas County) within our study area. A cause-effect relationship between these independent trends is hypothesized.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Bi-phasic trends in mercury concentrations in blood of Wisconsin common loons during 1992–2010
Series title Ecotoxicology
Volume 20
Issue 7
Year Published 2011
Language English
Publisher Springer
Publisher location Amsterdam,Netherlands
Contributing office(s) Upper Midwest Environmental Sciences Center
Description 10 p.
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Ecotoxicology
First page 1659
Last page 1668
Country United States
State Wisconsin
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