Monitoring of Contaminants in Nestling Bald Eagles of Grand Teton National Park

Abstract

We report on contaminants identified in nestling bald eagles of Grant Teton National Park (GTNP) and the Snake River Unit (SRU), Wyoming, during summers of 2006 and 2007. We focus primarily on mercury (Hg), lead (Pb), and selenium (Se) because each was detected in all nestlings during both summers at moderate levels. Independent t-tests were performed both on the raw data and log­transformed data (using the natural logarithm) as a comparative analysis to investigate if contaminant loads had significantly increased from summer 2006 to summer 2007. Also, as a comparative analysis and alternative procedure, nest site was treated as the experimental unit and a repeated-measures analysis (longitudinal study) was conducted on the raw data to investigate if contaminant loads had significantly increased from summer 2006 to summer 2007. Results of the analysis indicate that levels of Se essentially remained unchanged from summer 2006 to summer 2007 (p=0.466, log-transformed data). Levels of Pb in nestlings increased from summer 2006 to summer 2007 (p=0.000, log-transformed data). There was no difference in levels of Hg in nestlings from summer 2006 to summer 2007 (p=0.058, log-transformed data). The molar ratio (2.54ppm Se: 1 ppm Hg) of Se to Hg did not change from 2006 to 2007 (p=0.337, raw data), although a 45% decrease in molar ratio was observed. Analyses of contaminants (using geometric means) in the blood of nestlings (from summer 2006 to 2007) showed a 64% increase in Hg, a five-fold increase in Pb ( 481% ), and a 21% increase in Se. Potential localized sources of Pb contamination should be identified and removed from the proximity of any nest site(s) and the study area in general. Advancing global climate change and associated desiccation and emolation of temperate and boreal forests, exacerbated by extensive clear-cutting may increase poisoning of aquatic ecosystems with high levels of contaminants, especially Hg, in the future. A monitoring program may be indicated to identify potential long-term changes within the GYE. (p=O.OOO, log-transformed data). There was no difference in levels of Hg in nestlings from summer 2006 to summer 2007 (p=0.058, log­ transformed data). The molar ratio (2.54ppm Se: 1ppm Hg) of Se to Hg did not change from 2006 to 2007 (p=0.337, raw data), although a 45% decrease in molar ratio was observed. Analyses of contaminants (using geometric means) in the blood of nestlings (from summer 2006 to 2007) showed a 64% increase in Hg, a five-fold increase in Pb (481%), and a 21 % increase in Se. Potential localized sources of Pb contamination should be identified and removed from the proximity of any nest site(s) and the study area in general.