Abstract
BackgroundMercury is a persistent, biomagnifying contaminant that can cause negative effects on ecosystems. Marshes are often areas of relatively high mercury methylation and bioaccumulation. Nelson's Sparrows (Ammodramus nelsoni) use marsh habitats year-round and have been documented to exhibit tissue mercury concentrations that exceed negative effects thresholds. We sought to further characterize the potential risk of Nelson's Sparrows to mercury exposure by sampling individuals from sites within the range of each of its subspecies.Methodology/Principal FindingsFrom 2009 to 2011, we captured adult Nelson's Sparrows at sites within the breeding range of each subspecies (A. n. nelsoni: Grand Forks and Upham, North Dakota; A. n. alterus: Moosonee, Ontario; and A. n. subvirgatus: Grand Manan Island, New Brunswick) and sampled breast feathers, the first primary feather (P1), and blood for total mercury analysis. Mean blood mercury in nelsoni individuals captured near Grand Forks ranged from 0.84±0.37 to 1.65±1.02 SD ppm among years, between 2.0 and 4.9 times as high as concentrations at the other sites (P<0.01). Breast feather mercury did not vary among sites within a given sampling year (site means ranged from 0.98±0.69 to 2.71±2.93 ppm). Mean P1 mercury in alterus (2.96±1.84 ppm fw) was significantly lower than in any other sampled population (5.25±2.24–6.77±3.51 ppm; P≤0.03).Conclusions/SignificanceOur study further characterized mercury in Nelson's Sparrows near Grand Forks; we documented localized and potentially harmful mercury concentrations, indicating that this area may represent a biological mercury hotspot. This finding warrants further research to determine if wildlife populations of conservation or recreational interest in this area may be experiencing negative effects due to mercury exposure. We present preliminary conclusions about the risk of each sampled population to mercury exposure.
Highlights
Mercury biomagnifies in both aquatic and terrestrial food webs [1,2] and can reach concentrations that result in negative effects on wildlife as well as human populations [3,4,5]
11% of nelsoni, and 7% of alterus exhibited breast feather mercury concentrations that correspond with thresholds for 10–40% reductions in nest success for Carolina Wrens (2.4–6.2 ppm fw) [4]
Data from the present study provide evidence that GFND exhibits both of these characteristics and as such may represent a biological mercury hotspot
Summary
Mercury biomagnifies (as methylmercury) in both aquatic and terrestrial food webs [1,2] and can reach concentrations that result in negative effects on wildlife as well as human populations [3,4,5]. Nelson’s Sparrows (Ammodramus nelsoni) are omnivorous passerines, divided into three subspecies with geographically separate breeding ranges in freshwater wetlands and salt marshes in North America Mercury exposure may be an important conservation concern for Nelson’s Sparrows because high mercury availability has been reported in areas coinciding with degraded habitat for this species [16,17], and mean blood and feather mercury concentrations in some populations exceed negative effects thresholds established for other species [12,18]. Nelson’s Sparrows (Ammodramus nelsoni) use marsh habitats year-round and have been documented to exhibit tissue mercury concentrations that exceed negative effects thresholds. We sought to further characterize the potential risk of Nelson’s Sparrows to mercury exposure by sampling individuals from sites within the range of each of its subspecies
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
