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Understanding sources of methylmercury in songbirds with stable mercury isotopes: Challenges and future directions.
- Source :
-
Environmental toxicology and chemistry [Environ Toxicol Chem] 2018 Jan; Vol. 37 (1), pp. 166-174. Date of Electronic Publication: 2017 Oct 11. - Publication Year :
- 2018
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Abstract
- Mercury (Hg) stable isotope analysis is an emerging technique that has contributed to a better understanding of many aspects of the biogeochemical cycling of Hg in the environment. However, no study has yet evaluated its usefulness in elucidating the sources of methylmercury (MeHg) in songbird species, a common organism for biomonitoring of Hg in forested ecosystems. In the present pilot study, we examined stable mercury isotope ratios in blood of 4 species of songbirds and the invertebrates they are likely foraging on in multiple habitats in a small watershed of mixed forest and wetlands in Acadia National Park in Maine (USA). We found distinct isotopic signatures of MeHg in invertebrates (both mass-dependent fractionation [as δ <superscript>202</superscript> Hg] and mass-independent fractionation [as Δ <superscript>199</superscript> Hg]) among 3 interconnected aquatic habitats. It appears that the Hg isotopic compositions in bird blood cannot be fully accounted for by the isotopic compositions of MeHg in lower trophic levels in each of the habitats examined. Furthermore, the bird blood isotope results cannot be simply explained by an isotopic offset as a result of metabolic fractionation of δ <superscript>202</superscript> Hg (e.g., internal demethylation). Our results suggest that many of the birds sampled obtain MeHg from sources outside the habitat they were captured in. Our findings also indicate that mass-independent fractionation is a more reliable and conservative tracer than mass-dependent fractionation for identifying sources of MeHg in bird blood. The results demonstrate the feasibility of Hg isotope studies of songbirds but suggest that larger numbers of samples and an expanded geographic area of study may be required for conclusive interpretation. Environ Toxicol Chem 2018;37:166-174. © 2017 SETAC.<br /> (© 2017 SETAC.)
- Subjects :
- Animals
Chemical Fractionation
Female
Fishes
Food Chain
Geography
Invertebrates metabolism
Larva metabolism
Maine
Male
Mercury analysis
Mercury Isotopes blood
Methylmercury Compounds blood
Pilot Projects
Songbirds blood
Wetlands
Environmental Monitoring methods
Mercury Isotopes metabolism
Methylmercury Compounds analysis
Songbirds metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 1552-8618
- Volume :
- 37
- Issue :
- 1
- Database :
- MEDLINE
- Journal :
- Environmental toxicology and chemistry
- Publication Type :
- Academic Journal
- Accession number :
- 28792100
- Full Text :
- https://doi.org/10.1002/etc.3941