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Brasso R, Rittenhouse KA, Winder VL. Do songbirds in wetlands show higher mercury bioaccumulation relative to conspecifics in non-wetland habitats? ECOTOXICOLOGY (LONDON, ENGLAND) 2020; 29:1183-1194. [PMID: 31942663 DOI: 10.1007/s10646-020-02160-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 01/03/2020] [Indexed: 06/10/2023]
Abstract
Environmental conditions in wetlands facilitate favorable biogeochemical conditions for the conversion of inorganic mercury into methylmercury. For this reason, wetlands are increasingly classified as mercury hotspots, places where biota exhibit elevated mercury concentrations. While it is clear that wetlands play an important role in methylmercury production, factors such as geographic variation in mercury deposition, wetland type, and trophic dynamics can cause variation in mercury dynamics and bioaccumulation in biota occupying wetlands or connected to wetland trophic systems. Here, we use songbirds as bioindicators in a two-pronged approach aimed at evaluating the state of our understanding of mercury bioaccumulation by songbirds in wetland ecosystems. First, we use a case study in southeast Missouri to compare blood mercury concentrations in tree swallows (Tachycineta bicolor) and eastern bluebirds (Sialia sialis) occupying wetland and non-wetland habitats to test the hypothesis that songbirds in wetlands will have higher mercury bioaccumulation than those in non-wetlands. Adult tree swallows in wetlands had significantly higher blood mercury concentrations than those in non-wetlands; however, no difference between ecosystems was detected in eastern bluebirds. Second, we present a review of the current literature on mercury in songbirds in wetland ecosystems across North America. Mercury concentrations in songbirds varied among wetland types and with geographic location, often in an unpredictable manner. Mercury concentrations in songbird blood varied 3-10 fold at locations separated only by ~10 to several hundred kilometers. This magnitude of difference in blood mercury concentrations among wetlands exceeds documented differences between wetland and non-wetland ecosystems. Therefore, we caution against the automatic assumption that songbirds occupying wetlands will have higher mercury bioaccumulation than conspecifics living in other habitats.
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Affiliation(s)
- Rebecka Brasso
- Department of Zoology, Weber State University, Ogden, UT, 84408, USA.
| | - Katie Ann Rittenhouse
- Department of Biology, Southeast Missouri State University, Cape Girardeau, MO, 63701, USA
| | - Virginia L Winder
- Department of Biology, Benedictine College, Atchison, KS, 66002, USA
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Lane O, Adams EM, Pau N, O'Brien KM, Regan K, Farina M, Schneider-Moran T, Zarudsky J. Long-term monitoring of mercury in adult saltmarsh sparrows breeding in Maine, Massachusetts and New York, USA 2000-2017. ECOTOXICOLOGY (LONDON, ENGLAND) 2020; 29:1148-1160. [PMID: 32124146 DOI: 10.1007/s10646-020-02180-w] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 02/17/2020] [Indexed: 06/10/2023]
Abstract
Here we report on the results of a long-term study of mercury exposure in a songbird species, the saltmarsh sparrow (Ammodramus caudacutus). We measured total mercury concentrations in blood (n = 840) and feathers (n = 560) of adult saltmarsh sparrows at six locations between 2000 and 2017: Rachel Carson National Wildlife Refuge (RCNWR) in Wells, Maine; Scarborough Marsh State Wildlife Management Area in Scarborough, Maine; Parker River National Wildlife Refuge on Plum Island, Massachusetts; Pine Neck Preserve in Southampton, Long Island, New York; and North Cinder and North Green Sedge Islands off the coast of Long Island, New York. During the 12-17 year sampling periods, we found that mercury exposure differed by site and year but there was no consistent temporal trend across sites. Blood mercury concentrations declined only at RCNWR in Maine. We also found seasonal variation in blood mercury concentrations and a positive relationship between mercury concentrations of blood and innermost primary feather, but not between blood and tail feather.
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Affiliation(s)
- Oksana Lane
- Biodiversity Research Institute, 276 Canco Road, Portland, ME, 04103, USA.
| | - Evan M Adams
- Biodiversity Research Institute, 276 Canco Road, Portland, ME, 04103, USA
| | - Nancy Pau
- USFWS, Parker River NWR, 6 Plum Island Turnpike, Newburyport, MA, 01950, USA
| | | | - Kevin Regan
- Biodiversity Research Institute, 276 Canco Road, Portland, ME, 04103, USA
| | - Michael Farina
- Town of Hempstead: Department of Conservation and Waterways, 1401 Lido Blvd, Point Lookout, NY, 11561, USA
| | - Tara Schneider-Moran
- Town of Hempstead: Department of Conservation and Waterways, 1401 Lido Blvd, Point Lookout, NY, 11561, USA
| | - John Zarudsky
- Town of Hempstead: Department of Conservation and Waterways, 1401 Lido Blvd, Point Lookout, NY, 11561, USA
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Kardynal KJ, Jardine TD, Génier CSV, Bumelis KH, Mitchell GW, Evans M, Hobson KA. Mercury exposure to swallows breeding in Canada inferred from feathers grown on breeding and non-breeding grounds. ECOTOXICOLOGY (LONDON, ENGLAND) 2020; 29:876-891. [PMID: 32656653 DOI: 10.1007/s10646-020-02249-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 06/30/2020] [Indexed: 06/11/2023]
Abstract
Aerial insectivorous birds such as swallows have been the steepest declining groups of birds in North America over the last 50 years but whether such declines are linked to contaminants has not been examined. We sampled feathers from five species of swallow at multiple locations to assess total mercury [THg] exposure for adults during the non-breeding season, and for juveniles on the breeding grounds. We assessed Hg exposure to juvenile birds in crop- and grass-dominated landscapes to determine if land-use practices influenced feather [THg]. We assayed feathers for stable isotopes (δ2H, δ13C, δ15N) as proxies for relative habitat use and diet to determine their potential influence on feather [THg]. Feather [THg] was highest in adult bank swallows (Riparia riparia) and purple martins (Progne subis) from Saskatchewan and adult cliff swallows (Petrochelidon pyrrhonota) from western regions, indicating differential exposure to Hg on the non-breeding grounds. Juvenile bank, barn (Hirundo rustica) and tree (Tachycineta bicolor) swallows had lower feather [THg] in crop-dominated landscapes than grass-dominated landscapes in Saskatchewan, potentially resulting from lower use of wetland-derived insects due to wetland drainage and intensive agriculture. Feather [THg] was related to juvenile feather stable isotopes for several species, suggesting complex interactions with diet and environmental factors. Many individuals had feather [THg] values >2 µg/g, a threshold at which deleterious effects may occur. Our findings indicate differential Hg exposure among species of swallow, regions and land-uses and highlight the need for additional research to determine dietary and finer-scale land-use impacts on individual species and populations.
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Affiliation(s)
- Kevin J Kardynal
- Environment and Climate Change Canada, 11 Innovation Blvd., Saskatoon, SK, S7N 3H5, Canada.
| | - Timothy D Jardine
- School of Environment and Sustainability, Toxicology Centre, University of Saskatchewan, Saskatoon, SK, S7N 5B3, Canada
| | - Corrine S V Génier
- Department of Biology, University of Western Ontario, London, ON, N6A 3K7, Canada
| | - Kaelyn H Bumelis
- Department of Biology, University of Western Ontario, London, ON, N6A 3K7, Canada
| | - Greg W Mitchell
- Environment and Climate Change Canada, 1125 Colonel By Drive, Ottawa, ON, K1A 0H3, Canada
| | - Marlene Evans
- Environment and Climate Change Canada, 11 Innovation Blvd., Saskatoon, SK, S7N 3H5, Canada
| | - Keith A Hobson
- Environment and Climate Change Canada, 11 Innovation Blvd., Saskatoon, SK, S7N 3H5, Canada
- Department of Biology, University of Western Ontario, London, ON, N6A 3K7, Canada
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