Mercury in western North America: A synthesis of environmental contamination, fluxes, bioaccumulation, and risk to fish and wildlife.
Western North America is a region defined by extreme gradients in geomorphology and climate, which support a diverse array of ecological communities and natural resources. The region also has extreme gradients in mercury (Hg) contamination due to a broad distribution of inorganic Hg sources. These diverse Hg sources and a varied landscape create a unique and complex mosaic of ecological risk from Hg impairment associated with differential methylmercury (MeHg) production and bioaccumulation. Understanding the landscape-scale variation in the magnitude and relative importance of processes associated with Hg transport, methylation, and MeHg bioaccumulation requires a multidisciplinary synthesis that transcends small-scale variability. The Western North America Mercury Synthesis compiled, analyzed, and interpreted spatial and temporal patterns and drivers of Hg and MeHg in air, soil, vegetation, sediments, fish, and wildlife across western North America. This collaboration evaluated the potential risk from Hg to fish, and wildlife health, human exposure, and examined resource management activities that influenced the risk of Hg contamination. This paper integrates the key information presented across the individual papers that comprise the synthesis. The compiled information indicates that Hg contamination is widespread, but heterogeneous, across western North America. The storage and transport of inorganic Hg across landscape gradients are largely regulated by climate and land-cover factors such as plant productivity and precipitation. Importantly, there was a striking lack of concordance between pools and sources of inorganic Hg, and MeHg in aquatic food webs. Additionally, water management had a widespread influence on MeHg bioaccumulation in aquatic ecosystems, whereas mining impacts where relatively localized. These results highlight the decoupling of inorganic Hg sources with MeHg production and bioaccumulation. Together the findings indicate that developing efforts to control MeHg production in the West may be particularly beneficial for reducing food web exposure instead of efforts to simply control inorganic Hg sources.
U.S. Geological Survey, Forest and Rangeland Ecosystem Science Center, 3200 SW Jefferson Way, Corvallis, OR 97331, USA. Electronic address: ceagles-smith@usgs.gov.
Collin A
CA
Eagles-Smith
University of Wisconsin La Crosse, River Studies Center, 1725 State Street, La Crosse, WI 54601, USA.
James G
JG
Wiener
U.S. Environmental Protection Agency, Region-10, 2100 6th Ave., Suite 900, Seattle, WA 98101, USA.
Chris S
CS
Eckley
U.S. Geological Survey, Forest and Rangeland Ecosystem Science Center, 3200 SW Jefferson Way, Corvallis, OR 97331, USA.
James J
JJ
Willacker
Biodiversity Research Institute, 276 Canco Road, Portland, ME 04103, USA.
David C
DC
Evers
U.S. Geological Survey, 345 Middlefield Road, Menlo Park, CA 94025, USA.
Mark
M
Marvin-DiPasquale
Desert Research Institute, Division of Atmospheric Sciences, 2215 Raggio Parkway, Reno, NV 89512, USA.
Daniel
D
Obrist
U.S. Geological Survey, California Water Science Center, 6000 J St., Placer Hall, Sacramento, CA 95819, USA.
Jacob A
JA
Fleck
U.S. Geological Survey, National Research Program, 3215 Marine St., Boulder, CO 80303, USA.
George R
GR
Aiken
Colorado Parks and Wildlife, 317 West Prospect Road, Fort Collins, CO 80526, USA.
Jesse M
JM
Lepak
Oregon State University, Department of Fisheries and Wildlife, 104 Nash Hall, Corvallis, OR 97331, USA.
Allyson K
AK
Jackson
University of Colorado, Civil, Environmental, and Architectural Engineering, Boulder, CO 80309, USA.
Jackson P
JP
Webster
U.S. Geological Survey, 345 Middlefield Road, Menlo Park, CA 94025, USA.
A Robin
AR
Stewart
San Francisco Estuary Institute, 4911 Central Ave., Richmond, CA 94804, USA.
Jay A
JA
Davis
U.S. Geological Survey, California Water Science Center, 6000 J St., Placer Hall, Sacramento, CA 95819, USA.
Charles N
CN
Alpers
U.S. Geological Survey, Western Ecological Research Center, Dixon Field Station, 800 Business Park Drive, Dixon, CA 95620, USA.
Joshua T
JT
Ackerman
D000818:Animals; D002170:Canada; D004784:Environmental Monitoring; D004785:Environmental Pollutants / Q000032:analysis / Q000378:metabolism*; D005399:Fishes / Q000378:metabolism; D008628:Mercury / Q000032:analysis / Q000378:metabolism*; D008767:Methylmercury Compounds / Q000032:analysis / Q000378:metabolism*; D008800:Mexico; D014481:United States; D014714:Vertebrates / Q000378:metabolism*
D004785:Environmental Pollutants; D008767:Methylmercury Compounds; D008628:Mercury
Atmospheric deposition; Bigeochemistry; Bioaccumulation; Birds; Landscape; Legacy mining; Methylmercury exposure; Risk