Avian mercury exposure and toxicological risk across western North America: A synthesis.
Methylmercury contamination of the environment is an important issue globally, and birds are useful bioindicators for mercury monitoring programs. The available data on mercury contamination of birds in western North America were synthesized. Original data from multiple databases were obtained and a literature review was conducted to obtain additional mercury concentrations. In total, 29219 original bird mercury concentrations from 225 species were compiled, and an additional 1712 mean mercury concentrations, representing 19998 individuals and 176 species, from 200 publications were obtained. To make mercury data comparable across bird tissues, published equations of tissue mercury correlations were used to convert all mercury concentrations into blood-equivalent mercury concentrations. Blood-equivalent mercury concentrations differed among species, foraging guilds, habitat types, locations, and ecoregions. Piscivores and carnivores exhibited the greatest mercury concentrations, whereas herbivores and granivores exhibited the lowest mercury concentrations. Bird mercury concentrations were greatest in ocean and salt marsh habitats and lowest in terrestrial habitats. Bird mercury concentrations were above toxicity benchmarks in many areas throughout western North America, and multiple hotspots were identified. Additionally, published toxicity benchmarks established in multiple tissues were summarized and translated into a common blood-equivalent mercury concentration. Overall, 66% of birds sampled in western North American exceeded a blood-equivalent mercury concentration of 0.2 μg/g wet weight (ww; above background levels), which is the lowest-observed effect level, 28% exceeded 1.0 μg/g ww (moderate risk), 8% exceeded 3.0 μg/g ww (high risk), and 4% exceeded 4.0 μg/g ww (severe risk). Mercury monitoring programs should sample bird tissues, such as adult blood and eggs, that are most-easily translated into tissues with well-developed toxicity benchmarks and that are directly relevant to bird reproduction. Results indicate that mercury contamination of birds is prevalent in many areas throughout western North America, and large-scale ecological attributes are important factors influencing bird mercury concentrations.
U.S. Geological Survey, Western Ecological Research Center, Dixon Field Station, 800 Business Park Drive, Suite D, Dixon, California 95620, United States. Electronic address: jackerman@usgs.gov.
Joshua T
JT
Ackerman
U.S. Geological Survey, Forest and Rangeland Ecosystem Science Center, 3200 SW Jefferson Way, Corvallis, Oregon, 97331, United States.
Collin A
CA
Eagles-Smith
U.S. Geological Survey, Western Ecological Research Center, Dixon Field Station, 800 Business Park Drive, Suite D, Dixon, California 95620, United States.
Mark P
MP
Herzog
U.S. Geological Survey, Western Ecological Research Center, Dixon Field Station, 800 Business Park Drive, Suite D, Dixon, California 95620, United States.
C Alex
CA
Hartman
U.S. Geological Survey, Western Ecological Research Center, Dixon Field Station, 800 Business Park Drive, Suite D, Dixon, California 95620, United States.
Sarah H
SH
Peterson
Biodiversity Research Institute, 276 Canco Road, Portland, Maine, 04103, United States.
David C
DC
Evers
Oregon State University, Department of Fisheries and Wildlife, 104 Nash Hall, Corvallis, Oregon, 97331, United States.
Allyson K
AK
Jackson
Environment Canada, Science and Technology Branch, Pacific Wildlife Research Centre, Delta, British Columbia, V4K 3N2, Canada.
John E
JE
Elliott
National Institute of Standards and Technology, Chemical Sciences Division, Hollings Marine Laboratory, 331 Fort Johnson Road, Charleston, South Carolina, 29412, United States.
Stacy S
SS
Vander Pol
National Institute of Standards and Technology, Chemical Sciences Division, Hollings Marine Laboratory, 331 Fort Johnson Road, Charleston, South Carolina, 29412, United States.
Colleen E
CE
Bryan
D000818:Animals; D001717:Birds / Q000097:blood* / Q000145:classification; D002170:Canada; D016208:Databases, Factual; D004784:Environmental Monitoring / Q000379:methods*; D004785:Environmental Pollutants / Q000032:analysis* / Q000493:pharmacokinetics / Q000633:toxicity*; D040362:Geographic Information Systems; D008767:Methylmercury Compounds / Q000032:analysis* / Q000493:pharmacokinetics / Q000633:toxicity*; D015146:Midwestern United States; D008954:Models, Biological; D015205:Northwestern United States; D018570:Risk Assessment; D015206:Southwestern United States; D013045:Species Specificity; D014018:Tissue Distribution
D004785:Environmental Pollutants; D008767:Methylmercury Compounds
Bioaccumulation; Birds; Eggs; Mercury; Toxicity Benchmarks