Ecologically-Driven Exposure Pathways Science Team
The Team Determines Factors That Influence Fish and Wildlife Exposure
to toxicants such as mercury in the environment
Scientists Can Sample Tissues and Blood in Small Birds Without Harm
to understand factors such as maternal transfer of contaminants to offspring
The Team Studies Factors that Influence Exposure Risk in Mammals
such as foraging and fasting behavior in elephant seals
Factors that Influence Pathogen Transmission are Identified
Advanced Techniques are used to Understand Contaminant Sources
Science Center Objects
The Ecologically-Driven Exposure pathways team identifies internal and external pathways and processes that can alter exposure and toxicity of contaminants and pathogens to wildlife the environment. That information is used to distinguish actual health risks to fish and wildlife. If actual risks are identified this project will inform how to economically and effectively minimize risk by providing scientific data and understandings about the management practice as well as related environmental transport, fate, and exposure pathways of contaminants and pathogens. Emphasis will be placed on addressing these issues on public and Department of the Interior managed landscapes.
Photograph showing white-faced ibis nesting at Bear River Migratory Bird Refuge, Great Salt Lake, Utah. U.S. Geological Survey (USGS) scientists evaluated a nonlethal method to estimate mercury in the embryos of 23 bird species using mercury content in eggshells. This method was effective for a wide range of ages and species.
(Credit: Josh T. Ackerman, Western Ecological Research Center. Public domain.)
Contaminant and pathogen exposure alone does not necessarily result in adverse health outcomes in fish, wildlife, or humans. There are numerous pathways and processes that can alter the toxicity of naturally occurring and human-made contaminants in the environment.
The team uses their broad scientific expertise in hydrology, geochemistry, biology, and ecotoxicoogy to understand the complexities associated with the movement of toxicants and pathogens through the environment and within individual organisms. That information is used to determine how, where, and when exposure occurrs and if exposure results in health risks to wildlife and humans.
Current Science Questions and Activities
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What are the various ecological factors, such as habitats and foraging strategies, that influence the pathways of contaminant exposure, health risks to fish and wildlife?
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What are the major intrinsic and extrinsic drivers of mercury exposure and risk to humans, fish, and wildlife at a global scale?
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What are the internal physiological determinants such as metababolism, transfer of mercury to offspring, changes in body mass, and molting that influence exposure and health risks in fish and wildlife?
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How do the internal factors differ among species and life stages?
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What are the Influences of landscape alterations, perturbations, and restoration on pathways and movement of contaminants through ecosystems and bioaccumulation into the food web of aquatic biota?
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Do multiple types and chemical mixtures have additive, synergistic, or antagonistic effects that influence the health of fish and wildlife?
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What are the internal and external drivers and regulators of human exposure to mercury?
- What is the risk of pathogen exposure and transmission among wildlife, livestock, and humans?
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What are the key environmental factors that control the viability of avian influenza virus shed by wild birds and what are the key environmental pathways of exposure and transmission of the virus?
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What is the role of soil, water, and vegetation in disease transmission such as Chronic Wasting Disease?
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How do invasive species influence the timing of contaminant uptake and bioaccumulation in fish and wildlife?
USGS science related to this science team’s activities.
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Date published: November 13, 2019Status: Completed
Food Web Changes Dampen Expected Reductions in Lake Trout Mercury Levels in Lake Michigan—Invasive Species Play Major Role
Combined analyses of mercury, nitrogen, and carbon isotopes in archived lake trout (Salvelinus namaycush) tissues and sediment cores in Lake Michigan from 1978 to 2012 indicated that lake trout mercury concentrations mirrored declines in mercury sources prior to the arrival of invasive species that changed mercury transfer through the food and dampened the expected decreases in mercury...
Contacts: David P Krabbenhoft -
Date published: October 11, 2019Status: Completed
Mercury Isotope Ratios used to Determine Sources of Mercury to Fish in Northeast U.S. Streams
Mercury isotope analyses were used to distinguish different sources of mercury to fish in 23 streams along a forested-rural to urban-industrial land-use gradient in the Northeastern United States. The use of mercury isotope measurements in fish tissue allow for distinguishing different sources of mercury that are bioaccumulating into the food web. Mercury isotope signatures in fish in forested...
Contacts: David P Krabbenhoft, Sarah E Janssen -
Date published: October 4, 2019Status: Completed
Science to Help Understand Exposure and Toxicological Effects of Environmental Mercury to Representative Birds
Exposure and toxicity of environmental mercury to birds can be enhanced or lessened due to the available sources and forms of mercury and other species dependent factors such as life stage, migratory patterns, foraging and nesting behaviors, transfer of mercury from mothers to eggs, and sex. For example, mercury exposure can lead to sublethal toxicological effects that can influence parental...
Contacts: Josh T Ackerman -
Date published: October 1, 2019Status: Completed
No Adverse Reproductive Effects Observed in Tree Swallows Exposed to Perfluoroalkyl Substances in Clarks Marsh, Michigan
Perfluoroalkyl substance (PFAS) concentrations in tree swallows (Tachycineta bicolor) breeding at Clarks Marsh near a decommissioned U.S. Air Force base in Michigan were among the highest concentrations ever documented in birds indicating significant PFAS exposures. In contrast to previous studies where reproductive impairment was documented at lower PFAS exposure, there were no...
Contacts: Christine Custer -
Date published: February 25, 2019Status: Completed
Roadmap to Understanding Factors Influencing Mercury Exposure and Adverse Health Effects
In a comprehensive overview, scientists explain that human and wildlife exposure and toxicological responses to mercury are dependent on factors that operate across global, individual, and molecular scales. They provide a roadmap for unified research to facilitate a better understanding of human and wildlife health risks from mercury exposure.
Contacts: Collin Eagles-Smith -
Date published: August 23, 2018Status: Completed
Systematic Approach to Understanding Tree Swallow Health in the Great Lakes Region—Science to Inform Restoration
Four papers by U.S. Geological Survey (USGS) scientists document tree swallow (Tachycineta bicolor) chemical exposure, physiological responses, and reproductive success in the Great Lakes region. These studies were designed to understand if there are health threats to swallows from contaminant exposure, and to provide resource managers with information about the actual as opposed to...
Contacts: Christine Custer, Thomas Custer -
Date published: June 6, 2018Status: Completed
Scientists Identify Processes that Affect Fish Mercury Concentrations in Estuarine Wetlands
In a study designed to help resource managers when considering mercury exposure risk, scientists determined that sulfur cycling—a process closely related to mercury methylation rates—and ecological conditions that influence exposure are important factors affecting fish mercury concentrations in estuarine wetlands.
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Date published: May 25, 2018Status: Completed
Simple Ways to Avoid Public Exposures to Infectious Wildlife Diseases Summarized
The U.S. Geological Survey (USGS), in collaboration with the U.S. Fish and Wildlife Service (USFWS) and other disease specialists, have published reports during the past 12 years with information about the geographic distribution of diseases, specific pathogens, disease ecology, and strategies to avoid human exposure and infection for seven zoonotic diseases.
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Date published: May 18, 2018Status: Completed
New Method Can Measure Naturally Occurring Element Exposure in Hummingbirds Without Harm
Seventeen naturally occurring trace elements, including those associated with adverse health impacts when birds are exposed to toxic levels (iron, lead, mercury, selenium, zinc, cadmium, and arsenic) were measured in small birds without harm. The nonlethal method was developed for hummingbirds, with Anna's hummingbirds (Calypte anna) as a test species and can be more broadly applied...
Contacts: Josh T Ackerman, Lisa Tell, Robert Poppenga- DVM, PhD, DABVT -
Date published: October 18, 2017Status: Completed
Body Symmetry in Forster's Terns Related to Mercury Exposure
Body symmetry of Forster's terns (Sterna forsteri) in San Francisco Bay was related to blood and feather mercury concentrations. Body asymmetry can affect a bird's fitness by reducing flight efficiency, thus increasing energetic costs (especially during migration) and interrupting normal feeding and breeding behaviors.
Contacts: Collin Eagles-Smith
Below are publications associated with this science team. Get this science team’s complete bibliography.
Contaminant subsidies to riparian food webs in Appalachian streams impacted by mountaintop removal coal mining
Selenium is highly elevated in Appalachian streams and stream organisms that receive alkaline mine drainage from mountaintop removal coal mining compared to unimpacted streams in the region. Adult aquatic insects can be important vectors of waterborne contaminants to riparian food webs, yet pathways of Se transport and exposure of riparian...
Naslund, Laura C.; Gerson, Jacqueline R.; Brooks, Alexander C.; Walters, David; Bernhardt, Emily S.Prioritizing water security in the management of vector borne diseases: Lessons from Oaxaca, Mexico
Changes in human water use, along with temperature and rainfall patterns, are facilitating habitat spread and distribution of Aedes aegypti and Aedes albopictus mosquitoes, the primary vectors for the transmission of Dengue, Chikungunya, and Zika viruses in the Americas. Artificial containers and wetspots provide major sources of mosquito larval...
Akanda, Ali S; Johnson, Kristine D.; Ginsberg, Howard S.; Couret, JanelleMercury and selenium concentrations in fishes of the Upper Colorado River Basin, southwestern United States: A retrospective assessment
Mercury (Hg) and selenium (Se) are contaminants of concern for fish in the Upper Colorado River Basin (UCRB). We explored Hg and Se in fish tissues (2,324 individuals) collected over 50 years (1962–2011) from the UCRB. Samples include native and non-native fish collected from lotic waterbodies spanning 7 major tributaries to the Colorado River....
Day, Natalie; Schmidt, Travis; Roberts, James J.; Osmundson, Barbara C.; Willacker, James; Eagles-Smith, CollinThe assessment and remediation of mercury contaminated sites: A review of current approaches
Remediation of mercury (Hg) contaminated sites has long relied on traditional approaches, such as removal and containment/capping. Here we review contemporary practices in the assessment and remediation of industrial-scale Hg contaminated sites and discuss recent advances. Significant improvements have been made in site assessment, including the...
Eckley, Chris S.; Gilmour, Cynthia C; Janssen, Sarah E.; Luxton, Todd P; Randall, Paul M; Whalin, Lindsay; Carrie AustinAntibiotic resistant bacteria in wildlife: Perspectives on trends, acquisitions and dissemination, data gaps, and future directions
The proliferation of antibiotic resistant bacteria in the environment has potential negative economic and health consequences. Thus, previous investigations have targeted wild animals to understand the occurrence of antibiotic resistance in diverse environmental sources. In this critical review and synthesis, we summarize important concepts...
Ramey, Andrew M.; Ahlstrom, ChristinaMethylmercury exposure in wildlife: A review of the ecological and physiological processes affecting contaminant concentrations and their interpretation
Exposure to methylmercury (MeHg) can result in detrimental health effects in wildlife. With advances in ecological indicators and analytical techniques for measurement of MeHg in a variety of tissues, numerous processes have been identified that can influence MeHg concentrations in wildlife. This review presents a synthesis of theoretical...
Chételat, John; Ackerman, Joshua T.; Eagles-Smith, Collin; Hebert, Craig E.Wintering in the western subarctic pacific increases mercury contamination of Red-legged Kittiwakes
Marine methylmercury concentrations vary geographically and with depth, exposing organisms to different mercury levels in unique habitats. Red-legged kittiwakes (Rissa brevirostris), a specialist predator, forage on fish and invertebrates from the mesopelagic zone, a part of the ocean with elevated methylmercury concentrations. We used...
Fleishman, Abram S; Orben, Rachael; Kokubun, Nobuo; Will, Alexis; Paredes, Rosana; Ackerman, Joshua T.; Takahashi, Akinori; Kitaysky, Alexander; Shaffer, Scott A.Songbird feathers as indicators of mercury exposure: High variability and low predictive power suggest limitations
Although feathers are commonly used to monitor mercury (Hg) in avian populations, their reliability as a sampling matrix has not been thoroughly assessed for many avian species, including most songbirds (Order Passeriformes). To better understand relationships between total Hg (THg) concentrations in feathers and other tissues for birds in the...
Low, Katherine E.; Ramsden, Danielle K.; Jackson, Allyson K.; Emery, Colleen; Robinson, W. Douglas; Randolph, Jim; Eagles-Smith, Collin A.Synthesis of maternal transfer of mercury in birds: Implications for altered toxicity risk
Maternal transfer is the predominant route of methylmercury (MeHg) exposure to offspring. We reviewed and synthesized published and unpublished data on maternal transfer of MeHg in birds. Using paired samples of females’ blood (n=564) and their eggs (n=1814) from 26 bird species in 6 taxonomic orders, we conducted a meta-analysis to evaluate...
Ackerman, Joshua T.; Herzog, Mark P.; Evers, David C.; Cristol, Daniel A.; Kenow, Kevin P.; Heinz, Gary; Lavoie, Raphael A; Brasso, Rebecka L; Mallory, Mark L.; Provencher, Jennifer F; Braune, Birgit M; Matz, Angela; Schmutz, Joel A.; Eagles-Smith, Collin A.; Savoy, Lucas J; Meyer, Michael W.; Hartman, C. AlexIsolation of methylmercury using distillation and anion-exchange chromatography for isotopic analyses in natural matrices
The development of mercury (Hg) stable isotope measurements has enhanced the study of Hg sources and transformations in the environment. As a result of the mixing of inorganic Hg (iHg) and methylmercury (MeHg) species within organisms of the aquatic food web, understanding species-specific Hg stable isotopic compositions is of significant...
Rosera, Tylor; Janssen, Sarah E.; Tate, Michael T.; Lepak, Ryan F.; Ogorek, Jacob M.; DeWild, John F.; Babiarz, Christopher L.; Krabbenhoft, David P.; Hurley, James P.Mercury source changes and food web shifts alter contamination signatures of predatory fish from Lake Michigan
To understand the impact reduced mercury (Hg) loading and invasive species have had on methylmercury bioaccumulation in predator fish of Lake Michigan, we reconstructed bioaccumulation trends from a fish archive (1978 to 2012). By measuring fish Hg stable isotope ratios, we related temporal changes in Hg concentrations to varying Hg sources....
Lepak, Ryan F.; Hoffman, Joel C.; Janssen, Sarah E.; Krabbenhoft, David P.; Ogorek, Jacob M.; DeWild, John F.; Tate, Michael T.; Babiarz, Christopher L.; Yin, Runsheng; Murphy, Elizabeth W; Engstrom, Daniel R; Hurley, James P.Applying the ecology of aquatic–terrestrial linkages to freshwater and riparian management
Global stressors such as climate change, invasive species, urbanization, agricultural practices, and pollution can alter aquatic resource subsidies to terrestrial consumers. The effects of these stressors on timing, quality, and quantity of aquatic subsidies, such as adult aquatic insects, to birds, herpetofauna, and mammals, have large...
Kraus, Johanna M.The following are the data releases from this science team’s research activities.
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Date published: April 2, 2020
Total Mercury Concentrations in Smallmouth Bass from Chesapeake Bay Tributaries, USA Dataset, 2013-2017
This dataset includes fish scientific name, fish common name, site identification codes, latitude, longitude, site name, sample identification codes, collection date, tissue type, percent moisture content in fish samples, and wet and dry total mercury concentrations in fish tissues.
Attribution: Forest and Rangeland Ecosystem Science Center -
Date published: March 25, 2020
Biogeochemical Data for Mercury and other Constituents in Surface Sediment and Deep Cores from the Hells Canyon Reservoir Complex, Idaho and Oregon 2014-2018
Due to concerns regarding mercury (Hg) contamination within the HCC, in cooperation with Idaho Power Company, the U.S. Geological Survey has been leading an investigation into the sources, transport, microbial transformations, chemical speciation and bioaccumulation of Hg in this complex river-reservoir environment.
Attribution: Idaho Water Science Center -
Date published: January 16, 2020
Fish tissue mercury and selenium concentrations in Upper Colorado River Basin: 1962-2011
These data were compiled to study mercury and selenium concentrations in fish species and assemblages in lotic waterbodies across the Upper Colorado River Basin. Data were compiled from State and Federal agencies. This data table contains raw concentration data, as well as standardized concentrations corrected for differences based on sample type (i.e., tissue type), species-specific bi
Attribution: Southwest Biological Science Center -
Date published: December 30, 2019
Trask River Watershed Study Area Forestry Bioaccumulation Dataset, 2011-2015
This dataset includes timber harvest treatments; mercury concentrations in aquatic macroinvertebrates, salamanders, and riparian songbirds; carbon and nitrogen stable isotopes in aquatic macroinvertebrates and salamanders; and Bayesian estimates of food web length, basal resource diversity, and isotopic niche size for individual feeding guilds.
Attribution: Forest and Rangeland Ecosystem Science Center -
Date published: November 7, 2019
Mercury Contamination of Red-legged Kittiwakes in the Western Subarctic Pacific Ocean
This dataset contains mercury concentrations and locations of wintering red-legged kittiwakes in the western subartic Pacific Ocean.
Attribution: Western Ecological Research Center -
Date published: May 31, 2019
Incubation Constancy, Number of Incubation Recesses, Recess Duration and Mercury Concentrations for Tree Swallows at the Cosumnes River Preserve 2014
These metadata provide data used to examine tree swallow incubation behavior in relation to egg mercury concentration and maternal blood mercury concentration. These data were collected from tree swallows nesting in artificial wooden nest boxes at the Cosumnes River Preserved in California's Central Valley in 2014. Included are two datasets. One dataset provides daily incubation constancy (th...
Attribution: Western Ecological Research Center -
Date published: May 19, 2019
Element concentrations in nestling tree swallows (Tachycineta bicolor) from the U.S. and Binational Great Lakes’ Areas of Concern: Data
Tree swallow, Tachycineta bicolor, nestlings were collected from 76 sites in the Great Lakes which included multiple sites at 27 Areas of Concern (AOCs) and 12 sites not listed as AOCs from 2010 to 2015. Livers were harvested and analyzed for 21 elements. Mercury concentrations differed among AOCs; however, all livers analyzed had concentrations well within background and generally...
Attribution: Upper Midwest Environmental Sciences Center -
Date published: April 16, 2019
Perfluoroalkyl contaminant exposure in tree swallows nesting at Clarks Marsh, Oscoda, MI Dataset
A site in north eastern MI, Oscoda Township, has some of the highest recorded exposure in birds to perfluorinated substances (PFASs) in the U.S. Some egg and plasma concentrations at that location exceeded the lowest reproductive effect threshold established for two avian laboratory species. The objectives of this study were to determine whether there were reproductive effects or physio
Attribution: Upper Midwest Environmental Sciences Center -
Date published: February 28, 2019
Pore water chemistry of wetlands in Interior and Southcentral Alaska, 2015 and 2016
The pore water of eight wetlands in Interior and Southcentral Alaska were collected in 2015 (17 July – 22 July) and 2016 (12 July – 16 July). Wetlands were selected to span a range in trophic status (e.g., from bog to fen). Using ultraclean trace metal clean protocols, pore waters were sampled from shallow (10‑15 cm) and deep (20-35 cm) depths below
Attribution: Water Resources -
Date published: January 30, 2019
Patterns of mercury and selenium exposure in Minnesota common loons: Data
The concentrations of selected metals (mercury [Hg], lead, cadmium, selenium [Se], and aluminum) were determined in common loon (Gavia immer) blood samples collected from across a broad area of Minnesota. The observed pattern of loon Hg exposure was related to Hg concentrations in a standardized 12-cm whole organism yellow perch (Perca flavescens), based on fish Hg
Attribution: Upper Midwest Environmental Sciences Center