I am an Ecologist specializing in aquatic and trophic ecology at the USGS Forest and Rangeland Ecosystem Science Center in Corvallis, OR
I am broadly interested in aquatic ecology and in particular the application of trophic ecology to questions of ecotoxicology, evolution, physiology, and conservation biology. My current research focuses on understanding the interplay among ecological, biogeochemical, and physiological processes that govern contaminant accumulation in biota, particularly fishes and other aquatic taxa. My work is also aimed at quantifying ecological risk and toxicological impacts associated with contaminants, particularly mercury.
Professional Experience
2013 - Present: Ecologist, USGS Forest and Rangeland Ecosystem Science Center, Corvallis, OR
2009 - 2013: Doctoral Researcher, University of Alaska Fairbanks, Fairbanks, AK
2009 - 2012: Instructor, Alaska Community Action on Toxics, Anchorage, AK
2007 - 2009: Aquatic Ecologist, Environmental and Natural Resource Institute, Anchorage, AK
Education and Certifications
Ph.D., Biological Sciences, University of Alaska, Fairbanks, AK (2013)
M.S., Biological Sciences, University of Alaska, Anchorage, AK (2009)
B.S., Environmental and Forest Biology- Summa cum laude, State University of New York College of Environmental Science and Forestry (2006)
Honors and Awards
Outstanding Graduate Researcher Award, Environment and Natural Resources Institute, University of Alaska, Anchorage, AK. (2011)
Valedictorian, SUNY ESF (2007)
University Scholar, SUNY (2007)
Faculty Honors, Department of Environmental and Forest Biology, SUNY ESF (2007)
Robin Hood Oak Award, SUNY ESF (2006)
Science and Products
Bioaccumulation of Mercury in Fish Varied by Species and Location in the Chesapeake Bay Watershed—Summary of Existing Data and a Roadmap for Integrated Monitoring
Scientists Identify Processes that Affect Fish Mercury Concentrations in Estuarine Wetlands
Contaminant Ecology Research Team (FRESC)
Mercury cycling, bioaccumulation, and risk across western North America: a landscape scale synthesis linking long-term datasets
If you are unable to access or download a product, email fresc_outreach@usgs.gov a request, including the full citation, or call (541) 750-1030.
Mercury in smallmouth bass from the Snake River, USA, 2013-2022
Mercury and biogeochemical parameters in surface water and sediment from U.S. National Parks, 2014-2015
Total mercury and methylmercury in biota from Cottage Grove Reservoir and the Coast Fork Willamette River, Oregon, 2021
Biomass and methylmercury concentrations in biweekly biological samples from Brownlee and Oxbow Reservoir outflows, Snake River Hells Canyon Complex (Idaho-Oregon), 2018-2019
Total Mercury Concentrations in Dragonfly Larvae from U.S. National Parks (ver. 8.0, December 2022)
Mercury Bioaccumulation in US National Parks Using Dragonfly Larvae as Biosentinels, 2009-2018
Total Mercury Concentrations in Smallmouth Bass from Chesapeake Bay Tributaries, USA Dataset, 2013-2017
Fish tissue mercury and selenium concentrations in Upper Colorado River Basin: 1962-2011
Trask River Watershed Study Area Forestry Bioaccumulation Dataset, 2011-2015
If you are unable to access or download a product, email fresc_outreach@usgs.gov a request, including the full citation, or call (541) 750-1030.
A multi-level assessment of biological effects associated with mercury concentrations in smallmouth bass, Micropterus dolomieu
The influence of short-term temporal variability on the efficacy of dragonfly larvae as mercury biosentinels
In-reservoir physical processes modulate aqueous and biological methylmercury export from a seasonally anoxic reservoir
Small mammal shooting as a conduit for lead exposure in avian scavengers
Fish habitat use and food web structure following pond and plug restoration of a Montane Meadow in the Sierra Nevada, California
A national-scale assessment of mercury bioaccumulation in United States National Parks using dragonfly larvae as biosentinels through a citizen-science framework
Mercury bioaccumulation in freshwater fishes of the Chesapeake Bay watershed
Mercury and selenium concentrations in fishes of the Upper Colorado River Basin, southwestern United States: A retrospective assessment
Timber harvest alters mercury bioaccumulation and food web structure in headwater streams
Mercury bioaccumulation in estuarine fishes: Novel insights from sulfur stable isotopes
Reservoirs and water management influence fish mercury concentrations in the western United States and Canada
Assessing potential health risks to fish and humans using mercury concentrations in inland fish from across western Canada and the United States
Non-USGS Publications**
**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.
Mercury Condition Index Tool
Science and Products
- Science
Bioaccumulation of Mercury in Fish Varied by Species and Location in the Chesapeake Bay Watershed—Summary of Existing Data and a Roadmap for Integrated Monitoring
Fish mercury data from State monitoring programs and research studies within the Chesapeake Bay were compiled and summarized to provide a comprehensive overview of the variation in fish mercury concentrations among species and habitats within the watershed. These data are put into context with existing health benchmarks for humans, birds, and fish. Scientists also provide a roadmap for an...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.Contaminant Ecology Research Team (FRESC)
The FRESC Contaminant Ecology research program evaluates the distribution, movement, and ecological effects of environmental contaminants across the landscape and strives to provide relevant science in support of natural resource conservation, management, and decision making.Mercury cycling, bioaccumulation, and risk across western North America: a landscape scale synthesis linking long-term datasets
Mercury (Hg) is a serious environmental problem that is impacting ecological and human health on a global scale. However, local and regional processes are largely responsible for producing methylmercury, which drives ecological risk. This is particularly true in western North America where the combination of diverse landscapes, habitat types, climates, and Hg sources may disproportionally impact t - Data
If you are unable to access or download a product, email fresc_outreach@usgs.gov a request, including the full citation, or call (541) 750-1030.
Mercury in smallmouth bass from the Snake River, USA, 2013-2022
Comma-separated values (.csv) file containing data related to mercury in smallmouth bass (Micropterus dolomieu) collected from the Snake River, USA.Mercury and biogeochemical parameters in surface water and sediment from U.S. National Parks, 2014-2015
Comma-separated values (.csv) file containing data related to mercury and biogeochemical parameters in surface water and aquatic sediment collected from U.S. National Parks in 2014-2015.Total mercury and methylmercury in biota from Cottage Grove Reservoir and the Coast Fork Willamette River, Oregon, 2021
Comma-separated values (.csv) file containing data related to mercury in biota from Cottage Grove Reservoir, and the rivers upstream of Cottage Grove Reservoir, Oregon.Biomass and methylmercury concentrations in biweekly biological samples from Brownlee and Oxbow Reservoir outflows, Snake River Hells Canyon Complex (Idaho-Oregon), 2018-2019
This dataset describes biomass and methylmercury concentrations in zooplankton, other invertebrates, fish, and coarse and fine detritus samples collected at the outflow locations of Brownlee and Oxbow Reservoirs in the Snake River Hells Canyon Complex. Based on the sampling locations, the sampled materials were presumed to have flowed through the dam turbines or over the spillway, thereby represenTotal Mercury Concentrations in Dragonfly Larvae from U.S. National Parks (ver. 8.0, December 2022)
Comma-separated values (.csv) file containing data related to mercury concentrations in dragonfly samples from U.S. National Parks collected as part of the Dragonfly Mercury Project (DMP)Mercury Bioaccumulation in US National Parks Using Dragonfly Larvae as Biosentinels, 2009-2018
Comma-separated values (.csv) files containing data related to a National-scale assessment of mercury bioaccumulation in the US National Parks using dragonfly larvae as biosentinels through a citizen science framework.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.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 bioaccumulatiTrask 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. - Publications
If you are unable to access or download a product, email fresc_outreach@usgs.gov a request, including the full citation, or call (541) 750-1030.
Filter Total Items: 21A multi-level assessment of biological effects associated with mercury concentrations in smallmouth bass, Micropterus dolomieu
Total mercury (THg) was measured in muscle (fillet) and liver tissue of adult smallmouth bass Micropterus dolomieu collected at multiple sites in the Potomac and Susquehanna River drainages within the Chesapeake Bay watershed. Smallmouth bass in these drainages have experienced episodic mortality events, a high prevalence of skin lesions and reproductive endocrine disruption (intersex or testiculaAuthorsVicki S. Blazer, Heather L. Walsh, Adam Sperry, Brenna Raines, James Willacker, Collin Eagles-SmithThe influence of short-term temporal variability on the efficacy of dragonfly larvae as mercury biosentinels
Mercury (Hg) exposure to fish, wildlife, and humans is widespread and of global concern, thus stimulating efforts to reduce emissions. Because the relationships between rates of inorganic Hg loading, methylmercury (MeHg) production, and bioaccumulation are extremely complex and challenging to predict, there is a need for reliable biosentinels to understand the distribution of Hg in the environmentAuthorsJames Willacker, Collin Eagles-Smith, Sarah J. Nelson, Colleen M. Flanagan-Pritz, David P. KrabbenhoftIn-reservoir physical processes modulate aqueous and biological methylmercury export from a seasonally anoxic reservoir
Anoxic conditions within reservoirs related to thermal stratification and oxygen depletion lead to methylmercury (MeHg) production, a key process governing the uptake of mercury in aquatic food webs. Once formed within a reservoir, the timing and magnitude of the biological uptake of MeHg and the relative importance of MeHg export in water versus biological compartments remain poorly understood. WAuthorsAustin K. Baldwin, Collin Eagles-Smith, James Willacker, Brett Poulin, David P. Krabbenhoft, Jesse Naymik, Michael T. Tate, Dain Bates, Nick Gastelecutto, Charles Hoovestol, Christopher F. Larsen, Alysa Muir Yoder, James A. Chandler, Ralph MyersSmall mammal shooting as a conduit for lead exposure in avian scavengers
Lead (Pb) exposure is a widespread wildlife conservation threat. Although commonly associated with Pb-based ammunition from big-game hunting, small mammals (e.g., ground squirrels) shot for recreational or pest-management purposes represent a potentially important Pb vector in agricultural regions. We measured the responses of avian scavengers to pest-shooting events and examined their Pb exposureAuthorsGarth Herring, Collin Eagles-Smith, John Goodell, Jeremy A. Buck, James WillackerFish habitat use and food web structure following pond and plug restoration of a Montane Meadow in the Sierra Nevada, California
Montane meadows are areas of high biodiversity and provide many important ecosystem services; however, degradation of 40–60% of these habitats in the Sierra Nevada region of California has left many of these areas impaired. The “pond-and-plug” meadow-restoration technique is 1 type of treatment implemented to restore montane meadows. The objectives of this technique are to re-water the meadow andAuthorsLora Tennant, Collin Eagles-Smith, James Willacker, Matthew JohnsonA national-scale assessment of mercury bioaccumulation in United States National Parks using dragonfly larvae as biosentinels through a citizen-science framework
We conducted a national-scale assessment of mercury (Hg) bioaccumulation in aquatic ecosystems using dragonfly larvae as biosentinels, by developing a citizen science network to facilitate biological sampling. Implementing a carefully designed sampling methodology for citizen scientists, we developed an effective framework for landscape-level inquiry that might otherwise be resource limited. We asAuthorsCollin Eagles-Smith, James Willacker, Sarah J. Nelson, Collen M Flanagan Pritz, David P. Krabbenhoft, Celia Y. Chen, Joshua T. Ackerman, Evan H. Campbell Grant, David PilliodMercury bioaccumulation in freshwater fishes of the Chesapeake Bay watershed
Chemical contaminants are a threat to the Chesapeake Bay watershed, with mercury (Hg) among the most prevalent causes of impairment. Despite this, large-scale patterns of Hg concentrations, and the potential risks to fish, wildlife, and humans across the watershed, are poorly understood. We compiled fish Hg data from state monitoring programs and recent research efforts to address this knowledge gAuthorsJames Willacker, Collin Eagles-Smith, Vicki S. BlazerMercury 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. There was little variation of total mercury (THg) inAuthorsNatalie K. Day, Travis Schmidt, James Roberts, Barbara C. Osmundson, James Willacker, Collin Eagles-SmithTimber harvest alters mercury bioaccumulation and food web structure in headwater streams
Timber harvest has many effects on aquatic ecosystems, including changes in hydrological, biogeochemical, and ecological processes that can influence mercury (Hg) cycling. Although timber harvest’s influence on aqueous Hg transformation and transport are well studied, the effects on Hg bioaccumulation are not. We evaluated Hg bioaccumulation, biomagnification, and food web structure in 10 paired cAuthorsJames Willacker, Collin A. Eagles-Smith, Brandon M Kowalski, Robert J Danehy, Allyson K. Jackson, Evan M. Adams, David C. Evers, Chris S. Eckley, Michael T. Tate, David P. KrabbenhoftMercury bioaccumulation in estuarine fishes: Novel insights from sulfur stable isotopes
Estuaries are transitional habitats characterized by complex biogeochemical and ecological gradients that result in substantial variation in fish total mercury concentrations (THg). We leveraged these gradients and used carbon (δ13C), nitrogen (δ15N), and sulfur (δ34S) stable isotopes to examine the ecological and biogeochemical processes underlying THg bioaccumulation in fishes from the San FrancAuthorsJames J. Willacker, Collin A. Eagles-Smith, Joshua T. AckermanReservoirs and water management influence fish mercury concentrations in the western United States and Canada
Anthropogenic manipulation of aquatic habitats can profoundly alter mercury (Hg) cycling and bioaccumulation. The impoundment of fluvial systems is among the most common habitat manipulations and is known to increase fish Hg concentrations immediately following impoundment. However, it is not well understood how Hg concentrations differ between reservoirs and lakes at large spatial and temporal scAuthorsJames J. Willacker, Collin A. Eagles-Smith, Michelle A. Lutz, Michael T. Tate, Jesse M. Lepak, Joshua T. AckermanAssessing potential health risks to fish and humans using mercury concentrations in inland fish from across western Canada and the United States
Fish represent high quality protein and nutrient sources, but Hg contamination is ubiquitous in aquatic ecosystems and can pose health risks to fish and their consumers. Potential health risks posed to fish and humans by Hg contamination in fish were assessed in western Canada and the United States. A large compilation of inland fish Hg concentrations was evaluated in terms of potential health risAuthorsJesse M. Lepak, Mevin Hooten, Collin A. Eagles-Smith, Michael T. Tate, Michelle A. Lutz, Joshua T. Ackerman, James J. Willacker, Allyson K. Jackson, David C. Evers, James G. Wiener, Colleen Flanagan Pritz, Jay DavisNon-USGS Publications**
Willacker Jr., J.J., Sobczak, W.V., Colburn, E.A., 2009, Stream macroinvertebrate communities in paired hemlock and deciduous watersheds: Northeastern Naturalist, v. 16, no. 1, p. 101-112, https://doi.org/10.1656/045.016.0108.Willacker Jr., J.J., von Hippel, F.A., Wilton, P.R., Walton, K.M., 2010, Classification of threespine stickleback along the benthic–limnetic axis: Biological Journal of the Linnean Society, v. 101, p. 595-608, https://doi.org/10.1111/j.1095-8312.2010.01531.x.Kenney, L.A., von Hippel, F.A., Willacker Jr., J.J., O'Hara, T.M., 2012, Mercury concentrations of a resident freshwater forage fish at Adak Island, Aleutian Archipelago, Alaska: Environmental Toxicology and Chemistry, v. 31, no. 11, p. 2647-2652, https://doi.org/10.1002/etc.1990.Walton, K.M., Spalinger, D.E., Harris, N.R., Collins, W.B., Willacker Jr., J.J., 2013, High spatial resolution vegetation mapping for assessment of wildlife habitat: Wildlife Society Bulletin, v. 37, no. 4, p. 906-915, https://doi.org/10.1002/wsb.344.Willacker Jr., J.J., von Hippel, F.A., Ackerly, K.L., O'Hara, T.M., 2013, Habitat-specific foraging and sex determine mercury concentrations in sympatric benthic and limnetic ecotypes of threespine stickleback: Environmental Toxicology and Chemistry, v. 32, no. 7, p. 1623-1630, https://doi.org/10.1002/etc.2213.Shedd, K.R., F.A. von Hippel, J.J. Willacker, T.R. Hamon, O.L. Schlei, J.K. Wenburg, J.L. Miller, and S.A. Pavey. 2015. Ecological release leads to novel ontogenetic diet shift in kokanee (Oncorhynchus nerka). Canadian Journal of Fisheries and Aquatic Sciences 72: 1718-1730.Willacker, J.J. 2013. Ecological drivers of mercury accumulation in Threespine Stickleback fish. Doctor of Philosophy, University of Alaska Fairbanks, Fairbanks, AK, USA.Willacker, J.J. 2009. Geometric morphometrics of Threespine Stickleback in the Cook Inlet Basin, Alaska. Master of Science, University of Alaska Anchorage, Anchorage, AK, USA.Willacker, J.J., D. Rinella, and D. Bogan. 2008. Aquatic macroinvertebrate and diatom surveys in Tetlin National Wildlife Refuge, AK. Environmental and Natural Resources Institute Annual Progress Report to the U.S. Fish and Wildlife Service.Willacker, J.J., D. Rinella, and D. Bogan. 2007. Macroinvertebrate abundance in the Eklutna River, AK: an estimate of food supply for rearing salmonids. Environmental and Natural Resources Institute Final Report to the Eklutna River Restoration Project, U.S. Army Corps of Engineers.
**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.
- Software
Mercury Condition Index Tool
The Mercury Condition Index Tool uses existing data of mercury concentrations in invertebrates, fish, and birds within national parks to estimate a park level Condition Index (and associated uncertainty) for mercury, based on its potential risk to fish and wildlife health. The tool employs a series of logic steps to convert provided data into standardized units, based upon both basic stoichiometr - News