James J Willacker, Jr.
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
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: 31
Geographic drivers of mercury entry into aquatic food webs revealed by mercury stable isotopes in dragonfly larvae Geographic drivers of mercury entry into aquatic food webs revealed by mercury stable isotopes in dragonfly larvae
Atmospheric mercury (Hg) emissions and subsequent transport and deposition are major concerns within protected lands, including national parks, where Hg can bioaccumulate to levels detrimental to human and wildlife health. Despite this risk to biological resources, there is limited understanding of the relative importance of different Hg sources and delivery pathways within protected...
Authors
Sarah E. Janssen, Christopher James Kotalik, James Willacker, Michael T. Tate, Colleen M Flanagan-Pritz, Sarah Nelson, David P. Krabbenhoft, David Walters, Collin A. Eagles-Smith
Wildfire burn severity and stream chemistry influence aquatic invertebrate and riparian avian mercury exposure in forested ecosystems Wildfire burn severity and stream chemistry influence aquatic invertebrate and riparian avian mercury exposure in forested ecosystems
Terrestrial soils in forested landscapes represent some of the largest mercury (Hg) reserves globally. Wildfire can alter the storage and distribution of terrestrial-bound Hg via reemission to the atmosphere or mobilization in watersheds where it may become available for methylation and uptake into food webs. Using data associated with the 2007 Moonlight and Antelope Fires in California...
Authors
Garth Herring, Lora B. Tennant, James Willacker, Matthew Johnson, Rodney B. Siegel, Julie S. Polasik, Collin A. Eagles-Smith
Habitat and dissolved organic carbon modulate variation in the biogeochemical drivers of mercury bioaccumulation in dragonfly larvae at the national scale Habitat and dissolved organic carbon modulate variation in the biogeochemical drivers of mercury bioaccumulation in dragonfly larvae at the national scale
We paired mercury (Hg) concentrations in dragonfly larvae with water chemistry in 29 U.S. national parks to highlight how ecological and biogeochemical context (habitat, dissolved organic carbon [DOC]) influence drivers of Hg bioaccumulation. Although prior studies have defined influences of biogeochemical variables on Hg production and bioaccumulation, it has been challenging to...
Authors
Sarah J. Nelson, James Willacker, Collin A. Eagles-Smith, Colleen M Flanagan Pritz, Celia Y. Chen, Amanda J Klemmer, David P. Krabbenhoft
Reservoir stratification modulates the influence of impoundments on fish mercury concentrations along an arid land river system Reservoir stratification modulates the influence of impoundments on fish mercury concentrations along an arid land river system
Impoundment is among the most common hydrologic alterations with impacts on aquatic ecosystems that can include effects on mercury (Hg) cycling. However, landscape-scale differences in Hg bioaccumulation between reservoirs and other habitats are not well characterized nor are the processes driving these differences. We examined total Hg (THg) concentrations of Smallmouth Bass...
Authors
James Willacker, Collin A. Eagles-Smith, Jim Chandler, Jesse Naymik, Ralph Myers, David P. Krabbenhoft
A multi-level assessment of biological effects associated with mercury concentrations in smallmouth bass, Micropterus dolomieu A 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
Authors
Vicki S. Blazer, Heather L. Walsh, Adam Sperry, Brenna Raines, James Willacker, Collin A. Eagles-Smith
The influence of short-term temporal variability on the efficacy of dragonfly larvae as mercury biosentinels The 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...
Authors
James Willacker, Collin A. Eagles-Smith, Sarah J. Nelson, Colleen M. Flanagan-Pritz, David P. Krabbenhoft
Non-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.
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: 15
Mercury and biogeochemical parameters in surface water and sediment from U.S. National Parks, 2014-2015 (ver. 2.0, December 2023) Mercury and biogeochemical parameters in surface water and sediment from U.S. National Parks, 2014-2015 (ver. 2.0, December 2023)
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, Coast Fork Willamette River, and additional reservoirs in Oregon (ver. 2.0, February 2024) Total mercury and methylmercury in biota from Cottage Grove Reservoir, Coast Fork Willamette River, and additional reservoirs in Oregon (ver. 2.0, February 2024)
Comma Separated Value (CSV) file containing data related to total and methyl mercury concentrations in biota from the Willamette Basin in Oregon; specifically, Cottage Grove Reservoir, waters upstream of the reservoir, and additional reservoirs within the Willamette Basin.
Mercury Condition Index Tool 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
Biomass and methylmercury concentrations in biweekly biological samples from Brownlee and Oxbow Reservoir outflows, Snake River Hells Canyon Complex (Idaho-Oregon), 2018-2019 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...
Total Mercury Concentrations in Dragonfly Larvae from U.S. National Parks (ver. 11.0, January 2026) Total Mercury Concentrations in Dragonfly Larvae from U.S. National Parks (ver. 11.0, January 2026)
Comma-separated values (.csv) file containing data related to mercury concentrations in dragonfly samples from U.S. National Parks, Protected Places, and other federal lands collected as part of the Dragonfly Mercury Project (DMP). This data release supersedes Eagles-Smith, C.A., Nelson, S.J., Flanagan-Pritz, C.M., Willacker Jr., J.J., and Klemmer, A.J., 2018, Total mercury...
Mercury Bioaccumulation in US National Parks Using Dragonfly Larvae as Biosentinels, 2009-2018 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.
Science and Products
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: 31
Geographic drivers of mercury entry into aquatic food webs revealed by mercury stable isotopes in dragonfly larvae Geographic drivers of mercury entry into aquatic food webs revealed by mercury stable isotopes in dragonfly larvae
Atmospheric mercury (Hg) emissions and subsequent transport and deposition are major concerns within protected lands, including national parks, where Hg can bioaccumulate to levels detrimental to human and wildlife health. Despite this risk to biological resources, there is limited understanding of the relative importance of different Hg sources and delivery pathways within protected...
Authors
Sarah E. Janssen, Christopher James Kotalik, James Willacker, Michael T. Tate, Colleen M Flanagan-Pritz, Sarah Nelson, David P. Krabbenhoft, David Walters, Collin A. Eagles-Smith
Wildfire burn severity and stream chemistry influence aquatic invertebrate and riparian avian mercury exposure in forested ecosystems Wildfire burn severity and stream chemistry influence aquatic invertebrate and riparian avian mercury exposure in forested ecosystems
Terrestrial soils in forested landscapes represent some of the largest mercury (Hg) reserves globally. Wildfire can alter the storage and distribution of terrestrial-bound Hg via reemission to the atmosphere or mobilization in watersheds where it may become available for methylation and uptake into food webs. Using data associated with the 2007 Moonlight and Antelope Fires in California...
Authors
Garth Herring, Lora B. Tennant, James Willacker, Matthew Johnson, Rodney B. Siegel, Julie S. Polasik, Collin A. Eagles-Smith
Habitat and dissolved organic carbon modulate variation in the biogeochemical drivers of mercury bioaccumulation in dragonfly larvae at the national scale Habitat and dissolved organic carbon modulate variation in the biogeochemical drivers of mercury bioaccumulation in dragonfly larvae at the national scale
We paired mercury (Hg) concentrations in dragonfly larvae with water chemistry in 29 U.S. national parks to highlight how ecological and biogeochemical context (habitat, dissolved organic carbon [DOC]) influence drivers of Hg bioaccumulation. Although prior studies have defined influences of biogeochemical variables on Hg production and bioaccumulation, it has been challenging to...
Authors
Sarah J. Nelson, James Willacker, Collin A. Eagles-Smith, Colleen M Flanagan Pritz, Celia Y. Chen, Amanda J Klemmer, David P. Krabbenhoft
Reservoir stratification modulates the influence of impoundments on fish mercury concentrations along an arid land river system Reservoir stratification modulates the influence of impoundments on fish mercury concentrations along an arid land river system
Impoundment is among the most common hydrologic alterations with impacts on aquatic ecosystems that can include effects on mercury (Hg) cycling. However, landscape-scale differences in Hg bioaccumulation between reservoirs and other habitats are not well characterized nor are the processes driving these differences. We examined total Hg (THg) concentrations of Smallmouth Bass...
Authors
James Willacker, Collin A. Eagles-Smith, Jim Chandler, Jesse Naymik, Ralph Myers, David P. Krabbenhoft
A multi-level assessment of biological effects associated with mercury concentrations in smallmouth bass, Micropterus dolomieu A 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
Authors
Vicki S. Blazer, Heather L. Walsh, Adam Sperry, Brenna Raines, James Willacker, Collin A. Eagles-Smith
The influence of short-term temporal variability on the efficacy of dragonfly larvae as mercury biosentinels The 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...
Authors
James Willacker, Collin A. Eagles-Smith, Sarah J. Nelson, Colleen M. Flanagan-Pritz, David P. Krabbenhoft
Non-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.
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: 15
Mercury and biogeochemical parameters in surface water and sediment from U.S. National Parks, 2014-2015 (ver. 2.0, December 2023) Mercury and biogeochemical parameters in surface water and sediment from U.S. National Parks, 2014-2015 (ver. 2.0, December 2023)
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, Coast Fork Willamette River, and additional reservoirs in Oregon (ver. 2.0, February 2024) Total mercury and methylmercury in biota from Cottage Grove Reservoir, Coast Fork Willamette River, and additional reservoirs in Oregon (ver. 2.0, February 2024)
Comma Separated Value (CSV) file containing data related to total and methyl mercury concentrations in biota from the Willamette Basin in Oregon; specifically, Cottage Grove Reservoir, waters upstream of the reservoir, and additional reservoirs within the Willamette Basin.
Mercury Condition Index Tool 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
Biomass and methylmercury concentrations in biweekly biological samples from Brownlee and Oxbow Reservoir outflows, Snake River Hells Canyon Complex (Idaho-Oregon), 2018-2019 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...
Total Mercury Concentrations in Dragonfly Larvae from U.S. National Parks (ver. 11.0, January 2026) Total Mercury Concentrations in Dragonfly Larvae from U.S. National Parks (ver. 11.0, January 2026)
Comma-separated values (.csv) file containing data related to mercury concentrations in dragonfly samples from U.S. National Parks, Protected Places, and other federal lands collected as part of the Dragonfly Mercury Project (DMP). This data release supersedes Eagles-Smith, C.A., Nelson, S.J., Flanagan-Pritz, C.M., Willacker Jr., J.J., and Klemmer, A.J., 2018, Total mercury...
Mercury Bioaccumulation in US National Parks Using Dragonfly Larvae as Biosentinels, 2009-2018 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.