David Walters, PhD
Dr. David Walters is a Supervisory Research Ecologist at the Columbia Environmental Research Center.
David has been a research ecologist with the USGS since 2008. Prior to that, he was an ecologist for the U.S. EPA, National Exposure Research Laboratory for 6 years. He is a freshwater ecologist with broad training in stream ecology, human impacts on aquatic ecosystems, and ecotoxicology. His current research topics include food webs and contaminant flux, aquatic-riparian linkages, stream fish ecology, land use and climate change, and invasive species.
Current Projects/Areas of Interest
- Riparian indicators of contaminant exposure at Great Lakes Areas of Concern (AOCs)
We are investigating contaminant flux from aquatic to nearby terrestrial (riparian) shoreline habitats. In particular we use riparian spiders (many of which feed almost exclusively on adult aquatic insects) to characterize contamination at these sites and to evaluate the effectiveness of their remediation. - Leaky rivers: Nutrient retention and productivity in Rocky Mountain streams under alternative stable states
This project investigates how the volume of wood and log jams have declined in Rocky Mountain streams since European settlement, how the loss of wood affects stream geomorphology, communities, nutrient cycling, and productivity, and what management actions can be taken to restore lost ecosystem functions. - Mechanisms for metal uptake and trophic transfer in stream and riparian food webs in mineralized landscapes
We are investigating how metals in streams (derived from natural geologic sources as well as mines) are transferred from streams to riparian zones and how this contamination alters ecological linkages between these systems. This work combines large-scale field studies with mesocosm experiments to better understand processes driving the patterns we observe in nature. - “Metal webs” for the Grand Canyon
We are developing quantitative food webs to measure metal flux (mercury, selenium, and other trace metals) in the Colorado and Little Colorado rivers in Grand Canyon. These studies will identify key pathways of metal exposure to important fish species, such as the endangered humpback chub. - Consequences of climate change for alpine lake-stream networks and native fishes in the southern Rocky Mountains
This project investigates the importance of alpine lakes in the ecology of native cutthroat trout and how lakes could mitigate the negative effects of rising temperatures on these threatened populations.
Education and Certifications
Ph.D. Ecology, University of Georgia (UGA), 2002
M.S. Conservation Ecology, UGA, 1997
B.A. Anthropology, UGA, 1991
Science and Products
Per- and Polyfluoroalkyl Substance Exposure and Effects Research at Columbia Environmental Research Center (CERC)
Flood Redistributes Mercury in Grand Canyon Aquatic Food Webs
Areas of Concern: Technical Guidance for Assessing Remedy Effectiveness, Restoration, and Revitalization at Great Lakes AOCs and Great Lake Legacy Act (GLLA) Sites
Aquatic Ecology and Contaminants
Climate Change and Trout
Effects of Contaminants on Linked Aquatic and Terrestrial Food Webs
Surface Elevation Table (SET) data from the Blackwater National Wildlife Refuge (2010-2013)
Total PCB concentrations in sediment, water, macroinvertebrates and spiders and the lower Ottawa River (Toledo, OH) between 2009-2015
Plant and insect pollinator diversity data from Conservation Reserve Program fields across an agricultural gradient in eastern Iowa
Modeled Pacific salmon escapement biomass and nutrient and contaminant concentrations across western North America, 1976-2015
Assessment of Mercury and Mercury Stable Isotopes in Sediments and Biota from Reservoirs and Remedial Zones within the Saint Louis River, Minnesota
Images and Identifications of Wild Bees Collected in Eastern Iowa, 2019
Acute and chronic toxicity of two perfluoroalkyl substances to Neocloeon triangulifer
Total mercury, methylmercury, and isotopic composition in various life stages of boreal chorus frogs (Pseudacris maculata) at two subalpine ponds in the Rocky Mountains, CO, USA, 2015
Pesticide residues in passive samplers and bee tissue from Conservation Reserve Program fields across an agricultural gradient in eastern Iowa, USA, 2019 (ver 2.0, October 2023)
Survival, growth, behavior and mercury concentrations of mayflies exposed to elevated dietary methylmercury and aqueous selenium
Mercury concentrations, isotopic composition, biomass, and taxonomy of stream and riparian organisms in the vicinity of Yellow Pine, Idaho, 2015-2016.
Salt Marsh Turbidity at Mockhorn Island, VA; Plum Island, MA; York River, VA; and Altamaha River, GA
Geographic drivers of mercury entry into aquatic food webs revealed by mercury stable isotopes in dragonfly larvae
PCB concentrations in riparian spiders (Tetragnathidae) consistently reflect concentrations in water and aquatic macroinvertebrates, but not sediment: Analysis of a seven-year field study
Evolutionary and ecological correlates of thiaminase in fishes
A novel approach to assessing natural resource injury with Bayesian networks
Mercury isotope values in shoreline spiders reveal transfer of aquatic mercury sources to terrestrial food webs
Identifying invertebrate indicators for streamflow duration assessments in forested headwater streams
Perfluorooctanesulfonate adversely affects a mayfly (Neocloeon triangulifer) at environmentally realistic concentrations
Complex life histories alter patterns of mercury exposure and accumulation in a pond-breeding amphibian
Evaluation of Ziram as an oral toxic bait chemical for control of grass carp Ctenopharyngodon idella
Ecotoxicological studies indicate that sublethal and lethal processes limit insect-mediated contaminant flux
Riparian spiders: Sentinels of polychlorinated dibenzo-p-dioxin and dibenzofuran-contaminated sediment
GPS data from 2019 and 2020 campaigns in the Chesapeake Bay region towards quantifying vertical land motions
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.
North American Aquatic Macroinvertebrate Digital Reference Collection (NAAMDRC)
Aquatic invertebrates are a key component of freshwater ecosystems, and an understanding of aquatic invertebrate taxonomy is central to freshwater science. The North American Aquatic Macroinvertebrate Digital Reference Collection (NAAMDRC) was created by the USGS Aquatic Experimental Lab (AXL) to provide users with high-quality digital microscopy photographs.
Science and Products
Per- and Polyfluoroalkyl Substance Exposure and Effects Research at Columbia Environmental Research Center (CERC)
Flood Redistributes Mercury in Grand Canyon Aquatic Food Webs
Areas of Concern: Technical Guidance for Assessing Remedy Effectiveness, Restoration, and Revitalization at Great Lakes AOCs and Great Lake Legacy Act (GLLA) Sites
Aquatic Ecology and Contaminants
Climate Change and Trout
Effects of Contaminants on Linked Aquatic and Terrestrial Food Webs
Surface Elevation Table (SET) data from the Blackwater National Wildlife Refuge (2010-2013)
Total PCB concentrations in sediment, water, macroinvertebrates and spiders and the lower Ottawa River (Toledo, OH) between 2009-2015
Plant and insect pollinator diversity data from Conservation Reserve Program fields across an agricultural gradient in eastern Iowa
Modeled Pacific salmon escapement biomass and nutrient and contaminant concentrations across western North America, 1976-2015
Assessment of Mercury and Mercury Stable Isotopes in Sediments and Biota from Reservoirs and Remedial Zones within the Saint Louis River, Minnesota
Images and Identifications of Wild Bees Collected in Eastern Iowa, 2019
Acute and chronic toxicity of two perfluoroalkyl substances to Neocloeon triangulifer
Total mercury, methylmercury, and isotopic composition in various life stages of boreal chorus frogs (Pseudacris maculata) at two subalpine ponds in the Rocky Mountains, CO, USA, 2015
Pesticide residues in passive samplers and bee tissue from Conservation Reserve Program fields across an agricultural gradient in eastern Iowa, USA, 2019 (ver 2.0, October 2023)
Survival, growth, behavior and mercury concentrations of mayflies exposed to elevated dietary methylmercury and aqueous selenium
Mercury concentrations, isotopic composition, biomass, and taxonomy of stream and riparian organisms in the vicinity of Yellow Pine, Idaho, 2015-2016.
Salt Marsh Turbidity at Mockhorn Island, VA; Plum Island, MA; York River, VA; and Altamaha River, GA
Geographic drivers of mercury entry into aquatic food webs revealed by mercury stable isotopes in dragonfly larvae
PCB concentrations in riparian spiders (Tetragnathidae) consistently reflect concentrations in water and aquatic macroinvertebrates, but not sediment: Analysis of a seven-year field study
Evolutionary and ecological correlates of thiaminase in fishes
A novel approach to assessing natural resource injury with Bayesian networks
Mercury isotope values in shoreline spiders reveal transfer of aquatic mercury sources to terrestrial food webs
Identifying invertebrate indicators for streamflow duration assessments in forested headwater streams
Perfluorooctanesulfonate adversely affects a mayfly (Neocloeon triangulifer) at environmentally realistic concentrations
Complex life histories alter patterns of mercury exposure and accumulation in a pond-breeding amphibian
Evaluation of Ziram as an oral toxic bait chemical for control of grass carp Ctenopharyngodon idella
Ecotoxicological studies indicate that sublethal and lethal processes limit insect-mediated contaminant flux
Riparian spiders: Sentinels of polychlorinated dibenzo-p-dioxin and dibenzofuran-contaminated sediment
GPS data from 2019 and 2020 campaigns in the Chesapeake Bay region towards quantifying vertical land motions
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.
North American Aquatic Macroinvertebrate Digital Reference Collection (NAAMDRC)
Aquatic invertebrates are a key component of freshwater ecosystems, and an understanding of aquatic invertebrate taxonomy is central to freshwater science. The North American Aquatic Macroinvertebrate Digital Reference Collection (NAAMDRC) was created by the USGS Aquatic Experimental Lab (AXL) to provide users with high-quality digital microscopy photographs.