Johanna M. Kraus, Ph.D. is a Research Ecologist with the U.S. Geological Survey Columbia Environmental Research Center where she applies principles of community ecology to study the effects of chemical contaminants on food webs, biodiversity and environmental health in aquatic and terrestrial ecosystems. She began her career with the USGS in 2011 researching how trace metals from acid rock drainage impact adult aquatic insect emergence and contaminant flux to terrestrial insectivores near mountain streams. Since then she has improved understanding of how chemical contaminants impact linked aquatic-terrestrial food webs using large empirical field studies, laboratory manipulations and conceptual modelling. Dr. Kraus received her B.A. in Biology from Brown University and Ph.D. in Biology from the University of Virginia. David M. Walters, Ph.D. is a Research Ecologist with the U.S. Geological Survey (USGS) Columbia Environmental Research Center. His research focuses on the effects of human stressors on the form, function, and structure of aquatic and riparian ecosystems with an emphasis on food web dynamics and contaminants. He began his career at the U.S. Environmental Protection Agency National Exposure Research Laboratory in 2002 before joining the USGS in 2008. His publications have addressed the impacts of contaminants, land use and climate change, invasive species, and hydrologic alteration on aquatic and riparian organisms and are geared toward furthering the conservation and restoration of these valued ecosystems. He received an M.S. and Ph.D. from the Odum School of Ecology at the University of Georgia.Marc A. Mills, Ph.D. is an Environmental Engineer at the U.S. EPA’s Office of Research and Development and is a principal investigator for projects characterizing the occurrence, transport, and fate of contaminants of emerging concern (CECs) and legacy contaminants in the environment and the management of contaminated sediments. Dr. Mills leads research to identify sources of contaminants to aquatic systems and tracing their movement through the environment and food webs. He also leads the development of analytical methods for CECs (e.g. PFAS, EDCs, PPCPs) and stable isotope chemistry for environmental samples in water, wastewater, solids, and tissues at the Center for Environmental Solutions and Emergency Response (CESER) for U.S. EPA. These methods are used to characterize potential sources of CECs and legacy contaminants, their management in water, wastewater treatment, water bodies, and new technology development. Dr. Mills has a B.S. in Civil/Environmental Engineering from Texas A&M University and a M.S. and Ph.D. from the Texas A&M University.
