Water is fundamental to the biogeochemical cycles of Carbon and Nitrogen because it provides connectivity among ecosystems. Water links aquifers to surface waters, hillslopes to oceans, and our communities to our environments. However, there is still a disconnect between the study of most environmental hydrological and biogeochemical phenomena. This disconnect limits our ability to anticipate how global change will alter Carbon and Nitrogen cycles, ecosystems, and our water resources. By embracing multidisciplinary approaches that unify hydrological and biogeochemical theory, we can move beyond these limitations and develop novel approaches that address the complex nonlinear relationships inherent to biogeochemical systems. I will draw from my research program to illustrate how coupling hydrological and biogeochemical principles can uncover important processes and emergent patterns in Carbon and Nitrogen dynamics of river networks and groundwater-surface water interfaces. Specifically, I will discuss how δ15N stable isotope tracer experiments and numerical models can reveal the function of the “River’s Liver” (the hyporheic zone) and quantify sources or sinks of Nitrogen in our fluvial landscapes. I will also discuss new theory that incorporates the role of river flow regimes on organic Carbon export from watersheds across the United States and its implication for regional and global Carbon cycle models.

Dr. Zarnetske is an Assistant Professor of Hydrological Sciences at Michigan State University in the Department of Geological Sciences. Previously, he was a Gaylord Donnelly Environmental Postdoctoral Fellow at the Yale Institute for Biospheric Studies and the Yale School of Forestry & Environmental Studies. He received his PhD in Water Resource Science from Oregon State University. During his PhD, he was an NSF IGERT - Ecosystem Informatics Fellow in the Department of Geosciences and the Water Resources Graduate Program. Prior to receiving his PhD, he received my MS in Watershed Science from Utah State University's College of Natural Resources, and a BA in Geology from Colby College. He has also served as a visiting scientist for New Zealand's National Institute for Water and Atmospheric Research and a consulting groundwater hydrologist for CDM-Smith, Inc.