Watershed Dynamics and Evolution Science Focus Area Theme 1: Dynamic Headwaters


Alexander Johs1* (johsa@ornl.gov), Elizabeth Herndon1, Xin Gu1, Mircea Podar2, Melissa Cregger2, Kamini Singha3, Holly Barnard4, Macon J. Abernathy5, Ritimukta Sarangi5, Alan A. DiSpirito6, Jeremy D. Semrau7, Eric M. Pierce1


1Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN; 2Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN; 3Department of Geology and Geological Engineering, Colorado School of Mines, Golden, CO; 4Department of Geography, University of Colorado–Boulder, Boulder, CO; 5Structural Molecular Biology Division, SLAC National Accelerator Laboratory, Menlo Park, CA; 6Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, IA; 7Department of Civil and Environmental Engineering, University of Michigan, Ann Arbor, MI



Theme 1 in the Watershed Dynamics and Evolution SFA focuses on ecohydrology, biogeochemistry, and microbiology of nonperennial streams (dynamic headwaters) to evaluate the quantity and composition of water being transported from upland catchments into the stream network. The goal is to understand how variable saturation drives hydro-biogeochemical processes that influence downstream metabolism. Researchers will yield high spatially and temporally resolved data of surface flow in multiple headwater catchments that differ in land cover to inform numerical models describing flow in nonperennial streams, which will guide future field data collection. Researchers will also study surface and subsurface hydrology, plant water use, biogeochemical processes, and microbial community dynamics in a headwater catchment to capture how these processes respond to persistent or variable saturation. Field studies will be combined with laboratory investigations to understand how colloid and particle dynamics influence (micro)nutrient levels across saturation and redox gradients generated through intermittent flow. This project hypothesizes that highly dynamic redox-active zones in nonperennial stream channels contribute significantly to the export of carbon, nutrients, and trace metals to the downstream environment.

This research effort builds on expertise developed under the Critical Interfaces SFA that focused on biogeochemical transformations within streams. Microbial communities can rapidly respond to changing environmental conditions, as well as seasonal and episodic changes in flow, redox state, and nutrient availability. Such environmental changes control bioavailability of trace metals and may exert significant controls on the biosynthesis and function of metalloenzymes that are essential for many metabolic processes. Microbes have evolved various strategies to acquire essential trace metals. Interactions between copper(II) and several other transition metals with the chalkophore methanobactin were characterized using spectroscopic methods. The complexation of metal ions by methanobactin occurs through several steps, including rapid coordination of metal ions to functional groups, conformational rearrangement, and formation of oligomers dependent on metal ion and stoichiometry.