Collaborative Research: New Roles for Reactive Oxygen Species in Mediating Carbon Fluxes at the Terrestrial-Aquatic Interface

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Wetlands in the north central region of the United States are important ecosystems that play critical roles in the regional carbon cycle and are likely to be dramatically affected by climate change. Rates of greenhouse gas release from these wetlands may increase with warming and offset their ability to sequester carbon. By studying the chemical and microbiological processes in wetland sediments over space and time, predictions of the effects of climate change on these critical habitats will be possible. Documentation of the ecological importance of this region via photography will demonstrate the value of wetlands to a broad audience.The drivers of biogeochemical activity that dictate the emissions of carbon dioxide and methane in small, inland waters are poorly constrained, yet processes in these water bodies play an oversized role in understanding climate change. One process that is poorly understood is the role of chemical reactions in mediating carbon dioxide and methane formation in small lakes and wetlands, especially the abiotic production of reactive oxygen species (ROS) at the sediment-water interface (SWI). The hypothesis for this project is that the reaction of reduced soluble and particulate forms of iron, sulfur, and carbon with trace level oxygen to form ROS at the SWI is an under-appreciated, yet critical, control on microbiological activity and the cycling of carbon in small inland water bodies. Using a combination of field work in the prairie pothole region of North Dakota, controlled laboratory experiments, and mesocosm studies, this work will 1) identify the geochemical drivers of ROS generation at the SWI, 2) determine spatiotemporal patterns of linked pore water chemistry and ROS at the SWI, and 3) track the generation of specific labile carbon substrates produced through ROS-DOM reactions that affect rates of carbon mineralization and methane production in small lake and wetland sediments. A combination of in situ voltammetry measurements, detailed characterization of dissolved and particulate organic matter, iron, and sulfur species, and microbial -omics analyses will be used to understand the coupled biogeochemical processes. A key component of this work is understanding how abiotic ROS driven reactions at the sediment-water interface lead to turnover of terminal electron acceptors and generation of labile microbial substrates. Establishing a baseline understanding of these processes is needed to predict changes in carbon dioxide and methane fluxes under different climate scenarios. The collected data will enable understanding of how biogeochemical cycles are maintained through coupled abiotic/biotic pathways, and how these processes impact carbon cycling in aquatic environments. This approach is also applicable to other systems and the cycling of other elements, such as nitrogen, which may be especially important in urban wetland regions. The societal benefit will be improved understanding of processes that influence, and are influenced by, climate change. To reach as broad an audience as possible regarding the importance of this region, a photographer will document the landscape and its ecological function during field sampling trips.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.