Application of whole-ecosystem 15N tracer approaches to investigate the fate of nitrate in wetlands: Pilot experiments and met

As the impacts of anthropogenic nitrogen (N) pollution of the biosphere become increasingly evident, the fate of excess N in landscapes is recognized as one of the most pressing environmental research needs. Most of this N disappears somewhere in route from the sites of application (mainly on land) to coastal and offshore marine waters; however the precise regions and mechanisms of removal remains elusive. Wetlands along landscape hydrologic flow paths are likely to be important sites for removal of this nitrogen. Consequently, future wetland management, restoration and establishment decisions will likely be heavily impacted by understanding the role of wetlands as nitrogen sinks. The research proposed here involves the development and testing of new techniques for whole-ecosystem stable-isotope (N) tracer studies in wetlands. This venture grant was only partially spent when we obtained a CWS Postdoctoral Grant to further pursue similar research, and therefore the remaining funds were rolled into the new grant. The proposed experiments are designed to work out methods in a small groundwater discharge wetland and then apply the refined methods in a larger stream/beaver pond system. These kinds of experiments elucidate N cycle processes that transform and remove N in these complex ecosystems. This work builds on our extensive experience with such studies in streams, particularly through the LINX project, and dovetails with more in-depth research that we have recently initiated on the microbial processes responsible for N removal in aquatic sediments. This project is enabling us to establish a strong foundation with which to seek funding for a larger project to systematically examine the role of wetlands as N transformers and sinks.