CAREER: Nitrogen Sources, Pathways, and Fluxes in Chesapeake Bay Watershed Wetlands

The water quality of rivers, lakes, and coastal regions across the U.S. is at risk due to growing urban populations, large-scale use of commercial fertilizers, and runoff from high-density livestock production. Within the Chesapeake Bay Watershed, watershed managers and landowners continue to struggle with reducing nutrient runoff, despite decades of initiatives to improve the health of the Bay. In recent years, as stakeholders have worked to implement better watershed management practices, there has been increased interest in wetland restoration as a tool to improve water quality, while also providing aquatic habitat and increasing biodiversity. Unfortunately, our understanding of how to optimize the placement and function of restored wetlands to improve water quality remains limited. In this project, the investigator will use a combination of intensive wetland monitoring and large-scale data analysis to better understand how to reduce agricultural nutrient runoff to downstream waterways under changing climate and land-use conditions. The project also has an outreach component that will involve development of a pilot Chesapeake Summer Water Institute program. The program will bring graduate student researchers together with Chesapeake Bay-focused agency staff and other stakeholders to facilitate exchange of information, the development of ‘problem-focused’ research teams, and the use of process-based and data-driven modeling approaches to answer questions regarding improvement of Chesapeake Bay water quality. The primary objective of the proposed research is to better understand controls on fluxes of landscape nitrogen (N) to current and restorable wetland sites and, thus, to better predict the contributions of wetlands to water quality in the Chesapeake Bay Watershed. To meet this objective, the PI will use MESA–a metabolite of the widely used herbicide metolachlor–as a novel tracer of agricultural nitrate to identify the extent to which wetlands across a range of land-use types and positions intersect N flux pathways, and to quantify the resulting magnitudes of wetland N removal. The PI will leverage hundreds of existing water-quality samples from the National Wetland Condition Assessment together with more intensive monitoring of MESA at individual wetland sites to better our understanding of the spatially varying connectivity of wetlands with both groundwater N fluxes, and thus to refine estimates of wetland N removal magnitudes and associated N2O fluxes. In addition, analysis of MESA chirality will be used to estimate fluxes of legacy N to existing wetlands, thus bettering our understanding of the contribution of legacy N to current water quality. This award is co-funded by the Division of Earth Science's Hydrologic Sciences program and the Division of Environmental Biology's Ecosystems Sciences program. 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.