1133074 (Jaffe). Greenhouse gas (GHG) emissions of nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2) are largely unknown for estuarine wetland areas. The notion that constructed wetlands are net radiative sinks has not been verified for coastal wetlands and many of the studies informing this hypothesis have not considered N2O fluxes. Fluxes of nitrogen and carbon species between estuarine wetlands, the atmosphere, and an adjacent river will be measured along a hydroperiod-, salinity-, and mitigation gradient and scaled to the ecosystem level. The eddy covariance technique will be the principal method used to constrain estimates of the CO2 and CH4 fluxes. Flux chamber and subsurface dissolved CH4, N2O, and inorganic carbon measurements combined with modeling/scaling of these fluxes will be used to determine the N2O fluxes and verify the accuracy of this technique by comparing CO2 and CH4 fluxes from both techniques. Net losses of dissolved organic carbon, dissolved inorganic carbon, and dissolved nitrogen from selected marshes via tidal flow will also be monitored at point inlets to these marshes. Concurrent photosynthesis measurements of Phragmites australis, a C3-plant, and Spartina spp, C4-plants, will account for the CO2 exchange by these species. This gas-exchange is driven by biophysical, hydrological and hydrochemical drivers. The balance between carbon sequestration in brackish coastal wetlands and CH4 and N2O emissions from the same systems remains unclear. Thus, monitoring and modeling the effects of these drivers on overall greenhouse gas exchange, at the individual plant and ecosystem-level, will help assess these controls and scale GHG fluxes in urban tidal wetlands to the ecosystem level. A combination of bottom-up approaches, via measurements and process-based models developed by the PIs, and top-down approaches via eddy flux measurements will be used to tackle the different drivers of biosphere-atmosphere GHG exchange and enable scaling to ecosystem and regional levels. This research will enhance our understanding of coastal wetland GHG dynamics in urban tidal marshes. These new insights will be shared with the many visitors of the Meadowlands Environmental Center, including ca. 15,000 schoolchildren who participate in a wide range of workshops and educational activities about urban estuaries each year. This research will also include funding for a Louis Stokes Alliances for Minority Participation (LSAMP) student to be hired for a summer internship to assist the graduate students in field data collection and outreach activities. In addition, every four years since 2003, Meadowlands Environmental Research Institute (MERI) has collaborated with government agencies and universities to sponsor the Meadowlands Symposium, a gathering of over 200 research scientists, students, and professionals, to discuss and address environmental issues of urban estuaries. The project will also train two graduate students, one at Rutgers University and one at Princeton University. Results from this research will be disseminated via conference presentations and peer-reviewed journal articles. The experimental setup and data generated will be used by both PIs to augment hands-on experiences for students in their graduate and undergraduate experiments. This research will yield a rich data set, maintained by MERI, that will be highly valuable to the green-house-gas modeling scientific community
