Impact of sea level rise on sedimentary nitrogen removal processes in tidal freshwater ecosystem – Funded through NSF Grant Changes in land use and increasing population density have altered delivery rates and sources of N and OM to coastal.  Coastal habitats have responded with accelerated respiration and nutrient cycling, leading to areas of severe hypoxia and possible shifts in the N saturation status of sediments.  Because of their position in the landscape the coastal ocean is, sensitive to a changing climate as it imprints regionally and as sea level rise impinges.  Global change models predict acceleration of the hydrologic cycle that will result in increased intensity, frequency, and amount of heavy precipitation over land.  This tighter coupling between the continents coastal ocean will result in increased total flux of N and/or OM rich delivered in episodic pulses to estuaries that are undergoing salinization from rising sea level. There is currently no mechanistic picture of how the sedimentary N-cycle will respond to these two changing boundary conditions.  This project examines various geochemical controls on the ratio of N-cycling reactions that either export (denitrification and anammox) or conserve (dissimilatory nitrate reduction to ammonium; DNRA) N in coastal sediments. This project aims to examine the importance of anammox in tidal freshwater ecosystems, the effects of salinity on freshwater anammox bacteria and the sedimentary nitrogen (N) cycle, and to predict alternative N removal pathways in sedimentary communities that are threatened by sea level rise. The goal is to compare community structures and activities of nitrifiers, denitrifiers, anammox and DNRA bacteria in river sediments exposed with different tidal influences; characterize instantaneous responses of sediment microbial communities to salinity intrusion; examine changes in sediment community structures and activities in mesocosms with different salinity treatments; and estimate and predict sedimentary N removal capacity and alteration of N pathways in freshwater ecosystems under sea level rise based on new biogeochemical model.