Sediment fluxes and exchange between an urban salt marsh and Long Island Sound Troy

Salt marshes provide a broad range of valuable ecological services. In urban settings these services are magnified in importance, as marshes are typically smaller, serve more concentrated human populations, and face more dramatic anthropogenic pressures. Unfortunately, our knowledge of material exchange between marshes and coastal waters is limited, particularly in urban areas. Tidal flux studies offer a means of understanding how marshes interact with coastal waters and how they affect water quality in the coastal zone. The present study reports high resolution data on fluxes of water, salt, and sediment to and from an urban salt marsh in Norwalk, CT. This work focuses on shortterm sediment dynamics, and the role of storm events in sediment transport. Fieldbased measurements of precipitation, water velocity, salinity, and turbidity were collected continuously for two months. Uncertainties in the data are evaluated and compared with other flux studies. The feasibility of estimating particulate material fluxes based on these data benefits from low spatial variability of suspended sediment in the water column. A net influx of sediment was observed over the course of the study, but the system is characterized by large, short-term variations in sediment transport. Only a small fraction of the imported sediment appears to be deposited on the marsh surface. Moving towards an assessment of minor constituent fluxes, this project began optimizing a method for measuring trace metals in sea water, to be deployed in 2012. Experiments using chelating resin columns have highlighted the challenges of analyzing trace metals in seawater. This preliminary work has clarified essential methodological details such as the volume of eluent required to displace metals sorbed to the resin, and the necessity of purifying reagents.