BIOGEOCHEMISTRY OF A BACK-BARRIER SALT MARSH TIDAL POND AND WATERWAY IN SOUTHERN NEW JERSEY

Salt marshes are among the most valuable wetlands in the world. Currently, saltwater marshes are under threat from subsidence and sea level rise, which puts at risk their essential ecosystem services such as improving water quality, sequestering carbon, buffering storm energy, and providing nurseries for economically significant fish species. Understanding the biogeochemistry of these systems and how they may change in the future is essential to their preservation. The implementation of a long-term monitoring program at the Seven Mile Island Innovation Laboratory (SMIIL) in Stone Harbor, New Jersey provides an important way to improve understanding of current wetland carbon cycling processes and their responses to anthropogenic impacts. We measured timeseries of biogeochemical parameters (pH, dissolved oxygen, salinity, temperature, turbidity, nitrate) using multiparameter environmental sondes at three stations in the New Jersey Intracoastal Waterway from Townsend Inlet to Hereford Inlet, and a station in a nearby salt pond of a back-barrier island salt marsh ecosystem in late October 2021. Oxygen concentrations in the salt pond ranged from anoxic to saturated (0-366 μM) and pH levels varied from 7.17-7.69. In comparison, the pH values of the main waterway are higher, reflecting the influence of the coastal ocean. Our study compares the biogeochemical signals in the salt pond to the main waterway by examining the net ecosystem productivity at each site. Additionally, these timeseries of biogeochemical parameters present an opportunity to observe the effects of a storm event and its associated freshwater flux on the biogeochemistry in the salt pond and the three stations along the main waterway. Lastly, we collected water-column profiles of salinity, temperature, and backscatter, as well as surface-water and bottom-water samples for total dissolved solids (TSS) and dissolved inorganic nutrients along a transect in the main waterway. These samples are used to characterize both spatial variability within the water column and along the transect of the main marsh waterway. Ultimately, this study will help (1) establish baseline measurements of biogeochemical signals, and (2) understand how predicted sea-level rise affects the biogeochemistry in the salt marsh.