Influence of redox potential and hydrologic processes on DOC in the transition zone in salt marshes

Salt marshes provide vital ecosystem services locally and globally by their ability to sequester and cycle large quantities of carbon, store and filter out pollutants and excess nutrients, and host critical biogeochemical activity. The transition zone between upland and marsh ecosystems is an area of great importance as sea-level rise (SLR) causes ecosystem change and salt-marsh migration. Changes in inundation rates and hydrological processes in the transition zone impacts the cycling of redox species and dissolved organic carbon (DOC) in porewater. This research aims to identify the major drivers of carbon dynamics in porewater along the transition from salt marsh to upland, and to better understand how hydrological processes in the coastal critical zone impact redox conditions and DOC cycling. Porewaters were extracted from a transect along the transition zone for DOC analysis at depths of 45 cm and 122 cm and in-situ redox probes were installed at an agricultural and forest site in Delaware. DOC concentration and composition were characterized and compared to precipitation, ground water levels, tidal cycles, redox species, and redox conditions. Analysis was run to identify correlations between each variable and a principal component analysis was performed to better identify trends and patterns within the data set. Samples show higher DOC levels at the healthy upland transect and are expected to show higher levels of DOC during low tide. Results from this study can be applied to better understand how biogeochemical activity and redox conditions in salt marshes respond to storm and tidal events in the future.