Characterization of groundwater dissolved organic carbon along the transition zone from saltmarsh to upland in the Delmarva Peninsula: influences of redox conditions and hydrological processes
Date
2025
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
University of Delaware
Abstract
In the face of sea level rise (SLR), salt marshes are migrating inland creating a transition zone between the marsh and upland. Little is understood about how the critical ecosystem services and biogeochemical activity in this zone are evolving in response. This research aims to characterize the organic carbon in shallow groundwater along the transition from salt marsh to upland and identify the major drivers of biogeochemical dynamics; specifically, how hydrological processes impact redox conditions and dissolved organic carbon (DOC) cycling. Groundwater was extracted and in-situ redox probes installed along transects across the marsh-upland transition zone at agricultural and forested sites in Delaware, Maryland, and Virginia, USA. DOC concentration and composition (SUVA254 and PARAFAC component modeling) were characterized and related to groundwater level and redox conditions across storms, tidal cycles, and seasons. DOC concentrations did not significantly change during Hurricane Ian (October 2022), but the SUVA254 and carbon components did change throughout. Similarly, while DOC concentrations remained stable over a tidal cycle, DOC composition varied. Samples collected during the summer showed low DOC concentrations in comparison to samples collected in spring and winter, possibly influenced by seasonal decline in the water table. Land cover also influences DOC concentrations, which were higher in forested than agricultural sites. Results from this study can be applied to better predict how groundwater carbon dynamics along the marsh-upland transition will respond to hydrologic and climatic shifts.
Description
Keywords
Sea level rise, Dissolved organic carbon, Biogeochemical dynamics, Redox conditions, Delmarva Peninsula