Wind and salinity as drivers of dissolved organic carbon outwelling in two brackish coastal marshes (2023)
Undergraduate: Kayla Emerson
Faculty Advisor: Lindsay Dubbs
Department: Environment, Ecology, and Energy Program
Brackish marshes are coastal wetlands at the interface of land and the ocean. They are productive systems and offer a variety of ecosystem services, including sequestering and outwelling carbon. Coastal marshes are dynamic ecosystems, influenced by the ocean, land, and estuaries surrounding them. The Albemarle Sound is a fresh to brackish water estuary located between the Outer Banks and mainland North Carolina, with Oregon Inlet connecting the Sound to the Atlantic Ocean. Due to little influence from the ocean, the Albemarle Sound experiences wind-driven tides that blow water over marshes at high tide and flush marshes out, expelling dissolved organic carbon (DOC) at low tide. Within the Albemarle Sound are the smaller Currituck and Croatan Sounds, which are different in their proximity to Oregon Inlet, salinity, and exposure to wind. This study aims to better understand how DOC outwelling in brackish coastal marshes are influenced by wind and salinity. Groundwater wells were installed at different marshes in the Pine Island Audubon Sanctuary on the Currituck Sound to measure water level and salinity. In Fall 2022, water samples and in situ parameters were collected and measured from marshes at the Pine Island Audubon Sanctuary and at the Coastal Studies Institute on the Croatan Sound. These samples were then analyzed for DOC and compared across sites, salinity, and differing wind speeds and directions. The study documented higher DOC concentrations in porewater and surface water than global averages. However, concentrations varied between sites and on sampling dates. In addition, a relative and positive correlation was interpreted between high wind events and water level at Pine Island Audubon Sanctuary. This could be attributed to DOC rich rivers feeding the Currituck Sound and the Sound receiving onshore wind that pushes water over the marsh, thereby raising the water level. This study is a snapshot of the environmental processes and drivers on two different brackish coastal marsh systems in the Albemarle Sound with hopes for research to continue. Findings show that these are dynamic systems that are playing a role in the carbon cycle in the Albemarle Sound as they release DOC into the Atlantic Ocean.
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