Time and Tide: Hydrology, Biogeochemistry and Water Quality in an Estuary Headwaters
Abstract
Hydrology regulates biogeochemical process in wetland-rich watersheds, and for freshwater wetlands either precipitation or groundwater is assumed as the source of water. Tidal freshwater wetlands (TFW) occur at the interface of terrestrial and marine environments, and tides provide another source of water and chemical constituents in these systems. This project focuses on the role of tides on modifying biogeochemical and ecophysiological processes in TFWs. Also, extreme storm events and their increasing frequencies can comprise a large fraction of the annual freshwater inputs and the nitrogen (N), phosphorus (P) and carbon (C) loads to estuaries, but information on their net export is lacking. These blueways can affect downstream water quality but they also process C, N and P along the way. Water balance considerations in TFWs include a sustained shallow depth to water table and frequent inundation, both leading to a wetter hydro period as compared to non-tidal wetlands, thereby effectively delaying freshwater outflows and carbon exports, which affects C sequestration, greenhouse gas (GHG) emissions, and downstream fluxes of dissolved and particulate C, N and P. We have established a multi-institution, public-private partnership of research and monitoring in the headwaters of the Cooper River estuary in Charleston, SC (USA) across a gradient of non-tidal bottomland hardwood forest (NTBHF) -- TBHF -- Tidal Freshwater Marsh (TFM). One goal is to assess the tidal controls on wetland processes and ecosystem services in the stream and its floodplain. The forested tidal stream reach was gauged in 2020 with an acoustic Doppler velocity meter to develop discharge-stage relationships and quantify the bidirectional fluxes of nutrients and carbon in relation to the upstream non-tidal watersheds including one gauged since 2005. Ongoing research has also focused on the GHG dynamics and lateral fluxes of C, N and P in the TFWs. Surface elevation tables installed in 2020 monitor changes in land surface along this continuum over time. Sea level rise and rapid population growth (and related land use change) are two motivations to assess the residence time of water and biogeochemical dynamics in these coastal ecotones.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2021
- Bibcode:
- 2021AGUFM.H15V1301C