From Tides to Seasons: How Cyclic Tidal Drivers and Plant Physiology Interact to Affect Carbon Cycling at the Terrestrial-Estuarine Boundary
Authors
Inke Forbrich1,2* (inke.forbrich@utoledo.edu), Zoe Cardon1, Yongli Zhou1, Anne Giblin1, Mikaela Martiros1, Teri O’Meara3, Ben Sulman3, Cove Sturtevant4
Institutions
1Marine Biological Laboratory, Woods Hole, MA; 2University of Toledo, Toledo, OH; 3Oak Ridge National Laboratory, Oak Ridge, TN; 4National Ecological Observatory Network, Boulder, CO
Abstract
This project’s goal is to improve mechanistic process understanding and modeling of tidal wetland hydro-biogeochemistry in coastal terrestrial-aquatic interfaces (TAIs). Key characteristics distinguish coastal wetlands, including tidal oscillation, sulfur biogeochemistry, and plant structural adaptations to anaerobic soil. These characteristics have only very recently been incorporated into land surface models such as ELM-PFLOTRAN and there remains large uncertainty in their parameterization. Particularly challenging are (1) the small-scale, dynamic, heterogeneous redox conditions in wetland soils; (2) the aerenchyma tissue in wetland plants that greatly facilitate gas flow into and out of sediment; and (3) the temporal and spatial variability in salinity, which is a key determinant for plant species distribution and productivity, as well as organic matter decomposition. In 2023, researchers continued to monitor porewater data of nutrients, carbon (C) and methane (CH4) and stable isotopes of CH4 as well as ecosystem-scale flux measurements in a brackish marsh in the Parker River estuary in MA. In July 2023, the research team started to see an increase in CH4 fluxes. This indicates the start of recovery of microbial activity after the sharp drop researchers observed in summer 2022 during a high salinity flooding event. Researchers find that physicochemical variables are the most important predictors for this behavior, more so than C fluxes. Furthermore, researchers have started to experimentally test salinity impacts on CH4 production and oxidation (Cardon DE-SC0024270). The team also continued with field-testing spatially explicit sediment redox measurements. Researchers successfully captured tidal flooding impacts of belowground oxygen pools in two locations with contrasting hydrology (creekbank and marsh interior). In modelling work, the team has successfully set up different scenarios of root oxygen release in PFLOTRAN. Using these scenarios, researchers have then conducted a sensitivity analysis to assess to which the simulated CH4 flux responds the strongest. The team plans to transfer this information into ELM-PFLOTRAN.