2024 Abstracts

Exploring the Impact of Seawater Infiltration on Coastal Biogeochemistry: An Integrated Modeling Study of the Terrestrial Aquatic Interfaces


Bing Li1* (bing.li@pnnl.gov), Jun Yan Ding1, Jianqiu Zheng1, Peter J. Regier1, Nicholas D. Ward1, Theresa A. O’Meara2, Stephanie C. Pennington1, James Holmquist3, Glenn E. Hammond1, Allison Myers-Pigg1, Roy Rich3, Patrick Megonigal3, Vanessa L. Bailey1, Xingyuan Chen1


1Pacific Northwest National Laboratory, Richland, WA; 2Oak Ridge National Laboratory, Oak Ridge, TN; 3Smithsonian Environmental Research Center, Edgewater, MD



As the climate and environment continue to change, a comprehensive and predictive understanding of coastal terrestrial aquatic interfaces (TAIs) is increasingly critical. In this study, researchers investigate the impacts of seawater infiltration on the biogeochemical dynamics of coastal TAIs in the Chesapeake Bay region. An integrated approach that combines hydrological, biogeochemical, and vegetation dynamics models is applied along a gradient from coastal wetland marsh to upland forest. The Advanced Terrestrial Simulator (ATS) is used to simulate water flow, incorporating overland and subsurface dynamics under various scenarios. Outputs from the ATS, specifically water level and salinity data, are then fed into the FATES-Hydro model to predict vegetation responses to shifting hydrological conditions. These predictions include key parameters such as leaf fall and leaf area index, which are then used to refine the ATS simulations.

Additionally, the PFLOTRAN model, coupled with ATS through Alquimia, simulates biogeochemical processes considering the altered water table, microbial activity, salinity, and plant community dynamics due to seawater infiltration. These results show that dynamic seawater levels have a strong influence on dissolved oxygen and salinity in coastal TAIs. Dynamic changes in the oxygenated zone directly affected soil redox conditions and biogeochemical processes. Notably, higher salinity was associated with lower aerobic reaction rates and higher dissolved organic carbon content, suggesting that salinity plays a key role in regulating microbial activities and chemical reactions. In addition, the introduction of dissolved organic carbon (DOC) from degrading vegetation significantly altered local redox processes, suggesting a complex interaction between biogeochemical processes and vegetation dynamics. These results highlight the critical importance of integrated modeling in understanding the multiple impacts of seawater infiltration on coastal TAIs. Through this integrated approach, researchers gained a detailed understanding of the complex interactions occurring across coastal TAIs, enhancing the knowledge of their response to environmental change.