The Roles of Tidal Marshes in the Estuarine Biochemical Processes: A Numerical Modeling Study. Issue 2 (6th February 2023)

• Record Type: Journal Article
• Authors: Cai, Xun; Shen, Jian; Zhang, Yinglong J.; Qin, Qubin; Linker, Lewis
• Is Part Of: Journal of geophysical research. Volume 128:Issue 2(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2023-02-06
• Subjects: Geobiology -- Periodicals; Biogeochemistry -- Periodicals; Biotic communities -- Periodicals; Geophysics -- Periodicals; 577.14
• DOI: 10.1029/2022JG007066
• Languages: English
• ISSNs: 2169-8953

Abstract

Abstract: Observations suggest that the existence of tidal marsh can alter the oxygen and nutrient dynamics in adjacent water bodies, but assessing the impacts of large tidal marshes on an estuary is challenging. In this study, we use a modeling approach to investigate the roles of tidal marshes on the estuarine biochemical processes. The marsh model, which simulates the ecological functions of marshes at seasonal and annual time‐scales, is embedded inside an unstructured‐grid three‐dimensional hydrodynamic and eutrophication model (SCHISM‐ICM). This modeling system simulates the growth and metabolism of the tidal marshes and links biological processes to nutrient dynamics in the water column and sediment. This model dynamically simulates nutrient recycling and physical transport of the materials between marshes and open water through wetting‐drying processes. This coupled model system is validated and successfully applied to the York River Estuary. Model results suggest that tidal marshes influence the local diurnal dissolved oxygen (DO) cycle by exporting dissolved organic carbon and high sediment oxygen demand in the marsh system through the tidal exchange. The high deposition rates of organics and diurnal DO cycle enhance the sediment release of phosphorus. On the other hand, marshes tend to decrease dissolved inorganic nitrogen in the water column by settling particulate nutrients and enhancing the denitrification process. The study demonstrates that tidal marshes exert substantial impacts on the estuarine biochemical processes. The developed tidal marsh model enhances eutrophication modeling and advances the understanding of the feedback effects between marsh biogeochemistry and estuarine eutrophication processes on a systemic scale. Plain Language Summary: Tidal marshes are significant components in the estuarine ecosystem and are known to modify the estuarine biochemical processes. To complement the spatial and temporal limitations of field observation and experiments, we developed a modeling tool to study the role of tidal marshes. This model simulates the marsh biomass dynamics on seasonal and annual time scales. This marsh model is embedded in a complex 3D hydrodynamic‐water quality model (SCHISM‐ICM), so it explicitly includes the interactions of tidal marshes and the nutrient dynamics in the water column and sediment. We successfully implemented this coupled model in the York River Estuary, where extensive tidal marshes exist. This modeling study demonstrates that tidal marshes drive the local diurnal dissolved oxygen (DO) cycles and low‐DO events. In addition, tidal marshes tend to increase the phosphate release from the sediment but decrease the dissolved inorganic nitrogen in the water column. Overall, tidal marshes have substantial impacts on the estuarine biochemical processes. Key Points: A new dynamic marsh model coupled with 3D estuary model is developed to study impacts of tidal marshes on estuarine biochemical processes Model suggests tidal marshes drive the diurnal dissolved oxygen cycle, which increases denitrification and can enhance bottom phosphate release This study advances the eutrophication modeling and enhances the understanding of the tidal marsh biogeochemistry affecting the estuary