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Biogeochemical controls on dissolved organic carbon production and degradation in tidal marshes

EMSL Project ID


The overarching objective of our ongoing research is to determine environmental (biotic and abiotic) controls on organic matter (OM) production and decomposition in tidal marsh soils along an estuarine salinity gradient. The proposed field locations represent tidal marsh systems that vary in elevation, hydrology, salinity, plant and microbial communities, soil characteristics, and biogeochemistry. This presents an ideal opportunity to measure and identify variables that may be responsible for OM production and decomposition.

Tidal marshes are important components of the coastal carbon cycle due to their high productivity and carbon storage potential as well as their role in OM processing and export to adjacent waters. Most work to-date has focused on marsh surface waters even though belowground environments may be as equally important for OM processing and export. However, constraining the role of belowground OM in the coastal carbon cycle and in coastal carbon budgets has been difficult due to spatiotemporal differences in OM source and chemical composition, microbial community composition and function, and interactions between OM and microbial communities in soils and their porewaters.

To address our objectives, a coupled geochemical-microbiological approach is necessary to assess the metabolic processes and functional groups responsible for OM production and decomposition in relation to OM characteristics and other biogeochemical parameters. Data obtained from the MONet soil program would support our goals to couple these approaches by providing high resolution data on soil properties (e.g., composition, geochemistry, C and N) as well as information about the microbial community (e.g., metagenomics, biomass, potential enzyme activity). These data would also complement existing bulk measurements related to dissolved OM concentration, source, and composition in tidal marsh porewaters.

The proposed field locations and the subsequent data collected will provide information for the predictive understanding of soil processes that can be integrated into Earth system models and compared against other land types. This is especially critical along estuarine salinity gradients where soil processes are also traditionally thought to occur along a gradient (e.g., methane production decreases from freshwater to saltwater systems). However, gradients in salinity may not necessarily correlate to gradients in biogeochemical processes.

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Principal Investigator

Bongkeun Song
College of William and Mary

Team Members

Novia Mann
Virginia Institute of Marine Science

Derek Detweiler
Virginia Institute of Marine Science