ORCID
0000-0003-2422-3252 (Tamborski)
Document Type
Article
Publication Date
2025
DOI
10.1029/2025JG008758
Publication Title
Journal of Geophysical Research: Biogeosciences
Volume
130
Issue
5
Pages
e2025JG008758 (1-9)
Abstract
Subterranean estuaries (STE) in salt marshes are biogeochemically active zones where interactions between terrestrial groundwater and seawater drive complex cycling of carbon and trace elements, influenced by mineral dissolution. These systems, characterized by fine-grained organic-rich peat overlying permeable coastal aquifers, play a crucial role as a blue carbon sink, yet their geochemical dynamics remain poorly understood. We investigated dissolved trace elements, carbon, silica, and radium isotopes in a salt marsh STE (Sage Lot Pond, Waquoit Bay, MA) over seasonal and annual cycles. Our results reveal that groundwater and estuarine water circulation through marsh peat and aquifer sediments leads to enrichments of dissolved organic and inorganic carbon (DOC and DIC), Si, Ba, and Mn, with variable source/sink behavior of Fe and net removal of U. Submarine groundwater discharge dominated Ba fluxes, whereas pore water drainage from marsh peat acted as the main sink for U and source of Si. Fe cycling was variable, with terrestrial Fe largely removed as groundwater passed through the STE, consistent with Fe-sulfide and amorphous phase formation. Radium isotope ratios identified two distinct subsurface flow pathways, influenced by metal-oxide cycling and organic matter breakdown. Si production was decoupled from DIC, suggesting Si originates from mineral alteration, whereas DIC results from both mineral weathering and microbial respiration. Silicate mineral alteration, coupled with marsh pore water drainage, accounts for up to 16% of annual DIC exports (66 g C m-² y-¹), highlighting the importance of STEs in coastal carbon and trace element cycling, especially as marshes face environmental change.
Rights
© 2025. The Authors.
This is an open access article under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Data Availability
Article states: "Creek water, pore water, and groundwater data collected at Sage Lot Pond from 2014–2019 are publicly available through U.S. Geological Survey Data Releases (Brooks et al., 2025; Mann et al., 2019). Sediment Ra/Th and XRD data are available through HydroShare (Tamborski, 2024)."
Original Publication Citation
Tamborski, J. J., Eagle, M. J., Thorpe, M. T., Charette, M. A., Kurylyk, B. L., Rahman, S., Kroeger, K. D., O’Keefe Suttles, J., Mann, A. G., Brooks, T. W., & Wang, Z. A. (2025). Evidence of mineral alteration in a salt marsh subterranean estuary: Implications for carbon and trace element cycling. Journal of Geophysical Research: Biogeosciences, 130(5), 1-19, Article e2025JG008758. https://doi.org/10.1029/2025JG008758
Repository Citation
Tamborski, J. J.; Eagle, M. J.; Thorpe, M. T.; Charette, M. A.; Kurylyk, B. L.; Rahman, S.; Kroeger, K. D.; O'Keefe Suttles, J.; Mann, A. G.; Brooks, T. W.; and Wang, Z. A., "Evidence of Mineral Alteration in a Salt Marsh Subterranean Estuary: Implications for Carbon and Trace Element Cycling" (2025). OES Faculty Publications. 540.
https://digitalcommons.odu.edu/oeas_fac_pubs/540