ORCID
0000-0003-2422-3252 (Tamborski)
Document Type
Article
Publication Date
2025
DOI
10.1029/2025JG008898
Publication Title
Journal of Geophysical Research Biogeosciences
Volume
130
Issue
6
Pages
e2025JG008898 (1-17)
Abstract
Coastal wetlands have high rates of atmospheric CO₂ uptake, which is subsequently respired back to the atmosphere, stored as organic matter within flooded, anoxic soils, or exported to the coastal ocean. Transformation of fixed carbon occurs through a variety of subsurface aerobic and anaerobic microbial processes, and results in a large inventory of dissolved carbon. Carbon source and the roles of aerobic respiration, sulfate reduction, and methane cycling were evaluated within salt marsh peat and the underlying sandy subterranean estuary. There is a large increase in dissolved inorganic carbon (DIC, 7,350 ± 3,900 μmol L-¹), dissolved organic carbon (DOC, 1,040 ± 1,480 μmol L-¹) and CH₄ (14.5 ± 33.3 μmol L-¹) within the marsh porewaters compared to creek waters. Alkalinity production (5,730 ± 2,170 μeq L-¹) and sulfate removal (1,810 ± 1,970 μmol L-¹) indicate anaerobic respiration, however, relative contributions from the various decomposition pathways cannot be identified due to overlapping geochemical signatures. The ẟ¹³C of the DOC (-29.0 ± 3.7 parts per thousand) and DIC (-11.2 ± 1.1 parts per thousand) produced within the marsh differed from the bulk soil organic matter ẟ¹³C (-14.5 ± 0.2 parts per thousand). We explore a variety of mechanisms that could result in co-occurring depleted delta ¹³C-DOC and enriched delta ¹³C-DIC compared to the bulk soil organic carbon pool and salt marsh vegetation, including selective mineralization, production of delta ¹³C-depleted bacterial biomass, and methane-derived DOC. While important questions remain about carbon cycling pathways, we found evidence of a cryptic methane cycle. Alteration of the delta ¹³C of carbon species complicates source attribution in solid and dissolved phases and careful consideration should be used when carbon is partitioned between in situ salt marsh production and external marine and terrestrial sources.
Rights
Published 2025.
This article is a U.S. Government work and is in the public domain in the U.S.A.
Data Availability
Article states: "
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The water chemistry data used in the study are available at Science Base via https://doi.org/10.5066/P9MXLUZ1 (Brooks et al., 2025).
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2,023.06.0 + 421 of R was used for data analysis and figure preparation and is preserved at (https://dailies.rstudio.com/version/2023.06.0+421.pro1/) (R Core Team, 2023)."
Original Publication Citation
Eagle, M. J., Kroeger, K. D., Pohlman, J. W., Tamborski, J. J., Wang, Z. A., Brooks, T. W., Suttles, J. O., & Mann, A. (2025). The δ¹³C signature of dissolved organic and inorganic carbon reveals complex carbon transformations within a salt marsh. Journal of Geophysical Research Biogeosciences, 130(6), 1-17, Article e2025JG008898. https://doi.org/10.1029/2025JG008898
Repository Citation
Eagle, Meagan J.; Kroeger, Kevin D.; Pohlman, John W.; Tamborski, Joseph J.; Wang, Zhaohui Aleck; Brooks, T. W.; Keefe Suttles, Jennifer O.; and Mann, Adrian, "The δ¹³C Signature of Dissolved Organic and Inorganic Carbon Reveals Complex Carbon Transformations Within a Salt Marsh" (2025). OES Faculty Publications. 542.
https://digitalcommons.odu.edu/oeas_fac_pubs/542
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