Abstract
How sea level rise (SLR) alters carbon (C) dynamics in tidal salt marsh soils is unresolved. Changes in hydrodynamics could influence organo-mineral associations, influencing dissolved organic carbon (DOC) fluxes. As SLR increases the duration of inundation, we hypothesize that lateral DOC export will increase due to reductive dissolution of C-bearing iron (Fe) oxides, destabilizing soil C stocks and influencing greenhouse gas emissions. To test this, soil cores (0–8 cm depth) were collected from the high marsh of a temperate salt marsh that currently experiences changes in water level and soil redox oscillation due to spring-neap tides. Mesocosms experimentally simulated SLR by continuously inundating high marsh soils and were compared to mesocosms with Control conditions, where the water level oscillated on a spring-neap cycle. Porewater DOC, lateral DOC, and porewater reduced Fe (Fe2+) concentrations were significantly higher in SLR treatments (1.7 ± 0.5 mM, 0.63 ± 0.14 mM, and 0.15 ± 0.11 mM, respectively) than Control treatments (1.2 ± 0.35 mM, 0.56 ± 0.15 mM, and 0.08 ± 01 mM, respectively Solid phase analysis with Fe extended X-ray absorption fine-structure spectroscopy further revealed that SLR led to > 3 times less Fe oxide-C coprecipitates than Control conditions In addition, the overall global warming potential (GWP) decreased under SLR due to suppressed CO2 emissions. Our data suggest that SLR may increase lateral C export of current C stocks by dissolving C-bearing Fe oxides but decrease the overall GWP from emissions of soil trace gases. These findings have implications for understanding the fate of SOC dynamics under future SLR scenarios.
| Original language | English |
|---|---|
| Pages (from-to) | 103-120 |
| Number of pages | 18 |
| Journal | Biogeochemistry |
| Volume | 163 |
| Issue number | 2 |
| DOIs | |
| State | Published - Mar 2023 |
| Externally published | Yes |
Funding
We thank Chloe Kroll for sampling assistance, UD Soil Testing Laboratory for analytical assistance, Bruce Ravell for beamline assistance, Laurel Thomas Arrigo for the use of a ferrihydrite-galacturonic acid coprecipitate standard for Fe EXAFS, and the staff of the Delaware National Estuarine Research Reserve (DNERR). A.L.S. acknowledges support from the National Science Foundation Grants #1759879 and #2012484, S.F. acknowledges support from the Delaware Environmental Institute, and R.V. acknowledges support from the National Science Foundation grant #1652594 and U.S. Department of Energy (DOE) grant #DE-SC0023099 and #DE-SC0022185. Parts of this research used the BMM (6-BM) Beamline of the National Synchrotron Radiation Lightsource II, an Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No. DE-SC0012704. The authors acknowledge the land on which they conducted this study is the traditional home of the Lenni-Lenape tribal nation (Delaware nation). A.L.S. acknowledges support from the National Science Foundation Grants #1759879 and #2012484, S.F. acknowledges support from the Delaware Environmental Institute, and R.V. acknowledges support from the National Science Foundation grant #1652594 and U.S. Department of Energy (DOE) Grants #DE-SC0023099 and #DE-SC0022185.
Keywords
- Dissolved organic carbon
- Greenhouse gas fluxes
- Lateral carbon fluxes
- Organo-mineral associations
- Synchrotron
- Vertical carbon fluxes
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