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Tidal frequencies and quasiperiodic subsurface water level variations dominate redox dynamics in a salt marsh system
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  • Emilio Grande,
  • Bhavna Arora,
  • Ate Visser,
  • Maya Montalvo,
  • Anna Braswell,
  • Erin Seybold,
  • Corianne Tatariw,
  • Kathryn Beheshti,
  • Margaret Zimmer
Emilio Grande
University of California Santa Cruz
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Bhavna Arora
Lawrence Berkeley National Laboratory
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Ate Visser
Lawrence Livermore National Laboratory
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Maya Montalvo
University of California Santa Cruz
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Anna Braswell
University of Florida
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Erin Seybold
Kansas Geological Survey
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Corianne Tatariw
The University of Alabama College of Arts and Sciences
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Kathryn Beheshti
University of California Santa Cruz
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Margaret Zimmer
University of California Santa Cruz Department of Earth and Planetary Sciences
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Abstract

Salt marshes are hotspots of nutrient processing en route to sensitive coastal environments. While our understanding of these systems has improved over the years, we still have limited knowledge of the spatiotemporal variability of critical biogeochemical processes within salt marshes. Sea-level rise will continue to force change on salt marsh functioning, highlighting the urgency of filling this knowledge gap. Our study was conducted in a central California estuary experiencing extensive marsh drowning and relative sea-level rise, making it a model system for such an investigation. Here we instrumented three marsh positions with different degrees of inundation (6.7%, 8.9%, and 11.2% of the time for the upper, middle, and lower marsh positions, respectively), providing locations with varied geochemical characteristics and hydrological interaction at the site. We continuously monitored redox potential (Eh) at depths of 0.1, 0.3, and 0.5 m, subsurface water levels (WL), and temperature at each marsh position to understand how drivers of subsurface biogeochemical processes fluctuate across tidal cycles, using wavelet analyses to explain the interactions between Eh and WL. We found that tidal forcing significantly affects biogeochemical processes by imparting controls on Eh variability, likely driving subsurface hydro-biogeochemistry of the salt marsh. Wavelet coherence showed that the Eh-WL relationship is non-linear, and their lead-lag relationship is variable. We found that precipitation events perturb Eh at depth over timescales of hours, even though WL show relatively minimal change during events. This work highlights the importance of high-frequency measurements, such as Eh, to help explain factors that govern subsurface geochemistry and hydrological processes in salt marshes.
20 Nov 2021Submitted to Hydrological Processes
22 Nov 2021Submission Checks Completed
22 Nov 2021Assigned to Editor
01 Dec 2021Reviewer(s) Assigned
21 Jan 2022Review(s) Completed, Editorial Evaluation Pending
21 Jan 2022Editorial Decision: Revise Major
23 Feb 20221st Revision Received
24 Feb 2022Reviewer(s) Assigned
24 Feb 2022Submission Checks Completed
24 Feb 2022Assigned to Editor
22 Apr 2022Review(s) Completed, Editorial Evaluation Pending
25 Apr 2022Editorial Decision: Accept
07 May 2022Published in Hydrological Processes. 10.1002/hyp.14587