Abstract
Widespread and persistent flooding is submerging coastal ecosystems, particularly along the Louisiana Gulf coast, where flooding results from the compounding effects of ground subsidence and rising sea level. Restoration projects aim to mitigate land loss by diverting sediment loads from rivers into degraded areas to increase ground elevation. To predict how coastal ecosystems will change over time in response to projected changes in relative sea level and restoration, it is necessary to understand how subsurface biogeochemical processes respond to dynamic hydrologic forcings. This study evaluates how environmental parameters that integrate biogeochemical processes vary with water table fluctuations in the freshwater Wax Lake Delta (WLD) in Louisiana, USA, where water diversions have formed one of the only active deltas along the coast. High-frequency observations of water level, soil redox potential, specific conductance and pH were made for 1 year along elevation transects located on the older, proximal and younger, distal ends of a deltaic island. Redox responded rapidly to changing water tables, with fluctuations occurring primarily in shallow soils (< 20 cm) and at higher elevations. Deeper soils and those at lower elevation remained inundated and reduced. Semi-diurnal tidal fluctuations were pronounced in younger, distal soils, presumably due to rapid groundwater exchange with the river channel. Tidal signals were muted in older soils that instead exhibited seasonal variability associated with river discharge and evapotranspiration. Although much of the delta sediments are persistently reducing and anoxic, redox fluctuations in the natural levees that border the deltaic islands likely drive high rates of biogeochemical activity. Evaluating how hydrology drives the frequency and duration of redox fluctuations provides a basis for understanding how biogeochemical processes might vary with complex hydrological interactions in coastal systems.
| Original language | English |
|---|---|
| Article number | e70338 |
| Journal | Hydrological Processes |
| Volume | 39 |
| Issue number | 11 |
| DOIs | |
| State | Published - Nov 2025 |
Funding
We gratefully acknowledge Michael Jones and Sean Fettrow for their assistance in the field, Andre Rovai, Robert Twilley and Ivan Vargas‐Lopez for logistical support, and the boat operators at Dauterive Contractors for transport and field assistance. This work was funded by grant ERKPA45 through the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research, Environmental System Science Program under Funding Opportunity DE‐FOA‐0002563. This work was supported by U.S. Department of Energy. We gratefully acknowledge Michael Jones and Sean Fettrow for their assistance in the field, Andre Rovai, Robert Twilley and Ivan Vargas-Lopez for logistical support, and the boat operators at Dauterive Contractors for transport and field assistance. This work was funded by grant ERKPA45 through the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research, Environmental System Science Program under Funding Opportunity DE-FOA-0002563. This manuscript has been authored by UT‐Battelle LLC, under contract DE‐AC05‐00OR22725 with the US Department of Energy (DOE). The US government retains, and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid‐up, irrevocable, worldwide licence to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( https://www.energy.gov/doe‐public‐access‐plan ).
Keywords
- coastal hydrology
- environmental sensors
- freshwater delta
- redox potential