Impact of Tidal Inundation on the Soil Oxygen Dynamics of Two Salt Marsh Plant Species

• Anna Roat, Environmental Science, American University

• Claudia Zoccarato, Department of Earth Sciences, University of Delaware

Tidal marshes are increasingly threatened by a host of issues including sea level rise, salinization, and droughts. Tidal marsh ecosystems provide many ecosystem services including carbon storage, dissipation of wave energy, and habitat for plants and animals. Marsh vegetation contributes to the stability of the marsh through the structure of the soil matrix and organic sediment deposition. Nonetheless, physical and biogeochemical processes between plant roots and soil in marshes are poorly understood. A diurnally inundated mesocosm experiment containing two tidal marsh cordgrass species at varying elevations was installed in order to further understand how tidal inundation affects vegetation dynamics. 16 redox sensors were installed at depths of 5 cm and 10 cm to assess oxygen dynamics and monitor plant stress in the mesocosm. Field experimentation at a Delaware marsh provided further insights into how the compressibility of marsh soils differs depending on the plant species present. Healthier plants with intact and unstressed root systems could contribute to less compressible soil. At the end of the mesocosm experiment, compressibility of each plant’s soil-root matrix will be measured to evaluate the system’s vulnerability to compaction. Preliminary redox results indicate that the lowest, most inundated plants are more stressed than plants at higher elevations, potentially highlighting the role of oxygen dynamics and vegetation stress on marsh compressibility. This research will contribute to a better understanding of the consequences increased inundation has on marsh resilience over time as sea level rises.