262 Advances in Ecohydrogeology (Posters)
Ecohydrogeology is the unifying, synthetic field of study integrating the approaches from the ecological and hydrogeological sciences in the study of groundwater-related ecosystems, habitats, and organisms. We encourage submissions of research that advances the science, stewardship, and policy at the intersection of ecology and hydrogeology.
Wednesday, 22 October 2025
8:00 AM - 5:30 PM
HBGCC, Hall 1
The Hydrology Behind Plant Zone Migration in a Georgia (USA) Salt Marsh
Paper number: 262-0
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM
Authors
Abstract
Salt marsh encroachment is a visible indicator of sea level rise in low-lying coastal areas. The rate of salt marsh migration does not track directly with sea level, however. Field observations from 1998 to 2022 at Sapelo Island, Georgia (USA), show that salt marsh migration occurred in surges during droughts. Drought has the potential to affect salt marshes in multiple ways, including reduced infiltration of rainwater and reduced discharge of fresh groundwater from adjacent uplands to the marsh. To test these possibilities, in 2018 we began monitoring hydraulic head (every 20 minutes) and groundwater salinity (sporadically) in the root zone. We then developed a two-dimensional numerical model to simulate groundwater flow and salinity below the salt marsh from 1998 to 2022. Simulations revealed recurrent winter freshening of groundwater in the root zone in the high marsh, caused by winter expansion of the freshwater lens. In drought years, the simulated freshwater lens failed to expand, leading to higher simulated salinities during the spring growth period. It is not yet clear whether higher salinities alone could have contributed to plant zone migration, or whether the high marsh was subject to greater fluctuaions in salinity during winter/spring sea level lows, as suggested by prior studies of acute salt marsh dieback.
Geological Society of America Abstracts with Programs. Vol. 57, No. 6
doi: 10.1130/abs/2025AM-414539
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