Date of Award

Summer 8-2021

Degree Type

Masters Thesis

Degree Name

Master of Science (MS)


Biological, Environmental, and Earth Sciences

Committee Chair

Franklin Heitmuller

Committee Chair School

Biological, Environmental, and Earth Sciences

Committee Member 2

Patrick Biber

Committee Member 2 School

Ocean Science and Engineering

Committee Member 3

Kevin Kuehn

Committee Member 3 School

Biological, Environmental, and Earth Sciences

Committee Member 4

George Raber

Committee Member 4 School

Biological, Environmental, and Earth Sciences


Climate change and relative sea level rise is resulting in saltwater intrusion and inundation of coastal marshes. This study investigates factors affecting marsh hydrology, including sediment composition, seasonal variability, and coastal storms in Grand Bay National Estuarine Research Reserve (NERR) near Pascagoula, Mississippi. Analysis of sediment includes color, organic matter, carbonate, magnetic susceptibility, and particle size. Shallow groundwater hydrologic trends between Summer 2015 and Fall 2016 are established along a salinity gradient at four sites using water levels, temperature, and conductivity monitored at the surface and in piezometers at depths of 0.75m, 1.5m, and 2.25m.

Sediment analysis indicates reducing conditions throughout with redoximorphic concentrations of iron oxides and oxidation colors. Sediment is typically high in organic matter (avg 4.6% and up to 18.5%) and below 5% carbonate. Magnetic susceptibility increases seaward. The relative abundance of sand particles is a controlling factor for permeability in the clay and silt rich marsh sediments. Shallow groundwater levels fluctuate corresponding to diurnal tidal cycles, seasonal cycles, and short-term storm influences. Temperature and salinity fluctuate slowly, and do not have strong tidal signals indicating a distinction between the marine surface and terrestrial subsurface. The salinity gradient generally follows expected trends. However, the salinity gradient shifts to the middle of the marsh in drier periods such that salinity is higher than in outer marsh areas. Salinity generally decreases with depth suggesting that seaward flow of fresher water in the shallow subsurface coupled with low permeability fine-grained sediments resists the seepage of higher density saline surface water.

Included in

Geology Commons