Date of Award

Fall 12-2022

Degree Type

Masters Thesis

Degree Name

Master of Science (MS)

School

Ocean Science and Engineering

Committee Chair

Wei Wu

Committee Chair School

Ocean Science and Engineering

Committee Member 2

Chet Rakocinski

Committee Member 2 School

Ocean Science and Engineering

Committee Member 3

Tracy Quirk

Committee Member 4 School

Ocean Science and Engineering

Abstract

Wetlands are highly productive ecosystems that provide important ecosystem services and are threatened by extreme hydrological events. I evaluated how diversion of freshwater like Bonnet Carré Spillway openings in Louisiana, US, affected vegetation productivity and diversity in salt marshes on the neighboring Mississippi Gulf Coast, US. My study area is two estuarine systems that differ in their proximity to the Bonnet Carré Spillway, elevation, and salinity including Hancock County Marshes on the west, and Grand Bay National Estuarine Research Reserve (NERR) on the east in Mississippi. I collected above- and belowground biomass samples in 2020 and 2021, developed linear mixed-effects models to predict how the plant productivity and diversity changed with elevation and soil porewater salinity, and linked vegetation productivity to spectral information of Landsat and Sentinel satellite images. I applied the models to hindcast vegetation productivity based on historical satellite images approximately during May and August of years with and without Bonnet Carré Spillway openings to assess the openings’ impact on vegetation productivity. While elevation was included in most of the models to predict above- or belowground biomass in Hancock County marshes, soil porewater salinity was the more prevalent driver in the Grand Bay NERR. Additionally, vegetation biodiversity decreased with salinity in both salt marshes. As the frequency and duration of the Bonnet Carré Spillway openings increased, the peak green aboveground biomass decreased in both estuaries in the year when the spillway opened and was concentrated in the region that is closer in proximity to the Bonnet Carré Spillway.

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