Degree

Doctor of Oceanography and Coastal Sciences (POCS)

Department

Oceanography and Coastal Sciences

Document Type

Dissertation

Abstract

Coastal wetlands are one of the most productive ecosystems on the earth. They are increasingly recognized and valued for atmospheric carbon sequestration and storage for a long time. However, coastal wetlands acreage is shrinking, across the globe, due to several factors including sea-level rise, local subsidence, edge erosion, extreme weather events, and anthropogenic activities. The coastal wetlands in the Mississippi River Deltaic Plain experience high relative sea-level rise, limited sediment supply, and high marsh edge erosion, leading to substantial land loss. These wetlands require restoration and conservation to slown down land loss and continue providing ecosystem services. The coastal restoration projects can generate additional incentives through the inclusion of carbon offset components and crediting the carbon preserved through preventing wetland loss.

This dissertation sought to study the soil organic matter accretion, complexity, and degradation in eroding coastal wetlands. The existing carbon market and associated methodologies applicable to coastal wetland restoration in the United States were reviewed. The marsh edge erosion rates (mean = 1.42 ± 0.2 m yr-1) were monitored at Barataria Bay, Louisiana, in shorelines facing different cardinal directions. The erosion was occurring down to 1–1.5 m depth. The amount of carbon lost per meter shoreline length was calculated as 63.3 ± 10.1 kg m-1. The deep soil cores were (~ 2 m) collected and studied for carbon stock, carbon complexity, and microbial activities across the depth to understand the future fate of eroding carbon. Total carbon increased down to the depth of 1.2 m and then decreased. The labile carbon and microbial activities were present across the study depths indicating the potential degradation of eroded in the aerobic estuarine water. There was no evidence of reburial of eroded carbon in the estuarine bottom. The variability of carbon stock across depth was related to the past depositional environments including sea-level, sediment sources, and weather events. The findings of marsh edge erosion rates, depth of erosion depth, and future fate of eroded carbon could significantly contribute to the carbon offset projects in coastal wetland restoration, including the credits for preventing the wetland loss.

Date

8-3-2021

Committee Chair

White, John R.

DOI

10.31390/gradschool_dissertations.5631

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