Semester of Graduation

Spring 2026

Degree

Master of Science (MS)

Department

Department of Oceanography and Coastal Sciences

Document Type

Thesis

Abstract

The goal of this project is to evaluate nitrous oxide (N2O), carbon dioxide (CO2), and methane (CH4), in an active delta across a sediment organic matter gradient, which differences are due to different delta evolutionary stages. These values are significant because they contribute to the continuous effort to quantify greenhouse gas (GHG) (N2O, CO2, and CH4) emissions from wetlands, especially those in Louisiana, and broaden the knowledge of what regulates their release. GHG are released through both microbial respiration and vegetation. Different sizes of opaque chamber extenders were designed to include vegetation during the growing seasons and seasons of senescence. This study had three objectives: (1) ensure homogenous flux measurements using different sized chambers (2) investigate if GHG fluxes increase with sediment organic matter concentration (%) in a deltaic freshwater wetland, (3) examine if cooler and warmer seasons create GHG flux variation at sites along a sediment organic matter % gradient, and (4) to evaluate vegetation influence on GHG fluxes. I hypothesized that GHG emissions will increase with organic matter % and GHG emissions will increase with an increase in warmer seasons . Chamber extender fan testing in the lab and field ensured homogeneous flux measurements by ensuring no stratification and no differences between ambient sediment conditions and various chamber heights. A high (16.2%) and intermediate (9.9%) organic matter (%) site was used to explore objectives (2) and (3). Flux measurements were collected from August 2024 to August 2025 each month. The intermediate site (2094.08 nmol m-2s-1 had significantly greater CO2 emissions than the high site (1149 nmol m-2s-1). Similarly, there was a significant difference for N2O flux between the intermediate site (-0.014 nmol m-2s-1). and the high site (0.029 nmol m-2s-1). However, there was not a significant difference for CH4 flux (160.76 nmol m-2s-1) between the intermediate site and the high site (142.93 nmol m-2s-1). Sites were observed to have higher fluxes in the summertime than winter for CO2 and CH4, but not necessarily N2O. Seasonally variation and flux rates at independent sites were heavily influenced by vegetation whether that be from presence or type.

Date

3-19-2026

Committee Chair

Twilley, Robert R.

LSU Acknowledgement

1

LSU Accessibility Acknowledgment

1

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