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A Thesis Submitted to the University of North Carolina Wilmington in Partial Fulfillment Of the Requirements for the Degree of Master of Science

UNCW Author/Contributor (non-UNCW co-authors, if there are any, appear on document)
Lisa A. Thatcher (Creator)
Institution
The University of North Carolina Wilmington (UNCW )
Web Site: http://library.uncw.edu/
Advisor
G. Brooks Avery

Abstract: Global warming has generated extensive research into the sources and removal mechanisms for the greenhouse gases carbon dioxide and methane. Recent research, in which sulfate was added to freshwater and methanogenic brackish sediments, showed that under sulfate-reducing conditions rates of carbon remineralization were more rapid. Therefore, less carbon should be stored in these systems under saline conditions. In the current study, rates of carbon remineralization and storage were compared in Cape Fear River estuarine sediments with naturally-occurring spatial and temporal salinity variations. Trends were not evident along a salinity gradient for the percent organic matter content of sediments, sediment accumulation rates, or the total amount of carbon remineralized. These results show that there are no clear-cut patterns for biogeochemical parameters along a salinity gradient, likely due to variability in both primary productivity and remineralization rates. Although the quantity and quality of organic matter are generally thought to affect remineralization rates, rates in this study were controlled by sulfate concentrations. Most sediments responded to sulfate concentration increases with more rapid remineralization rates, showing that sulfate variations can potentially affect carbon storage in estuarine sediments. An unexpected microbial process was observed during the experiments conducted for this study. The two main processes by which sediments are remineralized in the estuary are sulfate reduction and methane production. Sulfate reduction has generally been shown to out-compete and inhibit methane production via mutually exclusive biogeochemical zonation through competitive inhibition. However, for the first time the coexistence of the two processes at rates of similar magnitudes was observed. A novel approach for calculating below-ground primary production within estuarine wetlands and carbon flux from estuarine wetlands, using sediment remineralization rates, 137Cesium accumulation rates, and above-ground biomass measurements, is presented in this study. The largest amount of carbon fluxed from a site that contained the most above-ground biomass during the growing season. This study has shown that remineralization rates in estuarine sediments could potentially respond to sulfate variations on a short-term basis, supporting the idea that stored carbon could be released to the atmosphere during a rapid sea level rise.

Additional Information

Publication
Thesis
A Thesis Submitted to the University of North Carolina Wilmington in Partial Fulfillment Of the Requirements for the Degree of Master of Science
Language: English
Date: 2009
Keywords
Carbon cycle (Biogeochemistry), Coastal ecology, Estuarine ecology--North Carolina--Cape Fear River Estuary, Estuarine sediments--North Carolina--Cape Fear River Estuary
Subjects
Estuarine sediments -- North Carolina -- Cape Fear River Estuary
Carbon cycle (Biogeochemistry)
Estuarine ecology -- North Carolina -- Cape Fear River Estuary
Coastal ecology