Date of Award
Master of Science (MS)
Ocean & Earth Sciences
H. Rodger Harvey
Fred C. Dobbs
Peter N. Sedwick
Amino acids comprise up to 50% of organic matter in cellular material and are a major fraction of oceanic organic carbon. Amino acids are also considered highly labile during organic matter recycling, making them useful proxies for organic carbon cycling. Nevertheless, analysis of individual amino acids has been burdened by lengthy derivatization and complex analysis since the 1950s. In this thesis, I describe the modification of advanced analytical techniques, developed in the biomedical field, for analysis of marine matrices which allow the determination of at least 40 amino acids without the need for lengthy sample preparation and derivatization, twice the number of most common biosynthetic amino acids. Combining ion pairing separation and mass selection software with liquid chromatography tandem mass spectrometry (LC/MS/MS) allows detection of amino acids that were previously difficult to measure due to coelution and incomplete derivatization. The method was validated by examining a suite of marine matrices of increasing complexity including free amino acids (FAA) in seagrasses, total hydrolyzable amino acids (THAA) in mixed diatom-bacteria cultures, and sediment THAA. This method was then combined with additional measures and applied to examine the carbon cycling and conditions of the Arctic Ocean Mackenzie shelf system. Analysis of organic carbon in particles and sediments, fatty acid and sterol biomarkers, and the developed amino acids method, together with sediment grain size and meiofaunal community structure, allowed characterization of organic carbon in the Mackenzie River shelf system during the fall of 2016. Results show the coastal shelf system near the Mackenzie River delta experience significant inputs of both in-situ marine production and terrestrial organic matter to the sediments. Overall results suggest that mid-shelf waters receive relatively higher contributions of labile marine carbon than shallow or deep waters along the eastern Beaufort Sea shelf and over time these inputs are reflected by increased meiofaunal diversity and abundance. Despite the large flux of terrestrial organic material exiting the delta, higher meiofaunal abundance appears to be the result of localized input of marine primary production rather than terrestrial carbon carried through the Mackenzie outflow.
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McMahon, Rachel M..
"Advances in Amino Acid Analysis for Marine Related Matrices and Its Application to Coastal Shelf Settings in The Canadian Arctic"
(2018). Master of Science (MS), Thesis, Ocean & Earth Sciences, Old Dominion University, DOI: 10.25777/tgw2-ph58