TRACKING THE SOURCES AND FATES OF FLUORESCENT ORGANIC MATTER IN THE EUTROPHIC NEUSE RIVER ESTUARY, NORTH CAROLINA

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  • July 24, 2019
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  • Hounshell, Alexandria
    • Affiliation: College of Arts and Sciences, Department of Marine Sciences
Abstract
  • Eutrophication is defined as ‘an increase in the rate of supply of organic matter (OM) to an ecosystem’. In estuaries, this can take two forms: an increase in allochthonous and an increase in autochthonous OM. The goal of this dissertation was to use spectrofluorometry, as excitation emission matrices (EEMs), and other measures of OM quantity and quality, to constrain the OM pool in the Neuse River Estuary (NRE) and to assess how climate change and human activities in the watershed are altering the quantity and quality of OM. EEMs can be coupled with the statistical decomposition technique, parallel factor analysis (PARAFAC), to identify broad classes of fluorescent OM (FOM). The first chapter assessed the use of PARAFAC as applied to fluorescent dissolved OM (FDOM) and base extracted fluorescent particulate OM (BEFPOM) and determined the dominate sources of these two pools were different. The second chapter used multivariate statistics to identify sources of FOM. Results suggest the FDOM pool is composed of terrestrial, humic-like OM while the FPOM pool contains terrestrial, humic-like and autochthonous OM. In the final chapters, I focused on how anthropogenic activities alter OM in the NRE. A dissolved organic carbon (DOC) source and sink term, under different riverine discharge conditions, was calculated to assess when the estuary acts as a processer versus a pipeline for DOC export. Results indicate the source and sink term was an order of magnitude less than riverine loading and contained large variability. They do suggest the estuary may act as a pipeline for riverine DOC export to the coastal ocean following extreme events. Finally, I assessed the ability of estuarine phytoplankton and bacterial assemblages to use watershed dissolved organic nitrogen (DON) as a nutrient source. I used DON addition bioassays to assess the impact of wastewater treatment facility effluent, chicken and turkey litter leachate, and river DON on phytoplankton growth. Chicken litter leachate was the only treatment which stimulated phytoplankton growth. This research serves as a baseline for understanding the current FOM pool in the NRE and demonstrates how the OM pool may be changing in response to climatic and anthropogenic pressures.
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Advisor
  • Hall, Nathaniel S
  • Alperin, Marc
  • Paerl, Hans W
  • Piehler, Michael F
  • Osburn, Christopher L
Degree
  • Doctor of Philosophy
Degree granting institution
  • University of North Carolina at Chapel Hill Graduate School
Graduation year
  • 2019

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