Date of Award

Summer 2012

Degree Type

Masters Thesis

Degree Name

Master of Science (MS)

Department

Marine Science

Committee Chair

Laodong Guo

Committee Chair Department

Marine Science

Committee Member 2

Alan Shiller

Committee Member 2 Department

Marine Science

Committee Member 3

Karen Orcutt

Committee Member 3 Department

Marine Science

Abstract

Dissolved carbohydrates (d-CHO), including monosaccharide (MCHO) and polysaccharides (PCHO), and particulate carbohydrates (p-CHO) are major components of natural organic matter and play an important role in biogeochemical cycles of carbon and other trace elements in marine environments. This study aimed to examine the abundance and partitioning of CHO between dissolved and particulate phases and their seasonal variations in the Mississippi Sound/Bight and Lake Pontchartrain. Laboratory mixing experiments were also carried out to examine the behaviour of CHO species along a salinity gradient. The phase partitioning of dioxin among three different phases, i.e., colloidal organic matter, particulate organic matter and sediments, was also determined for Mississippi River and Pearl samples. MCHO was the dominant species in the dissolved CHO, with high concentrations during high riverine discharge in March and May 2011, showing the influence of the Pearl River and flooding event from the Mississippi River through Bonnet Carr spillway. There was a strong seasonality in the distribution and partitioning of CHO. Terrestrial inputs seemed to play a significant role in the seasonal variation of dissolved and particulate CHO in the Mississippi Sound/Bight. The concentration of p-CHO and acidic polysaccharides (APS) increased with increasing salinity with a mid-salinity maximum and then decreased towards offshore. There was a positive correlation between p-CHO and chlorophyll-a (Chi-a) indicating phytoplankton as a source of p-CHO. The dioxin concentration increased from COM to POM to sediments, with much higher dioxin concentrations in the Mississippi River than the Pearl River, suggesting less anthropogenic impacts in the Pearl River Basin.

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