published_or_final_version / Zoology / Master / Master of Philosophy

published_or_final_version / Ecology and Biodiversity / Doctoral / Doctor of Philosophy

Thesis (M.S.)--University of North Carolina Wilmington, 2007. / Includes bibliographical references (Leaves: 59-65)

Dissertation (Ph.D.)--Auburn University, 2007. / Abstract. Vita. Includes bibliographic references.

Thesis (Ph. D.)--University of Washington, 2005. / Vita. Includes bibliographical references (leaves 122-143).

No description available.

The microbial composition of Pacific oysters (Crassostrea gigas) subjected to UV-treated seawater was determined by quantitative and qualitative means. A total of 2,779 microorganisms were identified from seawater and oysters during a 72 hour sampling period employing a computer assisted replica-plating technique. UV treatment effectively eliminated coliforms and Pseudomonas Type I from seawater but other gram-negative asporogenous rods were more resistant. The microogranisms commonly found in oysters, whether subjected to UV-treated seawater or not, were, in the order of predominance, Pseudomonas Type III or IV, Vibrio/Pseudomonas Type II, Flavobacterium/ Cytophaga and Acinetobacter /Moraxella. The composition of microbial flora in oysters remained relatively stable irrespective of the microorganisms present in the seawater. A total of 18 presumptive hemolytic vibrios were found in oysters but further confirmation revealed two isolates to be Vibrio parahaemolyticas and the remainder Aeromonas species. Approximately 10 percent of the microorganisms isolated from seawater and oysters were gram-positive cocci and 14 to 23 percent of these were coagulase positive, DNase positive, and (β-hemolytic on human blood agar. / Graduation date: 1971

Graduation date: 1953

Graduation date: 1992

Colloidal macromolecular organic matter (COM), which makes up a large portion of the bulk dissolved organic matter (DOM) in marine environments, has the capability to modify the bioavailability of potentially toxic metals to aquatic organisms. In order to better understand the bioavailability of some of these metals to estuarine bivalves, American Oysters (Crassostrea virginica) were exposed to different types of natural colloidal (COM) and model (alginic acid, carrageenan, and latex particles) organic biopolymers, tagged with gamma-emitting radioactive metal ions (110mAg, 109Cd, 57Co, 51Cr, 59Fe, 203Hg and 65Zn) or 14C (to sugar OH groups). Natural COM was obtained from Galveston Bay water by 0.5µm filtration, followed by cross-flow ultrafiltration, using a 1kDa ultrafilter, diafiltration and freeze-drying. COM and DOM model compounds were used in the bioavailability experiments at 2 ppm concentrations. Separate 16-hour experiments using varying sizes of latex particles assessed the lowest size of colloids that can be filtered from the water. Results showed that filter-feeding bivalves could efficiently remove particles as small as 0.04µm (40nm) in diameter, with removal halftimes of 2.5 to 5.5 hours, equivalent to filtration rates of about 50±15 ml/hour, or about 3 L d-1 g-1, which are typical values for these oysters. Results of the 20-hour bioavailability experiments demonstrated that oysters could effectively filter metals bound to COM, with the metals bound to alginic acid COM being removed at the highest rates from the water. However, the metals bound to alginic acid were not found in oyster meat in the highest amounts: it was the metals associated with the carrageenan COM. The 14C labeled biopolymer data also showed alginic acid to be removed from the water at the highest rate and, contrary to the metals, was also present in the meat in the greatest amounts. Thus, while previous experiments suggested that the quantity (i.e., concentration) of natural organic matter is important for metal bioavailability, it was shown here that the “quality”, i.e., the type of natural organic matter, is also a factor for controlling bioavailability, removal and incorporation rates of metals to oysters.