Thesis (M.Sc.)--College of William and Mary. / Vita. Includes bibliographical references. Also available online.

Thesis (Ph.D.)--University of Rhode Island, 2009. / Includes bibliographical references (leaves 122-138).

Thesis (Ph. D.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 192-206).

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2007. / Ph.D. in Marine Environmental Science. Includes bibliographical references. Also available in electronic version.

These (Ph.D.)--University of New Hampshire, 2008. / Title from PDF title page. Available through UMI ProQuest Digital Dissertations. Includes bibliographical references (leaves 145-157). Also issued in print.

Thesis (M.S.)--California Polytechnic State University, 2009. / Mode of access: Internet. Title from PDF title page; viewed on September 14, 2009. Major professor: Mark Moline, Ph.D. "Presented to the faculty of California Polytechnic State University, San Luis Obispo." "In partial fulfillment of the requirements for the degree [of] Master of Science in Biological Sciences." "August 2009." Includes bibliographical references (p. 53-62).

Thesis (doctoral)--Universität Hamburg, 1991. / Vita. Includes bibliographical references (p. 147-162).

Thesis (M.S.) in Oceanography--University of Maine, 2006. / Includes vita. Includes bibliographical references (leaves 42-48).

The results of this study suggest that NO^ uptake in many (but not all) species of marine phytoplankton is mediated by a membrane-bound (NO⁻₃, Cl⁻)-activated adenosine triphosphatase. In the presence of NO⁻₃ and Cl⁻, semi-purified membrane preparations exhibit enhanced adenosine triphosphatase activity. The enzyme has characteristics common to other membrane-bound proteins: a break in the Arrhenius plot of 30.9 Kcal/mole at 2.9 C, parallel purification with the (Na⁺ + K⁺)-activated transport adenosine triphosphatase, and activation of catalytic activity by non-ionic and anionic detergents. It is inferred from parallel purification of the (NO⁻₃,Cl⁻)-activated adenosine triphosphatase and the physiological kinetics of NO⁻₃ uptake by intact cells, that the enzyme translocates NO⁻₃ across the cell membrane, into the cytoplasm, against the chemical concentration gradient of the ion. The half-saturation constants for activation of the adenosine triphosphatase by NO⁻₃ are less than 1 µM for most species tested and correlate with half-saturation constants for NO⁻₃ uptake by whole cells. The three dinoflagellates tested did not exhibit any relationship between NO⁻₃ concentrations and ATP hydrolysis, and it is inferred that the (NO⁻₃,Cl⁻)-activated adenosine triphosphatase is probably absent from this group. Results of metabolic inhibitor studies (including KCN, 2,4-dinitrophenol, dichlorodimethylurea, and carbonyl cyanide m-chlorophenylhydrozone) imply that the source of ATP for the NO⁻₃ transport is primarily cyclic photo-phosphorylation in vivo. These results are consistent with observations of selective inhibition of NO⁻₃ uptake in unialgal cultures as well as in natural populations. Field studies with natural phytoplankton communities from Knight Inlet, B. C, suggest a physiological adaptation to external nitrogen concentrations may occur. This adaptation is characterized by increased intracellular chlorophyll a synthesis in response to 10-15% nitrogen enrichment over a 6-8 hr period. During the adaptive period carbon fixation is temporarily suppressed, apparently due to competition between inorganic carbon and inorganic nitrogen for high-energy nucleotides from the light reactions. The results of this study are related to previous proposals for the metabolic pathway of nitrogen in marine phytoplankton. In conclusion, a modified pathway is proposed stressing (1) group differences, in that nitrogen assimilation in dinoflagellates appears different from other groups, and (2) the energetics and biochemical feed-back controls of nitrogen assimilation. / Science, Faculty of / Botany, Department of / Graduate

Marine phytoplankton produce extracellular metabolites which may be important in controlling the interactions among species or the competition for a limiting nutrient. While the absolute amount of these metabolites may be small compared to the primary organics released by the phytoplankton cell, the control of the production of these unique metabolites may be an important factor in the ecology of the producing species. These compounds have not been extensively studied due to the difficulty in isolating these minute quantities from seawater. In this thesis, two externally produced metabolites have been investigated. The concentration of 1 -(2,6,6-trimethyl-4-hydroxycyclohexenyl)- 1,3-butanedione, a nor-caroteniod commonly referred to as the β-diketone, was quantitatively determined during the exponential and senescent stages of growth of Prorocentrum mi n imum in P-, N-, and iron-deficient batch cultures. The β-diketone was released extracellularly in a single 'pulse' during the stationary stage of growth. Several factors such as temperature, irradiance, type of nutrient-deficiency (N, P, or Fe), and the ambient nitrate concentration were important in establishing the amount of the β-diketone produced. The environmental factors did not influence the temporal pattern of production, only the absolute amount of the β-diketone produced. The limits of the range of production of the β-diketone were narrower than the range of maximum growth for any environmental influence. The inhibition of growth and the heterotrophic uptake of glucose by marine bacteria, demonstrated the antibacterial properties of the β-diketone. The second extracellular organic examined was prorocentrin. Prorocentrin is the extracellular siderophore produced by Prorocentrum minimum, P. mariae-lebouriae, and P.gracile. Functionally similar compounds are produced by Thalassiosira pseudonana and Dunaliella tertiolecta. This study is first to characterize this type of high-affinity iron (111)-transport system in marine eukaryotic phytoplankton. The pattern of siderophore production by all species is the same, although the absolute amount of the material produced is species specific. There is no intracellular or extracellular siderophore production under iron-sufficient culture conditions. When iron was deficient there was a short period of rapid extracellular siderophore production during the stationary stage of growth. The intracellular prorocentrin concentration was very low which suggests that de novo synthesis of the prorocentrin occurs just prior to extracellular release. The persistence of the extracellular siderophore in the culture medium was brief. There was an increase in the in vivo fluorescence following the loss of the siderophore from the medium. The increase in in vivo fluorescence was not accompanied by an increase in cell concentration. An hypothesis concerning the mechanism of the iron-uptake system is proposed. Procedures for the isolation and characterization of prorocentrin are presented. Prorocentrin appears to be a tri-hydroxamate siderophore with a molecular weight between 560 and 590 daltons. The iron-prorocentrin complex is stable over a wide pH range. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate