Thesis (M.Sc.)--Acadia University, 2000. / Includes bibliographical references (leaves 103-108). Also available on the Internet via the World Wide Web.

Thesis (Ph.D. (Zoology & Entomology)) - Rhodes University, 2009.

Thesis (Ph. D.)--Oregon State University, 2006. / Printout. Includes bibliographical references (leaves 223-233). Also available on the World Wide Web.

Thesis--Massachusetts Institute of Technology/Woods Hole Oceanographic Institution. / "WHOI-80-21." Vita. Includes bibliographical references (p. 187-206).

Thesis (M.E.)--University of Canterbury, 1997. / Typescript (photocopy). Includes bibliographical references (leaf 39). Also available via the World Wide Web.

Thesis (M.S.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains xi, 87 p. : ill. Vita. Includes abstract. Includes bibliographical references.

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references. Also available via the Internet.

The medicinal chemistry of selected marine algae indigenous to South Africa was investigated. Following the isolation and characterisation of a number of new and known compounds, the associated in vitro cytotoxic profiles of these new compounds was investigated. Plocamium maxillosum yielded two new cyclic polyhalogenated monoterpenes which were characterised as 2E-chloromethine-4E-chlorovinyl-4-methyl-5-cyclohexen-1-one (2.1) and 2Z-chloromethine-4E-chlorovinyl-4-methyl-5-cyclohexen-1-one (2.2) on the basis of one and two dimensional NMR spectroscopic data and MS analysis. These compounds were also found to have good cytotoxic activity against breast cancer cell lines. Although these compounds are based on a regular monoterpene skeleton, they represent an uncommon feature not often seen in cyclic halogenated monoterpenes from marine algae. Plocamium robertiae yielded one new cyclic polyhalogenated monoterpene identified as 4,5- dibromo-5-chloromethyl-1-chlorovinyl-2-chloro-methylcyclohexane (2.6) and one known compound called 2,4-dichloro-1-chlorovinyl-1-methylcyclohexane-5-ene or Plocamene D (2.9). Portieria hornemannii was collected from Port Edward in Natal and yielded three new compounds, namely; 3Z-1,6-dibromo-3-(bromomethylidene)-2,7-dichloro-7-methyloctane (3.1), 1E,3Z-1,6-dibromo-3-(bromomethylidene)-7-chloro-7-methyloct-1-ene (3.2), 1Z,3Z- 1,6-dibromo-3-(bromomethylidene)-7-chloro-7-methyloct-1-ene (3.3), and one known compound, namely; 3S,6R-6-bromo-3-(bromomethyl)-3,7-dichloro-7-methyloct-1-ene (3.4). Compounds 3.1 and 3.2 showed no cytotoxic activity against breast cancer cells. Another Portieria hornemannii sample was collected from Noordhoek in the Eastern Cape, it yielded one known compound referred to as 3Z-6-bromo-3-(bromomethylidene)-2,7- dichloro-7-methyloct-1-ene (3.5), as well as one new compound called portieric acid A (3.6) or 5-bromo-2-(bromomethylidene)-6-chloro-6-methylheptanoic acid. Portieric acid A showed slight cytotoxic activity and also represents a new class of compound within the genus Portieria. The isolation of secondary metabolites from the South African red alga, Laurencia glomerata, yielded two known compounds; 7-hydroxylaurene (4.9) and cis-neolaurencenyne (4.12), as well as one chamigrane related compound (4.11). Laurencia flexuosa yielded one known compound called 3Z-bromofucin (4.13). Using 1H NMR, GC and molecular systematics, a novel method for identifying different species of Laurencia was also investigated.

Magister Scientiae (Biodiversity and Conservation Biology) / This study investigated the role of grazing as a possible cause for the upper limit of distribution of algae on a typical South African south coast. / South Africa

A comprehensive field and laboratory study of nitrogen uptake in intertidal seaweeds was undertaken. Methods for measuring nitrogen uptake rates were evaluated. Short initial periods of rapid ammonium uptake were common in nitrogen deficient plants. The presence of ammonium inhibited nitrate uptake, but a certain degree of nitrogen starvation overcame this suppression. Laboratory studies with Porphyra perforata showed that nitrogen starved cultures maintained rapid initial ammonium uptake rates. The nitrate uptake system did not remain activated. Nitrogen starvation also resulted in a general decrease in soluble nitrogen content and a transient increase in nitrate reductase activity. The effectiveness of in vitro and in vivo nitrate reductase assays was investigated. The rate of nitrite production in the in vivo assay varied with incubation time. Therefore, the in vitro assay was used. Nitrate grown cultures of Porphyra perforata maintained high ammonium uptake rates. It was suggested that the rate of nitrate reduction was limiting the supply of nitrogen for further assimilation which may control ammonium uptake. Ammonium arid ammonium plus nitrate grown cultures had very low nitrogen uptake rates and nitrate reductase activities. Field studies with Gracilaria verrucosa confirmed that growth on ammonium inhibited nitrate uptake, nitrate accumulation and nitrate reductase activity. The presence of ammonium did not inhibit nitrate uptake rates in severely starved populations. All populations maintained high ammonium uptake rates suggesting that they were nitrogen limited at this time (August). Ammonium and nitrate uptake were saturable in the high intertidal G. verrucosa population but not in the low intertidal population. An investigation was made into the effect of nitrogen source and periodic exposure to air on growth, development and nitrogen uptake in Fucus distichus germlings. Gamete release, fertilization, germination and germling growth had no requirement for a specific form of nitrogen. Periodic exposure to air increased secondary rhizoid development. Ammonium and nitrate uptake rates of the germlings were much higher than for the mature thalli, but the affinity for nitrate was similar. The germlings showed saturable uptake kinetics but the mature thalli did not. The presence of ammonium inhibited nitrate uptake by the mature plants but not by the germlings. Mild desiccation enhanced nutrient uptake rates in several intertidal seaweeds. This uptake response occurred when growth was limited by that particular nutrient and when the thallus had been exposed to periodic desiccation for several weeks. The degree of enhancement, the percent desiccation producing maximum uptake rates and the tolerance to higher degrees of desiccation were related to intertidal location. This was shown to be an intraspecific as well as an interspecific adaptation. Transplant experiments with G. verrucosa showed that enhanced nutrient uptake rates after desiccation were related to intertidal height and not geographic location and that this response could be induced in approximately five weeks. It was suggested that this enhanced uptake response was an adaptation to nitrogen procurement and C/N homeostasis following periodic exposure when carbon was assimilated but when other nutrients were not available. / Science, Faculty of / Botany, Department of / Graduate