Thesis (Ph.D.)--Drexel University, 2009. / Includes abstract and vita. Includes bibliographical references (leaves 85-94).

Thesis (Ph.D.)--University of Delaware, 2007. / Principal faculty advisor: David A. Hutchins, College of Marine and Earth Studies. Includes bibliographical references.

No description available.

The purpose of this study was to examine the sequence of changes in the gross morphology and toxicity of the raphidophyte alga Heterosigma akashiwo in the context of blooms of this species in the Strait of Georgia, British Columbia. Field work focused on this alga’s 1989 fish-killing bloom. That bloom was extensive, with discolouration of the water extending from Jervis Inlet through Malaspina Strait into the Strait of Georgia, and south to Cypress Island in Washington State. Excystment events on Spanish Banks in Vancouver harbour preceded population development in the Strait of Georgia during July and August but toxicity was only noted in the last two days of August and through September. Fish kills occurred near Cypress Island, and in Jervis Inlet and the contiguous waters of Agamemnon channel. These locations represented the geographic extremes of the discoloured waters. In Malaspina Strait and Jervis Inlet, information was collected on water column structure, macronutrient concentrations, and the distribution of algae and fish mortalities. Fish mortalities were coincident with the first sighting of waters discoloured with Heterosigma akashiwo in Agamemnon Channel and Jervis Inlet. The alga appeared to be transported to the areas by currents. Algal concentrations were higher at the Malaspina Strait end of a transect into Jervis Inlet and during flood rather than ebb tides. The water column in Malaspina Strait and Jervis Inlet was stratified and both inorganic nitrogen and phosphorus in surfece waters were low enough to limit growth of H. akashiwo. Though this alga can migrate vertically to obtain nutrients at depth, there was no evidence of migration during this toxic event. Termination of the bloom was associated with a weakening of the water column stratification and the reappearance of non-limiting concentrations of nitrogen in the surface waters. Work in culture demonstrated that there was a sequence of reproducible changes in cell size and shape that improved uptake when nutrients were at the concentrations seen in the Strait at the start of the toxic bloom. These changes involved reduction in cell volume by a factor of between 2- and 4-fold and cells changing from rounded, almost football-shaped cells (oblate spheroids), to plate-like (prolate spheroids). Mathematical modeling suggests that the volume changes could improve nutrient uptake by a factor of 21 to 38%. The changes in shape could improve nutrient uptake dynamics by a further 7.5%. Depending on the nutrient history of the population, changes in cell shape could continue beyond the plate-like form with significant portions of the algal population developing surface protuberances when adequate nutrients and energy were available to the population. The elaboration of surface processes could further improve uptake dynamics. A numerical model to describe these shapes was not available so the degree of improvement could not be quantified. As cells reach the end of their life cycle in culture, they revert to the oblate spheroid form and, if no new nutrients are added, will form resting cysts. However, cyst formation can also be triggered earlier in the life cycle by the addition of nutrients. This may benefit the species by ensuring that cells form cysts in shallow waters where spring temperatures are adequate to fecilitate excystment of cells. In addition to changes in shape. Heterosigma akashiwo cells produce a toxic agent which can suppress growth of nutrient competitors and kill predators, or make the algae unpalatable. Production of those toxins begins and declines immediately prior to decline in population numbers. Toxic effects of the alga can be caused to disappear at any time by the addition of nutrients. Similar to the differentiation of cell shape, the level of toxicity expressed by the cells appears to be correlated with the nutrient history of the population. Cells grown in higher nutrient concentrations appear to be more toxic; however, the population need not have high numbers of cells with processes to be toxic. Heterosigma akashiwo would appear to have adaptations which enhance its ability to compete and survive in the nutrient-limited waters of late summer. The adaptions include both changes in gross morphology of the cells and in the production of toxins which reduce the effects of competition and predation. Population growth and formation of concentrations of the alga capable of discolouring the water can be independent of the occurrence of toxicity. Lack of vertical migration and a protracted period of a stable, stratified water column with depleted nutrients appear to be critical to the genesis of toxicity in wild populations. / Graduate

The variability in surf-zone phytoplankton community composition together with variability in nutrient concentrations was studied at seven beaches along the coast near Port Elizabeth, South Africa over a one-year sampling period. The nutrient requirements of selected diatoms and dinoflagellates that co-occur at these beaches were studied. The highest nutrient concentrations were recorded at Brighton beach, with phosphate concentration being substantially higher than standards set out for both South African and European waters. Nitrate, ammonium and silicate concentrations were consistent (low variability) at all beaches. The species composition of beaches without surf diatoms was also not variable (except for King’s Beach – an artificial beach). Maitland beach was the only beach that could be identified as a surf diatom beach due to the presence of Anaulus australis. The surf diatom Anaulus australis was found to be a superior competitor compared to all other species tested: the other surf diatom Asterionellopsis glacialis, and the dinoflagellates Gonyaulax spinifera, Prorocentrum micans, and Scrippsiella trochoidea. Gonyaulax spinifera could possibly outcompete Anaulus australis in systems should nitrate become limiting.

Four studies were conducted to evaluate the potential for post-extraction algal residue (PEAR) to be incorporated as a protein source in the grazing sector of the beef cattle industry. In Experiment 1, blends of PEAR and conventional protein supplements (dried distillers’ grains, DDG; cottonseed meal, CSM) were offered to steers consuming Bermudagrass to evaluate palatability of PEAR. Supplement completion, time required for consumption, and amount of supplement consumed were recorded. In Experiment 2, isonitrogenous amounts of PEAR and CSM (100 mg N/kg BW) were supplemented to steers consuming low-quality forage to compare effects on nutrient utilization. Experiment 3 evaluated the optimal inclusion rate of PEAR to steers consuming low-quality forage. Treatments included no supplemental protein, 3 levels of PEAR (50, 100, and 150 mg N/kg BW) and 1 level of CSM (100 mg N/kg BW). In Experiment 4, the effects of upstream operations on the nutritive value of PEAR were quantified. Observations indicate PEAR may be blended with existing protein sources in the beef industry without negatively affecting palatability, but there may be palatability concerns when PEAR is offered alone. Provision of 100 mg N/kg BW of PEAR or CSM stimulated forage intake (P ≤ 0.05) and increased N retention (P = 0.02) relative to unsupplemented animals. Imbalances in mineral intakes (Ca:P ratio of 8:1) were observed when PEAR was supplemented, but not CSM. Total digestible OM intake (TDOMI) responded quadratically (P = 0.01) to increasing provision of PEAR with maximization occurring when PEAR was provided at 100 mg N/kg BW. There was not a difference in TDOMI (P = 0.13) at isonitrogenous levels of PEAR and CSM, indicating forage utilization was stimulated to a similar extent. Excess mineral levels and imbalances in PEAR were largely a result of cultivation, harvesting, and extraction procedures which could be controlled. Thus, there is potential to alter production streams to optimize oil yield and co-product value. Overall, our results indicate PEAR can be incorporated as a protein source in the beef cattle industry, thus increasing economic viability of biofuel production from algal biomass.

Thesis (M.S.)--University of North Carolina at Wilmington, 2003. / Includes bibliographical references (leaves : [88]-96).

Thesis (Ph.D.)-University of California, Santa Cruz, 2007. / Includes bibliographical references. Also available online. Restricted to UC campuses.

Thesis (Ph.D.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 201-227) Also available in print.

Thesis (Ph. D.)--University of California, Los Angeles, 2002. / Vita. Includes bibliographical references.