published_or_final_version / Zoology / Doctoral / Doctor of Philosophy

Thesis (Ph. D.)--University of Hong Kong, 1999. / Includes bibliographical references (leaves 131-191).

No description available.

Thesis (degree (Master in Technology))--Cape Technikon, Cape Town,1996 / Red tides are a common feature of the southern Benguela upwelling system and are usually dominated by migratory flagellates and the ciliate Mesodinium rubrum. Seasonal blooms of dinoflagellates occur in response to seasonal upwelling and typically succeed diatom blooms. High biomass, multispecies red tides result from concentration by various physical forces and are characteristically found in warm, stratified, nutrient-depleted water overlying cold, nutrient-rich bottom water. The influence of turbulent mixing, light and the availability of nutrients on the migratory behaviour of red tide species was studied by means of both mesocosm and field studies. The mesocosm experiments were conducted in a 3m laboratory column in which a red tide community, collected from the field, was introduced above nutrient-rich bottom water. All the dominant species exhibited directed vertical migration, with ascent and descent starting before sunrise and before sunset respectively. Observations support the hypothesis that red tide organisms can sustain high concentrations in nitrogen depleted surface waters by growing at the expense of nitrate taken up during nocturnal descent. Vertical niche separation of different red tide species was evident both during the night and the day. Observations support the hypothesis that species are capable of coexisting within a red tide bloom. Division rates were determined from the frequency of paired nuclei and cells. C. furca recorded the highest growth rate (u = 0.24). The relatively low growth rates emphasise the importance of physical processes, as opposed to biological processes, in the formation of red tides within upwelling systems.

Thesis (Ph.D.). / Written for the Dept. of Geography. Title from title page of PDF (viewed 2008/08/04). Includes bibliographical references.

No description available.

Harmful algal blooms (HABs) along the Florida coast have been reported for many decades. Karenia brevis is a red tide species on the West Florida Shelf, producing a suite of toxins called brevetoxins that adversely affect marine organisms and humans. Dinoflagellate cysts have been studied as a tool for red tide studies since the location where cysts accumulate in the sediments and the size of the seed beds can be important for potential blooms. However, little attention has been paid on the dinoflagellate cysts on the West Florida Coast. This study describes the distribution of dinoflagellate cysts along the West Florida Coast and proposes the possibility of Karenia brevis cysts. Samples were collected with a box corer July 17-29 and October 5-17, 2009. Overall cyst concentrations are low. The sediments along the West Florida Coast compose of coarse-sized grains that generate large-sized pores. Thus, cysts in the coarse-grained sediments might easily move along with turbulence or water movements flowing above the sediments. Cyst concentrations gradually increased shoreward. The hydrographic features along the West Florida Coast are influenced by the coastal current. Southward coastal current flowed during two cruises might drive a subsequent offshore Ekman transport which might lead to a coastal upwelling, thereby transporting bottom sediments closer to the coast. Thus, cyst concentration was higher inshore compared to that offshore. The average concentration of heterotrophic dinoflagellate cysts was higher in July than that in October, whereas autotrophic dinoflagellate cysts did not have a noticeable difference between July and October. The heterotrophic group is dominated by a protoperidinioid group that mainly feeds on diatoms. The abundance of protoperidinioid was higher in July than in October and other groups have similar abundance between two periods. The highest abundance of diatoms is in June, July and August, whereas the lowest was in October, November and May. Therefore, the decrease in the abundance of protoperidinioid cysts correlates with the lower food supply for their motile cells. Based on a morphological similarity to a Karenia brevis cyst detected in culture by Walker (1982) and a morphological difference from other species belonging to the same genus, cysts that are probably Karenia brevis have been identified.

Thesis (M.Tech.)--Cape Technikon, 1996. / Bibliography: leaf 111-121. Also available online.

Karenia brevis is the major harmful bloom forming dinoflagellate in the Gulf of Mexico. The toxin produced by this dinoflagellate can cause large fish kills, marine mammal mortality, respiratory irritation, and neurotoxic shellfish poisoning in humans. Blooms can occur anywhere in the Gulf of Mexico (hereafter Gulf) but are predominantly observed off the west coast of Florida and the coast of Texas. The west coast of Florida has been hypothesized to be the origin for blooms of K. brevis in other regions within the Gulf based upon the frequent formation of blooms in this region. To investigate this possibility, microsatellite markers were used to determine the population-genetic structure of K. brevis in the Gulf of Mexico. The difficulties of culturing K. brevis required development and use of a single-cell PCR amplification protocol for preserved cells. Lugol's iodine-preserved bloom samples of K. brevis were destained with sodium thiosulfate and subjected to two rounds of PCR amplification. The destaining protocol resulted in the successful, simultaneous amplification of five microsatellite markers from single cells of K. brevis. A total of 18, highly polymorphic microsatellite markers are available for K. brevis. Each marker was amplified from 40 cultures of K. brevis isolated from water samples from Florida and Texas. Observed genetic diversity was high but similar to the genetic diversity observed in other phytoplankton species. No genetic divergence was detected between isolates from Florida and isolates from Texas. Single cells from a total of 38 field samples were analyzed at five microsatellite markers to determine if population-genetic structure was present in K. brevis in the Gulf. Significant genetic divergence between several individual samples was detected, reflecting the high genetic diversity present within the species. Observed genetic divergence was low between blooms from the west coast of Florida and the coast of Texas and supports the hypothesis of a common origin for blooms of K. brevis in the Gulf of Mexico.

This is the first study of the Upper Jurassic and Lower Cretaceous dinoflagellate cysts of the Kyuquot Group on Grassy Island, British Columbia. Thirty nine dinoflagellate cyst taxa were identified in 85 samples collected from the Upper Tithonian Kapoose and Berriasian to Middle Valanginian One Tree formations. Cyst recovery, concentrations and diversity are relatively high in the samples from of the Kapoose Formation, whereas samples from One Tree Formation had poor dinoflagellate cyst recovery. Four dinoflagellate cyst zones were identified. Three cyst zones (Cometodinium habibii-Endoscrinium campanula-Oligosphaeridium sp.-Pareodinia spp.- Gonyaulacysta jurassica zone; Cyst Type P zone; and Circulodinium spp.-Cyst Type P zone) correspond to the Buchia columbiana zone from of the Kapoose Formation and the fourth cyst zone (Cyst Type D-Cyst Type Q-Circulodinium spp.-Gonyaulacysta spp. zone) is identified from the One Tree Formation, where four Buchia zones are recognised. The change in the ratio of marine to terrestrial palynomorphs indicates that the basin went through progressive shallowing and/or the shore came closer to the site of deposition beginning in the Upper Tithonian and continuous through to the Valanginian. The zones resemble established Siberian dinoflagellate cyst zones of the same age. This correlation suggests that the two regions were a part of the Boreal Realm during the interval. / Graduate