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No description available.

Thesis (M.S.)--University of North Carolina at Wilmington, 2003. / Includes bibliographical references (leaves : 46-50).

Global warming from anthropogenic greenhouse gas emissions causes temperature increases in aquatic ecosystems. The rise in environmental temperatures places sensitive organisms under thermal stress. Reef-building corals are a critically important group of animals that provide many ecosystem services for coral reef ecology and the economy and are at a high risk of loss from thermal stress. Thermal stress causes corals to lose their colour, i.e. become bleached, resulting from the loss of symbiont zooxanthellae. This diminishes the energetic benefits that zooxanthellae provide to corals leading to a decline in coral health and high mortality rates. However, corals are also predators and can thus draw nutrients from zooplankton prey to supplement their nutritional requirements. This study investigated whether heterotrophic feeding can ameliorate the effects of thermal stress on coral physiology by providing an alternative energy source to zooxanthellar photosynthesis. Fragmented Pocillopora damicornis coral colonies were exposed to daily maximum temperatures of up to 31°C while being either starved or fed. During the experimental period coral nubbins were monitored for changes in polyp extension, oxygen consumption rate, feeding rate, colour, chlorophyll a content, zooxanthellae density, antioxidant potentials and DNA integrity during stress and after a short recovery period. It was found that, as expected, coral polyp extension, oxygen consumption rate, colour health, chlorophyll a content, zooxanthellae density and DNA integrity were all adversely affected by thermal stress. This indicted that all these measurements were viable biomarkers for assessing the negative effects of thermal stress on coral health. Coral colour, oxygen consumption rate, chlorophyll a content, lipid content, antioxidant potential and DNA integrity were all significantly improved by feeding. These results indicate that feeding does play a role in improving overall coral health and supports the physiological processes in coral tissue during and after thermal stress. The conclusions from this study also have great significance for coral reef ecology and management as predictions of reef resilience can be made from zooplankton ecology and boosting zooplankton availability to corals may be considered to mitigate the harmful effects of thermal stress and bleaching. / M.Sc. University of KwaZulu-Natal, Durban 2013.

Thesis (M.S.)--University of Hawaii at Manoa, 2006. / Includes bibliographical references (leaves 102-127). / ix, 127 leaves, bound ill., maps 29 cm

Thesis (Ph.D.) - James Cook University, 2004. / Typescript (photocopy) Bibliography: leaves 105-116.

Thesis (doctoral)--Universität, Bochum, 2003. / Includes bibliographical references (p. 215-227).

Halichoeres socialis Randall & Lobel, 2003, is the only wrasse species (Teleostei: Labridae) with a restricted distribution within the Caribbean Meso-American Barrier Reef (MABR), Central America. This study examined the early life history of H. socialis to gain insight into its natural history and to assess if any pattern in otolith microstructure could be linked to its endemism. The sagittal otoliths from 67 individuals (ranging 9.8–43.4mm SL) were analyzed to determine the daily age and increment profile. Results indicate that (1) H. socialis displays a typical “settlement mark”; (2) the pelagic larval duration (PLD) ranged from 22 to 32 (mean=27, n=59) days, which was similar to its congeners; and (3) the juvenile growth rate is 0.7mm/d, which was faster than most congeners. The endemism of H. socialis is not explained by its PLD. Alternatively, it is possible that larval behaviors (vertical migration and/or schooling) play a key factor in how H. socialis larvae are retained within the MABR region. / 2026-03-19T00:00:00Z

Ecologists have long questioned why fluctuating populations tend to persist rather than go extinct. Populations that persist indefinitely are regulated by mechanisms that cause demographic density dependence, which works to bound fluctuation above zero. In a series of studies, I have sought to determine the processes and mechanisms that regulate local populations of coral-reef fish. In the Exuma Keys, Bahamas, fairy basslets (Gramma loreto) live in aggregations on the undersides of coral-reef ledges. These aggregations often constitute local populations because movement between aggregations is rare. The largest individuals occupy prime feeding positions near the front of ledges and force smaller individuals remain near the back where they have lower feeding rates. Based on these initial observations, I designed two experimental studies of the demographic consequences of variation in basslet density. In the first study, I manipulated the density of newly-settled fish to explore the effects of high recruitment on population size. Populations with experimentally elevated recruitment converged in density with unmanipulated populations, primarily due to density-dependent mortality. I found no evidence that density dependence was caused by intraspecific competition; rather it appeared to be due to a short-term behavioral response by predators (aggregative and/or type 3 functional response). In a second study, I manipulated the densities of adults among populations with a standard average density of newly-settled fish. Two measures indicated that the intensity of competition increased at higher densities of adults, which likely made small fish more susceptible to predation, thereby causing density-dependent mortality. Long-term observations indicated that basslet populations were regulated at temporal scales exceeding two generations. At Lizard Island on the Great Barrier Reef, I also examined how patterns of recruitment of coral-reef fishes were modified across a range of natural recruit densities in the presence and absence of resident predators. Predators decreased recruitment and increased mortality for all species, but these effects varied considerably among species. The results of each of these studies stress the importance of both competitive and predatory mechanisms in modifying patterns of abundance established at the time of larval settlement, as well as regulating local population size. / Graduation date: 2002

M.Sc. (Geology) / Within the Black Reef Formation, which forms the basal unit of the Transvaal Supergroup, an auriferous and uraniferous reef occurs. This is known as the Buckshot Pyrite Leader reef. This reef is a conglomerate-hosted gold and uranium deposit, which is similar to the Witwatersrand reefs as they both contain significant amounts of pyrite and have similar depositional environments. This study seeks to identify the geometallurgical characteristics of the gold uranium and thorium that are hosted in the Black Reef at the Modder East operation in Springs. In terms of methodology, a detailed petrographic study was completed on the samples taken from underground and the surface run of mine samples. Mineralogy was conducted on these samples using SEM-based automated technology, namely the FEI Mineral liberation analyser (MLA). Using this, I could further characterise the gold and uranium bearing phases found across the Black Reef. Additionally, mill testing, grading analysis, major and trace element chemistry, density separation, gold and uranium dissolution as well as flotation testing was conducted on the ore in order to determine its geometallurgical characteristics. Through the combination of these methods, this study aims to evaluate the Au, U and Th within the Black Reef with regards to: the metallurgy; the extraction process in relation to the mineralogy of the samples; and the possible implications that these factors could have on the overall recovery of the economic minerals.