Cost-effective, post-mining environmental restoration of an open-cast phosphate mine at Langebaanweg, South Africa
- Authors: Van Eeden, Joseph Deon
- Date: 2010
- Subjects: Abandoned mined lands reclamation -- South Africa -- Langebaan , Phosphate mines and mining -- Environmental aspects -- South Africa -- Langebaan , Phytoremediation -- South Africa -- Langebaan
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4232 , http://hdl.handle.net/10962/d1003801 , Abandoned mined lands reclamation -- South Africa -- Langebaan , Phosphate mines and mining -- Environmental aspects -- South Africa -- Langebaan , Phytoremediation -- South Africa -- Langebaan
- Description: Approaching the ecological rehabilitation of an open-cast phosphate mine in the West Coast of South Africa during the post-operational phase presented some challenges. The area was extensively modified during the mining operations. Soils from different layers were mixed with topsoil being covered by subsoil, overburden dumps and tailing dams being constructed resulting in extensive cross-zoned soils. Large areas of subsoil areas were exposed on the mine floor with localized and small scale salinity being evident. The modified topography as well as the complex new surface material posed a challenge in terms of identifying suitable local species that could be used to rehabilitate the post-mining environment. The mine area was heavily infested with woody alien invasive plants, such as Acacia cyclops, established in an attempt to reduce the dust and little natural vegetation cover was present. In the arid west coast environment, the four-month-long winter growing season is followed by hot and windy dry summers (Chapter 2) presenting a challenge reestablishing local vegetation in modified soils. Moreover, little was known about the local vegetation in terms of their propagation and use in stabilization techniques as an alternative to exotic vegetation such as the A. cyclops, which had been more often used in revegetation projects. A study was conducted to determine the most efficient and cost-effective methods of vegetative rehabilitation of the Chemfos site (Chapter 1). A review of the literature available at the time as well as approaches that were successfully implemented in other Western Cape rehabilitation projects such as the Du Toitskloof Pass and the Sishen–Saldanha railway line (Chapter 3), were considered. Previous studies on the west coast dunes at Blaauwberg had shown using Marram grass as a dune stabilizer was most successful. Marram grass was tested in trials alongside local grasses, such as Chaetobromus dregeanus and Ehrharta villosa, that showed potential but had not been formally evaluated. The environmental context of Chemfos (Chapter 2) as well as the Conceptual Rehabilitation Plan that considered the modified environment, soils and closure objectives of the mine, were reviewed to determine the most pressing rehabilitationrelated questions that required answers. This led to the final experimental design that was implemented mid-winter in 1996 (Chapter 5). The trials were implemented in the areas perceived to be the most difficult to rehabilitate, namely the mobile sands in the tailings dam and the exposed subsoil or mine floor areas. The use of brushwood together with specific plants and seeds appropriate for the use in either sandy soil or subsoil were evaluated in a variety of combinations and application densities to determine the most effective treatment combination at the minimum effective density. The best initial cover of the tailings dam were recorded in the Ammophila arenaria trials but the use of the local grass species Ehrharta villosa, performed better from year two onwards and was much cheaper to establish. On the subsoil, the trials where a cover of topsoil was used performed better than the combination trials. This indicated that topsoil placement on post-operational phase shaped subsoils during the mining operation to be the most desirable treatment. Initial results of the trials were used as a basis for developing the rehabilitation techniques that were rolled out across the Chemfos landscape. The approaches were refined as indications of trial responses became evident. Lessons learned were incorporated in the adaptive management approach that was followed and the rehabilitation techniques (Chapter 6) were continually re-evaluated and adjusted. This resulted in a significant step towards achieving the overall research objective of finding cost-effective approaches to rehabilitation. Components such as refinement of the seed collection and processing techniques (Chapter 7) where the post-harvest processing cost was significantly reduced by introducing specially designed drying racks. Processing techniques were adjusted to suit the different species, and a variety of mechanical processing options were explored. The scale of the Chemfos project led to the development of new techniques of manufacturing a smoke-derived germination stimulant (Chapter 8) since commercial availability of these products was very limited. The development of FireGrow assisted in the overall aim of reducing cost by increasing germination of seed in the rehabilitation sites using a very cost-effective smoke concentrate. Socio-economical aspects were considered during the implementation as well as the post-closure phases of the rehabilitation and BHPBilliton invested through the agency of the SAMANCOR Trust. This led to the development of livelihoods of the staff that remained in the area and that lived in the mine village. The demography of the population has changed over time in the Green Village as well as the skills that the inhabitants have developed. Thus, the new economic opportunities that were pursued have brought a new lease on life beyond the lifespan of the mine (Chapter 9) once the closure certificate had been issued.
- Full Text:
- Date Issued: 2010
- Authors: Van Eeden, Joseph Deon
- Date: 2010
- Subjects: Abandoned mined lands reclamation -- South Africa -- Langebaan , Phosphate mines and mining -- Environmental aspects -- South Africa -- Langebaan , Phytoremediation -- South Africa -- Langebaan
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4232 , http://hdl.handle.net/10962/d1003801 , Abandoned mined lands reclamation -- South Africa -- Langebaan , Phosphate mines and mining -- Environmental aspects -- South Africa -- Langebaan , Phytoremediation -- South Africa -- Langebaan
- Description: Approaching the ecological rehabilitation of an open-cast phosphate mine in the West Coast of South Africa during the post-operational phase presented some challenges. The area was extensively modified during the mining operations. Soils from different layers were mixed with topsoil being covered by subsoil, overburden dumps and tailing dams being constructed resulting in extensive cross-zoned soils. Large areas of subsoil areas were exposed on the mine floor with localized and small scale salinity being evident. The modified topography as well as the complex new surface material posed a challenge in terms of identifying suitable local species that could be used to rehabilitate the post-mining environment. The mine area was heavily infested with woody alien invasive plants, such as Acacia cyclops, established in an attempt to reduce the dust and little natural vegetation cover was present. In the arid west coast environment, the four-month-long winter growing season is followed by hot and windy dry summers (Chapter 2) presenting a challenge reestablishing local vegetation in modified soils. Moreover, little was known about the local vegetation in terms of their propagation and use in stabilization techniques as an alternative to exotic vegetation such as the A. cyclops, which had been more often used in revegetation projects. A study was conducted to determine the most efficient and cost-effective methods of vegetative rehabilitation of the Chemfos site (Chapter 1). A review of the literature available at the time as well as approaches that were successfully implemented in other Western Cape rehabilitation projects such as the Du Toitskloof Pass and the Sishen–Saldanha railway line (Chapter 3), were considered. Previous studies on the west coast dunes at Blaauwberg had shown using Marram grass as a dune stabilizer was most successful. Marram grass was tested in trials alongside local grasses, such as Chaetobromus dregeanus and Ehrharta villosa, that showed potential but had not been formally evaluated. The environmental context of Chemfos (Chapter 2) as well as the Conceptual Rehabilitation Plan that considered the modified environment, soils and closure objectives of the mine, were reviewed to determine the most pressing rehabilitationrelated questions that required answers. This led to the final experimental design that was implemented mid-winter in 1996 (Chapter 5). The trials were implemented in the areas perceived to be the most difficult to rehabilitate, namely the mobile sands in the tailings dam and the exposed subsoil or mine floor areas. The use of brushwood together with specific plants and seeds appropriate for the use in either sandy soil or subsoil were evaluated in a variety of combinations and application densities to determine the most effective treatment combination at the minimum effective density. The best initial cover of the tailings dam were recorded in the Ammophila arenaria trials but the use of the local grass species Ehrharta villosa, performed better from year two onwards and was much cheaper to establish. On the subsoil, the trials where a cover of topsoil was used performed better than the combination trials. This indicated that topsoil placement on post-operational phase shaped subsoils during the mining operation to be the most desirable treatment. Initial results of the trials were used as a basis for developing the rehabilitation techniques that were rolled out across the Chemfos landscape. The approaches were refined as indications of trial responses became evident. Lessons learned were incorporated in the adaptive management approach that was followed and the rehabilitation techniques (Chapter 6) were continually re-evaluated and adjusted. This resulted in a significant step towards achieving the overall research objective of finding cost-effective approaches to rehabilitation. Components such as refinement of the seed collection and processing techniques (Chapter 7) where the post-harvest processing cost was significantly reduced by introducing specially designed drying racks. Processing techniques were adjusted to suit the different species, and a variety of mechanical processing options were explored. The scale of the Chemfos project led to the development of new techniques of manufacturing a smoke-derived germination stimulant (Chapter 8) since commercial availability of these products was very limited. The development of FireGrow assisted in the overall aim of reducing cost by increasing germination of seed in the rehabilitation sites using a very cost-effective smoke concentrate. Socio-economical aspects were considered during the implementation as well as the post-closure phases of the rehabilitation and BHPBilliton invested through the agency of the SAMANCOR Trust. This led to the development of livelihoods of the staff that remained in the area and that lived in the mine village. The demography of the population has changed over time in the Green Village as well as the skills that the inhabitants have developed. Thus, the new economic opportunities that were pursued have brought a new lease on life beyond the lifespan of the mine (Chapter 9) once the closure certificate had been issued.
- Full Text:
- Date Issued: 2010
The effects of booster breaks during a sedentary night shift on physiological, psychomotor, psycho-physiological, and cognitive performance over a 3 night shift habituation phase
- Authors: Lombard, Wesley Ross
- Date: 2010
- Subjects: Night work , Shift systems , Performance , Exercise , Exercise -- Physiological aspects , Exercise -- Psychological aspects , Cognition -- Effect of exercise on , Motor ability
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5116 , http://hdl.handle.net/10962/d1005194 , Night work , Shift systems , Performance , Exercise , Exercise -- Physiological aspects , Exercise -- Psychological aspects , Cognition -- Effect of exercise on , Motor ability
- Description: Despite extensive research into shift work, workers working under rotating shift conditions are still plagued by the effects of the desynchronisation resulting from working against their natural circadian rhythms. Additionally, modern industries are shifting towards tasks requiring greater cognitive demand with less manual labour incorporated into the tasks. Research into operator based tasks, and hence those of a sedentary cognitive base both during day and night shifts, has been focusing on the effectiveness of the standard rest/break schedule. Research indicating that the standard rest break schedule is often ineffective in eliminating operator discomfort and performance deterioration, with these affects argued to be more pronounced during a night shift schedule. Therefore current research set out to investigate alternative rest break schedules, incorporating a short bout of physical activity and stretching exercises which are proposed to enhance performance and subjective mood, while eliminating operator discomfort for sedentary based cognitive tasks. Three conditions were tested during a three day habituation shift cycle within a laboratory, incorporating two night shift groups (control and experimental) and a control day shift group. Twelve subjects made up each group, with the two night shift groups completing the shift schedule together. The control groups followed a typical 8 hour shift schedule while the experimental group performed a booster break (exercise and stretches) activity for 7.5 minutes every hour during the night shift schedule. Over the course of the shift, subjects completed a battery of six tests providing data on physiological measurements (heart rate and temperature), performance criteria (reaction time responses, memory and neurobiological) and subjective measures. Responses obtained for all the different parameters measured indicated a strong circadian influence for the majority of the variables, indicating the course of natural down regulation within physiological and performance criteria over the night shift. The booster break significantly improved reaction time performance, subjective ratings and resulted in a high sustainable activity level. Day shift comparisons indicating that within subjective measures and reaction time performance, the booster break resulted in similar responses to those of the day shift workers, while the control night shift groups reported significantly lowers results. Additionally, the booster break had positive influences during the circadian nadir, significantly improving parameters of performance and subjective ratings of sleepiness. The results of this study indicating which variables are strong predictors and indicators of the oscillations in performance and subjective ratings due to the circadian changes. The booster break interventions had positive effects on subjective ratings and reaction time performance, while also being argued to decrease the burden placed on the cardiac system as a result of increased sympathetic tone during the night shift, while additionally resulting in similar responses to those of day shift workers. Further studies are required, however, to provide conclusive evidence particularly within a working situation over a longer shift schedule.
- Full Text:
- Date Issued: 2010
- Authors: Lombard, Wesley Ross
- Date: 2010
- Subjects: Night work , Shift systems , Performance , Exercise , Exercise -- Physiological aspects , Exercise -- Psychological aspects , Cognition -- Effect of exercise on , Motor ability
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5116 , http://hdl.handle.net/10962/d1005194 , Night work , Shift systems , Performance , Exercise , Exercise -- Physiological aspects , Exercise -- Psychological aspects , Cognition -- Effect of exercise on , Motor ability
- Description: Despite extensive research into shift work, workers working under rotating shift conditions are still plagued by the effects of the desynchronisation resulting from working against their natural circadian rhythms. Additionally, modern industries are shifting towards tasks requiring greater cognitive demand with less manual labour incorporated into the tasks. Research into operator based tasks, and hence those of a sedentary cognitive base both during day and night shifts, has been focusing on the effectiveness of the standard rest/break schedule. Research indicating that the standard rest break schedule is often ineffective in eliminating operator discomfort and performance deterioration, with these affects argued to be more pronounced during a night shift schedule. Therefore current research set out to investigate alternative rest break schedules, incorporating a short bout of physical activity and stretching exercises which are proposed to enhance performance and subjective mood, while eliminating operator discomfort for sedentary based cognitive tasks. Three conditions were tested during a three day habituation shift cycle within a laboratory, incorporating two night shift groups (control and experimental) and a control day shift group. Twelve subjects made up each group, with the two night shift groups completing the shift schedule together. The control groups followed a typical 8 hour shift schedule while the experimental group performed a booster break (exercise and stretches) activity for 7.5 minutes every hour during the night shift schedule. Over the course of the shift, subjects completed a battery of six tests providing data on physiological measurements (heart rate and temperature), performance criteria (reaction time responses, memory and neurobiological) and subjective measures. Responses obtained for all the different parameters measured indicated a strong circadian influence for the majority of the variables, indicating the course of natural down regulation within physiological and performance criteria over the night shift. The booster break significantly improved reaction time performance, subjective ratings and resulted in a high sustainable activity level. Day shift comparisons indicating that within subjective measures and reaction time performance, the booster break resulted in similar responses to those of the day shift workers, while the control night shift groups reported significantly lowers results. Additionally, the booster break had positive influences during the circadian nadir, significantly improving parameters of performance and subjective ratings of sleepiness. The results of this study indicating which variables are strong predictors and indicators of the oscillations in performance and subjective ratings due to the circadian changes. The booster break interventions had positive effects on subjective ratings and reaction time performance, while also being argued to decrease the burden placed on the cardiac system as a result of increased sympathetic tone during the night shift, while additionally resulting in similar responses to those of day shift workers. Further studies are required, however, to provide conclusive evidence particularly within a working situation over a longer shift schedule.
- Full Text:
- Date Issued: 2010
Validation of high frequency propagation prediction models over Africa
- Authors: Tshisaphungo, Mpho
- Date: 2010
- Subjects: Ionospheric radio wave propagation , Ionospheric radio wave propagation -- Forecasting , Radio meteorology , Radio wave propagation -- Africa , Ionosphere -- Africa -- Radio waves , Atmospheric physics -- Africa , Shortwave radio -- Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5553 , http://hdl.handle.net/10962/d1015239
- Description: The ionosphere is an important factor in high frequency (HF) radio propagation providing an opportunity to study ionospheric variability as well as the space weather conditions under which HF communication can take place. This thesis presents the validation of HF propagation conditions for the Ionospheric Communication Enhanced Profile Analysis and Circuit (ICEPAC) and Advanced Stand Alone Prediction System (ASAPS) models over Africa by comparing predictions with the measured data obtained from the International Beacon Project (IBP). Since these models were not developed using information on the African region, a more accurate HF propagation prediction tool is required. Two IBP transmitter stations are considered, Ruaraka, Kenya (1.24°S, 36.88°E) and Pretoria, South Africa (25.45°S, 28.10°E) with one beacon receiver station located in Hermanus, South Africa (34.27°S, 19.l2°E). The potential of these models in terms of HF propagation conditions is illustrated. An attempt to draw conclusions for future improvement of the models is also presented. Results show a low prediction accuracy for both ICEPAC and ASAPS models, although ICEPAC provided more accurate predictions for daily HF propagation conditions. This thesis suggests that the development of a new HF propagation prediction tool for the African region or the modification of one of the existing models to accommodate the African region, taking into account the importance of the African ionospheric region, should be considered as an option to ensure more accurate HF Propagation predictions over this region.
- Full Text:
- Date Issued: 2010
- Authors: Tshisaphungo, Mpho
- Date: 2010
- Subjects: Ionospheric radio wave propagation , Ionospheric radio wave propagation -- Forecasting , Radio meteorology , Radio wave propagation -- Africa , Ionosphere -- Africa -- Radio waves , Atmospheric physics -- Africa , Shortwave radio -- Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5553 , http://hdl.handle.net/10962/d1015239
- Description: The ionosphere is an important factor in high frequency (HF) radio propagation providing an opportunity to study ionospheric variability as well as the space weather conditions under which HF communication can take place. This thesis presents the validation of HF propagation conditions for the Ionospheric Communication Enhanced Profile Analysis and Circuit (ICEPAC) and Advanced Stand Alone Prediction System (ASAPS) models over Africa by comparing predictions with the measured data obtained from the International Beacon Project (IBP). Since these models were not developed using information on the African region, a more accurate HF propagation prediction tool is required. Two IBP transmitter stations are considered, Ruaraka, Kenya (1.24°S, 36.88°E) and Pretoria, South Africa (25.45°S, 28.10°E) with one beacon receiver station located in Hermanus, South Africa (34.27°S, 19.l2°E). The potential of these models in terms of HF propagation conditions is illustrated. An attempt to draw conclusions for future improvement of the models is also presented. Results show a low prediction accuracy for both ICEPAC and ASAPS models, although ICEPAC provided more accurate predictions for daily HF propagation conditions. This thesis suggests that the development of a new HF propagation prediction tool for the African region or the modification of one of the existing models to accommodate the African region, taking into account the importance of the African ionospheric region, should be considered as an option to ensure more accurate HF Propagation predictions over this region.
- Full Text:
- Date Issued: 2010
Development and assessment of minocycline sustained release capsule formulations
- Sachikonye, Tinotenda Chipo Victoria
- Authors: Sachikonye, Tinotenda Chipo Victoria
- Date: 2010
- Subjects: Drugs -- Controlled release , Drugs -- Dosage forms , Capsules (Pharmacy) , Drugs -- Administration , Acne -- Treatment , Tetracyclines , Antibiotics -- Side effects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3854 , http://hdl.handle.net/10962/d1013127
- Description: The use of minocycline for the treatment of a broad range of systemic infections and for severe acne has been associated with vestibular side effects. The severity of side effects may lead to poor adherence to therapy by patients. The use of sustained release formulations of minocycline that display slow dissolution of minocycline following administration may be beneficial in reducing the incidence and severity of side effects. Therefore, sustained release capsule dosage forms containing 100 mg minocycline (base) were manufactured and assessed for use as sustained release oral dosage forms of minocycline. Minocycline sustained release capsules were manufactured based on matrix technologies using hydroxypropylmethyl cellulose (HPMC) and Compritol® as release retarding polymers. The rate and extent of minocycline release from the capsules was evaluated using USP Apparatus 1 and samples were analysed using a validated High Performance Liquid Chromatographic (HPLC) method with ultraviolet (UV) detection. Differences in the rate and extent of minocycline release from formulations manufactured using HPMC or Compritol® were influenced by the concentration of polymer used in the formulations. The rate and extent of minocycline release was faster and greater when low concentrations of polymer were used in formulations. The effect of different excipients on the release pattern(s) of minocycline and particularly their potential to optimise minocycline release from experimental formulations was investigated. The use of diluents such as lactose and microcrystalline cellulose (MCC) revealed that lactose facilitated minocycline release when HPMC was used as the polymer matrix. In contrast, the use of lactose as diluent resulted in slower release of minocycline from Compritol® based formulations. The addition of sodium starch glycolate to HPMC based formulations resulted in slower release of minocycline than when no sodium starch glycolate was used. Compritol® based formulations were observed to release minocycline faster following addition of sodium starch glycolate and Poloxamer 188 to experimental formulations. In vitro dissolution profiles were compared to a target or reference profile using the difference and similarity factors, ƒ1 and ƒ2 , and a one way analysis of variance (ANOVA). In addition, the mechanism of minocycline release was elucidated following fitting of dissolution data to the Korsmeyer-Peppas, Higuchi and Zero order models. Minocycline release kinetics were best described by the Korsmeyer-Peppas model and the values of the release exponent, n (italics), revealed that drug release was a result of the combined effects of minocycline diffusion through matrices and erosion of the matrices. These in vitro dissolution profiles were better fit to the Higuchi model than to the Zero order model. Two formulations that displayed a fit to the Zero order model were identified for further studies as potential dosage forms for sustained release minocycline.
- Full Text:
- Date Issued: 2010
- Authors: Sachikonye, Tinotenda Chipo Victoria
- Date: 2010
- Subjects: Drugs -- Controlled release , Drugs -- Dosage forms , Capsules (Pharmacy) , Drugs -- Administration , Acne -- Treatment , Tetracyclines , Antibiotics -- Side effects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3854 , http://hdl.handle.net/10962/d1013127
- Description: The use of minocycline for the treatment of a broad range of systemic infections and for severe acne has been associated with vestibular side effects. The severity of side effects may lead to poor adherence to therapy by patients. The use of sustained release formulations of minocycline that display slow dissolution of minocycline following administration may be beneficial in reducing the incidence and severity of side effects. Therefore, sustained release capsule dosage forms containing 100 mg minocycline (base) were manufactured and assessed for use as sustained release oral dosage forms of minocycline. Minocycline sustained release capsules were manufactured based on matrix technologies using hydroxypropylmethyl cellulose (HPMC) and Compritol® as release retarding polymers. The rate and extent of minocycline release from the capsules was evaluated using USP Apparatus 1 and samples were analysed using a validated High Performance Liquid Chromatographic (HPLC) method with ultraviolet (UV) detection. Differences in the rate and extent of minocycline release from formulations manufactured using HPMC or Compritol® were influenced by the concentration of polymer used in the formulations. The rate and extent of minocycline release was faster and greater when low concentrations of polymer were used in formulations. The effect of different excipients on the release pattern(s) of minocycline and particularly their potential to optimise minocycline release from experimental formulations was investigated. The use of diluents such as lactose and microcrystalline cellulose (MCC) revealed that lactose facilitated minocycline release when HPMC was used as the polymer matrix. In contrast, the use of lactose as diluent resulted in slower release of minocycline from Compritol® based formulations. The addition of sodium starch glycolate to HPMC based formulations resulted in slower release of minocycline than when no sodium starch glycolate was used. Compritol® based formulations were observed to release minocycline faster following addition of sodium starch glycolate and Poloxamer 188 to experimental formulations. In vitro dissolution profiles were compared to a target or reference profile using the difference and similarity factors, ƒ1 and ƒ2 , and a one way analysis of variance (ANOVA). In addition, the mechanism of minocycline release was elucidated following fitting of dissolution data to the Korsmeyer-Peppas, Higuchi and Zero order models. Minocycline release kinetics were best described by the Korsmeyer-Peppas model and the values of the release exponent, n (italics), revealed that drug release was a result of the combined effects of minocycline diffusion through matrices and erosion of the matrices. These in vitro dissolution profiles were better fit to the Higuchi model than to the Zero order model. Two formulations that displayed a fit to the Zero order model were identified for further studies as potential dosage forms for sustained release minocycline.
- Full Text:
- Date Issued: 2010
The relationship between nasal turbinate structure and the ecological attributes of ungulates
- Authors: Kietzmann, Michelle Ann
- Date: 2010
- Subjects: Ungulates -- Ecology , Nasal fossa , Tomography -- Data processing
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10682 , http://hdl.handle.net/10948/1524 , Ungulates -- Ecology , Nasal fossa , Tomography -- Data processing
- Description: The nasal turbinates of ungulates are complex bony scrolls within the nasal cavity. These intricate bony plates, covered by moist epithelium, provide a large surface area that facilitates a countercurrent exchange of both water and heat between turbinal lining and respired air. Given their functional importance, maxilloturbinate size and structural dimensions may vary among species of different body sizes, activity levels and from different habitats, and may also serve as a predictor of the ability of the species to cope with high temperatures or limiting water resources. This is the first study to measure nasal turbinate surface area in ungulates using high-resolution computed tomography (CT) scanning. Heads of eleven South African bovid species and one European bovid species were successfully scanned and surface area measurements made using stereological techniques. These species included Cape grysbok, springbuck, bushbuck, blesbok, impala, mountain reedbuck, fallow deer, kudu, nyala, gemsbok and blue wildebeest; and represent species of different body sizes, from a range of habitats and with different water dependencies and predator avoidance strategies. The total maxilloturbinate surface area increased with body size for all study species. The surface areas of the nasal turbinates varied rostrocaudally, with the highest surface area occurring approximately midway along the length of the maxilloturbinate bones. The Cape grysbok stood out as having a nasal turbinate surface area of 12.77 cm2/kg, which was lower than the observed trend, the reason for this not being clear from these data. Phylogenetic independent analyses showed that log body mass and water dependence had a significant effect on nasal turbinate surface area, with habitat, distributional range and anti-predator behaviour having no effect. Subsequent phylogenetic species comparisons showed that structural variations in nasal turbinate surface area were phylogeny based due to the close genetic relatedness of the study species, and not associated with any environmental factors. The environmentally linked results for water dependency need further investigation in future studies of larger sample sizes and a broader range of species. Changes in climatic conditions may impact on a species‟ activity patterns, with individuals being forced to make behavioural modifications rather than physiological or anatomical adjustments. However, there is no clear evidence to indicate large differences in nasal turbinate surface area in relation to water dependence. This subsequently rules out the use of nasal turbinate surface area as a predictor to which and how ungulate species will respond to increasing global temperatures.
- Full Text:
- Date Issued: 2010
- Authors: Kietzmann, Michelle Ann
- Date: 2010
- Subjects: Ungulates -- Ecology , Nasal fossa , Tomography -- Data processing
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10682 , http://hdl.handle.net/10948/1524 , Ungulates -- Ecology , Nasal fossa , Tomography -- Data processing
- Description: The nasal turbinates of ungulates are complex bony scrolls within the nasal cavity. These intricate bony plates, covered by moist epithelium, provide a large surface area that facilitates a countercurrent exchange of both water and heat between turbinal lining and respired air. Given their functional importance, maxilloturbinate size and structural dimensions may vary among species of different body sizes, activity levels and from different habitats, and may also serve as a predictor of the ability of the species to cope with high temperatures or limiting water resources. This is the first study to measure nasal turbinate surface area in ungulates using high-resolution computed tomography (CT) scanning. Heads of eleven South African bovid species and one European bovid species were successfully scanned and surface area measurements made using stereological techniques. These species included Cape grysbok, springbuck, bushbuck, blesbok, impala, mountain reedbuck, fallow deer, kudu, nyala, gemsbok and blue wildebeest; and represent species of different body sizes, from a range of habitats and with different water dependencies and predator avoidance strategies. The total maxilloturbinate surface area increased with body size for all study species. The surface areas of the nasal turbinates varied rostrocaudally, with the highest surface area occurring approximately midway along the length of the maxilloturbinate bones. The Cape grysbok stood out as having a nasal turbinate surface area of 12.77 cm2/kg, which was lower than the observed trend, the reason for this not being clear from these data. Phylogenetic independent analyses showed that log body mass and water dependence had a significant effect on nasal turbinate surface area, with habitat, distributional range and anti-predator behaviour having no effect. Subsequent phylogenetic species comparisons showed that structural variations in nasal turbinate surface area were phylogeny based due to the close genetic relatedness of the study species, and not associated with any environmental factors. The environmentally linked results for water dependency need further investigation in future studies of larger sample sizes and a broader range of species. Changes in climatic conditions may impact on a species‟ activity patterns, with individuals being forced to make behavioural modifications rather than physiological or anatomical adjustments. However, there is no clear evidence to indicate large differences in nasal turbinate surface area in relation to water dependence. This subsequently rules out the use of nasal turbinate surface area as a predictor to which and how ungulate species will respond to increasing global temperatures.
- Full Text:
- Date Issued: 2010
Economic consequences of ecological change: restoration options for the Mfolozi floodplain and implications for Lake St. Lucia, South Africa
- Authors: Collings, Sandy Lyn
- Date: 2010
- Subjects: Lake ecology -- South Africa -- Saint Lucia, Lake , Ecology -- Economic aspects -- South Africa -- Kwazulu-Natal , Wetland ecology -- South Africa -- Kwazulu-Natal , Ecosystem services -- South Africa -- Kwazulu-Natal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4744 , http://hdl.handle.net/10962/d1006950 , Lake ecology -- South Africa -- Saint Lucia, Lake , Ecology -- Economic aspects -- South Africa -- Kwazulu-Natal , Wetland ecology -- South Africa -- Kwazulu-Natal , Ecosystem services -- South Africa -- Kwazulu-Natal
- Description: Lake St Lucia in northern KwaZulu-Natal, South Africa, experiences severe ecological stress during dry periods largely as a result of diminishing freshwater supplies and conditions of hypersalinity. Possible intervention involves diverting the Mfolozi River to the St Lucia Lake system. However, due to high sediment loading, water from the Mfolozi river requires considerable filtration before a link can be established. A suggested option considered in this study is to restore the existing sugarcane farmlands on the Mfolozi Floodplain (~20 800 ha) to previous wetland conditions to reinstate a sediment removal function amongst other benefits. Proposed restoration will have a direct impact on the industries currently supported by the iSimangaliso Wetland Park and the Mfolozi Floodplain (tourism, sugar, conservation). to understand a measure of such impacts, ecosystem services for both Lake St Lucia and the Mfolozi Floodplain were analysed (flood alleviation, water provision, water purification, sediment regulation, tourism, fisheries, vegetation for harvest, existence, cultural and research). Annual economic values for each ecosystem service were determined by means of valuation methods that included benefit transfer and replacement cost. Results showed a current annual minimum value of the Mfolozi Floodplain and Lake St Lucia as greater than R21 million and R1.1 billion respectively. Partial restoration of the floodplain (~6 000 ha) is expected to increase the sum of all ecosystem services values by approximately 26% for the Mfolozi Floodplain and by 23% for the St Lucia System. Full restoration (~20 800 ha) increases the total ecosystem services value by 88% and 50% for the Mfolozi Floodplain and St Lucia System respectively. Results showed that economic values for existence, fisheries, tourism and water provision increase by the greatest percentage for the St Lucia System under both restoration scenarios. Partial and full restoration of the floodplain will result in the greatest increases in economic value for the services existence, tourism, fisheries and the harvesting of vegetation on the Mfolozi Floodplain.
- Full Text:
- Date Issued: 2010
- Authors: Collings, Sandy Lyn
- Date: 2010
- Subjects: Lake ecology -- South Africa -- Saint Lucia, Lake , Ecology -- Economic aspects -- South Africa -- Kwazulu-Natal , Wetland ecology -- South Africa -- Kwazulu-Natal , Ecosystem services -- South Africa -- Kwazulu-Natal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4744 , http://hdl.handle.net/10962/d1006950 , Lake ecology -- South Africa -- Saint Lucia, Lake , Ecology -- Economic aspects -- South Africa -- Kwazulu-Natal , Wetland ecology -- South Africa -- Kwazulu-Natal , Ecosystem services -- South Africa -- Kwazulu-Natal
- Description: Lake St Lucia in northern KwaZulu-Natal, South Africa, experiences severe ecological stress during dry periods largely as a result of diminishing freshwater supplies and conditions of hypersalinity. Possible intervention involves diverting the Mfolozi River to the St Lucia Lake system. However, due to high sediment loading, water from the Mfolozi river requires considerable filtration before a link can be established. A suggested option considered in this study is to restore the existing sugarcane farmlands on the Mfolozi Floodplain (~20 800 ha) to previous wetland conditions to reinstate a sediment removal function amongst other benefits. Proposed restoration will have a direct impact on the industries currently supported by the iSimangaliso Wetland Park and the Mfolozi Floodplain (tourism, sugar, conservation). to understand a measure of such impacts, ecosystem services for both Lake St Lucia and the Mfolozi Floodplain were analysed (flood alleviation, water provision, water purification, sediment regulation, tourism, fisheries, vegetation for harvest, existence, cultural and research). Annual economic values for each ecosystem service were determined by means of valuation methods that included benefit transfer and replacement cost. Results showed a current annual minimum value of the Mfolozi Floodplain and Lake St Lucia as greater than R21 million and R1.1 billion respectively. Partial restoration of the floodplain (~6 000 ha) is expected to increase the sum of all ecosystem services values by approximately 26% for the Mfolozi Floodplain and by 23% for the St Lucia System. Full restoration (~20 800 ha) increases the total ecosystem services value by 88% and 50% for the Mfolozi Floodplain and St Lucia System respectively. Results showed that economic values for existence, fisheries, tourism and water provision increase by the greatest percentage for the St Lucia System under both restoration scenarios. Partial and full restoration of the floodplain will result in the greatest increases in economic value for the services existence, tourism, fisheries and the harvesting of vegetation on the Mfolozi Floodplain.
- Full Text:
- Date Issued: 2010
Spatio-temporal dynamics of ichthyoplankton in the Kowie estuary, South Africa
- Authors: Kruger, Michelle
- Date: 2010
- Subjects: Fishes -- Larvae -- South Africa -- Port Alfred , Estuarine fishes -- South Africa -- Port Alfred
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5319 , http://hdl.handle.net/10962/d1005164 , Fishes -- Larvae -- South Africa -- Port Alfred , Estuarine fishes -- South Africa -- Port Alfred
- Description: Ichthyoplankton dynamics in the permanently open Kowie Estuary, in the warm temperate region of South Africa was investigated. The composition, abundance, distribution and seasonality of larval fishes were studied over a two year period between 2004 and 2006. Additionally, tidal exchange of ichthyoplankton and the use of frontal zones in the mouth region of the estuary were also explored between 2008 and 2009. Temporal and spatial trends in occurrence of larval fishes within the estuary and associated marina were obtained from data collected seasonally using boat-based plankton netting at 14 sampling stations along the length of the estuary. A total of 11 128 larval fishes were collected, representing 23 families and 38 taxa. Clupeidae and Gobiidae were the dominant fish families, contributing 47.0 % and 24.7 % respectively to the total catch. Estuarine resident species dominated the overall catch (91 %). A notable absence of older stage larvae and early juveniles characterised the artificial channels of the marina and estuary mouth region. This was attributed to the absence of a shallow, marginal water habitat typical of successful estuarine nursery areas. Tidal exchange of larval fishes was investigated in the Kowie Estuary using a new technique. A set of drifting light traps were set repetitively on the ebb and flood tide every second night for two consecutive 14 day periods during the peak estuarine recruitment period. A total of 553 larval fishes were caught during the study, representing nine families and 26 species. Blenniidae and Clupeidae dominated the catches. Family and species occurrence changed with tide state. Species richness (d) and diversity (H’) varied with tide and was highest on flood tides. Estuary-dependent species, such as Omobranchus woodii were more dominant on flood tides, whilst larvae of marine-spawned species, such as Sardinops sagax, were dominant on the ebb tide. Light trap catches yielded a different composition in terms of development stage / size and species, when compared to towed net studies. Towed plankton nets were again used to study the shear fronts that characterise the mouth region of the canalised Kowie Estuary. It was hypothesised that the convergence zone of the front provides feeding opportunities for ichthyoplankton. Ichthyoplankton, zooplankton and phytoplankton was collected from within and immediately outside of the convergence zone during frontal conditions. Species specific distribution trends emerged from this study. Postflexion larvae and early juvenile stages of the estuary dependent Mugilidae were only present in the foam line of the convergence zones. Some known predators of ichthyoplankton were also present in slightly higher numbers in the convergence zone (isopods) while other predators such as mysid shrimps, chaetognaths and cnidarians were more abundant out of the convergence zone. It appears that these zones may provide access to temporary food patches in the lower estuary but will be accompanied by a trade-off with increased isopod predators. The Kowie Estuary is a heavily impacted system and lack of adequate freshwater supply; artificial channelling and pollution ultimately have a negative impact of the success of this system as a nursery area. Rehabilitation of marginal areas in the lower estuary and marina is suggested as remedial action to re-establish the integrity of the nursery function this system could offer.
- Full Text:
- Date Issued: 2010
- Authors: Kruger, Michelle
- Date: 2010
- Subjects: Fishes -- Larvae -- South Africa -- Port Alfred , Estuarine fishes -- South Africa -- Port Alfred
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5319 , http://hdl.handle.net/10962/d1005164 , Fishes -- Larvae -- South Africa -- Port Alfred , Estuarine fishes -- South Africa -- Port Alfred
- Description: Ichthyoplankton dynamics in the permanently open Kowie Estuary, in the warm temperate region of South Africa was investigated. The composition, abundance, distribution and seasonality of larval fishes were studied over a two year period between 2004 and 2006. Additionally, tidal exchange of ichthyoplankton and the use of frontal zones in the mouth region of the estuary were also explored between 2008 and 2009. Temporal and spatial trends in occurrence of larval fishes within the estuary and associated marina were obtained from data collected seasonally using boat-based plankton netting at 14 sampling stations along the length of the estuary. A total of 11 128 larval fishes were collected, representing 23 families and 38 taxa. Clupeidae and Gobiidae were the dominant fish families, contributing 47.0 % and 24.7 % respectively to the total catch. Estuarine resident species dominated the overall catch (91 %). A notable absence of older stage larvae and early juveniles characterised the artificial channels of the marina and estuary mouth region. This was attributed to the absence of a shallow, marginal water habitat typical of successful estuarine nursery areas. Tidal exchange of larval fishes was investigated in the Kowie Estuary using a new technique. A set of drifting light traps were set repetitively on the ebb and flood tide every second night for two consecutive 14 day periods during the peak estuarine recruitment period. A total of 553 larval fishes were caught during the study, representing nine families and 26 species. Blenniidae and Clupeidae dominated the catches. Family and species occurrence changed with tide state. Species richness (d) and diversity (H’) varied with tide and was highest on flood tides. Estuary-dependent species, such as Omobranchus woodii were more dominant on flood tides, whilst larvae of marine-spawned species, such as Sardinops sagax, were dominant on the ebb tide. Light trap catches yielded a different composition in terms of development stage / size and species, when compared to towed net studies. Towed plankton nets were again used to study the shear fronts that characterise the mouth region of the canalised Kowie Estuary. It was hypothesised that the convergence zone of the front provides feeding opportunities for ichthyoplankton. Ichthyoplankton, zooplankton and phytoplankton was collected from within and immediately outside of the convergence zone during frontal conditions. Species specific distribution trends emerged from this study. Postflexion larvae and early juvenile stages of the estuary dependent Mugilidae were only present in the foam line of the convergence zones. Some known predators of ichthyoplankton were also present in slightly higher numbers in the convergence zone (isopods) while other predators such as mysid shrimps, chaetognaths and cnidarians were more abundant out of the convergence zone. It appears that these zones may provide access to temporary food patches in the lower estuary but will be accompanied by a trade-off with increased isopod predators. The Kowie Estuary is a heavily impacted system and lack of adequate freshwater supply; artificial channelling and pollution ultimately have a negative impact of the success of this system as a nursery area. Rehabilitation of marginal areas in the lower estuary and marina is suggested as remedial action to re-establish the integrity of the nursery function this system could offer.
- Full Text:
- Date Issued: 2010
Photophysical studies of zinc and indium tetraaminophthalocyanines in the presence of CdTe quantum dots
- Authors: Britton, Jonathan
- Date: 2010
- Subjects: Indium , Zinc , Quantum dots , Phthalocyanines , Photochemotherapy , Nonlinear optics , Nanocrystals
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4332 , http://hdl.handle.net/10962/d1004993 , Indium , Zinc , Quantum dots , Phthalocyanines , Photochemotherapy , Nonlinear optics , Nanocrystals
- Description: CdTe QDs capped with mercaptopropionic acid (MPA) and thioglycolic acid (TGA) were covalently linked to zinc and indium tetraaminophthalocyanines (TAPcs) using N-ethyl-N(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxy succinimide (NHS) as the coupling agents. The results presented give evidence in favour of formation of an amide bond between the MTAPc and CdTe QDs. Both the linked ZnTAPc–QD complexes and the mixture of QDs and ZnTAPc (without chemical linking) showed Förster resonance energy transfer (FRET), though the linked showed less FRET, whereas the QD interactions with InTAPc yielded no evidence of FRET. Both MTAPcs quenched the QDs emission, with quenching constants of the order of 103–104M−1, binding constants of the order of 108-1010M-1 and the number of binding sites for the MTAPc upon the QD being 2. High energy transfer efficiencies were obtained (in some cases as high as 93%), due to the low donor to acceptor distances. Lastly, both MTAPc were shown to be poor optical limiters because their imaginary third-order susceptibility (Im[χ(3)]) was of the order of 10-17-10-16 (optimal range is 10-9-10-11), the hyperpolarizability (γ) of the order of 10-37-10-36 (optimal range is 10-29-10-34) and the k values were above one but below ten.
- Full Text:
- Date Issued: 2010
- Authors: Britton, Jonathan
- Date: 2010
- Subjects: Indium , Zinc , Quantum dots , Phthalocyanines , Photochemotherapy , Nonlinear optics , Nanocrystals
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4332 , http://hdl.handle.net/10962/d1004993 , Indium , Zinc , Quantum dots , Phthalocyanines , Photochemotherapy , Nonlinear optics , Nanocrystals
- Description: CdTe QDs capped with mercaptopropionic acid (MPA) and thioglycolic acid (TGA) were covalently linked to zinc and indium tetraaminophthalocyanines (TAPcs) using N-ethyl-N(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxy succinimide (NHS) as the coupling agents. The results presented give evidence in favour of formation of an amide bond between the MTAPc and CdTe QDs. Both the linked ZnTAPc–QD complexes and the mixture of QDs and ZnTAPc (without chemical linking) showed Förster resonance energy transfer (FRET), though the linked showed less FRET, whereas the QD interactions with InTAPc yielded no evidence of FRET. Both MTAPcs quenched the QDs emission, with quenching constants of the order of 103–104M−1, binding constants of the order of 108-1010M-1 and the number of binding sites for the MTAPc upon the QD being 2. High energy transfer efficiencies were obtained (in some cases as high as 93%), due to the low donor to acceptor distances. Lastly, both MTAPc were shown to be poor optical limiters because their imaginary third-order susceptibility (Im[χ(3)]) was of the order of 10-17-10-16 (optimal range is 10-9-10-11), the hyperpolarizability (γ) of the order of 10-37-10-36 (optimal range is 10-29-10-34) and the k values were above one but below ten.
- Full Text:
- Date Issued: 2010
Application of multiserver queueing to call centres
- Authors: Majakwara, Jacob
- Date: 2010
- Subjects: Call centers , ERLANG (Computer program language) , Queuing theory
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5578 , http://hdl.handle.net/10962/d1015461
- Description: The simplest and most widely used queueing model in call centres is the M/M/k system, sometimes referred to as Erlang-C. For many applications the model is an over-simplification. Erlang-C model ignores among other things busy signals, customer impatience and services that span multiple visits. Although the Erlang-C formula is easily implemented, it is not easy to obtain insight from its answers (for example, to find an approximate answer to questions such as "how many additional agents do I need if the arrival rate doubles?"). An approximation of the Erlang-C formula that gives structural insight into this type of question would be of use to better understand economies of scale in call centre operations. Erlang-C based predictions can also turn out highly inaccurate because of violations of underlying assumptions and these violations are not straightforward to model. For example, non-exponential service times lead one to the M/G/k queue which, in stark contrast to the M/M/k system, is difficult to analyse. This thesis deals mainly with the general M/GI/k model with abandonment. The arrival process conforms to a Poisson process, service durations are independent and identically distributed with a general distribution, there are k servers, and independent and identically distributed customer abandoning times with a general distribution. This thesis will endeavour to analyse call centres using M/GI/k model with abandonment and the data to be used will be simulated using EZSIM-software. The paper by Brown et al. [3] entitled "Statistical Analysis of a Telephone Call Centre: A Queueing-Science Perspective," will be the basis upon which this thesis is built.
- Full Text:
- Date Issued: 2010
- Authors: Majakwara, Jacob
- Date: 2010
- Subjects: Call centers , ERLANG (Computer program language) , Queuing theory
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5578 , http://hdl.handle.net/10962/d1015461
- Description: The simplest and most widely used queueing model in call centres is the M/M/k system, sometimes referred to as Erlang-C. For many applications the model is an over-simplification. Erlang-C model ignores among other things busy signals, customer impatience and services that span multiple visits. Although the Erlang-C formula is easily implemented, it is not easy to obtain insight from its answers (for example, to find an approximate answer to questions such as "how many additional agents do I need if the arrival rate doubles?"). An approximation of the Erlang-C formula that gives structural insight into this type of question would be of use to better understand economies of scale in call centre operations. Erlang-C based predictions can also turn out highly inaccurate because of violations of underlying assumptions and these violations are not straightforward to model. For example, non-exponential service times lead one to the M/G/k queue which, in stark contrast to the M/M/k system, is difficult to analyse. This thesis deals mainly with the general M/GI/k model with abandonment. The arrival process conforms to a Poisson process, service durations are independent and identically distributed with a general distribution, there are k servers, and independent and identically distributed customer abandoning times with a general distribution. This thesis will endeavour to analyse call centres using M/GI/k model with abandonment and the data to be used will be simulated using EZSIM-software. The paper by Brown et al. [3] entitled "Statistical Analysis of a Telephone Call Centre: A Queueing-Science Perspective," will be the basis upon which this thesis is built.
- Full Text:
- Date Issued: 2010
Sandy beach food webs and trophic linkages with estuaries: a stable light isotope approach
- Authors: Bezuidenhout, Karien
- Date: 2010
- Subjects: Stable isotopes in ecological research -- South Africa -- Eastern Cape , Food chains (Ecology) -- South Africa -- Eastern Cape , Estuaries -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10694 , http://hdl.handle.net/10948/1269 , Stable isotopes in ecological research -- South Africa -- Eastern Cape , Food chains (Ecology) -- South Africa -- Eastern Cape , Estuaries -- South Africa -- Eastern Cape
- Description: Two pocket sandy beaches, Eastern Cape, South Africa, were investigated, to determine whether these beaches were subsidised by an adjacent mangrove estuary, by using stable light isotope (δ 13C and δ 15N) analyses. The trophodynamics and macrofaunal food webs of these two beaches, situated between the Mgazi and Mgazana estuaries (in a warm-temperate/subtropical transition zone,), were described. Two to 2.5 trophic levels were identified for the macrobenthic community, with suspension feeders and omnivorous scavengers as the primary consumers, and carnivores as the secondary consumers. Mangrove material and terrigenous inputs were not driving the sandy beach food webs. Instead, marine allochthonous inputs (carrion, macroalgae), possibly phytoplankton, sediment organic matter, and resident macroinfauna were the dominant food sources. Cattle dung could have been the only important terrigenous food source utilised by the beach benthos. The macroinfauna displayed generalist/omnivorous feeding strategies, but within the limits of predominantly marine food sources. There was evidence that carnivores actively preyed on resident beach fauna. Omnivory and intraguild feeding might also be important biological processes in these communities. Seasonal and spatial variability in stable isotope composition of the fauna was observed, but few patterns were evident. There was a general trend of more enriched δ 15N and δ 13C composition of animal tissues in summer as opposed to winter. This was accompanied by a general decrease in C:N ratios in summer. It was hypothesised that these isotopic and biochemical changes were in response to increased food availability during summer. Although mangrove material appeared not to play an important role in the nutrition of these sandy beach communities, it was suggested that a high retention time of particles in the bay could enhance bacterial decay of particulate mangrove material, which could then act as fine, bacterial-enriched particulate food to the macrobenthos. This remains to be tested.
- Full Text:
- Date Issued: 2010
- Authors: Bezuidenhout, Karien
- Date: 2010
- Subjects: Stable isotopes in ecological research -- South Africa -- Eastern Cape , Food chains (Ecology) -- South Africa -- Eastern Cape , Estuaries -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10694 , http://hdl.handle.net/10948/1269 , Stable isotopes in ecological research -- South Africa -- Eastern Cape , Food chains (Ecology) -- South Africa -- Eastern Cape , Estuaries -- South Africa -- Eastern Cape
- Description: Two pocket sandy beaches, Eastern Cape, South Africa, were investigated, to determine whether these beaches were subsidised by an adjacent mangrove estuary, by using stable light isotope (δ 13C and δ 15N) analyses. The trophodynamics and macrofaunal food webs of these two beaches, situated between the Mgazi and Mgazana estuaries (in a warm-temperate/subtropical transition zone,), were described. Two to 2.5 trophic levels were identified for the macrobenthic community, with suspension feeders and omnivorous scavengers as the primary consumers, and carnivores as the secondary consumers. Mangrove material and terrigenous inputs were not driving the sandy beach food webs. Instead, marine allochthonous inputs (carrion, macroalgae), possibly phytoplankton, sediment organic matter, and resident macroinfauna were the dominant food sources. Cattle dung could have been the only important terrigenous food source utilised by the beach benthos. The macroinfauna displayed generalist/omnivorous feeding strategies, but within the limits of predominantly marine food sources. There was evidence that carnivores actively preyed on resident beach fauna. Omnivory and intraguild feeding might also be important biological processes in these communities. Seasonal and spatial variability in stable isotope composition of the fauna was observed, but few patterns were evident. There was a general trend of more enriched δ 15N and δ 13C composition of animal tissues in summer as opposed to winter. This was accompanied by a general decrease in C:N ratios in summer. It was hypothesised that these isotopic and biochemical changes were in response to increased food availability during summer. Although mangrove material appeared not to play an important role in the nutrition of these sandy beach communities, it was suggested that a high retention time of particles in the bay could enhance bacterial decay of particulate mangrove material, which could then act as fine, bacterial-enriched particulate food to the macrobenthos. This remains to be tested.
- Full Text:
- Date Issued: 2010
The taxonomy, life-history and population dynamics of blacktail, Diplodus Capensis (Perciformes: Sparidae), in southern Angola
- Authors: Richardson, Timothy John
- Date: 2010
- Subjects: Diplodus -- Angola , Perciformes -- Angola , Sparidae -- Angola , Fish populations -- Angola , Fishes -- Classification -- Angola , Fisheries -- Angola
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5324 , http://hdl.handle.net/10962/d1005170 , Diplodus -- Angola , Perciformes -- Angola , Sparidae -- Angola , Fish populations -- Angola , Fishes -- Classification -- Angola , Fisheries -- Angola
- Description: The blacktail, Diplodus capensis, is an inshore sparid fish distributed from Mozambique to Angola. This species forms an important component of coastal fisheries within its distribution, one being the subsistence handline fishery in southern Angola. With this fishery being critically important to the livelihoods of local communities, a biological study and stock assessment was conducted to provide information for the management of this species in southern Angola. However, with molecular evidence suggesting that the Benguela current may have separated the southern African populations of many inshore fish species over two million years ago, a morphological, taxonomic analysis was considered necessary to first investigate whether there was evidence for allopatry in this species. A total of 46 morphometric measurements and 18 counts were carried out on specimens collected from various locations in southern Angola and South Africa. Results were analysed using multi-dimensional scaling (MDS) and the significance of clusters was tested using analysis of similarities (ANOSIM). Biological samples of D. capensis were collected monthly from an unexploited area from April 2008 to March 2009. Additional biological samples were collected from the subsistence fishers in an exploited area during May, June and December 2009. Standard biological laboratory techniques were employed for the lifehistory comparison between the exploited and unexploited area. A per-recruit analysis was conducted using the life-history parameters from both areas in order to assess the current status of the subsistence fishery and to investigate the potential short-falls of the per-recruit assessment approach. The morphometric comparison showed that there was not sufficient evidence for speciation between the southern Angolan and South African populations of D. capensis. There was, however, sufficient morphological evidence to suggest that these populations are separate stocks. This indicated that the existing reference points on which the management of the South African population is based are unsuitable for the Angolan population. Diplodus capensis in southern Angola is omnivorous, feeding predominantly on algae, barnacles and mussels. An ontogenetic shift from algae to barnacles and mussels was correlated with allometric growth patterns in their feeding apparatus. This species is a rudimentary hermaphrodite in southern Angola with peak spawning in June and July. The overall sex ratio (M: F) was 1: 4.7 in the unexploited area and 50% maturity was attained at 149.5mm FL and five years. Diplodus capensis in southern Angola exhibits very slow growth with the maximum age observed being 31 years (validated using mark recapture of chemically injected fish). Females [L(t) = 419.5(1-e⁻°·°⁴⁵⁽t⁻³·⁴ ⁾)] grew significantly faster (LRT, p < 0.05) than males [L(t) = 297.4(1-e⁻°·°⁷⁷⁽t⁻²·⁷⁾)], and females dominated the larger size classes and older age classes. In the exploited area, the length and age frequencies were severely truncated, the maximum observed age was greatly reduced (17 years) and the sex ratio was less female biased at 1: 2.2. Although there was no evidence for a physiological response to exploitation through alterations in growth or size/age at sexual maturity between the two areas, there was an increase in the proportion of small females in the exploited area, which may have been a compensatory response for the loss of large females. A combination of an underestimate of longevity, different estimates of the Von Bertalanffy growth parameters and overestimates of the natural mortality rate in the exploited population resulted in a 92% underestimate of the pristine spawner biomass-per-recruit (SBR) value. An assessment based on the actual pristine SBR estimate from the unexploited area revealed that the subsistence fishery had actually reduced D. capensis to 20% of its pristine SBR levels and highlighted the value of pre-exploitation life-history information for the application of per-recruit models. This study has shown that D. capensis in southern Angola displays life-history characteristics that render it susceptible to overexploitation, even at low levels of fishing pressure. The current lack of infrastructure and enforcement capacity in the fisheries department of Angola renders traditional linefish regulatory tools, such as size limits, bag limits and closed seasons, inappropriate. Therefore, suitably designed marine protected areas are recommended as the best management option for this species.
- Full Text:
- Date Issued: 2010
- Authors: Richardson, Timothy John
- Date: 2010
- Subjects: Diplodus -- Angola , Perciformes -- Angola , Sparidae -- Angola , Fish populations -- Angola , Fishes -- Classification -- Angola , Fisheries -- Angola
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5324 , http://hdl.handle.net/10962/d1005170 , Diplodus -- Angola , Perciformes -- Angola , Sparidae -- Angola , Fish populations -- Angola , Fishes -- Classification -- Angola , Fisheries -- Angola
- Description: The blacktail, Diplodus capensis, is an inshore sparid fish distributed from Mozambique to Angola. This species forms an important component of coastal fisheries within its distribution, one being the subsistence handline fishery in southern Angola. With this fishery being critically important to the livelihoods of local communities, a biological study and stock assessment was conducted to provide information for the management of this species in southern Angola. However, with molecular evidence suggesting that the Benguela current may have separated the southern African populations of many inshore fish species over two million years ago, a morphological, taxonomic analysis was considered necessary to first investigate whether there was evidence for allopatry in this species. A total of 46 morphometric measurements and 18 counts were carried out on specimens collected from various locations in southern Angola and South Africa. Results were analysed using multi-dimensional scaling (MDS) and the significance of clusters was tested using analysis of similarities (ANOSIM). Biological samples of D. capensis were collected monthly from an unexploited area from April 2008 to March 2009. Additional biological samples were collected from the subsistence fishers in an exploited area during May, June and December 2009. Standard biological laboratory techniques were employed for the lifehistory comparison between the exploited and unexploited area. A per-recruit analysis was conducted using the life-history parameters from both areas in order to assess the current status of the subsistence fishery and to investigate the potential short-falls of the per-recruit assessment approach. The morphometric comparison showed that there was not sufficient evidence for speciation between the southern Angolan and South African populations of D. capensis. There was, however, sufficient morphological evidence to suggest that these populations are separate stocks. This indicated that the existing reference points on which the management of the South African population is based are unsuitable for the Angolan population. Diplodus capensis in southern Angola is omnivorous, feeding predominantly on algae, barnacles and mussels. An ontogenetic shift from algae to barnacles and mussels was correlated with allometric growth patterns in their feeding apparatus. This species is a rudimentary hermaphrodite in southern Angola with peak spawning in June and July. The overall sex ratio (M: F) was 1: 4.7 in the unexploited area and 50% maturity was attained at 149.5mm FL and five years. Diplodus capensis in southern Angola exhibits very slow growth with the maximum age observed being 31 years (validated using mark recapture of chemically injected fish). Females [L(t) = 419.5(1-e⁻°·°⁴⁵⁽t⁻³·⁴ ⁾)] grew significantly faster (LRT, p < 0.05) than males [L(t) = 297.4(1-e⁻°·°⁷⁷⁽t⁻²·⁷⁾)], and females dominated the larger size classes and older age classes. In the exploited area, the length and age frequencies were severely truncated, the maximum observed age was greatly reduced (17 years) and the sex ratio was less female biased at 1: 2.2. Although there was no evidence for a physiological response to exploitation through alterations in growth or size/age at sexual maturity between the two areas, there was an increase in the proportion of small females in the exploited area, which may have been a compensatory response for the loss of large females. A combination of an underestimate of longevity, different estimates of the Von Bertalanffy growth parameters and overestimates of the natural mortality rate in the exploited population resulted in a 92% underestimate of the pristine spawner biomass-per-recruit (SBR) value. An assessment based on the actual pristine SBR estimate from the unexploited area revealed that the subsistence fishery had actually reduced D. capensis to 20% of its pristine SBR levels and highlighted the value of pre-exploitation life-history information for the application of per-recruit models. This study has shown that D. capensis in southern Angola displays life-history characteristics that render it susceptible to overexploitation, even at low levels of fishing pressure. The current lack of infrastructure and enforcement capacity in the fisheries department of Angola renders traditional linefish regulatory tools, such as size limits, bag limits and closed seasons, inappropriate. Therefore, suitably designed marine protected areas are recommended as the best management option for this species.
- Full Text:
- Date Issued: 2010
New platinum and palladium complexes: their anticancer application
- Authors: Louw, Marissa
- Date: 2010
- Subjects: Complex compounds -- Synthesis , Ligands (Biochemistry) , Antineoplastic antibiotics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10424 , http://hdl.handle.net/10948/d1016218
- Description: Novel non-leaving groups were employed in this dissertation to synthesize platinum complexes which can assist in the understanding or improvement of anticancer action. Emphasis was placed on (NS)-chelate and (NN)-chelate platinum complexes. Bidentate (NS)-donor ligands were used as non-leaving ligands in the synthesis of platinum(II) complexes with iodo, chloro, bromo and oxalato groups as leaving groups. These complexes were synthesized and studied since many questions regarding the interaction of sulfur-donors and platinum still exist. These relate to thermodynamic and kinetic factors and their influence on anticancer action. In this dissertation the properties of novel platinum(II) complexes of a bidentate ligand having an aromatic nitrogen-donor atom in combination with a thioethereal sulfur atom capable of forming a five-membered ring with platinum(II) were studied. The general structure of the (NS)-ligands used was 2-((alkylthio)methyl)pyridine. Alkyl groups used were methyl, ethyl, propyl, benzyl and phenyl. Amine complexes of platinum have been studied extensively in the past. However, attention was given to novel aspects of substituted pyridine and imidazole ligands and their corresponding complexes. Amongst these are 2-(2-methylaminoethyl)pyridine, 1-methyl-2-methylaminoethylimidazole and 1-methyl-2-methylaminobenzylimidazole. The leaving groups included chloro, bromo and oxalato. Mononitroplatinum(IV) complexes were prepared using novel synthetic methods. Selected platinum(II) amine complexes were used as starting materials for this synthesis. Some of these compounds exhibit promising anticancer behaviour. (Trans-(R,R)-1,2-diaminocyclohexane)(oxalato)(mononitrochloro)platinum(IV) is a particularly good anticancer agent and has been patented internationally. All these complexes were characterized using mass spectrometry, chromatography, thermogravimetric analysis, kinetic aspects such as ligand exchange rates and finally their anticancer action against three different cancer cell lines was evaluated via cytotoxicity assays. Some of the compounds exhibited particularly good anticancer potential.
- Full Text:
- Date Issued: 2010
- Authors: Louw, Marissa
- Date: 2010
- Subjects: Complex compounds -- Synthesis , Ligands (Biochemistry) , Antineoplastic antibiotics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10424 , http://hdl.handle.net/10948/d1016218
- Description: Novel non-leaving groups were employed in this dissertation to synthesize platinum complexes which can assist in the understanding or improvement of anticancer action. Emphasis was placed on (NS)-chelate and (NN)-chelate platinum complexes. Bidentate (NS)-donor ligands were used as non-leaving ligands in the synthesis of platinum(II) complexes with iodo, chloro, bromo and oxalato groups as leaving groups. These complexes were synthesized and studied since many questions regarding the interaction of sulfur-donors and platinum still exist. These relate to thermodynamic and kinetic factors and their influence on anticancer action. In this dissertation the properties of novel platinum(II) complexes of a bidentate ligand having an aromatic nitrogen-donor atom in combination with a thioethereal sulfur atom capable of forming a five-membered ring with platinum(II) were studied. The general structure of the (NS)-ligands used was 2-((alkylthio)methyl)pyridine. Alkyl groups used were methyl, ethyl, propyl, benzyl and phenyl. Amine complexes of platinum have been studied extensively in the past. However, attention was given to novel aspects of substituted pyridine and imidazole ligands and their corresponding complexes. Amongst these are 2-(2-methylaminoethyl)pyridine, 1-methyl-2-methylaminoethylimidazole and 1-methyl-2-methylaminobenzylimidazole. The leaving groups included chloro, bromo and oxalato. Mononitroplatinum(IV) complexes were prepared using novel synthetic methods. Selected platinum(II) amine complexes were used as starting materials for this synthesis. Some of these compounds exhibit promising anticancer behaviour. (Trans-(R,R)-1,2-diaminocyclohexane)(oxalato)(mononitrochloro)platinum(IV) is a particularly good anticancer agent and has been patented internationally. All these complexes were characterized using mass spectrometry, chromatography, thermogravimetric analysis, kinetic aspects such as ligand exchange rates and finally their anticancer action against three different cancer cell lines was evaluated via cytotoxicity assays. Some of the compounds exhibited particularly good anticancer potential.
- Full Text:
- Date Issued: 2010
Spatial and temporal patterns in the hyperbenthic community structure in a permanently open Eastern Cape estuary, South Africa
- Authors: Heyns, Elodie R
- Date: 2010
- Subjects: Sundays Estuary -- South Africa -- Eastern Cape , Groundfishes -- South Africa -- Eatern Cape , Estuaries -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5768 , http://hdl.handle.net/10962/d1005456
- Description: The spatial and temporal (seasonal and diel) patterns in the hyperbenthic community structure (>500 μm) was investigated in the warm temperate, permanently open Kariega Estuary situated along the south-eastern coastline of South Africa. Spatial and seasonal patterns in the hyperbenthic community structure were assessed monthly at six stations along the length of the estuary over a period of twelve months. Data were collected using a modified hyperbenthic sledge, comprising two super-imposed nets. Physico-chemical data indicate the presence of a constant reverse salinity gradient, with highest salinities measured in the upper reaches and lowest at the mouth of the estuary. Strong seasonal patterns in temperature, dissolved oxygen and total chlorophyll-a (chl-a) concentrations were evident. Total average hyperbenthic densities ranged between 0.04 and 166 ind.m-3 in the lower net and between 0.12 and 225 ind.m-3 in the upper net. Hyperbenthic biomass values ranged between 0.02 and 11.9 mg.dry weight.m-3 in the lower net and between 0.02 and 17.4 mg.dry weight.m-3 in the upper net. A spatial and temporal pattern in total densities was detected with an increase in abundance over the period of September to October 2008 particularly in the middle reaches (Stations 3 and 4). Both the lower and upper nets were numerically dominated by decapods (mainly brachyuran crab zoeae) with the exception of June and July 2008 when mysids (mainly Mesopodopsis wooldridgei) dominated, making up 72.4 ± 58.14% of the total abundance in the lower net. A redundancy analysis (RDA) indicated that 99.2% of the variance in the hyperbenthic community structure could be explained by the first two canonical axes. Axis one, which accounted for 96.8% of the total variation detected in the ordination plot was highly correlated with sedimentary organic content and to a lesser extent the chl-a concentration within the Kariega Estuary. The correlations with the second canonical axis (2.4%) were less obvious, however, salinity and seston concentration were weakly correlated with this axis. Diel variability in the hyperbenthic community structure was assessed during March 2009. Samples were collected during the day and night (n = 6 for each period) using sampling gear described above. Total average hyperbenthic densities during the day (497.9 ± 254.1 ind.m-3) were significantly higher than night-time estimates (129.9 ± 38.5 ind.m-3; p<0.05). There were no significant differences in the average dayand night-time estimates of hyperbenthic biomass (p>0.05). A hierarchical cluster analysis identified two significantly distinct groupings, designated the day and night samples. Results from the SIMPER procedure indicated that the high densities of crab zoeae recorded during the day-time accounted for the majority of the dissimilarity between the day and night groupings (44.7%). In addition, it is apparent that several benthic species, especially from the cumacean and isopod orders, were absent from the hyperbenthos during the day-time and emerged into the water column at night.
- Full Text:
- Date Issued: 2010
- Authors: Heyns, Elodie R
- Date: 2010
- Subjects: Sundays Estuary -- South Africa -- Eastern Cape , Groundfishes -- South Africa -- Eatern Cape , Estuaries -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5768 , http://hdl.handle.net/10962/d1005456
- Description: The spatial and temporal (seasonal and diel) patterns in the hyperbenthic community structure (>500 μm) was investigated in the warm temperate, permanently open Kariega Estuary situated along the south-eastern coastline of South Africa. Spatial and seasonal patterns in the hyperbenthic community structure were assessed monthly at six stations along the length of the estuary over a period of twelve months. Data were collected using a modified hyperbenthic sledge, comprising two super-imposed nets. Physico-chemical data indicate the presence of a constant reverse salinity gradient, with highest salinities measured in the upper reaches and lowest at the mouth of the estuary. Strong seasonal patterns in temperature, dissolved oxygen and total chlorophyll-a (chl-a) concentrations were evident. Total average hyperbenthic densities ranged between 0.04 and 166 ind.m-3 in the lower net and between 0.12 and 225 ind.m-3 in the upper net. Hyperbenthic biomass values ranged between 0.02 and 11.9 mg.dry weight.m-3 in the lower net and between 0.02 and 17.4 mg.dry weight.m-3 in the upper net. A spatial and temporal pattern in total densities was detected with an increase in abundance over the period of September to October 2008 particularly in the middle reaches (Stations 3 and 4). Both the lower and upper nets were numerically dominated by decapods (mainly brachyuran crab zoeae) with the exception of June and July 2008 when mysids (mainly Mesopodopsis wooldridgei) dominated, making up 72.4 ± 58.14% of the total abundance in the lower net. A redundancy analysis (RDA) indicated that 99.2% of the variance in the hyperbenthic community structure could be explained by the first two canonical axes. Axis one, which accounted for 96.8% of the total variation detected in the ordination plot was highly correlated with sedimentary organic content and to a lesser extent the chl-a concentration within the Kariega Estuary. The correlations with the second canonical axis (2.4%) were less obvious, however, salinity and seston concentration were weakly correlated with this axis. Diel variability in the hyperbenthic community structure was assessed during March 2009. Samples were collected during the day and night (n = 6 for each period) using sampling gear described above. Total average hyperbenthic densities during the day (497.9 ± 254.1 ind.m-3) were significantly higher than night-time estimates (129.9 ± 38.5 ind.m-3; p<0.05). There were no significant differences in the average dayand night-time estimates of hyperbenthic biomass (p>0.05). A hierarchical cluster analysis identified two significantly distinct groupings, designated the day and night samples. Results from the SIMPER procedure indicated that the high densities of crab zoeae recorded during the day-time accounted for the majority of the dissimilarity between the day and night groupings (44.7%). In addition, it is apparent that several benthic species, especially from the cumacean and isopod orders, were absent from the hyperbenthos during the day-time and emerged into the water column at night.
- Full Text:
- Date Issued: 2010
Movement patterns and population dynamics of four catsharks endemic to South Africa
- Authors: Escobar-Porras, Jessica
- Date: 2010
- Subjects: Chondrichthyes -- South Africa , Fish populations -- South Africa , Fishes -- Behavior -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5303 , http://hdl.handle.net/10962/d1005148 , Chondrichthyes -- South Africa , Fish populations -- South Africa , Fishes -- Behavior -- South Africa
- Description: Sharks are particularly vulnerable to over-exploitation. Although catsharks are an important component of the near-shore marine biodiversity in South Africa and most of the species are endemic, little is known about their movement patterns, home range and population size. With an increasing number of recreational fishers this information is crucial for their conservation. The aims of this study were threefold. Firstly, to identify and analyze existing data sources on movement patterns and population dynamics for four catshark species: pyjama (Poroderma africanum), leopard (P. pantherinum), puffadder (Haploblepharus edwarsii) and brown (H. fuscus). This highlighted a number of shortcomings with existing data sets, largely because these studies had diverse objectives and were not aimed solely at catsharks. Secondly, a dedicated study was carried out for a limited area, testing a number of methods for data collection, and where appropriate the data was analyzed to determine movement patterns and population numbers. Thirdly, the most appropriate methodology for future studies (with similar objectives) was identified, and the results of the study were used to propose a number of conservation measures. All species of catsharks exhibited strong site fidelity and limited dispersal for extended periods. A few individuals did, however, travel distances in excess of 150 km. Significant trends in temporal abundance were not observed, nevertheless, there was some evidence for higher catches from September to December. Population estimates for the study area were low, with P. africanum having the smallest population size while H. fuscus had the highest population size within the restricted study area. Limited movements, high site fidelity and small population sizes emphasize their vulnerability and suggest that catsharks would benefit from no-take marine protected areas.
- Full Text:
- Date Issued: 2010
- Authors: Escobar-Porras, Jessica
- Date: 2010
- Subjects: Chondrichthyes -- South Africa , Fish populations -- South Africa , Fishes -- Behavior -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5303 , http://hdl.handle.net/10962/d1005148 , Chondrichthyes -- South Africa , Fish populations -- South Africa , Fishes -- Behavior -- South Africa
- Description: Sharks are particularly vulnerable to over-exploitation. Although catsharks are an important component of the near-shore marine biodiversity in South Africa and most of the species are endemic, little is known about their movement patterns, home range and population size. With an increasing number of recreational fishers this information is crucial for their conservation. The aims of this study were threefold. Firstly, to identify and analyze existing data sources on movement patterns and population dynamics for four catshark species: pyjama (Poroderma africanum), leopard (P. pantherinum), puffadder (Haploblepharus edwarsii) and brown (H. fuscus). This highlighted a number of shortcomings with existing data sets, largely because these studies had diverse objectives and were not aimed solely at catsharks. Secondly, a dedicated study was carried out for a limited area, testing a number of methods for data collection, and where appropriate the data was analyzed to determine movement patterns and population numbers. Thirdly, the most appropriate methodology for future studies (with similar objectives) was identified, and the results of the study were used to propose a number of conservation measures. All species of catsharks exhibited strong site fidelity and limited dispersal for extended periods. A few individuals did, however, travel distances in excess of 150 km. Significant trends in temporal abundance were not observed, nevertheless, there was some evidence for higher catches from September to December. Population estimates for the study area were low, with P. africanum having the smallest population size while H. fuscus had the highest population size within the restricted study area. Limited movements, high site fidelity and small population sizes emphasize their vulnerability and suggest that catsharks would benefit from no-take marine protected areas.
- Full Text:
- Date Issued: 2010