Assessing the impacts of Lantana camara and opportunities for ecological restoration after its removal: does clearing facilitate both soil and native vegetation recovery?
- Authors: Bolosha, Uviwe
- Date: 2024-10-11
- Subjects: Lantana camara , Restoration and conservation , Restoration ecology , Invasive plants , Physicochemical process , Soil seed banks , Invasion driver
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466524 , vital:76738 , DOI https://doi.org/10.21504/10962/466524
- Description: Invasive alien plants (IAPs) are one of the major contributing factors to biodiversity loss, and Lantana camara is among the top ten alien invaders worldwide. Lantana camara threatens native biodiversity and human health, prevents natural succession, and has an economic and environmental impact globally. With current climate change and future predictions, these IAPs are anticipated to continue posing huge threats to ecosystem composition, structure, and function. Even though L. camara is a widespread IAP, there is still limited knowledge in South Africa on how it influences soil physicochemical properties at the species level, vegetation communities, and soil seed banks at the community level following its invasion. There is also minimal knowledge on the management and control (i.e., clearing for restoration purposes) of L. camara in South Africa, especially in the Eastern Cape province of South Africa. To address the knowledge gap, this thesis was structured into three main aspects: understanding L. camara invasion mechanisms, evaluating invasion impacts on both the aboveground and belowground communities, and invasion management. The main objectives of this thesis were (i) to examine how L. camara invasion (at a species level) affected soil physicochemical properties across different seasons, (ii) to assess how L. camara influences natural vegetation (at a community level), (iii) to examine the effects of L. camara invasion (at the community level) on belowground soil seed banks and also assess the availability of pioneer native species and IAPs in the soil seed banks, and (iv) to evaluate soil and vegetation responses following L. camara clearing in comparison to invaded and uninvaded conditions. To answer these objectives, different studies were carried out in the Eastern Cape province, South Africa, on various farms within the Albany Thicket Biome. The results (Chapter 3) show that L. camara alters and modifies some soil physical properties, such as soil infiltration rate, repellency, and soil penetration resistance, in the communities it invades. A significant decrease in soil penetration under the L. camara canopy was observed compared to soils from the edge and out position. Moreover, significantly faster infiltration rates were observed in the canopy and edge positions than in the out position. The study also observed that these modifications in soil physical properties vary depending on the season. A seasonal comparison in soil penetration showed that soil was more compact in the dry season than the wet season, and significantly faster infiltration rates were observed in summer than in the other seasons. The soil collected under the invaded sampling positions was mostly wettable (80–100%), and not strongly, severely, or extremely repellent across all the seasons. The changes in soil properties caused by L. camara could create favourable conditions for its growth and invasion. Seasonal changes in soil properties also highlight how environmental conditions, especially temperature and rainfall patterns, can affect soil physical properties. The findings in Chapter 4 observed both the negative and positive impacts of L. camara, where the species did not have negative effects on species richness, diversity, or cover of some native species growth forms (i.e., graminoids and forbs). For all species, both species richness and Shannon-Wiener (H’) were significantly higher in the L. camara invaded condition compared to the uninvaded condition. The Simpson’s (J’) and Pielou’s evenness (D’) indices, however, showed no differences between the invasion conditions. Furthermore, the effects of L. camara on vegetation cover were growth form-dependent, with differences being noted for trees and shrubs but not for graminoids and forbs. Changes in vegetation structure and composition were also noted where L. camara created favourable conditions for some species to co-occur with it, meaning that its known trait of changing soil physicochemical properties could benefit some species. Generally, the results of this study showed that the effects of L. camara on vegetation are varied and do not have a predictable pattern, so they should not be generalised. The findings (Chapter 5) also indicate that the L. camara invasion had a negative impact on seedling abundance and composition but not species diversity and richness. This is evident through the decrease in seedling abundance of forbs and graminoids in the L. camara invaded condition. Lantana camara also acted as a refuge for some plant species, mostly native forbs and grasses, including Aptenia cordifolia, Chamaesyce prostrata, Oxalis spp., and Setaria spp., as well as alien forbs such as Bidens pilosa, Plantago lanceolata, and Taraxacum officinale, suggesting L. camara does not entirely eliminate less competitive plant species but can co-exist with them. Lantana camara also displaced some native species, and this could be associated with their displacement in the standing vegetation. Moreover, the species also displaced the seed banks of some alien species, thus showing its competitive ability. Overall, L. camara invasion negatively influenced soil seed bank seedling abundance and composition of some species, but not diversity and richness. The results in Chapter 6 indicated that clearing L. camara is an effective method for reducing its population. However, our findings suggest that clearing alone may not be enough to re-establish these communities with native species. This is because the results of this study showed varied changes in soil properties and native vegetation (species richness, species diversity, percentage cover, and composition) after L. camara clearing. For example, soil moisture and soil penetration resistance showed no significant differences among the invasion conditions; only monthly variations were observed. This is an indication that seasonality influenced these properties. Significantly lower soil infiltration rates were observed in the cleared condition compared to the other conditions and were influenced by the months and the interaction of the clearing conditions and months. The water droplet penetration time showed no significant difference among the clearing conditions over the three months, and all the soil collected from the three clearing conditions was mostly wettable. Soil chemical properties showed that the L. camara invaded and cleared conditions had significantly lower soil pH compared to the uninvaded condition, and an increase in soil pH was observed after clearing L. camara. Vegetation characteristics showed that both the Shannon-Wiener index (H') and the Simpson’s index (D') were lower in the invaded and cleared conditions compared to the uninvaded condition, and significant differences were observed. A slight increase in the H' and D' indices was also observed after clearing L. camara. The mean percentage cover for trees and shrubs was significantly higher in the invaded condition than in the cleared and uninvaded conditions. However, the mean percentage cover of forbs and graminoids was similar among the invaded, cleared, and uninvaded conditions, and no significant differences were observed. When L. camara was cleared, native species recovery was observed and was more notable in the understory species. Overall, some signs of vegetation recovery were observed, although challenges such as secondary invaders and re-invasion by L. camara were noted in the cleared areas. This chapter then concluded that active restoration interventions should be incorporated during restoration to fast-track soil and vegetation recovery. The findings of this thesis will make several significant contributions to the field of biological invasions and provide baseline information that can be used in future studies. These are discussed in the various research chapters. Overall, the thesis concludes that L. camara invasion has varied impacts on native vegetation and soil, and its clearance, should be prioritised to reduce the negative impacts. However, L. camara cleared areas (by WfW in South Africa) require follow-up and monitoring at an early stage to assess vegetation and soil restoration success. In addition, active management measures after L. camara’s removal should be considered for clearing programmes to yield positive ecosystem recovery. , Thesis (PhD) -- Faculty of Science, Environmental Science, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Bolosha, Uviwe
- Date: 2024-10-11
- Subjects: Lantana camara , Restoration and conservation , Restoration ecology , Invasive plants , Physicochemical process , Soil seed banks , Invasion driver
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466524 , vital:76738 , DOI https://doi.org/10.21504/10962/466524
- Description: Invasive alien plants (IAPs) are one of the major contributing factors to biodiversity loss, and Lantana camara is among the top ten alien invaders worldwide. Lantana camara threatens native biodiversity and human health, prevents natural succession, and has an economic and environmental impact globally. With current climate change and future predictions, these IAPs are anticipated to continue posing huge threats to ecosystem composition, structure, and function. Even though L. camara is a widespread IAP, there is still limited knowledge in South Africa on how it influences soil physicochemical properties at the species level, vegetation communities, and soil seed banks at the community level following its invasion. There is also minimal knowledge on the management and control (i.e., clearing for restoration purposes) of L. camara in South Africa, especially in the Eastern Cape province of South Africa. To address the knowledge gap, this thesis was structured into three main aspects: understanding L. camara invasion mechanisms, evaluating invasion impacts on both the aboveground and belowground communities, and invasion management. The main objectives of this thesis were (i) to examine how L. camara invasion (at a species level) affected soil physicochemical properties across different seasons, (ii) to assess how L. camara influences natural vegetation (at a community level), (iii) to examine the effects of L. camara invasion (at the community level) on belowground soil seed banks and also assess the availability of pioneer native species and IAPs in the soil seed banks, and (iv) to evaluate soil and vegetation responses following L. camara clearing in comparison to invaded and uninvaded conditions. To answer these objectives, different studies were carried out in the Eastern Cape province, South Africa, on various farms within the Albany Thicket Biome. The results (Chapter 3) show that L. camara alters and modifies some soil physical properties, such as soil infiltration rate, repellency, and soil penetration resistance, in the communities it invades. A significant decrease in soil penetration under the L. camara canopy was observed compared to soils from the edge and out position. Moreover, significantly faster infiltration rates were observed in the canopy and edge positions than in the out position. The study also observed that these modifications in soil physical properties vary depending on the season. A seasonal comparison in soil penetration showed that soil was more compact in the dry season than the wet season, and significantly faster infiltration rates were observed in summer than in the other seasons. The soil collected under the invaded sampling positions was mostly wettable (80–100%), and not strongly, severely, or extremely repellent across all the seasons. The changes in soil properties caused by L. camara could create favourable conditions for its growth and invasion. Seasonal changes in soil properties also highlight how environmental conditions, especially temperature and rainfall patterns, can affect soil physical properties. The findings in Chapter 4 observed both the negative and positive impacts of L. camara, where the species did not have negative effects on species richness, diversity, or cover of some native species growth forms (i.e., graminoids and forbs). For all species, both species richness and Shannon-Wiener (H’) were significantly higher in the L. camara invaded condition compared to the uninvaded condition. The Simpson’s (J’) and Pielou’s evenness (D’) indices, however, showed no differences between the invasion conditions. Furthermore, the effects of L. camara on vegetation cover were growth form-dependent, with differences being noted for trees and shrubs but not for graminoids and forbs. Changes in vegetation structure and composition were also noted where L. camara created favourable conditions for some species to co-occur with it, meaning that its known trait of changing soil physicochemical properties could benefit some species. Generally, the results of this study showed that the effects of L. camara on vegetation are varied and do not have a predictable pattern, so they should not be generalised. The findings (Chapter 5) also indicate that the L. camara invasion had a negative impact on seedling abundance and composition but not species diversity and richness. This is evident through the decrease in seedling abundance of forbs and graminoids in the L. camara invaded condition. Lantana camara also acted as a refuge for some plant species, mostly native forbs and grasses, including Aptenia cordifolia, Chamaesyce prostrata, Oxalis spp., and Setaria spp., as well as alien forbs such as Bidens pilosa, Plantago lanceolata, and Taraxacum officinale, suggesting L. camara does not entirely eliminate less competitive plant species but can co-exist with them. Lantana camara also displaced some native species, and this could be associated with their displacement in the standing vegetation. Moreover, the species also displaced the seed banks of some alien species, thus showing its competitive ability. Overall, L. camara invasion negatively influenced soil seed bank seedling abundance and composition of some species, but not diversity and richness. The results in Chapter 6 indicated that clearing L. camara is an effective method for reducing its population. However, our findings suggest that clearing alone may not be enough to re-establish these communities with native species. This is because the results of this study showed varied changes in soil properties and native vegetation (species richness, species diversity, percentage cover, and composition) after L. camara clearing. For example, soil moisture and soil penetration resistance showed no significant differences among the invasion conditions; only monthly variations were observed. This is an indication that seasonality influenced these properties. Significantly lower soil infiltration rates were observed in the cleared condition compared to the other conditions and were influenced by the months and the interaction of the clearing conditions and months. The water droplet penetration time showed no significant difference among the clearing conditions over the three months, and all the soil collected from the three clearing conditions was mostly wettable. Soil chemical properties showed that the L. camara invaded and cleared conditions had significantly lower soil pH compared to the uninvaded condition, and an increase in soil pH was observed after clearing L. camara. Vegetation characteristics showed that both the Shannon-Wiener index (H') and the Simpson’s index (D') were lower in the invaded and cleared conditions compared to the uninvaded condition, and significant differences were observed. A slight increase in the H' and D' indices was also observed after clearing L. camara. The mean percentage cover for trees and shrubs was significantly higher in the invaded condition than in the cleared and uninvaded conditions. However, the mean percentage cover of forbs and graminoids was similar among the invaded, cleared, and uninvaded conditions, and no significant differences were observed. When L. camara was cleared, native species recovery was observed and was more notable in the understory species. Overall, some signs of vegetation recovery were observed, although challenges such as secondary invaders and re-invasion by L. camara were noted in the cleared areas. This chapter then concluded that active restoration interventions should be incorporated during restoration to fast-track soil and vegetation recovery. The findings of this thesis will make several significant contributions to the field of biological invasions and provide baseline information that can be used in future studies. These are discussed in the various research chapters. Overall, the thesis concludes that L. camara invasion has varied impacts on native vegetation and soil, and its clearance, should be prioritised to reduce the negative impacts. However, L. camara cleared areas (by WfW in South Africa) require follow-up and monitoring at an early stage to assess vegetation and soil restoration success. In addition, active management measures after L. camara’s removal should be considered for clearing programmes to yield positive ecosystem recovery. , Thesis (PhD) -- Faculty of Science, Environmental Science, 2024
- Full Text:
- Date Issued: 2024-10-11
Assessing the status of the Barotse floodplain fishery and the implications of Australian redclaw crayfish Cherax quadricarinatus invasion on the fishery
- Authors: Nawa, Nawa
- Date: 2024-10-11
- Subjects: Zambezi Floodplains , Fishery resources Zambia Barotse Flood Plain , Introduced fishes Economic aspects , Cherax quadricarinatus , Fishery management
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466803 , vital:76780 , DOI https://doi.org/10.21504/10962/466803
- Description: Inland capture fisheries play an important role of supporting livelihoods of people in developing countries. Despite their significance these fisheries are often poorly monitored resulting in them being undervalued and often missing from policy and decision-making relating to food security and water use, particularly in third world countries. The Anthropocene has given rise to increased pressure on these systems, further justifying the need for monitoring activities to determine the ecosystem service provision status and the levels of existing and emerging threats to such services. This thesis focuses on the Barotse floodplain fishery of the Upper Zambezi system and the potential implications of the recent Cherax quadricarinatus invasion on the floodplain fishery. The thesis specifically assesses the current status of the fishery (Chapter 3), invasion dynamics of C. quadricarinatus (Chapter 4), economic impact of C. quadricarinatus on the fishery (Chapter 5) and fishers’ knowledge, awareness and perception of C. quadricarinatus (Chapter 6). To evaluate the current status of the fishery (Chapter 3), fisheries dependant surveys were conducted. The study revealed a multi-gear multi-species fishery with average catch rates of 5.83 kg per fisher per day and estimated annual harvest of 3123 tonnes per annum. The decline in catch rate, low mean sizes of species harvested, change in species composition, and predominant use of illegal fishing gear compared to previous surveys, suggested further overexploitation of fishery resources. The invasive C. quadricarinatus was identified as the most dominant by-catch species and more prevalent among fishers at the invasion core and in dry season. Analysis of the invasion dynamics of C. quadricarinatus (Chapter 4) involved extensive survey of the Barotse floodplain using collapsible promar traps. The study revealed significant up and down-stream spread from the 2019 range on the floodplain. Relative abundance was higher at the invasion core compared to the invasion edge while male to female sex ratio was not different between these zones, implying both sexes were acting as dispersers. Signals of environmental filtering were not detected while density dependent spatial sorting, and hydrological variation had a strong influence on C. quadricarinatus spread. To quantify economic impact C. quadricarinatus (Chapter 5) creel surveys were conducted during wet and dry season across the invasion range. The study showed that fish damage due to crayfish was limited to gillnets at the invasion core during the dry season and equated to the monetary loss of ~ US$ 21,000 per annum. In addition, gear damage and loss of time due to crayfish was experienced for various fishing gears but most prevalent at the invasion core and more so in dry season. Assessment of fishers’ awareness, knowledge and perception (Chapter 6) involved the use of social surveys administered at the invasion core. This component revealed that most of the respondents were aware of, but not knowledgeable about C. quadricarinatus. Respondents were not aware of any management information relating to C. quadricarinatus and consequently did not follow any management practices. The respondents were supportive of management interventions due to their perceived threat of C. quadricarinatus to the fishery. Age, education, and residence of respondents significantly influenced knowledge and perceptions of C. quadricarinatus. Findings from this study have important implications for the conservation of floodplain wetlands as it informs policy makers to put in place measures that address both overexploitation and aquatic invasive species dynamics to better facilitate sustainability of fisheries and conservation of biodiversity. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Nawa, Nawa
- Date: 2024-10-11
- Subjects: Zambezi Floodplains , Fishery resources Zambia Barotse Flood Plain , Introduced fishes Economic aspects , Cherax quadricarinatus , Fishery management
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466803 , vital:76780 , DOI https://doi.org/10.21504/10962/466803
- Description: Inland capture fisheries play an important role of supporting livelihoods of people in developing countries. Despite their significance these fisheries are often poorly monitored resulting in them being undervalued and often missing from policy and decision-making relating to food security and water use, particularly in third world countries. The Anthropocene has given rise to increased pressure on these systems, further justifying the need for monitoring activities to determine the ecosystem service provision status and the levels of existing and emerging threats to such services. This thesis focuses on the Barotse floodplain fishery of the Upper Zambezi system and the potential implications of the recent Cherax quadricarinatus invasion on the floodplain fishery. The thesis specifically assesses the current status of the fishery (Chapter 3), invasion dynamics of C. quadricarinatus (Chapter 4), economic impact of C. quadricarinatus on the fishery (Chapter 5) and fishers’ knowledge, awareness and perception of C. quadricarinatus (Chapter 6). To evaluate the current status of the fishery (Chapter 3), fisheries dependant surveys were conducted. The study revealed a multi-gear multi-species fishery with average catch rates of 5.83 kg per fisher per day and estimated annual harvest of 3123 tonnes per annum. The decline in catch rate, low mean sizes of species harvested, change in species composition, and predominant use of illegal fishing gear compared to previous surveys, suggested further overexploitation of fishery resources. The invasive C. quadricarinatus was identified as the most dominant by-catch species and more prevalent among fishers at the invasion core and in dry season. Analysis of the invasion dynamics of C. quadricarinatus (Chapter 4) involved extensive survey of the Barotse floodplain using collapsible promar traps. The study revealed significant up and down-stream spread from the 2019 range on the floodplain. Relative abundance was higher at the invasion core compared to the invasion edge while male to female sex ratio was not different between these zones, implying both sexes were acting as dispersers. Signals of environmental filtering were not detected while density dependent spatial sorting, and hydrological variation had a strong influence on C. quadricarinatus spread. To quantify economic impact C. quadricarinatus (Chapter 5) creel surveys were conducted during wet and dry season across the invasion range. The study showed that fish damage due to crayfish was limited to gillnets at the invasion core during the dry season and equated to the monetary loss of ~ US$ 21,000 per annum. In addition, gear damage and loss of time due to crayfish was experienced for various fishing gears but most prevalent at the invasion core and more so in dry season. Assessment of fishers’ awareness, knowledge and perception (Chapter 6) involved the use of social surveys administered at the invasion core. This component revealed that most of the respondents were aware of, but not knowledgeable about C. quadricarinatus. Respondents were not aware of any management information relating to C. quadricarinatus and consequently did not follow any management practices. The respondents were supportive of management interventions due to their perceived threat of C. quadricarinatus to the fishery. Age, education, and residence of respondents significantly influenced knowledge and perceptions of C. quadricarinatus. Findings from this study have important implications for the conservation of floodplain wetlands as it informs policy makers to put in place measures that address both overexploitation and aquatic invasive species dynamics to better facilitate sustainability of fisheries and conservation of biodiversity. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2024
- Full Text:
- Date Issued: 2024-10-11
Assessing the vulnerability of inland fisheries to human-induced perturbation in Lake Kariba fishery, Zambia
- Authors: Imikendu, Imbwae
- Date: 2024-10-11
- Subjects: Fisheries Kariba, Lake (Zambia and Zimbabwe) , Small-scale fisheries , Fishery policy , Biodiversity Kariba, Lake (Zambia and Zimbabwe) , Sustainable livelihood
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466725 , vital:76774 , DOI https://doi.org/10.21504/10962/466725
- Description: Inland fisheries play a critical role in providing nutrition, employment, and ensuring food security among vulnerable groups in Lake Kariba. However, their value is usually undermined in developmental plans, and their contribution to a broader economic development is often undervalued. Over the past two decades, inland fisheries have stagnated. Simultaneously, there have been wide reports of increased fishing effort and declining trends in commercially valuable fish species. This has resulted into a wide socio-economic and environmental problems in various fishing communities. Lake Kariba Zambia, exemplifies this sustainability challenge, where fisheries resources and livelihoods are interlinked. A systematic peer review paper on this topic was documented, published and used for analytical work, focusing on governance and how it affects the utilization of the fisheries resources for food security and biodiversity conservation. This study had four major objectives: (i) to identify threats to fisheries’ productivity in Lake Kariba; (ii) to understand the socio-economic and environmental conditions of small-scale fisheries in Lake Kariba; (iii) to determine adaptation strategies adopted by small-scale fishers in light of the changing socio-economic and environmental conditions in Lake Kariba; (iv) to determine how management of fisheries has to change in response to the wide socio-economic and environmental challenges in the region. Using Ostrom’s framework for analysing socio-ecological systems, various socioeconomic and environmental problems faced by fishing communities in Lake Kariba were examined to devise a sustainable fisheries management plan. The study employed explorative surveys, household questionnaires, key informant interviews, focus group discussions, observations, and a review of literature to elicit secondary data. A proportional quota sampling technique was used to draw a representative sample of 300 small-scale fishers and a typology was developed using a bivariate analysis. Chi-square was used to determine fishing effort over time. Using a curve fitting estimation regression test, a trend analysis in fish production for the past thirteen years (13) years was performed. Results did not show a significant decline in fish production over the past 13 years, yet experts and the fishers reported declining trends in valuable fish species. The finding of this study provides both practical and theoretical lessons that can enhance adaptive capacity and support sustainable livelihoods in the region. A fisheries sector policy is urgently required to guide governance process and coordinate a multi-sectoral perspective to fisheries management if socio-economic progression is to be attained. , Thesis (PhD) -- Faculty of Science, Ichthyology and Fisheries Science, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Imikendu, Imbwae
- Date: 2024-10-11
- Subjects: Fisheries Kariba, Lake (Zambia and Zimbabwe) , Small-scale fisheries , Fishery policy , Biodiversity Kariba, Lake (Zambia and Zimbabwe) , Sustainable livelihood
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466725 , vital:76774 , DOI https://doi.org/10.21504/10962/466725
- Description: Inland fisheries play a critical role in providing nutrition, employment, and ensuring food security among vulnerable groups in Lake Kariba. However, their value is usually undermined in developmental plans, and their contribution to a broader economic development is often undervalued. Over the past two decades, inland fisheries have stagnated. Simultaneously, there have been wide reports of increased fishing effort and declining trends in commercially valuable fish species. This has resulted into a wide socio-economic and environmental problems in various fishing communities. Lake Kariba Zambia, exemplifies this sustainability challenge, where fisheries resources and livelihoods are interlinked. A systematic peer review paper on this topic was documented, published and used for analytical work, focusing on governance and how it affects the utilization of the fisheries resources for food security and biodiversity conservation. This study had four major objectives: (i) to identify threats to fisheries’ productivity in Lake Kariba; (ii) to understand the socio-economic and environmental conditions of small-scale fisheries in Lake Kariba; (iii) to determine adaptation strategies adopted by small-scale fishers in light of the changing socio-economic and environmental conditions in Lake Kariba; (iv) to determine how management of fisheries has to change in response to the wide socio-economic and environmental challenges in the region. Using Ostrom’s framework for analysing socio-ecological systems, various socioeconomic and environmental problems faced by fishing communities in Lake Kariba were examined to devise a sustainable fisheries management plan. The study employed explorative surveys, household questionnaires, key informant interviews, focus group discussions, observations, and a review of literature to elicit secondary data. A proportional quota sampling technique was used to draw a representative sample of 300 small-scale fishers and a typology was developed using a bivariate analysis. Chi-square was used to determine fishing effort over time. Using a curve fitting estimation regression test, a trend analysis in fish production for the past thirteen years (13) years was performed. Results did not show a significant decline in fish production over the past 13 years, yet experts and the fishers reported declining trends in valuable fish species. The finding of this study provides both practical and theoretical lessons that can enhance adaptive capacity and support sustainable livelihoods in the region. A fisheries sector policy is urgently required to guide governance process and coordinate a multi-sectoral perspective to fisheries management if socio-economic progression is to be attained. , Thesis (PhD) -- Faculty of Science, Ichthyology and Fisheries Science, 2024
- Full Text:
- Date Issued: 2024-10-11
Assessment and mitigation of biosecurity risks associated with macroalgae inclusion in farmed abalone diets in South Africa
- Mwangudza, Petronilla Masika
- Authors: Mwangudza, Petronilla Masika
- Date: 2024-10-11
- Subjects: Biosecurity , Seaweed , Abalone culture South Africa , Abalones Feeding and feeds , Haliotis midae , High-throughput nucleotide sequencing
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466748 , vital:76775 , DOI https://doi.org/10.21504/10962/466748
- Description: The provision of biosecure diets for use in intensive aquaculture conditions requires attention, to reduce the risk of introducing potential pathogens to the farmed stock. Such introductions could lead to infections and disease outbreaks. Despite the benefits associated with macroalgae inclusion in abalone diets, several microbial hazard cases have been reported in the animal feed and human food industries. This has necessitated the application of biosecurity measures on fresh macroalgae to reduce or eliminate potential hazards and the risks of pathogen transfer to abalone stock when used as a feed or feed supplement. The present thesis assessed the efficacy of different processing treatments, including heat, ultra-violet irradiation (UVC), different pH levels, salinity concentrations, and povo-iodine on the inactivation of potential macroalgaetransmitted abalone pathogens. The effect of the processed macroalgae on the growth, health and gut microbial composition of abalone were also explored and compared with abalone fed non-processed diets. The efficacy of the different processing treatments was initially assessed on pure cultures of the test pathogens, which included a bacterium (Vibrio anguillarum), an oomycete (Halioticida noduliformans) and the bacteriophage lambda. Data from the initial assessments were then used to select the most optimal treatments for further assessment on the test pathogens inoculated in a macroalgae matrix, to simulate a more natural scenario. The viability of the three test pathogens following exposure to different processing treatments was assessed using culture methods. The results indicated that a combination of three treatments; disinfection using povo-iodine solution (5000 mg/L) for 20 min, oven drying 40 ℃ for 8.0 h and UVC treatment for 10 min rendered all the test pathogens non-culturable. Growth trials were conducted to assess the effect of the biosecure macroalgae Ecklonia maxima, Ulva lacinulata and Gracilaria gracilis on the growth performance of the abalone Haliotis midae. The macroalgae were subjected to the combination of three biosecurity processing treatments and experimental diets were then formulated to incorporate the macroalgae that had been subjected to the biosecurity processing treatments as well as macroalgae that were not. Growth parameters of the abalone after a 150-day feeding trial were compared between the biosecure and non-bioseeure macroalgae dietary treatments. Overall, the lowest growth was observed in the abalone fed with the control diet (AbfeedTM S34R) compared to all the macroalgae diets. However, no significant differences in abalone weight and shell length were recorded between the dietary treatments after the 150-day growth trial with an overall mean final weight (} standard error) of 56.55 } 0.78 g and a mean final length of 66.26 } 0.344 mm (RM-ANOVA: F(18,63) = 0.706; p = 0.792; : F(18,63) = 0.941; p = 0.535 respectively). Similarly, the biosecurity process method (biosecure vs. non-biosecure) did not have an impact on abalone weights and shell length (p > 0.05). Moreover, specific growth rate, length gain and condition factor of abalone did not differ between the biosecure and nonbiosecure dietary treatments with overall means (}standard error) of 0.27 } 0.01 % bw/d, 1.79 } 0.07 mm/month and 1.13 } 0.01, respectively (p > 0.05). Dietary macroalgae are known to contribute to the gut microflora of abalone. To determine if the biosecure process influenced this community complex, a next generation sequencing (NGS) approach was used to identify and compare the bacterial communities in abalone that were fed diets containing macroalgae that had been subjected to biosecurity treatment and those that were not. The NGS approach was also used to determine the gut microbiome profile of the abalone fed with a formulated diet supplemented with fresh U. lacinulata and G. gracilis to assess the potential modulatory effect seaweeds and their associated microbiota may have on the gut microbiome of H. midae. The bacterial alpha diversity did not differ significantly across all the diets at family, genus and species levels (p > 0.05). No significant differences in the microbiome composition were detected indicating little or no dissimilarities of the bacterial communities between the diets for all the biosecure and non-biosecure macroalgae diets. A similar core microbiome was also observed in the digestive tracts of abalone fed with the biosecure and non-biosecure diets. It was concluded that the biosecure process did not influence the natural microbiota of abalone that were fed dietary ingredients that were subjected to the process. The findings of this research have contributed to understanding the production of biosecure macroalgae formulated diets without compromising their benefits to the growth and health of farmed abalone. The combined treatment used in this study can be applied in the macroalgae and the feed industry to produce biosecure feeds. , Thesis (PhD) -- Faculty of Science, Ichthyology and Fisheries Science, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Mwangudza, Petronilla Masika
- Date: 2024-10-11
- Subjects: Biosecurity , Seaweed , Abalone culture South Africa , Abalones Feeding and feeds , Haliotis midae , High-throughput nucleotide sequencing
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466748 , vital:76775 , DOI https://doi.org/10.21504/10962/466748
- Description: The provision of biosecure diets for use in intensive aquaculture conditions requires attention, to reduce the risk of introducing potential pathogens to the farmed stock. Such introductions could lead to infections and disease outbreaks. Despite the benefits associated with macroalgae inclusion in abalone diets, several microbial hazard cases have been reported in the animal feed and human food industries. This has necessitated the application of biosecurity measures on fresh macroalgae to reduce or eliminate potential hazards and the risks of pathogen transfer to abalone stock when used as a feed or feed supplement. The present thesis assessed the efficacy of different processing treatments, including heat, ultra-violet irradiation (UVC), different pH levels, salinity concentrations, and povo-iodine on the inactivation of potential macroalgaetransmitted abalone pathogens. The effect of the processed macroalgae on the growth, health and gut microbial composition of abalone were also explored and compared with abalone fed non-processed diets. The efficacy of the different processing treatments was initially assessed on pure cultures of the test pathogens, which included a bacterium (Vibrio anguillarum), an oomycete (Halioticida noduliformans) and the bacteriophage lambda. Data from the initial assessments were then used to select the most optimal treatments for further assessment on the test pathogens inoculated in a macroalgae matrix, to simulate a more natural scenario. The viability of the three test pathogens following exposure to different processing treatments was assessed using culture methods. The results indicated that a combination of three treatments; disinfection using povo-iodine solution (5000 mg/L) for 20 min, oven drying 40 ℃ for 8.0 h and UVC treatment for 10 min rendered all the test pathogens non-culturable. Growth trials were conducted to assess the effect of the biosecure macroalgae Ecklonia maxima, Ulva lacinulata and Gracilaria gracilis on the growth performance of the abalone Haliotis midae. The macroalgae were subjected to the combination of three biosecurity processing treatments and experimental diets were then formulated to incorporate the macroalgae that had been subjected to the biosecurity processing treatments as well as macroalgae that were not. Growth parameters of the abalone after a 150-day feeding trial were compared between the biosecure and non-bioseeure macroalgae dietary treatments. Overall, the lowest growth was observed in the abalone fed with the control diet (AbfeedTM S34R) compared to all the macroalgae diets. However, no significant differences in abalone weight and shell length were recorded between the dietary treatments after the 150-day growth trial with an overall mean final weight (} standard error) of 56.55 } 0.78 g and a mean final length of 66.26 } 0.344 mm (RM-ANOVA: F(18,63) = 0.706; p = 0.792; : F(18,63) = 0.941; p = 0.535 respectively). Similarly, the biosecurity process method (biosecure vs. non-biosecure) did not have an impact on abalone weights and shell length (p > 0.05). Moreover, specific growth rate, length gain and condition factor of abalone did not differ between the biosecure and nonbiosecure dietary treatments with overall means (}standard error) of 0.27 } 0.01 % bw/d, 1.79 } 0.07 mm/month and 1.13 } 0.01, respectively (p > 0.05). Dietary macroalgae are known to contribute to the gut microflora of abalone. To determine if the biosecure process influenced this community complex, a next generation sequencing (NGS) approach was used to identify and compare the bacterial communities in abalone that were fed diets containing macroalgae that had been subjected to biosecurity treatment and those that were not. The NGS approach was also used to determine the gut microbiome profile of the abalone fed with a formulated diet supplemented with fresh U. lacinulata and G. gracilis to assess the potential modulatory effect seaweeds and their associated microbiota may have on the gut microbiome of H. midae. The bacterial alpha diversity did not differ significantly across all the diets at family, genus and species levels (p > 0.05). No significant differences in the microbiome composition were detected indicating little or no dissimilarities of the bacterial communities between the diets for all the biosecure and non-biosecure macroalgae diets. A similar core microbiome was also observed in the digestive tracts of abalone fed with the biosecure and non-biosecure diets. It was concluded that the biosecure process did not influence the natural microbiota of abalone that were fed dietary ingredients that were subjected to the process. The findings of this research have contributed to understanding the production of biosecure macroalgae formulated diets without compromising their benefits to the growth and health of farmed abalone. The combined treatment used in this study can be applied in the macroalgae and the feed industry to produce biosecure feeds. , Thesis (PhD) -- Faculty of Science, Ichthyology and Fisheries Science, 2024
- Full Text:
- Date Issued: 2024-10-11
Becoming a [COVID] student?: assessing the impact of COVID-19 on first-year students’ experiences of higher education in the Eastern Cape, South Africa
- Authors: Nebbe, Kelsey Ann
- Date: 2024-10-11
- Subjects: Rite of passage , COVID-19 Pandemic, 2020-2023 Influence , College freshmen South Africa Eastern Cape , Liminality , Communitas
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/466295 , vital:76715
- Description: In 2020, the COVID-19 pandemic disrupted South African higher education which forced the shift to emergency distance learning to save the academic years of 2020-2022. The repercussions of this are still emerging, but current literature focuses on understanding the impact of first-year students is focused on the impact of academics caused by the emergency shift to online, the “double transition” as Nyar (2021) termed the adjustment to university and then again to the online emergency academics. There is also a niche for holistic research to be done regarding the student experience - pandemic times and elsewise. My thesis focuses on the journey of studenthood of three cohorts at a residential university in the Eastern Cape, South Africa, through the COVID-19 pandemic of 2020-2022. This research utilises ethnographic iterative mixed methods (questionnaire, interviews, focus groups and participant observation) and the theoretical lens of Rites of Passage to understand my research participant’s experiences. My findings are that due to the circumstances of an incomplete student experience of just online academics provided an continuous liminal period for first-year students of 2020-2021, with little to no opportunity for them to develop a connection to the university community. The opportunity for them to holistically become students arises at the end of the pandemic in 2022, with the restrictions lifting and the return to on-campus and in-person academic activities allowing them to have a first-year experienced that COVID-19 prohibited. , Thesis (MSocSci) -- Faculty of Humanities, Anthropology, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Nebbe, Kelsey Ann
- Date: 2024-10-11
- Subjects: Rite of passage , COVID-19 Pandemic, 2020-2023 Influence , College freshmen South Africa Eastern Cape , Liminality , Communitas
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/466295 , vital:76715
- Description: In 2020, the COVID-19 pandemic disrupted South African higher education which forced the shift to emergency distance learning to save the academic years of 2020-2022. The repercussions of this are still emerging, but current literature focuses on understanding the impact of first-year students is focused on the impact of academics caused by the emergency shift to online, the “double transition” as Nyar (2021) termed the adjustment to university and then again to the online emergency academics. There is also a niche for holistic research to be done regarding the student experience - pandemic times and elsewise. My thesis focuses on the journey of studenthood of three cohorts at a residential university in the Eastern Cape, South Africa, through the COVID-19 pandemic of 2020-2022. This research utilises ethnographic iterative mixed methods (questionnaire, interviews, focus groups and participant observation) and the theoretical lens of Rites of Passage to understand my research participant’s experiences. My findings are that due to the circumstances of an incomplete student experience of just online academics provided an continuous liminal period for first-year students of 2020-2021, with little to no opportunity for them to develop a connection to the university community. The opportunity for them to holistically become students arises at the end of the pandemic in 2022, with the restrictions lifting and the return to on-campus and in-person academic activities allowing them to have a first-year experienced that COVID-19 prohibited. , Thesis (MSocSci) -- Faculty of Humanities, Anthropology, 2024
- Full Text:
- Date Issued: 2024-10-11
Bio-vectoring by honeybees and symbiosis: a combined approach to controlling Botrytis mould on strawberry
- Authors: Starbuck, Megan
- Date: 2024-10-11
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/463985 , vital:76463
- Description: Access restricted. Exxpected release in 2026. , Thesis (MSc) -- Faculty of Science, Biochemistry, Microbiology & Bioinformatics, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Starbuck, Megan
- Date: 2024-10-11
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/463985 , vital:76463
- Description: Access restricted. Exxpected release in 2026. , Thesis (MSc) -- Faculty of Science, Biochemistry, Microbiology & Bioinformatics, 2024
- Full Text:
- Date Issued: 2024-10-11
Biological control of torch cactus in South Africa: finding a suitable agent for a non-native weed with an unknown indigenous distribution
- Authors: Griffith, Tamzin Camilla
- Date: 2024-10-11
- Subjects: Trichocereus spachianus , Invasive plants Biological control , Dactylopius , Hypogeococcus , Host specificity
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466781 , vital:76778 , DOI https://doi.org/10.21504/10962/466781
- Description: Trichocereus spachianus is an invasive cactus species in South Africa and poses challenges as a target for biological control due to confusion around its taxonomy and origin. Adapted to arid environments, this cactus is of particular concern in dry savannah and Karoo biomes, where its invasion of rangelands reduces grazing capacity for both indigenous wildlife and livestock. While previous records indicate that T. spachianus is indigenous to Argentina, recent field surveys have failed to verify its presence. Determining the origin of the target weed was important in developing a biological control programme since it enables the collection of potential agents directly from native populations of the target plant. Successful biological control programmes against cactus species in South Africa have often involved utilising both new associations and oligophagous insects, made possible because of the lack of indigenous and valued cacti in the region. Lack of T. spachianus locations in the native distribution, meant direct collection of insects from the target weed was not possible. Efforts to find biological control agents were focused on new associations between closely related cacti and their oligophagous herbivores. Suitability of multiple Hypogeococcus (mealybug) entities and a cochineal species, Dactylopius confertus, were investigated for their efficacy on various South African weedy cactus species, including T. spachianus. Findings revealed that none of the Hypogeococcus entities (species or lineages) were effective biological control agents, but D. confertus demonstrated potential as a biological control agent with a relatively high fecundity and survival rate on T. spachianus. Efficacy trials indicated that D. confertus could reach population densities sufficient to cause mortality of T. spachianus plants. Limited host specificity trials revealed that D. confertus was suitably host specific for release in South Africa, provided host specificity testing was conducted on additional plants. Approval and release of D. confertus has the potential to reduce the invasiveness of this damaging cactus in a sustainable and environmentally friendly manner. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Griffith, Tamzin Camilla
- Date: 2024-10-11
- Subjects: Trichocereus spachianus , Invasive plants Biological control , Dactylopius , Hypogeococcus , Host specificity
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466781 , vital:76778 , DOI https://doi.org/10.21504/10962/466781
- Description: Trichocereus spachianus is an invasive cactus species in South Africa and poses challenges as a target for biological control due to confusion around its taxonomy and origin. Adapted to arid environments, this cactus is of particular concern in dry savannah and Karoo biomes, where its invasion of rangelands reduces grazing capacity for both indigenous wildlife and livestock. While previous records indicate that T. spachianus is indigenous to Argentina, recent field surveys have failed to verify its presence. Determining the origin of the target weed was important in developing a biological control programme since it enables the collection of potential agents directly from native populations of the target plant. Successful biological control programmes against cactus species in South Africa have often involved utilising both new associations and oligophagous insects, made possible because of the lack of indigenous and valued cacti in the region. Lack of T. spachianus locations in the native distribution, meant direct collection of insects from the target weed was not possible. Efforts to find biological control agents were focused on new associations between closely related cacti and their oligophagous herbivores. Suitability of multiple Hypogeococcus (mealybug) entities and a cochineal species, Dactylopius confertus, were investigated for their efficacy on various South African weedy cactus species, including T. spachianus. Findings revealed that none of the Hypogeococcus entities (species or lineages) were effective biological control agents, but D. confertus demonstrated potential as a biological control agent with a relatively high fecundity and survival rate on T. spachianus. Efficacy trials indicated that D. confertus could reach population densities sufficient to cause mortality of T. spachianus plants. Limited host specificity trials revealed that D. confertus was suitably host specific for release in South Africa, provided host specificity testing was conducted on additional plants. Approval and release of D. confertus has the potential to reduce the invasiveness of this damaging cactus in a sustainable and environmentally friendly manner. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2024
- Full Text:
- Date Issued: 2024-10-11
Biology and management of the fruit piercing moth Serrodes partita in citrus orchards
- Authors: Mushore, Tapiwa Gift
- Date: 2024-10-11
- Subjects: Baculoviruses , Moths Monitoring , Pests Control , Insect traps , Citrus Diseases and pests South Africa Kat River Valley , Catapult moth
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466792 , vital:76779 , DOI https://doi.org/10.21504/10962/466792
- Description: The fruit-piercing moth, Serrodes partita (Fabricius) (Lepidoptera: Erebidae), is a polyphagous, multivoltine pest of citrus. This insect has a distinct geographical separation between its larval and adult stages, each with different feeding patterns. During the larval stage, it primarily acts as a forest defoliator, feeding mostly on Jacket plum, Pappea capensis Eckl. & Zeyh. (Sapindaceae). In contrast, the adult stage of this moth feeds on both tropical and subtropical fruit, including citrus and can cause serious economic losses. The adult moth uses its sclerotised proboscis to pierce the skin of ripening or ripe fruit, from which it extracts the juice. This piercing action initiates a fermentation process within the fruit, attracting other secondary-feeding moths, commonly referred to as fruit-sucking moths. As a result of the feeding activity, the affected fruit eventually rot, drop to the ground, and become unsuitable for the market. Serrodes partita exhibits an outbreak life strategy, reoccurring every 5 to 10 years. In South Africa's Eastern Cape Province, specifically in the Upper Kat River Valley, citrus growers have expressed concerns about the impact of this moth on soft citrus (Satsumas and Clementines). This raises the possibility of a shift in the population dynamics of S. partita, where these occurrences become more frequent and less sporadic. Such a trend poses a significant threat to fruit arboriculture in the Eastern Cape region. Currently, there are limited management strategies available for managing fruit-piecing moths. The use of pesticides is not a feasible option for ripe or nearly ripe fruit, and is ineffective against the adult moth. Alternative control methods, such as orchard netting and light barriers, either come with high costs or are impractical for large-scale citrus production. Given the limited range of management options, combined with the moth's tendency for sudden outbreaks, citrus growers find themselves without effective means to manage this pest. The objective of this study was, therefore, to investigate the biology of S. partita and explore various control options to effectively manage this pest. Research focused on the biology and laboratory rearing of larval stages of S. partita. The flight behaviour, feeding patterns, and preferences of adult S. partita within citrus orchards were also explored. The aim was to elucidate key fundamental aspects, including whether the same population frequents a particular orchard, and if infestations within orchards exhibit a specific direction. Lure type and lure presentation method trials were conducted to determine the most effective lure and trap design. Seasonal monitoring of S. partita in soft citrus orchards was conducted over three years to determine its outbreak status in the Committee’s Drift area and the role of weather variables in the activity of the moth. Damage assessments were also conducted alongside monitoring to determine the level of damage inflicted by S. partita. Natural enemies associated with S. partita were explored to determine the prevalence and causes of mortality in late instars during laboratory rearing. Rearing S. partita on an artificial diet was unsuccessful despite several modifications. The moth, however, completed its entire life cycle on its natural host, P. capensis in the laboratory. The total life cycle from egg to adult took 80.7 ± 3.6 days, the larval stage lasted 52.3 ± 2.8 days, and the pupal stage lasted 25.8 ± 3.6 days at 21°C. The investigation into the biology of S. partita also brought attention to the most susceptible stages of its growth, with high mortality rates recorded among neonates and late instars. The findings of the study revealed directional patterns of moth infestations, with higher numbers observed at the orchard's periphery leading towards natural vegetation. This raises the prospect of using sacrificial rows on the edge of a citrus orchard to concentrate moth feeding damage during outbreak years. Using a mark and recapture technique, the study showed that a relatively small proportion (4.5 %) of moths tended to revisit the same orchard. The moths strongly preferred damaged fruit (85 %) over undamaged fruit. Visible damage (rotting symptoms) typically became apparent within 3 to 5 days. Satsumas had a higher number of feeding scars (2.1) than Clementines (1.08), highlighting their susceptibility. The study also established that, on average, pierced soft citrus fruit takes about four days to display symptoms of decay. Synthetic proprietary Australian lures were ineffective at attracting the moth, whereas fresh bananas proved to be a successful lure. Furthermore, the addition of both Agar and Super absorbent polymer showed promise as thickening agents to enhance the longevity of fresh bananas in traps. The effectiveness of various trap designs was compared, including the funnel trap, delta trap, bucket trap, and circular trap, in capturing fruit-feeding moths. The funnel trap performed best as it captured the most moths, followed by the delta trap, Lynfield trap and disc trap, respectively. Additionally, an electronic enhancement to the funnel trap, incorporating a zapper element, improved efficiency. However, efforts to exploit both visual and olfactory cues through the inclusion of an Ultraviolet (UV) light component did not improve its effectiveness. No extensive outbreaks were recorded during the study; however, population variations of S. partita populations were recorded. Annual trends showed two population peaks, with the first peak recorded from December to March, while the second peak was recorded from April to July. The activity of the moths also differed across different months, with the highest peaks recorded in May, while no moths were recorded from August to November. Both cultivar type and farm location did not influence the occurrence of the moth. Meanwhile cumulative weather parameters (rainfall, temperature and humidity) from the four months prior to occurrence influenced the activity of S. partita. Temperature determined the timing of the outbreak, while rainfall determined the magnitude of the outbreak. Damage assessment showed very low fruit damage by S. partita throughout the monitoring period. Varying levels of infestation by a tachinid fly, 4 % and 35 %, were recorded for 2021 and 2022, respectively. The tachinid parasitoid could not be identified at the species level. A novel baculovirus, tentatively classified as S. partita NPV (SepaNPV), was identified as the larval mortality causative agent. This study enhanced our understanding of S. partita's biology and population dynamics, providing valuable insights for developing effective management strategies against this economically impactful citrus pest. Future research should focus on refining control measures and addressing the challenges of the adult moth's elusive nature. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Mushore, Tapiwa Gift
- Date: 2024-10-11
- Subjects: Baculoviruses , Moths Monitoring , Pests Control , Insect traps , Citrus Diseases and pests South Africa Kat River Valley , Catapult moth
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466792 , vital:76779 , DOI https://doi.org/10.21504/10962/466792
- Description: The fruit-piercing moth, Serrodes partita (Fabricius) (Lepidoptera: Erebidae), is a polyphagous, multivoltine pest of citrus. This insect has a distinct geographical separation between its larval and adult stages, each with different feeding patterns. During the larval stage, it primarily acts as a forest defoliator, feeding mostly on Jacket plum, Pappea capensis Eckl. & Zeyh. (Sapindaceae). In contrast, the adult stage of this moth feeds on both tropical and subtropical fruit, including citrus and can cause serious economic losses. The adult moth uses its sclerotised proboscis to pierce the skin of ripening or ripe fruit, from which it extracts the juice. This piercing action initiates a fermentation process within the fruit, attracting other secondary-feeding moths, commonly referred to as fruit-sucking moths. As a result of the feeding activity, the affected fruit eventually rot, drop to the ground, and become unsuitable for the market. Serrodes partita exhibits an outbreak life strategy, reoccurring every 5 to 10 years. In South Africa's Eastern Cape Province, specifically in the Upper Kat River Valley, citrus growers have expressed concerns about the impact of this moth on soft citrus (Satsumas and Clementines). This raises the possibility of a shift in the population dynamics of S. partita, where these occurrences become more frequent and less sporadic. Such a trend poses a significant threat to fruit arboriculture in the Eastern Cape region. Currently, there are limited management strategies available for managing fruit-piecing moths. The use of pesticides is not a feasible option for ripe or nearly ripe fruit, and is ineffective against the adult moth. Alternative control methods, such as orchard netting and light barriers, either come with high costs or are impractical for large-scale citrus production. Given the limited range of management options, combined with the moth's tendency for sudden outbreaks, citrus growers find themselves without effective means to manage this pest. The objective of this study was, therefore, to investigate the biology of S. partita and explore various control options to effectively manage this pest. Research focused on the biology and laboratory rearing of larval stages of S. partita. The flight behaviour, feeding patterns, and preferences of adult S. partita within citrus orchards were also explored. The aim was to elucidate key fundamental aspects, including whether the same population frequents a particular orchard, and if infestations within orchards exhibit a specific direction. Lure type and lure presentation method trials were conducted to determine the most effective lure and trap design. Seasonal monitoring of S. partita in soft citrus orchards was conducted over three years to determine its outbreak status in the Committee’s Drift area and the role of weather variables in the activity of the moth. Damage assessments were also conducted alongside monitoring to determine the level of damage inflicted by S. partita. Natural enemies associated with S. partita were explored to determine the prevalence and causes of mortality in late instars during laboratory rearing. Rearing S. partita on an artificial diet was unsuccessful despite several modifications. The moth, however, completed its entire life cycle on its natural host, P. capensis in the laboratory. The total life cycle from egg to adult took 80.7 ± 3.6 days, the larval stage lasted 52.3 ± 2.8 days, and the pupal stage lasted 25.8 ± 3.6 days at 21°C. The investigation into the biology of S. partita also brought attention to the most susceptible stages of its growth, with high mortality rates recorded among neonates and late instars. The findings of the study revealed directional patterns of moth infestations, with higher numbers observed at the orchard's periphery leading towards natural vegetation. This raises the prospect of using sacrificial rows on the edge of a citrus orchard to concentrate moth feeding damage during outbreak years. Using a mark and recapture technique, the study showed that a relatively small proportion (4.5 %) of moths tended to revisit the same orchard. The moths strongly preferred damaged fruit (85 %) over undamaged fruit. Visible damage (rotting symptoms) typically became apparent within 3 to 5 days. Satsumas had a higher number of feeding scars (2.1) than Clementines (1.08), highlighting their susceptibility. The study also established that, on average, pierced soft citrus fruit takes about four days to display symptoms of decay. Synthetic proprietary Australian lures were ineffective at attracting the moth, whereas fresh bananas proved to be a successful lure. Furthermore, the addition of both Agar and Super absorbent polymer showed promise as thickening agents to enhance the longevity of fresh bananas in traps. The effectiveness of various trap designs was compared, including the funnel trap, delta trap, bucket trap, and circular trap, in capturing fruit-feeding moths. The funnel trap performed best as it captured the most moths, followed by the delta trap, Lynfield trap and disc trap, respectively. Additionally, an electronic enhancement to the funnel trap, incorporating a zapper element, improved efficiency. However, efforts to exploit both visual and olfactory cues through the inclusion of an Ultraviolet (UV) light component did not improve its effectiveness. No extensive outbreaks were recorded during the study; however, population variations of S. partita populations were recorded. Annual trends showed two population peaks, with the first peak recorded from December to March, while the second peak was recorded from April to July. The activity of the moths also differed across different months, with the highest peaks recorded in May, while no moths were recorded from August to November. Both cultivar type and farm location did not influence the occurrence of the moth. Meanwhile cumulative weather parameters (rainfall, temperature and humidity) from the four months prior to occurrence influenced the activity of S. partita. Temperature determined the timing of the outbreak, while rainfall determined the magnitude of the outbreak. Damage assessment showed very low fruit damage by S. partita throughout the monitoring period. Varying levels of infestation by a tachinid fly, 4 % and 35 %, were recorded for 2021 and 2022, respectively. The tachinid parasitoid could not be identified at the species level. A novel baculovirus, tentatively classified as S. partita NPV (SepaNPV), was identified as the larval mortality causative agent. This study enhanced our understanding of S. partita's biology and population dynamics, providing valuable insights for developing effective management strategies against this economically impactful citrus pest. Future research should focus on refining control measures and addressing the challenges of the adult moth's elusive nature. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2024
- Full Text:
- Date Issued: 2024-10-11
Border crossing, collecting, gravitating: small narratives of three ordinary collectors in the Chinese diaspora in South Africa since the late 1980s
- Authors: Grobbelaar, Binjun
- Date: 2024-10-11
- Subjects: Chinese diaspora , Art Collectors and collecting South Africa , Autobiography in art , Art History , Knowledge, Sociology of , Proximity
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/467039 , vital:76809 , DOI https://doi.org/10.21504/10962/467039
- Description: Shifting away from the conventional viewpoint that confines art collecting predominantly to established structures like art institutions, markets, and exclusive collector networks, a trajectory historically influenced by Western collecting traditions and museology, this thesis takes a radical turn by delving into the small narratives of three ordinary Chinese collectors, namely Shengkai Wu, Yiyuan Yang and Shudi Li, who immigrated to South Africa since the late 1980s. The focus on Chinese collectors and migration resonates with my positionality as a recent Chinese immigrant in South Africa and aligns with Boaventura de Sousa Santos’s approach to proximity in knowledge-making, which emphasises ‘knowing with’ and ‘walking alongside’ the subjects of study. The selected immigrant collectors were chosen based on their current low-to-middle economic status in South Africa. These three individuals have decades of living and artcollecting experience in the country, having held professional backgrounds in China prior to their immigration. The number of collectors was determined through an in-depth qualitative biographical research method, taking into account the niche field of art collecting and the relatively small Chinese population within the broader South African demographic. It approaches collecting as a method of pursuing clues and explores it as a socio-cultural practice by collaging the biographies of three ordinary collectors as micro-histories. Details of these ordinary lives are entangled with the lives of objects that traverse China and South Africa. The use of non-official data, at times fragmented and partially obscured, is employed to craft a narrative that weaves together diverse and complex perspectives. The aim of this thesis is to attempt to shift from elite collecting narratives to a more diverse understanding of the global circulation and appropriation of art and cultural objects in relation to grassroots migration. This shift is explored through the unique insights derived from recovering the personal narratives of ordinary immigrant collectors and their associated objects in overlooked geographical locations and states of transformation within the context of China– Africa relations. I engage China–Africa relations within the framework Global South, seeks to address the limitations of describing the multi-dimensional interweaving of low-profile individual and objecthood, unofficial and official, historical and ephemeral relationships in the burgeoning field of China-Africa relations. The investigation unfolds through two interconnected aspects embedded in the development of each collector’s biography. Firstly, it delves into how the collecting practices of these three Chinese collectors are interwoven with their experiences in both China and South Africa. Secondly, it examines the agencies of the collectors and the relationships they establish with the objects they collect. I approach these collectors as curators of their autobiographical exhibitions in the process of preliminary data collection and subsequent thematic and object-oriented interviews. Through the analysis of collectors’ oral, visual and written narratives, as well as the biographies of objects, this PhD thesis in Art History uncovers a multilayered influx of crossways of knowledge-making by the collectors on the ground. Inspired by practical material re-ordering and personal interests, these collectors engage in configuring the border-crossing process within the Chinese diaspora in South Africa. Recurring narratives of critical socialist experiences in Maoist China are linked to their suppressed agency and subsequent recovery through emigration to South Africa. They negotiate a complex diasporic terrain marked by engaging with socialist philately materials, persistently gravitating towards China. Concurrently, they transcend conventional nation-state framework, accentuating the convergent aesthetic qualities inherent in transnational artefacts and community-based art practices. The collectors’ engagement with exported Chinese “specialised arts and crafts”, and unconventional artefacts, such as philately materials, creates a bottom-up fresh interpretation of what constitutes collecting Chinese art in the context of South Africa. Fragments of British colonial history on the Rand, Chinese semi-colonial history, and contemporary printmaking in both China and South Africa, embedded in tangible material artefacts and in intangible visual connection, become visible through their logics of collecting and affective approach from the bottom up. Highlighting the often-overlooked Chinese agency in the creation of these objects, this research illustrates how individual mobility between China and Africa can contribute to the nuanced role of aesthetics through collecting, redefining what is visible and meaningful in the context of the Chinese diaspora and art collecting in South Africa. Specifically, discourses on the border poetics of Zheng He, colonial postcards and notices on the Rand, visual connection in printmaking, and Chinese semi-colonial artefacts of a converged “Chinese–British” aesthetic and a controversial Tang blue-and-white dish are instances where ordinary Chinese collectors in the Global South strategically mobilise collecting as a means to migrate towards an alternative politics of hope, as conceptualised by Chiara Brambilla. This hope presents a “strategic Southerness,” cultivates an “alter-geopolitics of knowledge” (Simbao 2017) that, pushing against the often-dominant representation of spectacle within the structured frameworks of art institutions, markets and networks of elite collectors. I argue that these emerging themes and objects in the collectors’ narratives represent a grounded, localised knowledge-making from below, unfolding practices underpinned by the material conditions of ordinary collectors of art and material culture in the Global South, aspects that have not been given adequate attention in history. In the process of encountering, reassembling, and appropriating these material objects and associating people in South Africa, I argue that collecting becomes not only an act of diasporic agency in constructing memories of the past, but also offers insight into the complex Chinese diaspora within the dynamics of a rising Chinese presence in Africa. On the one hand, these ordinary collectors employ collecting as an act of resistance against the aftermath of political turmoil and the epistemological inequality imposed on grassroots communities. Their emergence has contributed to transforming the residual colonial culture of the “othering” in the landscape of art collecting in South Africa. On the other hand, their agency intersects with Chinese diasporic nationalism, which lingers in the tension between internalised Eurocentric exploitation and romanticised appreciation and cultural preservation, a question that awaits for further investigation. , Thesis (PhD) -- Faculty of Humanities, Fine Art, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Grobbelaar, Binjun
- Date: 2024-10-11
- Subjects: Chinese diaspora , Art Collectors and collecting South Africa , Autobiography in art , Art History , Knowledge, Sociology of , Proximity
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/467039 , vital:76809 , DOI https://doi.org/10.21504/10962/467039
- Description: Shifting away from the conventional viewpoint that confines art collecting predominantly to established structures like art institutions, markets, and exclusive collector networks, a trajectory historically influenced by Western collecting traditions and museology, this thesis takes a radical turn by delving into the small narratives of three ordinary Chinese collectors, namely Shengkai Wu, Yiyuan Yang and Shudi Li, who immigrated to South Africa since the late 1980s. The focus on Chinese collectors and migration resonates with my positionality as a recent Chinese immigrant in South Africa and aligns with Boaventura de Sousa Santos’s approach to proximity in knowledge-making, which emphasises ‘knowing with’ and ‘walking alongside’ the subjects of study. The selected immigrant collectors were chosen based on their current low-to-middle economic status in South Africa. These three individuals have decades of living and artcollecting experience in the country, having held professional backgrounds in China prior to their immigration. The number of collectors was determined through an in-depth qualitative biographical research method, taking into account the niche field of art collecting and the relatively small Chinese population within the broader South African demographic. It approaches collecting as a method of pursuing clues and explores it as a socio-cultural practice by collaging the biographies of three ordinary collectors as micro-histories. Details of these ordinary lives are entangled with the lives of objects that traverse China and South Africa. The use of non-official data, at times fragmented and partially obscured, is employed to craft a narrative that weaves together diverse and complex perspectives. The aim of this thesis is to attempt to shift from elite collecting narratives to a more diverse understanding of the global circulation and appropriation of art and cultural objects in relation to grassroots migration. This shift is explored through the unique insights derived from recovering the personal narratives of ordinary immigrant collectors and their associated objects in overlooked geographical locations and states of transformation within the context of China– Africa relations. I engage China–Africa relations within the framework Global South, seeks to address the limitations of describing the multi-dimensional interweaving of low-profile individual and objecthood, unofficial and official, historical and ephemeral relationships in the burgeoning field of China-Africa relations. The investigation unfolds through two interconnected aspects embedded in the development of each collector’s biography. Firstly, it delves into how the collecting practices of these three Chinese collectors are interwoven with their experiences in both China and South Africa. Secondly, it examines the agencies of the collectors and the relationships they establish with the objects they collect. I approach these collectors as curators of their autobiographical exhibitions in the process of preliminary data collection and subsequent thematic and object-oriented interviews. Through the analysis of collectors’ oral, visual and written narratives, as well as the biographies of objects, this PhD thesis in Art History uncovers a multilayered influx of crossways of knowledge-making by the collectors on the ground. Inspired by practical material re-ordering and personal interests, these collectors engage in configuring the border-crossing process within the Chinese diaspora in South Africa. Recurring narratives of critical socialist experiences in Maoist China are linked to their suppressed agency and subsequent recovery through emigration to South Africa. They negotiate a complex diasporic terrain marked by engaging with socialist philately materials, persistently gravitating towards China. Concurrently, they transcend conventional nation-state framework, accentuating the convergent aesthetic qualities inherent in transnational artefacts and community-based art practices. The collectors’ engagement with exported Chinese “specialised arts and crafts”, and unconventional artefacts, such as philately materials, creates a bottom-up fresh interpretation of what constitutes collecting Chinese art in the context of South Africa. Fragments of British colonial history on the Rand, Chinese semi-colonial history, and contemporary printmaking in both China and South Africa, embedded in tangible material artefacts and in intangible visual connection, become visible through their logics of collecting and affective approach from the bottom up. Highlighting the often-overlooked Chinese agency in the creation of these objects, this research illustrates how individual mobility between China and Africa can contribute to the nuanced role of aesthetics through collecting, redefining what is visible and meaningful in the context of the Chinese diaspora and art collecting in South Africa. Specifically, discourses on the border poetics of Zheng He, colonial postcards and notices on the Rand, visual connection in printmaking, and Chinese semi-colonial artefacts of a converged “Chinese–British” aesthetic and a controversial Tang blue-and-white dish are instances where ordinary Chinese collectors in the Global South strategically mobilise collecting as a means to migrate towards an alternative politics of hope, as conceptualised by Chiara Brambilla. This hope presents a “strategic Southerness,” cultivates an “alter-geopolitics of knowledge” (Simbao 2017) that, pushing against the often-dominant representation of spectacle within the structured frameworks of art institutions, markets and networks of elite collectors. I argue that these emerging themes and objects in the collectors’ narratives represent a grounded, localised knowledge-making from below, unfolding practices underpinned by the material conditions of ordinary collectors of art and material culture in the Global South, aspects that have not been given adequate attention in history. In the process of encountering, reassembling, and appropriating these material objects and associating people in South Africa, I argue that collecting becomes not only an act of diasporic agency in constructing memories of the past, but also offers insight into the complex Chinese diaspora within the dynamics of a rising Chinese presence in Africa. On the one hand, these ordinary collectors employ collecting as an act of resistance against the aftermath of political turmoil and the epistemological inequality imposed on grassroots communities. Their emergence has contributed to transforming the residual colonial culture of the “othering” in the landscape of art collecting in South Africa. On the other hand, their agency intersects with Chinese diasporic nationalism, which lingers in the tension between internalised Eurocentric exploitation and romanticised appreciation and cultural preservation, a question that awaits for further investigation. , Thesis (PhD) -- Faculty of Humanities, Fine Art, 2024
- Full Text:
- Date Issued: 2024-10-11
Burgernomics: Raw BMI vs Adjusted BMI. A comparative analysis of appropriate exchange rate valuation measures
- Gumedze, Siyanda Nakiwe Nomfundo
- Authors: Gumedze, Siyanda Nakiwe Nomfundo
- Date: 2024-10-11
- Subjects: Big Mac Index , Purchasing power parity , Foreign exchange rates , Foreign exchange market , Economic theory
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/462702 , vital:76327
- Description: The Big Mac Index was developed in 1986 by The Economist magazine as a playful take on the Purchasing Power Parity theory. Its purpose is to indicate whether a currency is overpriced or undervalued in relation to the real exchange rate and whether it can be used as a reliable indicator of exchange rate predictions. There are two versions of the Big Mac Index: the raw Big Mac Index and the adjusted Big Mac Index. If appropriate, this index might be developed into an economic theory that can be applied to corporate finance, international trade, and international finance. To determine which Big Mac Index measure is a better indicator of exchange rate valuation, a comparison analysis was conducted. This study set out to determine how well the adjusted Big Mac Index performed as a gauge for exchange rate valuation. The research then compares the two Big Mac Index measures' ability to anticipate future exchange rates in order to determine which is more accurate. Data from the South African Reserve Bank and The Economist databases covering 37 nations from 2000 to 2022 were used for the analysis. Exchange rate misalignment trends were assessed globally, and the results indicated that the adjusted BMI was a more accurate measure of purchasing power. Tests of correlation revealed that there was a positive association between the real exchange rate and the Big Mac Index. Findings from a panel ARDL Model indicated that taking into consideration country-specific GDP variations and group heterogeneity can enhance the real exchange rates' ability to predict the raw BMI. The research also focused on the South African Rand to ascertain whether the Big Mac Index validates the Purchasing Power Parity theoretical framework. Using cointegration tests and graphic analysis, it was possible to find evidence for a cointegrating relationship between the real exchange rate and the Big Mac Index measures during the last 20 years. Additionally, a positive correlation between the modified Big Mac Index and terms of trade was discovered in the results, confirming the hypothesis that the Big Mac Index satisfies current account assumptions. Finally, a VEC model demonstrated that the modified BMI outperforms the raw BMI in terms of forecasting estimates. Overall, the study found that the Big Mac Index is more than a bit of fun as per its origin. The results showed that the adjusted Big Mac Index has practical applications and the potential to be considered as an economic theory. , Thesis (MCom) -- Faculty of Commerce, Economics and Economic History, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Gumedze, Siyanda Nakiwe Nomfundo
- Date: 2024-10-11
- Subjects: Big Mac Index , Purchasing power parity , Foreign exchange rates , Foreign exchange market , Economic theory
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/462702 , vital:76327
- Description: The Big Mac Index was developed in 1986 by The Economist magazine as a playful take on the Purchasing Power Parity theory. Its purpose is to indicate whether a currency is overpriced or undervalued in relation to the real exchange rate and whether it can be used as a reliable indicator of exchange rate predictions. There are two versions of the Big Mac Index: the raw Big Mac Index and the adjusted Big Mac Index. If appropriate, this index might be developed into an economic theory that can be applied to corporate finance, international trade, and international finance. To determine which Big Mac Index measure is a better indicator of exchange rate valuation, a comparison analysis was conducted. This study set out to determine how well the adjusted Big Mac Index performed as a gauge for exchange rate valuation. The research then compares the two Big Mac Index measures' ability to anticipate future exchange rates in order to determine which is more accurate. Data from the South African Reserve Bank and The Economist databases covering 37 nations from 2000 to 2022 were used for the analysis. Exchange rate misalignment trends were assessed globally, and the results indicated that the adjusted BMI was a more accurate measure of purchasing power. Tests of correlation revealed that there was a positive association between the real exchange rate and the Big Mac Index. Findings from a panel ARDL Model indicated that taking into consideration country-specific GDP variations and group heterogeneity can enhance the real exchange rates' ability to predict the raw BMI. The research also focused on the South African Rand to ascertain whether the Big Mac Index validates the Purchasing Power Parity theoretical framework. Using cointegration tests and graphic analysis, it was possible to find evidence for a cointegrating relationship between the real exchange rate and the Big Mac Index measures during the last 20 years. Additionally, a positive correlation between the modified Big Mac Index and terms of trade was discovered in the results, confirming the hypothesis that the Big Mac Index satisfies current account assumptions. Finally, a VEC model demonstrated that the modified BMI outperforms the raw BMI in terms of forecasting estimates. Overall, the study found that the Big Mac Index is more than a bit of fun as per its origin. The results showed that the adjusted Big Mac Index has practical applications and the potential to be considered as an economic theory. , Thesis (MCom) -- Faculty of Commerce, Economics and Economic History, 2024
- Full Text:
- Date Issued: 2024-10-11
Carbonylation of cyclohexene with carbon dioxide (CO2) using transition metals as heterogeneous and homogeneous catalysts
- Authors: Sekaleli, Bafokeng Thabelo
- Date: 2024-10-11
- Subjects: Carbonylation , Carbon dioxide , Catalysts , Transition metals , Cyclohexene
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/464565 , vital:76522
- Description: From a green chemistry perspective, carbon dioxide (CO2) emerges as an appealing C1 synthon, given its abundance in the atmosphere and cost-effectiveness. Many essential chemicals for daily life are derived from fossilized carbon sources like coal, petroleum, and natural gas. However, the by-product of these processes, CO2, poses environmental risks when excessively emitted as a greenhouse gas. Achieving a balance between carbon emissions and removal is crucial to address environmental concerns surrounding CO2. Utilizing CO2 as a C1 source in organic synthesis holds promise for mitigating this balance in the long term. Combining CO2 with other underutilized fine chemicals, such as alkanes, alkenes, and alkynes, to produce more valuable platform chemicals presents an economically viable strategy due to carbon dioxide’s abundance, low cost, and recyclability. Despite its simplicity, CO2's high thermodynamic stability and low kinetic reactivity, owing to its highly oxidized state, pose challenges to its use as a feedstock. Overcoming these hurdles requires catalysts to enhance CO2 reactivity. Our work focuses on developing and employing catalytic systems capable of activating CO2 as a C1 synthon in reactions with cyclohexene and a reducing agent to yield carboxylic acids or esters. In one approach, we have developed heterogeneous catalyst systems comprising transition metals (Au, Fe, Ni, Ru) supported on metal oxide (TiO2). Characterization techniques such as TEM, EDX, UV-Vis, BET, and XRD were used to study the properties of these materials. The catalysts were evaluated in a reaction involving cyclohexene, CO2, and H2O. In another approach, we explored the use of cyclo-tris(tetracarbonylruthenium) [Ru3(CO)12] as a homogeneous catalyst in a reaction involving cyclohexene, methanol, and CO2 in the presence of an ionic liquid, 1-Butyl-3-methylimidazolium chloride ([BMIM]+Cl-). 1H NMR and ATR-FT-IR were utilized to characterize [BMIM]+Cl-. The reaction product was characterised utilizing GC-MS. Upon seeing that Ru3(CO)12 changes color from orange to black when exposed to heat, an investigation was undertaken on the kind of transformations that the catalyst undergoes. This investigation was carried out with the hopes of finding the structures that could be resulting from Ru3(CO)12 during the reaction and their significance to it. The orange and black Ru complexes were characterized utilizing DSC, TGA, ATR-FT-IR and PXRD. , Thesis (MSc) -- Faculty of Science, Chemistry, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Sekaleli, Bafokeng Thabelo
- Date: 2024-10-11
- Subjects: Carbonylation , Carbon dioxide , Catalysts , Transition metals , Cyclohexene
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/464565 , vital:76522
- Description: From a green chemistry perspective, carbon dioxide (CO2) emerges as an appealing C1 synthon, given its abundance in the atmosphere and cost-effectiveness. Many essential chemicals for daily life are derived from fossilized carbon sources like coal, petroleum, and natural gas. However, the by-product of these processes, CO2, poses environmental risks when excessively emitted as a greenhouse gas. Achieving a balance between carbon emissions and removal is crucial to address environmental concerns surrounding CO2. Utilizing CO2 as a C1 source in organic synthesis holds promise for mitigating this balance in the long term. Combining CO2 with other underutilized fine chemicals, such as alkanes, alkenes, and alkynes, to produce more valuable platform chemicals presents an economically viable strategy due to carbon dioxide’s abundance, low cost, and recyclability. Despite its simplicity, CO2's high thermodynamic stability and low kinetic reactivity, owing to its highly oxidized state, pose challenges to its use as a feedstock. Overcoming these hurdles requires catalysts to enhance CO2 reactivity. Our work focuses on developing and employing catalytic systems capable of activating CO2 as a C1 synthon in reactions with cyclohexene and a reducing agent to yield carboxylic acids or esters. In one approach, we have developed heterogeneous catalyst systems comprising transition metals (Au, Fe, Ni, Ru) supported on metal oxide (TiO2). Characterization techniques such as TEM, EDX, UV-Vis, BET, and XRD were used to study the properties of these materials. The catalysts were evaluated in a reaction involving cyclohexene, CO2, and H2O. In another approach, we explored the use of cyclo-tris(tetracarbonylruthenium) [Ru3(CO)12] as a homogeneous catalyst in a reaction involving cyclohexene, methanol, and CO2 in the presence of an ionic liquid, 1-Butyl-3-methylimidazolium chloride ([BMIM]+Cl-). 1H NMR and ATR-FT-IR were utilized to characterize [BMIM]+Cl-. The reaction product was characterised utilizing GC-MS. Upon seeing that Ru3(CO)12 changes color from orange to black when exposed to heat, an investigation was undertaken on the kind of transformations that the catalyst undergoes. This investigation was carried out with the hopes of finding the structures that could be resulting from Ru3(CO)12 during the reaction and their significance to it. The orange and black Ru complexes were characterized utilizing DSC, TGA, ATR-FT-IR and PXRD. , Thesis (MSc) -- Faculty of Science, Chemistry, 2024
- Full Text:
- Date Issued: 2024-10-11
Care as dissent in the art of Georgina Maxim, Gladys Kalichini, Kresiah Mukwazhi, Masimba Hwati and Léonard Pongo
- Authors: Muchemwa, Fadzai Veronica
- Date: 2024-10-11
- Subjects: Dissenting opinions , Ethics of care , Disruption , Art Political aspects Africa , Recognition , Art and society
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/466049 , vital:76680
- Description: The concept of care is proposed as an ethical and practical framework for the reading of the artistic and writing practices of Georgina Maxim, Kresiah Mukwazhi, Gladys Kalichini, Léonard Pongo and Masimba Hwati. In their practices, dissent is both an existential crisis and a constitutive practice. Through small actions, they offer up new narratives. The notion of seeing care as a form of dissent is to simply reflect on the artistic practices that are integrated with or responsive to forms of political protest and dissent based on ethical care practices and what it means to align with those things that matter to us and distancing ourselves from those things that do not. The thesis explores the ethic of care, its possibilities as a dissenting approach, and provides a narrative description of five case studies that exhibit different expressions of care in contemporary art. By prioritising care, there is an educational interest in creating resources and themes for a politically engaged approach to artistic practice and the creation of art. This study also aims to shed light on the power of art as a tool for social and political commentary, and the role of artists as agents of change in society. The study focuses on how these artists use their art to challenge societal norms and political structures, embodying the concept of care as a form of resistance. It underscores the importance of understanding the context in which art is created and the messages it conveys, particularly in societies where freedom of expression may be constrained. The study further investigates how these elements are presented in different ways to show the different manifestations of care and dissent. Through semi-structured interviews, analysis of relevant texts, and a detailed visual analysis of selected works from the five artists, the situational approach was used to explore how meanings are negotiated. The outcome is an expanded proposal for care as dissent and a listening guide as a tool or approach in helping us to listen to marginalised voices, validate experiences, identify barriers and building empathy. , Thesis (MA) -- Faculty of Humanities, Fine Art, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Muchemwa, Fadzai Veronica
- Date: 2024-10-11
- Subjects: Dissenting opinions , Ethics of care , Disruption , Art Political aspects Africa , Recognition , Art and society
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/466049 , vital:76680
- Description: The concept of care is proposed as an ethical and practical framework for the reading of the artistic and writing practices of Georgina Maxim, Kresiah Mukwazhi, Gladys Kalichini, Léonard Pongo and Masimba Hwati. In their practices, dissent is both an existential crisis and a constitutive practice. Through small actions, they offer up new narratives. The notion of seeing care as a form of dissent is to simply reflect on the artistic practices that are integrated with or responsive to forms of political protest and dissent based on ethical care practices and what it means to align with those things that matter to us and distancing ourselves from those things that do not. The thesis explores the ethic of care, its possibilities as a dissenting approach, and provides a narrative description of five case studies that exhibit different expressions of care in contemporary art. By prioritising care, there is an educational interest in creating resources and themes for a politically engaged approach to artistic practice and the creation of art. This study also aims to shed light on the power of art as a tool for social and political commentary, and the role of artists as agents of change in society. The study focuses on how these artists use their art to challenge societal norms and political structures, embodying the concept of care as a form of resistance. It underscores the importance of understanding the context in which art is created and the messages it conveys, particularly in societies where freedom of expression may be constrained. The study further investigates how these elements are presented in different ways to show the different manifestations of care and dissent. Through semi-structured interviews, analysis of relevant texts, and a detailed visual analysis of selected works from the five artists, the situational approach was used to explore how meanings are negotiated. The outcome is an expanded proposal for care as dissent and a listening guide as a tool or approach in helping us to listen to marginalised voices, validate experiences, identify barriers and building empathy. , Thesis (MA) -- Faculty of Humanities, Fine Art, 2024
- Full Text:
- Date Issued: 2024-10-11
Carnivory submerged: aspects of the ecology and ecophysiology of the aquatic Utricularia stellaris L. fil. (Lentibulariaceae) in South Africa
- Authors: Marais, Alice-Jane
- Date: 2024-10-11
- Subjects: Submerged aquatic vegetation , Bladderworts South Africa , Carnivorous plants , Bladderworts Ecology , Bladderworts Ecophysiology , Plant-microbe relationships
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/464473 , vital:76514
- Description: The trapping structures produced by aquatic species of Utricularia have traditionally been interpreted to function as adaptations to capture and break down zooplankton prey, as in other carnivorous plants, to overcome nutrient limitations. However, an increasing number of studies have found that these plants may also rely on benefits derived from living mutualistic microbial communities contained within traps. This study documents aspects of the environmental, growth and physiological characteristics of U. stellaris to inform and to form a basis for future investigation into the plant-microbe interaction. The environmental conditions in which U. stellaris grows were documented to identify potential adverse conditions plants are subject to in situ, from which nutrient limitation was identified as a primary limitation. Plant growth and trapping structures were then assessed to identify possible adaptations of plants to overcome these limitations. The production of trapping structures likely constitutes an adaptive trait, with 30% of total biomass per node allocated to the production of these structures. Based on their capture function, traps may aid plants based on their contents, possibly supplementing plants with nutrients. Although assessments of the habitats of U. stellaris indicate that dissolved CO₂ concentrations in the ambient water are high, CO₂ may still be limiting to the photosynthetic rates of these plants due to viscous water resisting the diffusion of CO₂. The primary site of photosynthesis in U. stellaris is leaves and trap tissue’s contribution to photosynthetic output is negligible. U. stellaris plants are subject to CO₂ limitations in natural pond conditions, making the substantial allocation of resources to non-photosynthetic trapping tissue even more costly. Therefore, benefits gained from trapping structures are likely to be derived from trap contents; having ruled out the possibility that the trap tissue itself is photosynthetic. Trap contents of U. stellaris were assessed. The proportion of traps containing living microbial communities greatly exceeded the proportion containing zooplankton prey. In addition, these communities were found to be diverse, stable, and self-sustaining. These results suggest that trapping structures may be beneficial for both the carnivorous capture of prey and the housing of living microbial communities. These results indicate the plantmicrobe interaction in U. stellaris warrants further study. , Thesis (MSc) -- Faculty of Science, Botany, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Marais, Alice-Jane
- Date: 2024-10-11
- Subjects: Submerged aquatic vegetation , Bladderworts South Africa , Carnivorous plants , Bladderworts Ecology , Bladderworts Ecophysiology , Plant-microbe relationships
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/464473 , vital:76514
- Description: The trapping structures produced by aquatic species of Utricularia have traditionally been interpreted to function as adaptations to capture and break down zooplankton prey, as in other carnivorous plants, to overcome nutrient limitations. However, an increasing number of studies have found that these plants may also rely on benefits derived from living mutualistic microbial communities contained within traps. This study documents aspects of the environmental, growth and physiological characteristics of U. stellaris to inform and to form a basis for future investigation into the plant-microbe interaction. The environmental conditions in which U. stellaris grows were documented to identify potential adverse conditions plants are subject to in situ, from which nutrient limitation was identified as a primary limitation. Plant growth and trapping structures were then assessed to identify possible adaptations of plants to overcome these limitations. The production of trapping structures likely constitutes an adaptive trait, with 30% of total biomass per node allocated to the production of these structures. Based on their capture function, traps may aid plants based on their contents, possibly supplementing plants with nutrients. Although assessments of the habitats of U. stellaris indicate that dissolved CO₂ concentrations in the ambient water are high, CO₂ may still be limiting to the photosynthetic rates of these plants due to viscous water resisting the diffusion of CO₂. The primary site of photosynthesis in U. stellaris is leaves and trap tissue’s contribution to photosynthetic output is negligible. U. stellaris plants are subject to CO₂ limitations in natural pond conditions, making the substantial allocation of resources to non-photosynthetic trapping tissue even more costly. Therefore, benefits gained from trapping structures are likely to be derived from trap contents; having ruled out the possibility that the trap tissue itself is photosynthetic. Trap contents of U. stellaris were assessed. The proportion of traps containing living microbial communities greatly exceeded the proportion containing zooplankton prey. In addition, these communities were found to be diverse, stable, and self-sustaining. These results suggest that trapping structures may be beneficial for both the carnivorous capture of prey and the housing of living microbial communities. These results indicate the plantmicrobe interaction in U. stellaris warrants further study. , Thesis (MSc) -- Faculty of Science, Botany, 2024
- Full Text:
- Date Issued: 2024-10-11
Characterisation, and remote sensing exploration potential, of a hydrothermally mineralised Diorite, Chris Hani district, Eastern Cape, South Africa
- Authors: Johnstone, Shawn Douglas
- Date: 2024-10-11
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/464930 , vital:76558
- Description: Access restricted. Expected release in 2026. , Thesis (MSc) -- Faculty of Science, Geology, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Johnstone, Shawn Douglas
- Date: 2024-10-11
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/464930 , vital:76558
- Description: Access restricted. Expected release in 2026. , Thesis (MSc) -- Faculty of Science, Geology, 2024
- Full Text:
- Date Issued: 2024-10-11
Church music as pedagogy: An investigation through digital storytelling into the role that Southern African Christian Church music praxis played in the musical development of five professional musicians
- Authors: Mathebula, Praise Ntsako
- Date: 2024-10-11
- Subjects: Church music Africa, Southern , Indigenous music , Digital storytelling , Music of Southern Africa , Musicians Africa, Southern , Western education
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/465975 , vital:76673
- Description: Using an ethnographic and autoethnographic approach, this study investigated how the church has influenced the development and practice of five professional musicians practicing in South Africa. This research resulted from discussions with numerous musicians who had their music genesis at church, some of them well-known professionals in the country. Reflecting on the history of church music education that can be traced back to the arrival of the missionaries on the African continent and the different types of music education settings that can be found in South Africa, this thesis analyses the approach and delivery of music pedagogy that exists in the South African church setting. Discussing the introduction of Western musical tools such as tonic-solfa, choral music and four-part singing, this research contextualises the historical effect of mission education of several South African composers, including Tiyo Soga, Enoch Sontonga and John Knox Bokwe. Thereafter, using Digital Storytelling (DS) as a methodology for data collection and Ethnographic Content Analysis (ECA) as an analytic tool, co-researchers were given the opportunity to create data or share their stories in a novel manner, which has proven to develop powerful, honest and self-reflexive results. Important pedagogic themes that emerged as being part of a shared church-led approach to music teaching and learning include practice and consistent performance; collaboration; imitation; embodied and experiential learning, rote learning, and memorisation. Central to using DS as a methodology, this study found that musical identity and early pedagogical approaches to learning music play an important factor in further musical development and education. , Thesis (MA) -- Faculty of Humanities, Music and Musicology, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Mathebula, Praise Ntsako
- Date: 2024-10-11
- Subjects: Church music Africa, Southern , Indigenous music , Digital storytelling , Music of Southern Africa , Musicians Africa, Southern , Western education
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/465975 , vital:76673
- Description: Using an ethnographic and autoethnographic approach, this study investigated how the church has influenced the development and practice of five professional musicians practicing in South Africa. This research resulted from discussions with numerous musicians who had their music genesis at church, some of them well-known professionals in the country. Reflecting on the history of church music education that can be traced back to the arrival of the missionaries on the African continent and the different types of music education settings that can be found in South Africa, this thesis analyses the approach and delivery of music pedagogy that exists in the South African church setting. Discussing the introduction of Western musical tools such as tonic-solfa, choral music and four-part singing, this research contextualises the historical effect of mission education of several South African composers, including Tiyo Soga, Enoch Sontonga and John Knox Bokwe. Thereafter, using Digital Storytelling (DS) as a methodology for data collection and Ethnographic Content Analysis (ECA) as an analytic tool, co-researchers were given the opportunity to create data or share their stories in a novel manner, which has proven to develop powerful, honest and self-reflexive results. Important pedagogic themes that emerged as being part of a shared church-led approach to music teaching and learning include practice and consistent performance; collaboration; imitation; embodied and experiential learning, rote learning, and memorisation. Central to using DS as a methodology, this study found that musical identity and early pedagogical approaches to learning music play an important factor in further musical development and education. , Thesis (MA) -- Faculty of Humanities, Music and Musicology, 2024
- Full Text:
- Date Issued: 2024-10-11
Co-creating a pedagogy of care for our hydrocommons in South Africa
- Authors: Martin, Aaniyah
- Date: 2024-10-11
- Subjects: Teaching Social aspects , Reparations for historical injustices South Africa , Posthumanism , Creation (Literary, artistic, etc.) , Feminism and higher education , Social justice , Environmental justice
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466418 , vital:76726 , DOI https://doi.org/10.21504/10962/466418
- Description: My research focuses on watery relations in a South African context. Our planet, predominantly covered by water, relies on healthy oceans to sustain life by producing oxygen. Oceans, rivers, and wetlands constitute our natural water resources, integral to the hydrological cycle, collectively forming what Neimanis (2009) terms as hydrocommons. Hydrocommons encompass the shared water bodies and resources vital for human and more-than-human inhabitants alike. Caring for our hydrocommons is imperative for the well-being of the planet and all its inhabitants. Yet, the notion of responsibility for their upkeep sparks debate, as it intertwines with concepts of justice, extensively explored in academic discourse (Bozalek & Zembylas 2023). In South Africa, historical patterns of privilege tied to skin colour significantly influence perceptions of responsibility and care. This doctoral research engages with the enduring impacts of the apartheid legacy, which continues to shape notions of belonging, especially for Black and Brown South Africans who were forcibly displaced and restricted from accessing various areas, including urban spaces and natural environments such as beaches and game reserves. My perspective stems from my background as a scientist in the conservation field for over two decades, and transitioning into an educational doctorate with an emphasis on feminist, posthumanist, and care frameworks to address environmental and social justice concerns. Furthermore, I am a Brown Creole woman who was raised as a Muslim in Camissa, South Africa. The overarching question this dissertation seeks to address is; How can reparative care pedagogies reshape the hydrocommons for Black and Brown communities in post-apartheid South Africa? In order to respond to this question, I think diffractively with theory from feminism(s), posthumanism, research-creation and Slow scholarship - all of these are predicated on relational ontologies which embrace diverse ways of knowledge production in caring and meaning-making ways (Springgay & Truman, 2018; Stengers, 2011; Taylor et al, 2020). The research question I have posed is addressed through two key methods of enquiry namely strandlooping (beach walking) and hydro-rugging (stitching and mending). While there has been some literature on walking and mending methodologies from Northern contexts, I have opted to contextualise them within a South African framework with indigenous origins. By developing such methodologies in the local context, I aim to understand their application and relevance within South Africa's diverse cultural and environmental landscape. I have deliberately incorporated indigenous perspectives and practices in order to contribute to a more holistic and nuanced exploration of watery relations through iterative and collaborative events with participants. Chapter One provides an overview of my positionality and research practice by giving voice to those who have been marginalised, silenced and erased for three decades. The 30th anniversary for our first democratic elections was celebrated on the 27th April 2024 whilst I have been finalising my manuscript. The silence and erasure persist today, even though apartheid laws and regulations are no longer in effect. This lingering silence continues to permeate our lives and linger as a haunting presence. Consequently, strandlooping and hydro-rugging emerge as methods of enquiry that foster and provide avenues for care and healing. Chapter Two shares the stories of four Brown bodies and a tidal pool each of whom have a relationship with False Bay. The chapter shows how watery stories are shared through the process of hydro-rugging at the tidal pools. Chapter Three unravels the practice of strandlooping and develops propositions or watermarks to assist other researchers with this practice in their own contexts. Chapter Four articulates hydro-rugging as a method of enquiry and elucidates how the individual hydro-rugs are stitched alongside each other to create the Mother Hydro-rug. Chapter Five introduces three experiential research-creation events with fourth year students to meander and learn from them with regards to care for our hydrocommons. Drawing on relational ways of understanding and engaging with the world, this research culminates in several key implications for reparative care pedagogies in reshaping the hydrocommons. It underscores the importance of not only acknowledging but including diverse modes of knowledge and existence, particularly within Black and Brown communities marginalised by apartheid's racial and ethnic divisions. Additionally, it highlights the significance of challenging traditional educational paradigms entrenched in colonial and apartheid legacies. By prioritising embodied, experiential, and inclusive methodologies, the doctoral thesis advocates for a pedagogical shift toward relationality and process-oriented learning. This thesis prompts a reevaluation of extractive and exploitative educational practices, advocating instead for conviviality and the exploration of relational and embodied meanings and approaches. , Thesis (PhD) -- Faculty of Education, Secondary and Post-School Education, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Martin, Aaniyah
- Date: 2024-10-11
- Subjects: Teaching Social aspects , Reparations for historical injustices South Africa , Posthumanism , Creation (Literary, artistic, etc.) , Feminism and higher education , Social justice , Environmental justice
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466418 , vital:76726 , DOI https://doi.org/10.21504/10962/466418
- Description: My research focuses on watery relations in a South African context. Our planet, predominantly covered by water, relies on healthy oceans to sustain life by producing oxygen. Oceans, rivers, and wetlands constitute our natural water resources, integral to the hydrological cycle, collectively forming what Neimanis (2009) terms as hydrocommons. Hydrocommons encompass the shared water bodies and resources vital for human and more-than-human inhabitants alike. Caring for our hydrocommons is imperative for the well-being of the planet and all its inhabitants. Yet, the notion of responsibility for their upkeep sparks debate, as it intertwines with concepts of justice, extensively explored in academic discourse (Bozalek & Zembylas 2023). In South Africa, historical patterns of privilege tied to skin colour significantly influence perceptions of responsibility and care. This doctoral research engages with the enduring impacts of the apartheid legacy, which continues to shape notions of belonging, especially for Black and Brown South Africans who were forcibly displaced and restricted from accessing various areas, including urban spaces and natural environments such as beaches and game reserves. My perspective stems from my background as a scientist in the conservation field for over two decades, and transitioning into an educational doctorate with an emphasis on feminist, posthumanist, and care frameworks to address environmental and social justice concerns. Furthermore, I am a Brown Creole woman who was raised as a Muslim in Camissa, South Africa. The overarching question this dissertation seeks to address is; How can reparative care pedagogies reshape the hydrocommons for Black and Brown communities in post-apartheid South Africa? In order to respond to this question, I think diffractively with theory from feminism(s), posthumanism, research-creation and Slow scholarship - all of these are predicated on relational ontologies which embrace diverse ways of knowledge production in caring and meaning-making ways (Springgay & Truman, 2018; Stengers, 2011; Taylor et al, 2020). The research question I have posed is addressed through two key methods of enquiry namely strandlooping (beach walking) and hydro-rugging (stitching and mending). While there has been some literature on walking and mending methodologies from Northern contexts, I have opted to contextualise them within a South African framework with indigenous origins. By developing such methodologies in the local context, I aim to understand their application and relevance within South Africa's diverse cultural and environmental landscape. I have deliberately incorporated indigenous perspectives and practices in order to contribute to a more holistic and nuanced exploration of watery relations through iterative and collaborative events with participants. Chapter One provides an overview of my positionality and research practice by giving voice to those who have been marginalised, silenced and erased for three decades. The 30th anniversary for our first democratic elections was celebrated on the 27th April 2024 whilst I have been finalising my manuscript. The silence and erasure persist today, even though apartheid laws and regulations are no longer in effect. This lingering silence continues to permeate our lives and linger as a haunting presence. Consequently, strandlooping and hydro-rugging emerge as methods of enquiry that foster and provide avenues for care and healing. Chapter Two shares the stories of four Brown bodies and a tidal pool each of whom have a relationship with False Bay. The chapter shows how watery stories are shared through the process of hydro-rugging at the tidal pools. Chapter Three unravels the practice of strandlooping and develops propositions or watermarks to assist other researchers with this practice in their own contexts. Chapter Four articulates hydro-rugging as a method of enquiry and elucidates how the individual hydro-rugs are stitched alongside each other to create the Mother Hydro-rug. Chapter Five introduces three experiential research-creation events with fourth year students to meander and learn from them with regards to care for our hydrocommons. Drawing on relational ways of understanding and engaging with the world, this research culminates in several key implications for reparative care pedagogies in reshaping the hydrocommons. It underscores the importance of not only acknowledging but including diverse modes of knowledge and existence, particularly within Black and Brown communities marginalised by apartheid's racial and ethnic divisions. Additionally, it highlights the significance of challenging traditional educational paradigms entrenched in colonial and apartheid legacies. By prioritising embodied, experiential, and inclusive methodologies, the doctoral thesis advocates for a pedagogical shift toward relationality and process-oriented learning. This thesis prompts a reevaluation of extractive and exploitative educational practices, advocating instead for conviviality and the exploration of relational and embodied meanings and approaches. , Thesis (PhD) -- Faculty of Education, Secondary and Post-School Education, 2024
- Full Text:
- Date Issued: 2024-10-11
Co-crystal formation of pharmaceutical and veterinary tranquilizer molecules
- Mngwengwe, Bongeka Naledi Precious
- Authors: Mngwengwe, Bongeka Naledi Precious
- Date: 2024-10-11
- Subjects: Cocrystal , Benzodiazepines , Mechanical chemistry , Midazolam , Tranquilizing drugs
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/464532 , vital:76519
- Description: Midazolam, a 1,4-benzodiazepine derivative is commonly used to treat anxiety, insomnia and may be used as a sedative in anaesthesia as it has calming, anti-convulsant and muscle relaxant properties. Midazolam has a rapid onset but a short duration of action resulting in fewer adverse effects. Midazolam also has the potential to form insoluble crystalline precipitates in pharmaceutical dosage forms such as syrups and solutions, which is a challenge in formulation and process development activities. The primary goal of this research was to prepare multicomponent crystals of midazolam free base, specifically targeting interactions with coformers structurally similar to methyl paraben. Key preparation techniques included neat grinding, liquid-assisted grinding, and slow evaporation. The resulting solid forms were characterized using Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), and powder X-Ray Diffraction (PXRD). In addition, Single-Crystal X-Ray Diffraction (SCXRD) was used to elucidate detailed structural information on the novel multicomponent crystals formed. Successful preparation of midazolam free base from the hydrochloride salt was confirmed through FTIR, DSC, and PXRD analysis. Different co-crystals and salts of midazolam with coformers such as salicylic acid (SA), benzoic acid (BA), 3-hydroxybenzoic acid (3-HBA) and p-aminobenzoic acid (PABA) were synthesized and characterized. The structure of the single crystal obtained from a veterinary tranquilizer solution was solved and found to be a salt that had formed between midazolam free base, midazolam HCl, and methyl paraben. This finding inspired further investigation of similar multicomponent crystals of midazolam and methyl paraben analogues. This study demonstrated the effectiveness of both mechanochemical and slow evaporation methods for the preparation of multicomponent crystals. PXRD and DSC provided insights into the stability and purity of the crystals that had formed and the differences in melting points and PXRD patterns were particularly important in this regard. Differences in FTIR spectra were used to distinguish between different solid forms and to confirm the successful formation of new solid forms. Extensive searches in the Cambridge Structural Database (CSD) confirmed that the multicomponent crystals of midazolam, such as MDZ‧SA, MDZ‧BA, MDZ‧3-HBA, and MDZ‧PABA, had not previously been reported, highlighting the novelty of these findings. The research successfully isolated and characterized several novel multicomponent crystals of midazolam, demonstrating the potential of mechanochemistry and solvent evaporation techniques in the development of pharmaceutical and veterinary medicinal applications. These findings contribute to the understanding of cocrystal formation and provide a foundation for future studies in which the stability and efficacy of midazolam-based formulations can be evaluated. , Thesis (MSc) -- Faculty of Science, Chemistry, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Mngwengwe, Bongeka Naledi Precious
- Date: 2024-10-11
- Subjects: Cocrystal , Benzodiazepines , Mechanical chemistry , Midazolam , Tranquilizing drugs
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/464532 , vital:76519
- Description: Midazolam, a 1,4-benzodiazepine derivative is commonly used to treat anxiety, insomnia and may be used as a sedative in anaesthesia as it has calming, anti-convulsant and muscle relaxant properties. Midazolam has a rapid onset but a short duration of action resulting in fewer adverse effects. Midazolam also has the potential to form insoluble crystalline precipitates in pharmaceutical dosage forms such as syrups and solutions, which is a challenge in formulation and process development activities. The primary goal of this research was to prepare multicomponent crystals of midazolam free base, specifically targeting interactions with coformers structurally similar to methyl paraben. Key preparation techniques included neat grinding, liquid-assisted grinding, and slow evaporation. The resulting solid forms were characterized using Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), and powder X-Ray Diffraction (PXRD). In addition, Single-Crystal X-Ray Diffraction (SCXRD) was used to elucidate detailed structural information on the novel multicomponent crystals formed. Successful preparation of midazolam free base from the hydrochloride salt was confirmed through FTIR, DSC, and PXRD analysis. Different co-crystals and salts of midazolam with coformers such as salicylic acid (SA), benzoic acid (BA), 3-hydroxybenzoic acid (3-HBA) and p-aminobenzoic acid (PABA) were synthesized and characterized. The structure of the single crystal obtained from a veterinary tranquilizer solution was solved and found to be a salt that had formed between midazolam free base, midazolam HCl, and methyl paraben. This finding inspired further investigation of similar multicomponent crystals of midazolam and methyl paraben analogues. This study demonstrated the effectiveness of both mechanochemical and slow evaporation methods for the preparation of multicomponent crystals. PXRD and DSC provided insights into the stability and purity of the crystals that had formed and the differences in melting points and PXRD patterns were particularly important in this regard. Differences in FTIR spectra were used to distinguish between different solid forms and to confirm the successful formation of new solid forms. Extensive searches in the Cambridge Structural Database (CSD) confirmed that the multicomponent crystals of midazolam, such as MDZ‧SA, MDZ‧BA, MDZ‧3-HBA, and MDZ‧PABA, had not previously been reported, highlighting the novelty of these findings. The research successfully isolated and characterized several novel multicomponent crystals of midazolam, demonstrating the potential of mechanochemistry and solvent evaporation techniques in the development of pharmaceutical and veterinary medicinal applications. These findings contribute to the understanding of cocrystal formation and provide a foundation for future studies in which the stability and efficacy of midazolam-based formulations can be evaluated. , Thesis (MSc) -- Faculty of Science, Chemistry, 2024
- Full Text:
- Date Issued: 2024-10-11
Co-management and social equity at Silaka and Hluleka Nature Reserves, South Africa
- Authors: Mtshintsho, Anda
- Date: 2024-10-11
- Subjects: Natural resources Co-management , Social equity , Benefit sharing , Protected areas Public use South Africa Eastern Cape , Indigenous peoples Attitudes
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/464834 , vital:76549
- Description: Co-management of protected areas (PAs) is a desired conservation approach aimed at balancing ecological goals and livelihood needs. Central to co-management are issues related to power sharing, responsibilities and benefit sharing. However, there still remains a dominance of an ecological emphasis in PA management, with studies focusing more on ‘objective’ biodiversity indicators for measuring the effectiveness of protected areas. However, focusing only on ecological indicators addresses a narrow perspective of achieving ecological integrity and misses social dimensions that, in some cases, might be considered more important than technical considerations. Particularly, in contexts with a history of socio-physical displacement of Indigenous people and local communities (IPLC), the social dimensions of wellbeing are complexly embedded into the economic and ecological dimensions, such that ignoring these linkages might jeopardise the success of protected areas. Thus, the aim of this study was to examine the state of research and conceptual advances on social indicators of conservation success in co-managed PAs and stakeholder views and perceptions on socially just conservation in co-managed protected areas in Silaka and Hluleka Nature Reserves, South Africa. To achieve this, a scoping review, semi-structured interviews and futures workshops (using the three horizons framework) were conducted. Findings from the scoping review (chapter 2) revealed that much of the reported social monitoring indicators still rely on quantifiable metrics (i.e., economic benefits) and less on subjective and relational metrics (i.e., qualitative strength of social networks and perceptions). Unsurprisingly, many of the reviewed case studies revealed the use of participation as an indicator of evaluating co-management success. Further, the interviews and futures workshop results in chapter 3 showed that the non-accrual of key co-management expectations such as the employment of local people, benefit-sharing (material or otherwise), participation in decision-making and community development has led to heightened conflicts between the reserve management agency and local people. Consequently, the respondents did not value the co-management arrangements, citing unfulfilled promises. Broadly, the findings of this study emphasise the need for collective and collaborative efforts in developing indicators that are not only socially just but those that are context dependent and sensitive. , Thesis (MSc) -- Faculty of Science, Environmental Science, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Mtshintsho, Anda
- Date: 2024-10-11
- Subjects: Natural resources Co-management , Social equity , Benefit sharing , Protected areas Public use South Africa Eastern Cape , Indigenous peoples Attitudes
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/464834 , vital:76549
- Description: Co-management of protected areas (PAs) is a desired conservation approach aimed at balancing ecological goals and livelihood needs. Central to co-management are issues related to power sharing, responsibilities and benefit sharing. However, there still remains a dominance of an ecological emphasis in PA management, with studies focusing more on ‘objective’ biodiversity indicators for measuring the effectiveness of protected areas. However, focusing only on ecological indicators addresses a narrow perspective of achieving ecological integrity and misses social dimensions that, in some cases, might be considered more important than technical considerations. Particularly, in contexts with a history of socio-physical displacement of Indigenous people and local communities (IPLC), the social dimensions of wellbeing are complexly embedded into the economic and ecological dimensions, such that ignoring these linkages might jeopardise the success of protected areas. Thus, the aim of this study was to examine the state of research and conceptual advances on social indicators of conservation success in co-managed PAs and stakeholder views and perceptions on socially just conservation in co-managed protected areas in Silaka and Hluleka Nature Reserves, South Africa. To achieve this, a scoping review, semi-structured interviews and futures workshops (using the three horizons framework) were conducted. Findings from the scoping review (chapter 2) revealed that much of the reported social monitoring indicators still rely on quantifiable metrics (i.e., economic benefits) and less on subjective and relational metrics (i.e., qualitative strength of social networks and perceptions). Unsurprisingly, many of the reviewed case studies revealed the use of participation as an indicator of evaluating co-management success. Further, the interviews and futures workshop results in chapter 3 showed that the non-accrual of key co-management expectations such as the employment of local people, benefit-sharing (material or otherwise), participation in decision-making and community development has led to heightened conflicts between the reserve management agency and local people. Consequently, the respondents did not value the co-management arrangements, citing unfulfilled promises. Broadly, the findings of this study emphasise the need for collective and collaborative efforts in developing indicators that are not only socially just but those that are context dependent and sensitive. , Thesis (MSc) -- Faculty of Science, Environmental Science, 2024
- Full Text:
- Date Issued: 2024-10-11
Cocrystals, salts and eutectics of anti-tuberculosis medicines
- Authors: Matlapeng, Tsebang Alice
- Date: 2024-10-11
- Subjects: Cocrystal , Tuberculosis , 4-aminosalicylic acid , Isoniazid , Pyrazinamide , Pyrazinoic acid
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/464521 , vital:76518
- Description: Tuberculosis remains as a prominent cause of death worldwide. This infectious disease is treated with first and second line drugs. However, challenges of multi drug resistant tuberculosis and adverse side effects such as depletion of essential B group vitamins in the body by first line drugs, as well as poor physicochemical properties of second line drugs persist. Cocrystallisation of anti-tubercular drugs with various coformers has therefore been used as an alternative method to improve the physicochemical properties of active pharmaceutical ingredients (API) while maintaining their efficacy. The main objective of this study was to carry out cocrystal screening of anti-tubercular API and vitamin B coformers to make drug-drug or drug-vitamin multicomponent complexes. Preparation of the multicomponent complexes was carried out by mechanochemical grinding (neat grinding (NG), liquid assisted grinding (LAG) and slow evaporation. All complexes were characterised using Fourier-transform infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and crystal structures were elucidated using single-crystal X-ray diffraction (SCXRD). The cocrystal screening resulted in the formation of various solid forms, which included cocrystals, salts and eutectic products. Two cocrystals of 4-aminosalicylic acid (PAS) were isolated and characterised. The cocrystal of PAS with isoniazid (INH) demonstrated similar characteristics for both the bulk crystalline material and milled materials. The cocrystal of PAS and pyrazinamide (PYR) prepared using mechanochemical synthesis was met with challenges, while difficulties were also encountered in obtaining suitable crystals for SCXRD analysis. The ground and recrystallised samples of the PAS and pyrazinecarboxylic acid (PCBA) showed distinct differences in their thermal behaviour, with SCXRD revealing the decomposition product phenolammonium-pyrazinecarboxylate salt ‘sans’ the CO2 moiety. Salt formation involving pyridoxine (PN) yielded a salt hydrate with PAS (PN-PAS) and an anhydrous salt with PCBA (PN-PCBA). Both salts exhibited very complex packing arrangements with equally complex thermal behaviour depending on the solvent used during preparation, and the method of preparation. Three eutectic systems involving INH with PYR, PN and pyridoxine hydrochloride (PNꞏHCl) were identified, and their phase diagrams were constructed from DSC data. The eutectic compositions obtained were 1:1 for INH:PYR, 1:1 for INH:PN and 6:4 for INH:PNꞏHCl. Finally, a total of eight multicomponent complexes were prepared using selected API and vitamin B6 components. The results presented here provide motivation for further investigation and evaluation of the pharmacochemical properties of these API. , Thesis (MSc) -- Faculty of Science, Chemistry, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Matlapeng, Tsebang Alice
- Date: 2024-10-11
- Subjects: Cocrystal , Tuberculosis , 4-aminosalicylic acid , Isoniazid , Pyrazinamide , Pyrazinoic acid
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/464521 , vital:76518
- Description: Tuberculosis remains as a prominent cause of death worldwide. This infectious disease is treated with first and second line drugs. However, challenges of multi drug resistant tuberculosis and adverse side effects such as depletion of essential B group vitamins in the body by first line drugs, as well as poor physicochemical properties of second line drugs persist. Cocrystallisation of anti-tubercular drugs with various coformers has therefore been used as an alternative method to improve the physicochemical properties of active pharmaceutical ingredients (API) while maintaining their efficacy. The main objective of this study was to carry out cocrystal screening of anti-tubercular API and vitamin B coformers to make drug-drug or drug-vitamin multicomponent complexes. Preparation of the multicomponent complexes was carried out by mechanochemical grinding (neat grinding (NG), liquid assisted grinding (LAG) and slow evaporation. All complexes were characterised using Fourier-transform infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and crystal structures were elucidated using single-crystal X-ray diffraction (SCXRD). The cocrystal screening resulted in the formation of various solid forms, which included cocrystals, salts and eutectic products. Two cocrystals of 4-aminosalicylic acid (PAS) were isolated and characterised. The cocrystal of PAS with isoniazid (INH) demonstrated similar characteristics for both the bulk crystalline material and milled materials. The cocrystal of PAS and pyrazinamide (PYR) prepared using mechanochemical synthesis was met with challenges, while difficulties were also encountered in obtaining suitable crystals for SCXRD analysis. The ground and recrystallised samples of the PAS and pyrazinecarboxylic acid (PCBA) showed distinct differences in their thermal behaviour, with SCXRD revealing the decomposition product phenolammonium-pyrazinecarboxylate salt ‘sans’ the CO2 moiety. Salt formation involving pyridoxine (PN) yielded a salt hydrate with PAS (PN-PAS) and an anhydrous salt with PCBA (PN-PCBA). Both salts exhibited very complex packing arrangements with equally complex thermal behaviour depending on the solvent used during preparation, and the method of preparation. Three eutectic systems involving INH with PYR, PN and pyridoxine hydrochloride (PNꞏHCl) were identified, and their phase diagrams were constructed from DSC data. The eutectic compositions obtained were 1:1 for INH:PYR, 1:1 for INH:PN and 6:4 for INH:PNꞏHCl. Finally, a total of eight multicomponent complexes were prepared using selected API and vitamin B6 components. The results presented here provide motivation for further investigation and evaluation of the pharmacochemical properties of these API. , Thesis (MSc) -- Faculty of Science, Chemistry, 2024
- Full Text:
- Date Issued: 2024-10-11
Combined biological and chemical control of Fusarium associated with Eldana Saccharina walker in South African sugarcane production
- Authors: Cele, Tholakele Gladness
- Date: 2024-10-11
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466502 , vital:76736
- Description: Restricted access. Expected release in 2026. , Thesis (PhD) -- Faculty of Science, Biochemistry, Microbiology and Bioinformatics, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Cele, Tholakele Gladness
- Date: 2024-10-11
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466502 , vital:76736
- Description: Restricted access. Expected release in 2026. , Thesis (PhD) -- Faculty of Science, Biochemistry, Microbiology and Bioinformatics, 2024
- Full Text:
- Date Issued: 2024-10-11