Localizing selected endocytosis protein candidates in Plasmodium falciparum using GFP-tagged fusion constructs
- Authors: Basson, Travis
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/2680 , vital:20316
- Description: Malaria is a mosquito-borne infectious disease caused by several obligate intracellular protozoan parasites in the Plasmodium genus, with Plasmodium falciparum causing the most widespread cases and malaria deaths. In 2013 there were approximately 190 million cases of the disease and between 584,000 and 855,000 deaths. It is essential to identify novel drug targets and develop novel drug candidates due to the increase in resistance of P. falciparum parasites to the current arsenal of antimalarial drugs. Endocytosis is an essential process in eukaryotic cells in which the external environment is internalized by the cell in order to obtain various particles from the extracellular space. This extracellular cytoplasm is internalized in membrane-bound invaginations at the plasma membrane. During the blood stage of malaria infection, the parasite requires nutrients from the host red blood cell. To obtain these nutrients, the parasite internalizes haemoglobin in large amounts and degrades it in an acidic, lysosome-like organelle, known as the digestive vacuole. Whilst the exact molecular mechanism of malaria parasite endocytosis is not yet fully understood, a number of proteins have been suggested to be involved. The most expedient approach in identifying candidate endocytosis proteins is to investigate parasite homologues of proteins known to be involved in endocytosis in mammalian cells. The three proteins selected for investigation in this study were the P. falciparum homologues of coronin, dynamin 2, and μ4. The coding sequences for the candidate endocytosis proteins were amplified by PCR and cloned into the pARL2-GFP expression vector. P. falciparum 3D7 parasites were transfected with these vectors and the episomal expression of full-length GFP-tagged fusion protein was confirmed by Western blot analysis using commercially available anti-GFP antibodies. Microscopic analysis of live parasites using fluorescence and confocal microscopy was used to determine the localization of the candidate endocytosis proteins. Coronin appeared to display diffuse cytoplasmic GFP localization during the trophozoite stage, arguing against a role in endocytosis. However, distinct localization during the schizont stage at what appears to be the inner membrane complex was observed. Coronin is thus likely required to coordinate the formation of the actin network between the merozoite IMC and the plasma membrane on which the glideosome is dependant for generating the motile forces required for the merozoite motility and invasion of RBCs. Dynamin 2 displayed localization at three potential locii: the parasite periphery (plasma membrane), punctuate regions within the cytoplasm (potentially at membrane bound organelles) and at the parasite food vacuole. The data suggested that dynamin 2 is involved in endocytosis and membrane trafficking in a similar manner to classical dynamins, potentially as a vesicle scission molecule at the plasma membrane, mediating vesicle formation at the food vacuole to recycle membrane to the plasma membrane, and possibly mitochondria organelle division. μ4 displayed transient localization, cycling between cytosolic localization, and localization to distinct regions at the plasma membrane and the food vacuole. Localization of Pfμ4 to the plasma membrane is indicative of a role for μ4 as a part of an adaptor protein (AP) complex which may be responsible for recruitment of clathrin to initiate endocytosis in a manner similar to mammalian AP-2. As was observed with PfDYN2, Pfμ4 localizes to the FV, which suggests that Pfμ4 forms part of a coat complex that mediates the formation of vesicles that recycle membrane from the FV to the parasite plasma membrane. This study showed that expressing proteins as full-length GFP-tagged fusion constructs is an effective approach in the early stages of determining the localization and function of P. falciparum proteins in vitro, and distinguishing between candidates that have a potential role in endocytosis and those that are unlikely to do so.
- Full Text:
- Date Issued: 2016
- Authors: Basson, Travis
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/2680 , vital:20316
- Description: Malaria is a mosquito-borne infectious disease caused by several obligate intracellular protozoan parasites in the Plasmodium genus, with Plasmodium falciparum causing the most widespread cases and malaria deaths. In 2013 there were approximately 190 million cases of the disease and between 584,000 and 855,000 deaths. It is essential to identify novel drug targets and develop novel drug candidates due to the increase in resistance of P. falciparum parasites to the current arsenal of antimalarial drugs. Endocytosis is an essential process in eukaryotic cells in which the external environment is internalized by the cell in order to obtain various particles from the extracellular space. This extracellular cytoplasm is internalized in membrane-bound invaginations at the plasma membrane. During the blood stage of malaria infection, the parasite requires nutrients from the host red blood cell. To obtain these nutrients, the parasite internalizes haemoglobin in large amounts and degrades it in an acidic, lysosome-like organelle, known as the digestive vacuole. Whilst the exact molecular mechanism of malaria parasite endocytosis is not yet fully understood, a number of proteins have been suggested to be involved. The most expedient approach in identifying candidate endocytosis proteins is to investigate parasite homologues of proteins known to be involved in endocytosis in mammalian cells. The three proteins selected for investigation in this study were the P. falciparum homologues of coronin, dynamin 2, and μ4. The coding sequences for the candidate endocytosis proteins were amplified by PCR and cloned into the pARL2-GFP expression vector. P. falciparum 3D7 parasites were transfected with these vectors and the episomal expression of full-length GFP-tagged fusion protein was confirmed by Western blot analysis using commercially available anti-GFP antibodies. Microscopic analysis of live parasites using fluorescence and confocal microscopy was used to determine the localization of the candidate endocytosis proteins. Coronin appeared to display diffuse cytoplasmic GFP localization during the trophozoite stage, arguing against a role in endocytosis. However, distinct localization during the schizont stage at what appears to be the inner membrane complex was observed. Coronin is thus likely required to coordinate the formation of the actin network between the merozoite IMC and the plasma membrane on which the glideosome is dependant for generating the motile forces required for the merozoite motility and invasion of RBCs. Dynamin 2 displayed localization at three potential locii: the parasite periphery (plasma membrane), punctuate regions within the cytoplasm (potentially at membrane bound organelles) and at the parasite food vacuole. The data suggested that dynamin 2 is involved in endocytosis and membrane trafficking in a similar manner to classical dynamins, potentially as a vesicle scission molecule at the plasma membrane, mediating vesicle formation at the food vacuole to recycle membrane to the plasma membrane, and possibly mitochondria organelle division. μ4 displayed transient localization, cycling between cytosolic localization, and localization to distinct regions at the plasma membrane and the food vacuole. Localization of Pfμ4 to the plasma membrane is indicative of a role for μ4 as a part of an adaptor protein (AP) complex which may be responsible for recruitment of clathrin to initiate endocytosis in a manner similar to mammalian AP-2. As was observed with PfDYN2, Pfμ4 localizes to the FV, which suggests that Pfμ4 forms part of a coat complex that mediates the formation of vesicles that recycle membrane from the FV to the parasite plasma membrane. This study showed that expressing proteins as full-length GFP-tagged fusion constructs is an effective approach in the early stages of determining the localization and function of P. falciparum proteins in vitro, and distinguishing between candidates that have a potential role in endocytosis and those that are unlikely to do so.
- Full Text:
- Date Issued: 2016
Mapping Nitrogen Loading in Freshwater Systems: Using Aquatic Biota to Trace Nutrients
- Authors: Motitsoe, Samuel Nkopane
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5945 , http://hdl.handle.net/10962/d1020819
- Description: The majority of river systems in developing countries like South Africa, are found in catchments areas that are densely human populated, therefore are subjected to intense land-use and developmental pressures. Anthropogenic nutrient pollution or the excessive addition of nutrients is one important type of stressors that river systems often experience through intense land-use, which includes poor waste management and agricultural practices. Such events are referred to as the “urban syndrome”, were human populations and developmental demands outpace ecosystem services. Traditional measurements of water quality (e.g. physicochemical and micro-nutrient assessments) and biological monitoring (e.g. South African Scoring System 5, SASS5) techniques for assessing ecosystem health have being widely used to reflect the ecological health and status of river systems. However these techniques have a number of challenges associated with their application. SASS5 which is used most prevalently in southern Africa for example, can only be applied in lotic systems, it is habitat dependent and finally (but arguably most importantly) it cannot identify the source of pollution inputs. Recent laboratory studies using stable isotopic ratios (δ15N and δ13C) of aquatic macrophytes (duckweed: Spirodela sp.) have shown successful differentiation between different N-sources and the mapping of temporal and spatial nitrogen dynamics in freshwater systems. Furthermore δ15N isotopic values of Spirodela sp. showed the capability to act as an early warning indicator of eutrophication, before the onset of aquatic ecosystem degradation. Therefore, this study aimed to field test the potential of sewage plume mapping using the stable isotopic values of Spirodela sp. and aquatic macroinvertebrates at nine study sites on the Bloukrans-Kowie River and ten study sites on the Bushman-New Year’s River systems in the Eastern Cape, South Africa. And more...
- Full Text:
- Date Issued: 2016
- Authors: Motitsoe, Samuel Nkopane
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5945 , http://hdl.handle.net/10962/d1020819
- Description: The majority of river systems in developing countries like South Africa, are found in catchments areas that are densely human populated, therefore are subjected to intense land-use and developmental pressures. Anthropogenic nutrient pollution or the excessive addition of nutrients is one important type of stressors that river systems often experience through intense land-use, which includes poor waste management and agricultural practices. Such events are referred to as the “urban syndrome”, were human populations and developmental demands outpace ecosystem services. Traditional measurements of water quality (e.g. physicochemical and micro-nutrient assessments) and biological monitoring (e.g. South African Scoring System 5, SASS5) techniques for assessing ecosystem health have being widely used to reflect the ecological health and status of river systems. However these techniques have a number of challenges associated with their application. SASS5 which is used most prevalently in southern Africa for example, can only be applied in lotic systems, it is habitat dependent and finally (but arguably most importantly) it cannot identify the source of pollution inputs. Recent laboratory studies using stable isotopic ratios (δ15N and δ13C) of aquatic macrophytes (duckweed: Spirodela sp.) have shown successful differentiation between different N-sources and the mapping of temporal and spatial nitrogen dynamics in freshwater systems. Furthermore δ15N isotopic values of Spirodela sp. showed the capability to act as an early warning indicator of eutrophication, before the onset of aquatic ecosystem degradation. Therefore, this study aimed to field test the potential of sewage plume mapping using the stable isotopic values of Spirodela sp. and aquatic macroinvertebrates at nine study sites on the Bloukrans-Kowie River and ten study sites on the Bushman-New Year’s River systems in the Eastern Cape, South Africa. And more...
- Full Text:
- Date Issued: 2016
Measuring changes in residential segregation in Port Elizabeth, South Africa, from 1996-2011
- Authors: Odayar, Luveshni
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/3641 , vital:20532
- Description: Racial segregation and inequality were the prime objectives of the colonial and apartheid spatial planning policies that governed the spatial development of the South African urban landscape. Since South Africa’s democratic transition after 1994, efforts have been made by government to facilitate racial integration and transform the apartheid urban fabric. Research into post-apartheid segregation is crucial to assess the success of governmental actions enacted thus far, while informing future spatial planning strategies. Most studies of these processes have relied solely on dichotomous indices to measure the extent of segregation between two groups. Few have utilized multi-group indices, which are more suited to investigating changes in multi-ethnic cases. Furthermore, the segregation indices used are typically aspatial. This study investigates the extent to which the segregationist legacy prevails in Port Elizabeth, a place widely considered to be the founding city of urban racial segregation. It also aims to investigate the impact of geographical scale on segregation. Theil’s multi-group Entropy Index and Duncan and Duncan’s Dissimilarity Index were derived from racial population data from the 1996, 2001 and 2011 National Censuses, and GIS was used to map changes in racial diversity both at tract level and across a range of geographical scales. To generate a more holistic understanding of the observed trends, statistical tests were performed to relate the observed patterns to socio-economic determinants, and feedback from the relevant government department was obtained. The results from the entropy indices reveal that segregation levels in Port Elizabeth have declined but still remain high: 84.6 % (1996), 79.2 % (2001) to 71.5 % (2011). This is a similar trend to those found in Cape Town and Johannesburg. The integration that did occur was characterized by one-way patterns of movement into former-White areas; this was predominantly confined to the Indian population, and to a lesser extent, the Coloured population. The vast majority of the African population remains confined to their former designated location areas. The White population remains the most segregated group, despite most of the racial integration occurring in former-White areas. Interview results and statistical tests revealed that persisting racial discrepancies in socio-economic factors (income, employment and education) can be considered major drivers influencing the observed trends in racial integration and persisting desegregation, as well as self-segregation.
- Full Text:
- Date Issued: 2016
- Authors: Odayar, Luveshni
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/3641 , vital:20532
- Description: Racial segregation and inequality were the prime objectives of the colonial and apartheid spatial planning policies that governed the spatial development of the South African urban landscape. Since South Africa’s democratic transition after 1994, efforts have been made by government to facilitate racial integration and transform the apartheid urban fabric. Research into post-apartheid segregation is crucial to assess the success of governmental actions enacted thus far, while informing future spatial planning strategies. Most studies of these processes have relied solely on dichotomous indices to measure the extent of segregation between two groups. Few have utilized multi-group indices, which are more suited to investigating changes in multi-ethnic cases. Furthermore, the segregation indices used are typically aspatial. This study investigates the extent to which the segregationist legacy prevails in Port Elizabeth, a place widely considered to be the founding city of urban racial segregation. It also aims to investigate the impact of geographical scale on segregation. Theil’s multi-group Entropy Index and Duncan and Duncan’s Dissimilarity Index were derived from racial population data from the 1996, 2001 and 2011 National Censuses, and GIS was used to map changes in racial diversity both at tract level and across a range of geographical scales. To generate a more holistic understanding of the observed trends, statistical tests were performed to relate the observed patterns to socio-economic determinants, and feedback from the relevant government department was obtained. The results from the entropy indices reveal that segregation levels in Port Elizabeth have declined but still remain high: 84.6 % (1996), 79.2 % (2001) to 71.5 % (2011). This is a similar trend to those found in Cape Town and Johannesburg. The integration that did occur was characterized by one-way patterns of movement into former-White areas; this was predominantly confined to the Indian population, and to a lesser extent, the Coloured population. The vast majority of the African population remains confined to their former designated location areas. The White population remains the most segregated group, despite most of the racial integration occurring in former-White areas. Interview results and statistical tests revealed that persisting racial discrepancies in socio-economic factors (income, employment and education) can be considered major drivers influencing the observed trends in racial integration and persisting desegregation, as well as self-segregation.
- Full Text:
- Date Issued: 2016
Mental stress among civil engineering construction site agents and foremen in the Nelson Mandela Bay Metropole
- Authors: Haydam, Erich
- Date: 2016
- Subjects: Project management -- South Africa -- Nelson Mandela Bay Municipality , Civil engineers -- Job stress -- South Africa -- Nelson Mandela Bay Municipality , Construction industry -- South Africa -- Nelson Mandela Bay Municipality
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/5545 , vital:20901
- Description: The civil engineering sector of the construction industry as a whole has been suffering from mental stress due to a lack of stress management interventions, rendering employees vulnerable to burnout, poor mental health, and subject to injury on site. The rationale of this study is to explore the prevalence of mental stress in the civil engineering sector of the construction industry, and the potential causes of stress, vis-à-vis the effects it has on an individual. An empirical study based on a descriptive and analytical survey method was conducted among medium to large civil engineering contractors in the Nelson Mandela Bay Metropole (NMBM). The study adopted the use of questionnaires, and a review of the related literature to effectively summarise and describe the collected field data. The sample stratum included civil engineering site agents and foremen. The salient findings include: high job demands, low job control, and low job social support are contributors to stress; site agents and foremen long for more time spent with family and friends; site agents and foremen are exposed to various physical, organisational and socio-economic stressors; site agents and foremen are displaying coping strategies unsupportive of a healthy lifestyle; there is a lack of awareness of stress management in the civil engineering sector of the construction industry; the level of stress experienced by site agents and foremen is rated as a lesser extent; the prevalence of depression among site agents and foremen is rated as a lesser extent; site agents and foremen are at risk of injury due to feeling stressed, and site agents and foremen are exposed to a range of musculoskeletal disorders (MSDs) due to poor ergonomics, and possibly stress too. It can be concluded that stress negatively affects the civil engineering sector of the construction industry by, inter alia, increased employee absence, injuries and accidents, higher staff turnover, depression, and lower levels of production. Furthermore, stress may lead to eventual burnout, rendering an individual at a significantly higher risk of developing physical health complications. Recommendations include: organisations to address the problem of work-family imbalance, by providing more time off to spend with family and loved ones. v Organisations need to promote and implement internal coping strategies, to assist those who are facing strain to effectively deal with their stress. More support from line managers to employees should be provided, as this will increase their resources in terms of job support, job demand, and job control in their working environment. Also, organisations need to promote teambuilding activities and exercise among their employees. Lastly, organisational policy and government legislation need to be revised in the long term, to provide for individual mental wellbeing, and reduced occupational stress.
- Full Text:
- Date Issued: 2016
- Authors: Haydam, Erich
- Date: 2016
- Subjects: Project management -- South Africa -- Nelson Mandela Bay Municipality , Civil engineers -- Job stress -- South Africa -- Nelson Mandela Bay Municipality , Construction industry -- South Africa -- Nelson Mandela Bay Municipality
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/5545 , vital:20901
- Description: The civil engineering sector of the construction industry as a whole has been suffering from mental stress due to a lack of stress management interventions, rendering employees vulnerable to burnout, poor mental health, and subject to injury on site. The rationale of this study is to explore the prevalence of mental stress in the civil engineering sector of the construction industry, and the potential causes of stress, vis-à-vis the effects it has on an individual. An empirical study based on a descriptive and analytical survey method was conducted among medium to large civil engineering contractors in the Nelson Mandela Bay Metropole (NMBM). The study adopted the use of questionnaires, and a review of the related literature to effectively summarise and describe the collected field data. The sample stratum included civil engineering site agents and foremen. The salient findings include: high job demands, low job control, and low job social support are contributors to stress; site agents and foremen long for more time spent with family and friends; site agents and foremen are exposed to various physical, organisational and socio-economic stressors; site agents and foremen are displaying coping strategies unsupportive of a healthy lifestyle; there is a lack of awareness of stress management in the civil engineering sector of the construction industry; the level of stress experienced by site agents and foremen is rated as a lesser extent; the prevalence of depression among site agents and foremen is rated as a lesser extent; site agents and foremen are at risk of injury due to feeling stressed, and site agents and foremen are exposed to a range of musculoskeletal disorders (MSDs) due to poor ergonomics, and possibly stress too. It can be concluded that stress negatively affects the civil engineering sector of the construction industry by, inter alia, increased employee absence, injuries and accidents, higher staff turnover, depression, and lower levels of production. Furthermore, stress may lead to eventual burnout, rendering an individual at a significantly higher risk of developing physical health complications. Recommendations include: organisations to address the problem of work-family imbalance, by providing more time off to spend with family and loved ones. v Organisations need to promote and implement internal coping strategies, to assist those who are facing strain to effectively deal with their stress. More support from line managers to employees should be provided, as this will increase their resources in terms of job support, job demand, and job control in their working environment. Also, organisations need to promote teambuilding activities and exercise among their employees. Lastly, organisational policy and government legislation need to be revised in the long term, to provide for individual mental wellbeing, and reduced occupational stress.
- Full Text:
- Date Issued: 2016
Mesopredator release and the effectiveness of camera traps for estimating mammal abundances in the Eastern Cape, South Africa
- Authors: Taylor, Jonathan Michael
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/3587 , vital:20527
- Description: Remotely operated cameras (camera traps) have become an indispensable tool for many ecologists, particularly those studying rare and elusive animals. A plethora of camera trap makes and models are now commercially available, yet the effects of their varying design features on the quality and quantity of data recorded remains principally unknown. Better understanding of differing camera trap designs is needed before adequate management policies can be implemented, especially when the aim is to protect vulnerable and endangered species such as many carnivores. Habitat loss and human conflict has prompted worldwide declines of apex predator populations. Following this, many smaller predators have undergone population ‘explosions’ due to the lack of top-down forcing, a phenomenon known as mesopredator release. Land use changes in the Eastern Cape of South Africa have caused extensive degradation and fragmentation of the Subtropical Thicket Biome. In addition, coupled with anthropogenic persecution, apex predators including lions (Panthera leo), leopards (P. pardus), and brown hyaenas (Hyaena brunnea) have been extirpated from large areas of their historic range. Removal of these apex predators may provide opportunity for mesopredators, such as black-backed jackals (Canis mesomelas) and caracals (Caracal caracal), to be released from top-down forcing and possibly initiate trophic cascade effects. Therefore, using randomly distributed camera traps, my study aimed to explore the quality and quantity of data collected by different camera trap designs, and to investigate the mesopredator release hypothesis in the Eastern Cape of South Africa. A total of 2,989 trap nights was used to compare camera trap designs. Camera traps with narrow detection zones and fast trigger speeds (≤ 0.25 seconds) recorded a higher diversity of carnivores, but there was no significant difference in the relative abundances of carnivore species recorded by different camera trap models. A total of 19,659 trap nights was used to assess mesopredator relative abundance, occupancy, distribution and daily activity patterns at one site with, and one site without, apex predators. Consistent with the mesopredator release hypothesis, black-backed jackal relative abundance was significantly higher in the absence of apex predators, and this was supported by occupancy analyses. Further, black-backed jackal distribution was significantly concentrated in areas where apex predator activity was low, possibly indicating spatial avoidance. There was no significant difference in caracal relative abundance, occupancy, distribution, or daily activity between sites. These results provide the first indication of mesopredator release of blackbacked jackals in the Eastern Cape. The implications of black-backed jackal release including prey population structure, local extinctions, altered seed dispersal and disease dynamics are discussed.
- Full Text:
- Date Issued: 2016
- Authors: Taylor, Jonathan Michael
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/3587 , vital:20527
- Description: Remotely operated cameras (camera traps) have become an indispensable tool for many ecologists, particularly those studying rare and elusive animals. A plethora of camera trap makes and models are now commercially available, yet the effects of their varying design features on the quality and quantity of data recorded remains principally unknown. Better understanding of differing camera trap designs is needed before adequate management policies can be implemented, especially when the aim is to protect vulnerable and endangered species such as many carnivores. Habitat loss and human conflict has prompted worldwide declines of apex predator populations. Following this, many smaller predators have undergone population ‘explosions’ due to the lack of top-down forcing, a phenomenon known as mesopredator release. Land use changes in the Eastern Cape of South Africa have caused extensive degradation and fragmentation of the Subtropical Thicket Biome. In addition, coupled with anthropogenic persecution, apex predators including lions (Panthera leo), leopards (P. pardus), and brown hyaenas (Hyaena brunnea) have been extirpated from large areas of their historic range. Removal of these apex predators may provide opportunity for mesopredators, such as black-backed jackals (Canis mesomelas) and caracals (Caracal caracal), to be released from top-down forcing and possibly initiate trophic cascade effects. Therefore, using randomly distributed camera traps, my study aimed to explore the quality and quantity of data collected by different camera trap designs, and to investigate the mesopredator release hypothesis in the Eastern Cape of South Africa. A total of 2,989 trap nights was used to compare camera trap designs. Camera traps with narrow detection zones and fast trigger speeds (≤ 0.25 seconds) recorded a higher diversity of carnivores, but there was no significant difference in the relative abundances of carnivore species recorded by different camera trap models. A total of 19,659 trap nights was used to assess mesopredator relative abundance, occupancy, distribution and daily activity patterns at one site with, and one site without, apex predators. Consistent with the mesopredator release hypothesis, black-backed jackal relative abundance was significantly higher in the absence of apex predators, and this was supported by occupancy analyses. Further, black-backed jackal distribution was significantly concentrated in areas where apex predator activity was low, possibly indicating spatial avoidance. There was no significant difference in caracal relative abundance, occupancy, distribution, or daily activity between sites. These results provide the first indication of mesopredator release of blackbacked jackals in the Eastern Cape. The implications of black-backed jackal release including prey population structure, local extinctions, altered seed dispersal and disease dynamics are discussed.
- Full Text:
- Date Issued: 2016
Mesoscale mechanisms of larval transport and settlement in relation to physical factors off the south coast of South Africa: a topographic approach
- Authors: Mian, Shana Iva
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5947 , http://hdl.handle.net/10962/d1020844
- Description: The majority of benthic marine invertebrate life cycles include a meroplanktonic phase. Most marine biologists recognise that this stage could play an important role in dispersal, especially for sedentary or sessile organisms. Recent studies on larval dispersal have found that dispersal does not occur to the extent that was previously believed. Some larvae instead remain close to their natal populations through larval nearshore retention mechanisms, both active and passive. This study attempted to a) describe nearshore distribution patterns of several intertidal larvae in relation to nearshore hydrodynamics, b) infer whether larvae are active or passive in the water column and whether this differs among taxa and c) compare pelagic mussel larval abundance with settlement rates, at 2 bay and 2 open coast sites on the south coast of South Africa to note any topographical effects. At each of the four sites, pelagic samples were collected along 2 transects. Larvae and current speed data were collected at various depths (surface, mid-depth and bottom) at distances of 200, 400, 900 and 2400m offshore of the coast. Settlement samples were collected at sites that were onshore of the pelagic transects using plastic souring pads following previous studies. Pelagic larval distribution showed no effect of topography. Instead larval abundance was highly variable among sample periods and among different taxa. Slow swimming D-stage mussel larvae were found to be positively correlated with both upwelling and turbulence indices suggesting that they behave as passive particles in the water column. The abundances of larval taxa with faster swimming speeds than the D-larvae were negatively correlated with upwelling and did not correlate with turbulence. This suggests that these larvae are more active within the water column than the D-larvae which would theoretically allow them to maintain their position in the water column. Further analysis revealed that mean larval depth correlated with mean depth of shoreward moving water masses regardless of the state of upwelling. These results suggest that larvae were actively selecting the depth at which they were found presumably in order to associate themselves with shoreward moving currents. This interpretation was supported by ontogenetic patterns in the behaviour of barnacle larvae, the nauplii of which were found further offshore as they aged, and closer onshore again once they reach the faster swimming cyprid stage. Although there was no detectable effect of topography on the abundances of planktonic larvae, the settlement section of this study revealed an effect of topography, with higher settlement and recruitment rates at bay sites than at the open coast sites. Settlement rates were seen to be negatively correlated with turbulence at bay sites but not open coast sites. Recruitment rates for each sample event were positively correlated with upwelling at each site. This study found pelagic larvae to be generally active within the water column which allowed them to remain close to the shore regardless of topography and upwelling/turbulence regimes. Although meaningful correlation analyses between pelagic larval supply and settlement rates could not be conducted due to loss of settlement collectors, settlement rates were affected by local topography with higher settlement and recruitment in bay sites.
- Full Text:
- Date Issued: 2016
- Authors: Mian, Shana Iva
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5947 , http://hdl.handle.net/10962/d1020844
- Description: The majority of benthic marine invertebrate life cycles include a meroplanktonic phase. Most marine biologists recognise that this stage could play an important role in dispersal, especially for sedentary or sessile organisms. Recent studies on larval dispersal have found that dispersal does not occur to the extent that was previously believed. Some larvae instead remain close to their natal populations through larval nearshore retention mechanisms, both active and passive. This study attempted to a) describe nearshore distribution patterns of several intertidal larvae in relation to nearshore hydrodynamics, b) infer whether larvae are active or passive in the water column and whether this differs among taxa and c) compare pelagic mussel larval abundance with settlement rates, at 2 bay and 2 open coast sites on the south coast of South Africa to note any topographical effects. At each of the four sites, pelagic samples were collected along 2 transects. Larvae and current speed data were collected at various depths (surface, mid-depth and bottom) at distances of 200, 400, 900 and 2400m offshore of the coast. Settlement samples were collected at sites that were onshore of the pelagic transects using plastic souring pads following previous studies. Pelagic larval distribution showed no effect of topography. Instead larval abundance was highly variable among sample periods and among different taxa. Slow swimming D-stage mussel larvae were found to be positively correlated with both upwelling and turbulence indices suggesting that they behave as passive particles in the water column. The abundances of larval taxa with faster swimming speeds than the D-larvae were negatively correlated with upwelling and did not correlate with turbulence. This suggests that these larvae are more active within the water column than the D-larvae which would theoretically allow them to maintain their position in the water column. Further analysis revealed that mean larval depth correlated with mean depth of shoreward moving water masses regardless of the state of upwelling. These results suggest that larvae were actively selecting the depth at which they were found presumably in order to associate themselves with shoreward moving currents. This interpretation was supported by ontogenetic patterns in the behaviour of barnacle larvae, the nauplii of which were found further offshore as they aged, and closer onshore again once they reach the faster swimming cyprid stage. Although there was no detectable effect of topography on the abundances of planktonic larvae, the settlement section of this study revealed an effect of topography, with higher settlement and recruitment rates at bay sites than at the open coast sites. Settlement rates were seen to be negatively correlated with turbulence at bay sites but not open coast sites. Recruitment rates for each sample event were positively correlated with upwelling at each site. This study found pelagic larvae to be generally active within the water column which allowed them to remain close to the shore regardless of topography and upwelling/turbulence regimes. Although meaningful correlation analyses between pelagic larval supply and settlement rates could not be conducted due to loss of settlement collectors, settlement rates were affected by local topography with higher settlement and recruitment in bay sites.
- Full Text:
- Date Issued: 2016
Monitoring changes in vegetation distribution to ascertain the extent of degradation in the savannas of Nkonkobe Local Municipality, Eastern Cape, South Africa
- Authors: Masiza, Wonga
- Date: 2016
- Subjects: Savanna ecology -- South Africa -- Eastern Cape Land degradation -- South Africa -- Eastern Cape Vegetation management -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/2027 , vital:27598
- Description: Savanna degradation is an environmental problem occurring in most countries around the world and it poses threats to biodiversity conservation, the food industry, and other economic sectors. According to FAO, South Africa’s rangelands exhibit the highest rate of fragmentation in comparison to range ecosystems in neighbouring countries including Lesotho and Swaziland, and consensus among researchers is that communal rangelands are more degraded than commercial rangelands. Although researchers and communities have identified the occurrence of land degradation in communal savannas at a local scale, land degradation has been poorly estimated because little has been done to quantify the extent and dynamics of perceived and observed changes associated with land degradation. The main goal of this study is to provide empirical insights on the direction of changes in the communal savannas of Nkonkobe Local Municipality in order to inform policy formulation and implementation. Additional to the communal sites is a private farm included for comparative analysis of trends in communal and commercial savannas. Landsat imagery was used to map, assess, and quantify the extent of land degradation in Nkonkobe Local Municipality, over a period of 30 years between 1984 and 2014. Field investigations were undertaken in June 2015 to acquire reference data to guide supervised classification of Landsat images. Three algorithms (Mahalanobis-distance, Minimum-distance, and Maximum likelihood classification) were compared to identify a classifier that produced the best results. The maximum likelihood classifier produced the best results with classification accuracy levels of 95.24 percent, 89.66 percent, and 95.65 percent for Honeydale Farm, Thyume, and Sheshegu respectively. Regression analysis revealed that both communal and private lands have experienced statistically significant increases in bush encroachment and decreases in surface water. Communal savannas have been confronted more by expansion of built-up area, decrease in open grassland, abandonment of arable land, soil erosion, and a steady invasion by Acacia Karroo compared to the privately owned commercial farm. The land cover changes measured through this investigation suggest an environmental shift that threatens biodiversity and agricultural activity. The study provides empirically informed insights about the direction to which these savannas are changing with the hope that the findings will prompt formulation and implementation of effective policies.
- Full Text:
- Date Issued: 2016
- Authors: Masiza, Wonga
- Date: 2016
- Subjects: Savanna ecology -- South Africa -- Eastern Cape Land degradation -- South Africa -- Eastern Cape Vegetation management -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/2027 , vital:27598
- Description: Savanna degradation is an environmental problem occurring in most countries around the world and it poses threats to biodiversity conservation, the food industry, and other economic sectors. According to FAO, South Africa’s rangelands exhibit the highest rate of fragmentation in comparison to range ecosystems in neighbouring countries including Lesotho and Swaziland, and consensus among researchers is that communal rangelands are more degraded than commercial rangelands. Although researchers and communities have identified the occurrence of land degradation in communal savannas at a local scale, land degradation has been poorly estimated because little has been done to quantify the extent and dynamics of perceived and observed changes associated with land degradation. The main goal of this study is to provide empirical insights on the direction of changes in the communal savannas of Nkonkobe Local Municipality in order to inform policy formulation and implementation. Additional to the communal sites is a private farm included for comparative analysis of trends in communal and commercial savannas. Landsat imagery was used to map, assess, and quantify the extent of land degradation in Nkonkobe Local Municipality, over a period of 30 years between 1984 and 2014. Field investigations were undertaken in June 2015 to acquire reference data to guide supervised classification of Landsat images. Three algorithms (Mahalanobis-distance, Minimum-distance, and Maximum likelihood classification) were compared to identify a classifier that produced the best results. The maximum likelihood classifier produced the best results with classification accuracy levels of 95.24 percent, 89.66 percent, and 95.65 percent for Honeydale Farm, Thyume, and Sheshegu respectively. Regression analysis revealed that both communal and private lands have experienced statistically significant increases in bush encroachment and decreases in surface water. Communal savannas have been confronted more by expansion of built-up area, decrease in open grassland, abandonment of arable land, soil erosion, and a steady invasion by Acacia Karroo compared to the privately owned commercial farm. The land cover changes measured through this investigation suggest an environmental shift that threatens biodiversity and agricultural activity. The study provides empirically informed insights about the direction to which these savannas are changing with the hope that the findings will prompt formulation and implementation of effective policies.
- Full Text:
- Date Issued: 2016
Movement patterns of Cape stumpnose, Rhabdosargus holubi (Sparidae), in the Kowie Estuary, South Africa
- Authors: Grant, Gareth Neil
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/982 , vital:20010
- Description: Rhabdosargus holubi is an ubiquitous estuary-dependent fishery species endemic to southern Africa. Although aspects of its recruitment dynamics from sea to estuary have received considerable research attention, little is known about its movement behaviour within estuarine systems. Fishery surveys have also revealed that R. holubi is a dominant species in catches within several temperate estuaries in South Africa. Therefore, investigating movement behaviour is fundamental to understanding the ecology of this species and providing a means for implementing effective fisheries management strategies. This study made use of passive acoustic telemetry to quantify the movement patterns of juvenile R. holubi in the Kowie Estuary, in the Eastern Cape Province of South Africa. Previous studies have revealed that surgically implanted transmitters may have adverse effects on the physiology and behaviour of tagged fish. Therefore, due to the small size of juvenile R. holubi, an a priori transmitter-effect experiment was undertaken. This experiment revealed that juvenile R. holubi (146-217 mm fork length) were not adversely affected by the surgical implantation of acoustic transmitters (7 mm Ø, 1.6 g out of water) and hence acoustic telemetry was well suited to monitoring the movements of this species. A 4-month telemetry study evaluated the movement patterns of 21 juveniles (140-190 mm fork length) tagged in three equal batches along the length of the estuary. Specific aspects of their movement included space use patterns, habitat connectivity, and the influences of geophysical cycles and environmental variables. Tagged fish exhibited high residency, which varied between each release site area. The mean length of estuary used was greater for the upper batch (15.65 ± 6.49 km) than the middle and lower batches (7.36 ± 3.68 and 2.67 ± 2 km, respectively). In terms of habitat connectivity, once the tagged fish left the estuary, they generally did not return. Tagged R. holubi spent the majority (83%) of their monitoring periods within the estuarine environment, with the sea (16%) and riverine (1%) environments being utilised to a lesser extent. Diel and tidal cycles influenced the movement patterns of juvenile R. holubi. However, the high levels of residency meant that fine-scale movements were difficult to detect due to the acoustic receiver deployment configuration (i.e. receivers moored one kilometer apart). The influence of environmental variables on the movement of individuals, modelled with general linear mixed models (GLMMs), revealed that the effects of river inflow and water temperature were greatest. Increased river inflow caused individuals to use larger portions of the estuary. Increased water temperature, particularly river temperature, caused individuals to shift their distributions downstream (towards the mouth of the estuary). This study highlighted the importance of estuarine nursery habitats to R. holubi, suggesting that a loss or reduction of healthy estuarine habitats may lead to significant declines in the abundance of this species. Furthermore, extreme resident behaviour suggests that no-take area closures (estuarine protected areas) would be an effective management strategy for this important fishery species.
- Full Text:
- Date Issued: 2016
- Authors: Grant, Gareth Neil
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/982 , vital:20010
- Description: Rhabdosargus holubi is an ubiquitous estuary-dependent fishery species endemic to southern Africa. Although aspects of its recruitment dynamics from sea to estuary have received considerable research attention, little is known about its movement behaviour within estuarine systems. Fishery surveys have also revealed that R. holubi is a dominant species in catches within several temperate estuaries in South Africa. Therefore, investigating movement behaviour is fundamental to understanding the ecology of this species and providing a means for implementing effective fisheries management strategies. This study made use of passive acoustic telemetry to quantify the movement patterns of juvenile R. holubi in the Kowie Estuary, in the Eastern Cape Province of South Africa. Previous studies have revealed that surgically implanted transmitters may have adverse effects on the physiology and behaviour of tagged fish. Therefore, due to the small size of juvenile R. holubi, an a priori transmitter-effect experiment was undertaken. This experiment revealed that juvenile R. holubi (146-217 mm fork length) were not adversely affected by the surgical implantation of acoustic transmitters (7 mm Ø, 1.6 g out of water) and hence acoustic telemetry was well suited to monitoring the movements of this species. A 4-month telemetry study evaluated the movement patterns of 21 juveniles (140-190 mm fork length) tagged in three equal batches along the length of the estuary. Specific aspects of their movement included space use patterns, habitat connectivity, and the influences of geophysical cycles and environmental variables. Tagged fish exhibited high residency, which varied between each release site area. The mean length of estuary used was greater for the upper batch (15.65 ± 6.49 km) than the middle and lower batches (7.36 ± 3.68 and 2.67 ± 2 km, respectively). In terms of habitat connectivity, once the tagged fish left the estuary, they generally did not return. Tagged R. holubi spent the majority (83%) of their monitoring periods within the estuarine environment, with the sea (16%) and riverine (1%) environments being utilised to a lesser extent. Diel and tidal cycles influenced the movement patterns of juvenile R. holubi. However, the high levels of residency meant that fine-scale movements were difficult to detect due to the acoustic receiver deployment configuration (i.e. receivers moored one kilometer apart). The influence of environmental variables on the movement of individuals, modelled with general linear mixed models (GLMMs), revealed that the effects of river inflow and water temperature were greatest. Increased river inflow caused individuals to use larger portions of the estuary. Increased water temperature, particularly river temperature, caused individuals to shift their distributions downstream (towards the mouth of the estuary). This study highlighted the importance of estuarine nursery habitats to R. holubi, suggesting that a loss or reduction of healthy estuarine habitats may lead to significant declines in the abundance of this species. Furthermore, extreme resident behaviour suggests that no-take area closures (estuarine protected areas) would be an effective management strategy for this important fishery species.
- Full Text:
- Date Issued: 2016
Penguin parenting : assortative mating, nest attendance and sex-specific chick provisioning in the African Penguin (Spheniscus demersus)
- Authors: Smith, Diane Lauren
- Date: 2016
- Subjects: African penguin , Penguins -- South Africa , Penguins -- Sexual behavior , Parental behavior in animals
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5943 , http://hdl.handle.net/10962/d1019993
- Description: Animal behaviour is especially sensitive to environmental variability and prey availability during the breeding season, and this is particularly true for non-volant, central place foragers such as the endangered African Penguin (Spheniscus demersus). Individual sex and morphology, as well as the level of assortment within mated pairs can influence both the behaviour and the reproductive success of species exhibiting biparental care. This study made use of a large biometric database and nest attendance video footage to determine the influence of intrinsic (assortative mating, brood size and chick age) and extrinsic (environmental conditions, anthropic disturbance) factors on breeding behaviour and performance of African Penguins on Bird Island, Algoa Bay, during peak breeding (March - July) in 2013. While sexual dimorphism in African Penguins is subtle, the colony-specific discriminant functions presented here provide an accurate sexing tool when only bill and flipper length are available. Despite the premise that selection of a large, high-quality mate in this longlived, monogamous seabird governs lifetime fitness, only low levels of assortative mating were found, and this only for earlier breeders, when larger females (but not males) bred. The 2013 season was a particularly successful one, coinciding with above-average sardine and anchovy abundance, and almost 80 percent of monitored nests were double-brooded, with very low levels of mortality. A- and B-chicks of double broods and singleton chicks grew at similar rates and exhibited similar body condition indices. In these conditions, chick developmental rates were independent of parental size, assortment or provisioning behaviour. Females raising a double brood were significantly lighter and in poorer body condition than those raising a single chick, although the same trend was not evident in males. Offspring sex ratio in 2013 (2.27:1) favoured male chicks, suggesting that there is potential to over-produce the larger sex when resources are plentiful. Peak nest arrival and departure times of parents did not change over the course of monitored breeding attempts (March-June), nor were they different for disturbed and undisturbed nests or for a single or double brood. The increase in CCTV-observed provisioning rate as chicks grew larger was best explained by brood size, at-sea chlorophyll a concentration, and maximum air temperature, but was unrelated to parental morphology or assortative index. Importantly, parental absenteeism commenced earlier and was markedly greater in nests frequently handled by researchers than in undisturbed nests. Both the time spent together by parents, and absenteeism were measurably affected by maximum afternoon air temperatures, the effects of which are expected to be exacerbated by poorer foraging conditions and climate change. A third of manually-monitored nests shared chick-guarding duties unequally, although this phenomenon was independent of parental sex or morphology. The adaptive benefits of mating patterns and division of labour during chick-rearing may only become apparent in a year of below-average food availability and it is highly recommended that this study be repeated in a year of scarce food resources. These findings augment past foraging ecology studies and demonstrate that investigator disturbance and environmental conditions can affect the nesting behaviour of this highly threatened seabird.
- Full Text:
- Date Issued: 2016
- Authors: Smith, Diane Lauren
- Date: 2016
- Subjects: African penguin , Penguins -- South Africa , Penguins -- Sexual behavior , Parental behavior in animals
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5943 , http://hdl.handle.net/10962/d1019993
- Description: Animal behaviour is especially sensitive to environmental variability and prey availability during the breeding season, and this is particularly true for non-volant, central place foragers such as the endangered African Penguin (Spheniscus demersus). Individual sex and morphology, as well as the level of assortment within mated pairs can influence both the behaviour and the reproductive success of species exhibiting biparental care. This study made use of a large biometric database and nest attendance video footage to determine the influence of intrinsic (assortative mating, brood size and chick age) and extrinsic (environmental conditions, anthropic disturbance) factors on breeding behaviour and performance of African Penguins on Bird Island, Algoa Bay, during peak breeding (March - July) in 2013. While sexual dimorphism in African Penguins is subtle, the colony-specific discriminant functions presented here provide an accurate sexing tool when only bill and flipper length are available. Despite the premise that selection of a large, high-quality mate in this longlived, monogamous seabird governs lifetime fitness, only low levels of assortative mating were found, and this only for earlier breeders, when larger females (but not males) bred. The 2013 season was a particularly successful one, coinciding with above-average sardine and anchovy abundance, and almost 80 percent of monitored nests were double-brooded, with very low levels of mortality. A- and B-chicks of double broods and singleton chicks grew at similar rates and exhibited similar body condition indices. In these conditions, chick developmental rates were independent of parental size, assortment or provisioning behaviour. Females raising a double brood were significantly lighter and in poorer body condition than those raising a single chick, although the same trend was not evident in males. Offspring sex ratio in 2013 (2.27:1) favoured male chicks, suggesting that there is potential to over-produce the larger sex when resources are plentiful. Peak nest arrival and departure times of parents did not change over the course of monitored breeding attempts (March-June), nor were they different for disturbed and undisturbed nests or for a single or double brood. The increase in CCTV-observed provisioning rate as chicks grew larger was best explained by brood size, at-sea chlorophyll a concentration, and maximum air temperature, but was unrelated to parental morphology or assortative index. Importantly, parental absenteeism commenced earlier and was markedly greater in nests frequently handled by researchers than in undisturbed nests. Both the time spent together by parents, and absenteeism were measurably affected by maximum afternoon air temperatures, the effects of which are expected to be exacerbated by poorer foraging conditions and climate change. A third of manually-monitored nests shared chick-guarding duties unequally, although this phenomenon was independent of parental sex or morphology. The adaptive benefits of mating patterns and division of labour during chick-rearing may only become apparent in a year of below-average food availability and it is highly recommended that this study be repeated in a year of scarce food resources. These findings augment past foraging ecology studies and demonstrate that investigator disturbance and environmental conditions can affect the nesting behaviour of this highly threatened seabird.
- Full Text:
- Date Issued: 2016
Petrogenetic implications for the Merensky Reef: a platinum-group element distribution study from wide-reef facies in the western Bushveld Complex, RSA
- Authors: Largatzis, Savvas Anthony
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/3167 , vital:20380
- Description: Despite decades of research and its economic importance, the formation of the Merensky Reef still remains controversial. This study reports on the distribution of platinum-group elements within widereef facies in an attempt to identify petrogenetic controls in the formation of the Merensky Reef. Widereef Merensky was sampled from Eland Platinum Mines in the western Bushveld. Macroscopic investigation of the drillcore identified a basal chromitite stringer overlying an anorthositic footwall. The reef comprised a pyroxenite unit while the hangingwall comprised noritic, leuconoritic and anorthositic units (upwards the stratigraphy). Furthermore, an anorthositic seam was identified within the pyroxenite reef, near the top of the unit. Ophitic textures of orthopyroxene oikocrysts comprising inclusions of plagioclase chadacrysts suggest that the crystallization of plagioclase preceded the crystallization of orthopyroxene. Furthermore, plagioclase and orthopyroxene were shown to be in mineral disequilibrium with one another. Pervasive hydrous alteration features throughout the Merensky Reef suggest late stage deuteric alteration. Mineral chemistry of plagioclase cores recorded ranges for An content in the Merensky Reef as follows: An72-79 in the anorthositic footwall, An71-77 in the chromitite stringer, An45-78 in the pyroxenite reef unit, An47-73 in the anorthosite reef unit, An72-76 in the norite hangingwall, An75-77 in the leuconorite hangingwall and An72-77 in the anorthosite hangingwall. This suggest that the reef units were more evolved than the footwall and hangingwall units. Furthermore, plagioclase showed reverse zoning in the anorthosite footwall unit while normal zoning was identified in the anorthosite reef unit. This suggested that the footwall unit underwent reheating and re-equilibration with a hotter, more primitive magma (also evident in recrystallization textures) while the anorthositic reef unit cooled relatively slowly and interstitial plagioclase present within this unit equilibrated with a trapped, more evolved liquid. The pyroxenite reef unit shows enrichment in incompatible elements and corresponding negative Eu anomalies, indicating the presence of trapped liquids. Cu, Ni and S concentrations remained low throughout the reef with the exception of a peak underlying the anorthositic seam and further enrichment underlying this peak. Platinum-group element geochemistry identified two major peaks: an upper peak which coincided with the peaks for Cu, Ni and S, and showed preferential enrichment in Pd and Au relative to other PGE, and a lower peak which coincided with the presence of chromitite and showed the preferential enrichment of Os, Ir, Ru, Rh and Pt relative to Pd, Au, Cu and Ni. The formation of the lower peak was consistent with a model involving the co-precipitation of chromite and PGE clusters (as PGM) while the upper peak was attributed to a model involving the collection of PGE by an immiscible sulphide liquid. Moreover, high Cu/Pd and Pt/Pd ratios in the lower pyroxenite unit indicated a process involving sulphide fractional segregation and scavenging while the inverse, present within the upper pyroxenite unit, suggested a more dynamic system involving the introduction of PGE-undepleted magma and S during simultaneous sulphide precipitation. Furthermore, a separation of PPGE peaks from IPGE peaks was observed within the pyroxenite unit, indicating a different partitioning behavior between PPGE and IPGE. The separation of these peaks is attributed to a sulphide liquid fractionation model while depletion haloes occurring in the proximity of the main PGE peaks was suggested to form through an Ostwald-ripening type mechanism. The results of this study are consistent with a model for the formation of the Merensky Reef involving a combination of geochemical processes, including sulphide segregation and fractionation, as well as multiple replenishments of magma.
- Full Text:
- Date Issued: 2016
- Authors: Largatzis, Savvas Anthony
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/3167 , vital:20380
- Description: Despite decades of research and its economic importance, the formation of the Merensky Reef still remains controversial. This study reports on the distribution of platinum-group elements within widereef facies in an attempt to identify petrogenetic controls in the formation of the Merensky Reef. Widereef Merensky was sampled from Eland Platinum Mines in the western Bushveld. Macroscopic investigation of the drillcore identified a basal chromitite stringer overlying an anorthositic footwall. The reef comprised a pyroxenite unit while the hangingwall comprised noritic, leuconoritic and anorthositic units (upwards the stratigraphy). Furthermore, an anorthositic seam was identified within the pyroxenite reef, near the top of the unit. Ophitic textures of orthopyroxene oikocrysts comprising inclusions of plagioclase chadacrysts suggest that the crystallization of plagioclase preceded the crystallization of orthopyroxene. Furthermore, plagioclase and orthopyroxene were shown to be in mineral disequilibrium with one another. Pervasive hydrous alteration features throughout the Merensky Reef suggest late stage deuteric alteration. Mineral chemistry of plagioclase cores recorded ranges for An content in the Merensky Reef as follows: An72-79 in the anorthositic footwall, An71-77 in the chromitite stringer, An45-78 in the pyroxenite reef unit, An47-73 in the anorthosite reef unit, An72-76 in the norite hangingwall, An75-77 in the leuconorite hangingwall and An72-77 in the anorthosite hangingwall. This suggest that the reef units were more evolved than the footwall and hangingwall units. Furthermore, plagioclase showed reverse zoning in the anorthosite footwall unit while normal zoning was identified in the anorthosite reef unit. This suggested that the footwall unit underwent reheating and re-equilibration with a hotter, more primitive magma (also evident in recrystallization textures) while the anorthositic reef unit cooled relatively slowly and interstitial plagioclase present within this unit equilibrated with a trapped, more evolved liquid. The pyroxenite reef unit shows enrichment in incompatible elements and corresponding negative Eu anomalies, indicating the presence of trapped liquids. Cu, Ni and S concentrations remained low throughout the reef with the exception of a peak underlying the anorthositic seam and further enrichment underlying this peak. Platinum-group element geochemistry identified two major peaks: an upper peak which coincided with the peaks for Cu, Ni and S, and showed preferential enrichment in Pd and Au relative to other PGE, and a lower peak which coincided with the presence of chromitite and showed the preferential enrichment of Os, Ir, Ru, Rh and Pt relative to Pd, Au, Cu and Ni. The formation of the lower peak was consistent with a model involving the co-precipitation of chromite and PGE clusters (as PGM) while the upper peak was attributed to a model involving the collection of PGE by an immiscible sulphide liquid. Moreover, high Cu/Pd and Pt/Pd ratios in the lower pyroxenite unit indicated a process involving sulphide fractional segregation and scavenging while the inverse, present within the upper pyroxenite unit, suggested a more dynamic system involving the introduction of PGE-undepleted magma and S during simultaneous sulphide precipitation. Furthermore, a separation of PPGE peaks from IPGE peaks was observed within the pyroxenite unit, indicating a different partitioning behavior between PPGE and IPGE. The separation of these peaks is attributed to a sulphide liquid fractionation model while depletion haloes occurring in the proximity of the main PGE peaks was suggested to form through an Ostwald-ripening type mechanism. The results of this study are consistent with a model for the formation of the Merensky Reef involving a combination of geochemical processes, including sulphide segregation and fractionation, as well as multiple replenishments of magma.
- Full Text:
- Date Issued: 2016
Population assessment and feeding ecology of brown hyenas (hyaena brunnea) in Mountain Zebra National Park, Eastern Cape, South Africa
- Authors: Comley, Jessica
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/2862 , vital:20336
- Description: The development of many small (<400 km2), enclosed game reserves in the Eastern Cape Province of South Africa over the past 25 years has contributed greatly to the conservation of large carnivores. However, the brown hyena (Hyaena brunnea) is one of the least studied large carnivores in South Africa. Nevertheless, the reintroduction of this species (n=3 in 2008) into Mountain Zebra National Park (MZNP) provided the perfect opportunity to broaden our understanding of the role that this carnivore plays in an enclosed system. Camera trap data was collected for just over a year from April 2014 to April 2015 and brown hyena density estimates were calculated using spatially explicit capture-recapture analysis. Left-side images of brown hyenas were used in the analysis and 12 individuals were positively identified. The best model to estimate brown hyena density included a road covariate and estimated brown hyena density to be 6-10 individuals/100 km2 (an absolute abundance of between 12 and 21 individuals), which is higher than densities calculated for brown hyenas in other arid, open systems. In, addition, brown hyena scat samples were collected over a five year period from April 2011 to June 2015 and standard techniques for scat analysis were used to identify prey items. Cheetah (Acinonyx jubatus) and lion (Panthera leo) kill site data were used to investigate the impacts of these species on the diet of brown hyenas. Before the release of lions brown hyenas predominantly scavenged on medium-sized mammals, which was what the cheetahs mainly killed. However, after the release of the lions, brown hyenas predominantly scavenged on large mammals, which was what the lions primarily killed. The results from my study indicate that brown hyenas are most likely reaching high densities in enclosed systems, due to increased scavenging opportunities provided by other large predators. The rapid increase of brown hyena densities from small founder populations in enclosed reserves could result in inbreeding. Therefore, in order to successfully conserve brown hyenas and other large carnivores in South Africa, continual post-release monitoring and possible implementation of meta-population management schemes is required.
- Full Text:
- Date Issued: 2016
- Authors: Comley, Jessica
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/2862 , vital:20336
- Description: The development of many small (<400 km2), enclosed game reserves in the Eastern Cape Province of South Africa over the past 25 years has contributed greatly to the conservation of large carnivores. However, the brown hyena (Hyaena brunnea) is one of the least studied large carnivores in South Africa. Nevertheless, the reintroduction of this species (n=3 in 2008) into Mountain Zebra National Park (MZNP) provided the perfect opportunity to broaden our understanding of the role that this carnivore plays in an enclosed system. Camera trap data was collected for just over a year from April 2014 to April 2015 and brown hyena density estimates were calculated using spatially explicit capture-recapture analysis. Left-side images of brown hyenas were used in the analysis and 12 individuals were positively identified. The best model to estimate brown hyena density included a road covariate and estimated brown hyena density to be 6-10 individuals/100 km2 (an absolute abundance of between 12 and 21 individuals), which is higher than densities calculated for brown hyenas in other arid, open systems. In, addition, brown hyena scat samples were collected over a five year period from April 2011 to June 2015 and standard techniques for scat analysis were used to identify prey items. Cheetah (Acinonyx jubatus) and lion (Panthera leo) kill site data were used to investigate the impacts of these species on the diet of brown hyenas. Before the release of lions brown hyenas predominantly scavenged on medium-sized mammals, which was what the cheetahs mainly killed. However, after the release of the lions, brown hyenas predominantly scavenged on large mammals, which was what the lions primarily killed. The results from my study indicate that brown hyenas are most likely reaching high densities in enclosed systems, due to increased scavenging opportunities provided by other large predators. The rapid increase of brown hyena densities from small founder populations in enclosed reserves could result in inbreeding. Therefore, in order to successfully conserve brown hyenas and other large carnivores in South Africa, continual post-release monitoring and possible implementation of meta-population management schemes is required.
- Full Text:
- Date Issued: 2016
Potential benefits and experienced challenges of small household biogas-digesters for rural households
- Authors: Langley, Kyle Anthony
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4789 , http://hdl.handle.net/10962/d1021268
- Description: Access to renewable energy supplies is a critical foundation for sustainable development and poverty alleviation. Anaerobic biogas-digesters also referred to as bio-digesters, have been identified as one of the leading technologies with regards to assisting in improving energy access for remote rural areas that still remain dependent upon biomass usage. This thesis assesses the potential feasibility of bio-digesters for rural households in South Africa by focusing on the experiences of a remote and rural community in Eastern Cape. A standardised survey was used to capture household details and energy use patterns of households with 180 interviews being conducted. Field observations were also conducted on the five bio-digesters installed in the community over a three month period. Despite the predominance of electrification in the community, households were heavily reliant upon biomass in the form of fuelwood and cattle dung to supplement their energy needs. Households supplemented their energy usage with alternative energy sources such as LPG gas and paraffin, especially during periods when electricity was unavailable or deemed too expensive. Initial knowledge of bio-digester technology in the community was non-existent, however with the installation of bio-digesters within the targeted villages, social learning was observed. Despite low temperatures bio-digesters continued to function throughout the study period, though malfunctions did occur and gas production did not reach optimal levels. Primary challenges encountered were the lack of financial subsidies for wide-spread adoption; the limited technical capacity of the community to conduct repairs and minimal gas production due to a build-up of ligneous materials within the gas chamber of the bio-digesters. Bio-digesters were found to provide significant benefits for households and further studies into maximising their effectiveness for rural South African households are recommended.
- Full Text:
- Date Issued: 2016
- Authors: Langley, Kyle Anthony
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4789 , http://hdl.handle.net/10962/d1021268
- Description: Access to renewable energy supplies is a critical foundation for sustainable development and poverty alleviation. Anaerobic biogas-digesters also referred to as bio-digesters, have been identified as one of the leading technologies with regards to assisting in improving energy access for remote rural areas that still remain dependent upon biomass usage. This thesis assesses the potential feasibility of bio-digesters for rural households in South Africa by focusing on the experiences of a remote and rural community in Eastern Cape. A standardised survey was used to capture household details and energy use patterns of households with 180 interviews being conducted. Field observations were also conducted on the five bio-digesters installed in the community over a three month period. Despite the predominance of electrification in the community, households were heavily reliant upon biomass in the form of fuelwood and cattle dung to supplement their energy needs. Households supplemented their energy usage with alternative energy sources such as LPG gas and paraffin, especially during periods when electricity was unavailable or deemed too expensive. Initial knowledge of bio-digester technology in the community was non-existent, however with the installation of bio-digesters within the targeted villages, social learning was observed. Despite low temperatures bio-digesters continued to function throughout the study period, though malfunctions did occur and gas production did not reach optimal levels. Primary challenges encountered were the lack of financial subsidies for wide-spread adoption; the limited technical capacity of the community to conduct repairs and minimal gas production due to a build-up of ligneous materials within the gas chamber of the bio-digesters. Bio-digesters were found to provide significant benefits for households and further studies into maximising their effectiveness for rural South African households are recommended.
- Full Text:
- Date Issued: 2016
Prediction of protein secondary structure using binary classificationtrees, naive Bayes classifiers and the Logistic Regression Classifier
- Eldud Omer, Ahmed Abdelkarim
- Authors: Eldud Omer, Ahmed Abdelkarim
- Date: 2016
- Subjects: Bayesian statistical decision theory , Logistic regression analysis , Biostatistics , Proteins -- Structure
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5581 , http://hdl.handle.net/10962/d1019985
- Description: The secondary structure of proteins is predicted using various binary classifiers. The data are adopted from the RS126 database. The original data consists of protein primary and secondary structure sequences. The original data is encoded using alphabetic letters. These data are encoded into unary vectors comprising ones and zeros only. Different binary classifiers, namely the naive Bayes, logistic regression and classification trees using hold-out and 5-fold cross validation are trained using the encoded data. For each of the classifiers three classification tasks are considered, namely helix against not helix (H/∼H), sheet against not sheet (S/∼S) and coil against not coil (C/∼C). The performance of these binary classifiers are compared using the overall accuracy in predicting the protein secondary structure for various window sizes. Our result indicate that hold-out cross validation achieved higher accuracy than 5-fold cross validation. The Naive Bayes classifier, using 5-fold cross validation achieved, the lowest accuracy for predicting helix against not helix. The classification tree classifiers, using 5-fold cross validation, achieved the lowest accuracies for both coil against not coil and sheet against not sheet classifications. The logistic regression classier accuracy is dependent on the window size; there is a positive relationship between the accuracy and window size. The logistic regression classier approach achieved the highest accuracy when compared to the classification tree and Naive Bayes classifiers for each classification task; predicting helix against not helix with accuracy 77.74 percent, for sheet against not sheet with accuracy 81.22 percent and for coil against not coil with accuracy 73.39 percent. It is noted that it is easier to compare classifiers if the classification process could be completely facilitated in R. Alternatively, it would be easier to assess these logistic regression classifiers if SPSS had a function to determine the accuracy of the logistic regression classifier.
- Full Text:
- Date Issued: 2016
- Authors: Eldud Omer, Ahmed Abdelkarim
- Date: 2016
- Subjects: Bayesian statistical decision theory , Logistic regression analysis , Biostatistics , Proteins -- Structure
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5581 , http://hdl.handle.net/10962/d1019985
- Description: The secondary structure of proteins is predicted using various binary classifiers. The data are adopted from the RS126 database. The original data consists of protein primary and secondary structure sequences. The original data is encoded using alphabetic letters. These data are encoded into unary vectors comprising ones and zeros only. Different binary classifiers, namely the naive Bayes, logistic regression and classification trees using hold-out and 5-fold cross validation are trained using the encoded data. For each of the classifiers three classification tasks are considered, namely helix against not helix (H/∼H), sheet against not sheet (S/∼S) and coil against not coil (C/∼C). The performance of these binary classifiers are compared using the overall accuracy in predicting the protein secondary structure for various window sizes. Our result indicate that hold-out cross validation achieved higher accuracy than 5-fold cross validation. The Naive Bayes classifier, using 5-fold cross validation achieved, the lowest accuracy for predicting helix against not helix. The classification tree classifiers, using 5-fold cross validation, achieved the lowest accuracies for both coil against not coil and sheet against not sheet classifications. The logistic regression classier accuracy is dependent on the window size; there is a positive relationship between the accuracy and window size. The logistic regression classier approach achieved the highest accuracy when compared to the classification tree and Naive Bayes classifiers for each classification task; predicting helix against not helix with accuracy 77.74 percent, for sheet against not sheet with accuracy 81.22 percent and for coil against not coil with accuracy 73.39 percent. It is noted that it is easier to compare classifiers if the classification process could be completely facilitated in R. Alternatively, it would be easier to assess these logistic regression classifiers if SPSS had a function to determine the accuracy of the logistic regression classifier.
- Full Text:
- Date Issued: 2016
Quantitative microstructural evaluation of 12 Cr creep aged steels after welding
- Marx, Genevéve, Neethling, Jan
- Authors: Marx, Genevéve , Neethling, Jan
- Date: 2016
- Subjects: Stainless steel -- Welding , Electron microscopy
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/7232 , vital:21307
- Description: This dissertation focuses on the quantitative microstructural evaluation of new and creep aged X20 (12 Cr) stainless steel after welding. X20 stainless steel has been widely used in the high temperature and pressure pipework of coal-fired power plants. Consequently, this material has to withstand extreme conditions of high temperature and stress during service exposure. Under these conditions, creep deteriorates the strength of the material. The material’s resistance to creep damage due to its microstructure can be quantitatively described by the back-stress. There are four microstructural contributions to the back-stress: Precipitate Hardening, Sub-Boundary Hardening, Solid-Solution Hardening and Dislocation Hardening. Fusion welding is performed on creep aged materials when a component needs to be replaced. This high temperature process results in the formation of different microstructural regions within the weldment. These creep damaged components have a weldability limit as set by the life management strategy of the power plant company. Measuring techniques capable of quantifying the microstructural contributions (precipitates, subgrains and dislocations) were developed and evaluated in this study. These techniques were then used to characterise the different microstructural regions within a new and creep aged X20 steel weldment. Differences in the microstructure of the new and creep aged X20 steel was illustrated by the results of this study. The measured size and number densities of the precipitates in the creep aged X20 material showed that there is a decrease in PH during creep exposure. There was a decrease in SBH and DH stress for the creep aged X20 material due to coarsening of the subgrains and annealing of dislocations during creep exposure. The quantitative techniques demonstrated in this study opens up the possibility to perform life assessment on weldments with inhomogeneous microstructures by following a microstructural based approach.
- Full Text:
- Date Issued: 2016
- Authors: Marx, Genevéve , Neethling, Jan
- Date: 2016
- Subjects: Stainless steel -- Welding , Electron microscopy
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/7232 , vital:21307
- Description: This dissertation focuses on the quantitative microstructural evaluation of new and creep aged X20 (12 Cr) stainless steel after welding. X20 stainless steel has been widely used in the high temperature and pressure pipework of coal-fired power plants. Consequently, this material has to withstand extreme conditions of high temperature and stress during service exposure. Under these conditions, creep deteriorates the strength of the material. The material’s resistance to creep damage due to its microstructure can be quantitatively described by the back-stress. There are four microstructural contributions to the back-stress: Precipitate Hardening, Sub-Boundary Hardening, Solid-Solution Hardening and Dislocation Hardening. Fusion welding is performed on creep aged materials when a component needs to be replaced. This high temperature process results in the formation of different microstructural regions within the weldment. These creep damaged components have a weldability limit as set by the life management strategy of the power plant company. Measuring techniques capable of quantifying the microstructural contributions (precipitates, subgrains and dislocations) were developed and evaluated in this study. These techniques were then used to characterise the different microstructural regions within a new and creep aged X20 steel weldment. Differences in the microstructure of the new and creep aged X20 steel was illustrated by the results of this study. The measured size and number densities of the precipitates in the creep aged X20 material showed that there is a decrease in PH during creep exposure. There was a decrease in SBH and DH stress for the creep aged X20 material due to coarsening of the subgrains and annealing of dislocations during creep exposure. The quantitative techniques demonstrated in this study opens up the possibility to perform life assessment on weldments with inhomogeneous microstructures by following a microstructural based approach.
- Full Text:
- Date Issued: 2016
Recombinant expression, purification and in vitro interaction analysis of HOP and RhoC
- Vaaltyn, Michaelone Chantelle
- Authors: Vaaltyn, Michaelone Chantelle
- Date: 2016
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/64523 , vital:28555
- Description: Expected release date-May 2019
- Full Text:
- Date Issued: 2016
- Authors: Vaaltyn, Michaelone Chantelle
- Date: 2016
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/64523 , vital:28555
- Description: Expected release date-May 2019
- Full Text:
- Date Issued: 2016
Relevance of the family assessment for least developed countries (FALDC) assessment tool rendering child protection services in the Eastern Cape, South Africa
- Authors: Mgidi, Siphelele
- Date: 2016
- Subjects: Child abuse -- South Africa -- Prevention Family social work -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/6335 , vital:29578
- Description: Assessment tools have been used for various purposes, including for protecting children from maltreatment. The main aim of this study was to to evaluate and determine the relevance of the Family Assessment for Leased Developed Countries (FALDC) assessment tool for child protection services in the Eastern Cape Province. The research was conducted using the social developmental welfare approach (Patel, 2005) and ecological systems theory (Healy, 2005). The study made use of the qualitative research method; in doing so the study made use of the case study design. In using the qualitative research method, focus group discussions were conducted with 29 social workers involved in child protection services. The findings of the study indicated that the FALDC assessment tool provides information useful for child protection services even though it contains sections that are regarded as less relevant to child protection. The study also founded that the FALDC assessment tool is relevant to child protection in the South African context, yet it needs to be aligned so that it provides much of the information desired by those involved in child protection. A conclusion drawn from this study is that the FALDC assessment tool appears to be relevant for child protection services. The FALDC assessment tool needs to be adjusted taking into consideration other aspects important to child protection in the South African child protection context.
- Full Text:
- Date Issued: 2016
- Authors: Mgidi, Siphelele
- Date: 2016
- Subjects: Child abuse -- South Africa -- Prevention Family social work -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/6335 , vital:29578
- Description: Assessment tools have been used for various purposes, including for protecting children from maltreatment. The main aim of this study was to to evaluate and determine the relevance of the Family Assessment for Leased Developed Countries (FALDC) assessment tool for child protection services in the Eastern Cape Province. The research was conducted using the social developmental welfare approach (Patel, 2005) and ecological systems theory (Healy, 2005). The study made use of the qualitative research method; in doing so the study made use of the case study design. In using the qualitative research method, focus group discussions were conducted with 29 social workers involved in child protection services. The findings of the study indicated that the FALDC assessment tool provides information useful for child protection services even though it contains sections that are regarded as less relevant to child protection. The study also founded that the FALDC assessment tool is relevant to child protection in the South African context, yet it needs to be aligned so that it provides much of the information desired by those involved in child protection. A conclusion drawn from this study is that the FALDC assessment tool appears to be relevant for child protection services. The FALDC assessment tool needs to be adjusted taking into consideration other aspects important to child protection in the South African child protection context.
- Full Text:
- Date Issued: 2016
Reproductive biology of important invasive plants in the Eastern Cape Province of South Africa
- Authors: Thorne, Cara-Jayne
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/3683 , vital:20535
- Description: Baker’s rule predicts species capable of uniparental reproduction are more likely to establish after long distance dispersal (or introduction in the case of invasive plants), thus the ability to undergo autonomous self-pollination should promote colonization. An investigation into the reproductive biology of eleven invasive species in the Eastern Cape Province of South Africa between 2012 and 2014 showed strong support for Baker’s law. Breeding system results showed evidence of self-compatibility in eight species, ten species were capable of autonomous self-pollination, and only three species showed evidence of varying levels of self-incompatibility. These results provide evdence that autonomous self-pollination occurs more frequently among invasive species, self-compatible species more frequently become invasive compared with self-incompatible species and that autogamous species should have a larger invasive range. Co-opting suitable local pollinators may be problematic for invasive plants, especially those with highly specialized pollination systems. The species investigated appear to be largely independent of pollinators, mostly setting seed in the absence of pollinators. Despite this, all eleven invasive plant species are regularly visited by a variety of generalist pollinators including Apis mellifera, Xylocopa bees and Allodapini species. Pollinators all carried substantial pollen loads, even managing to extract pollen from more specialized plants, such as the poricidal anthers of Solanum species, and frequently came into contact with both anthers and stigmas. Considering most of theses species are capable of autonomous self-pollination, their reliance on pollinators may be low. Even the most self-incompatible species, Passiflora caerulea, appears to have successfully co-opted local pollinators (honeybees and carpenter bees), ensuring successful pollination and seed set. The ability for cross-pollination by local pollinators allows for some degree of genetic variation within invasive plant populations, especially for self-incompatible species. Inadequate pollen deposition by unreliable or inefficient pollinators, or reduced resource availability, can result in pollen limitation. Invasive plant species may be especially susceptible, with three of the plant species investiagted showing possible pollen limitation at the level of seed set, while the remaining nine invasive plant species showed no evidence of pollen limitation in South Africa. The ability to utilize uniparental reproduction (as Baker’s law predicted), and co-opt local pollinators has allowed invasive plants in the Eastern Cape to successfully establish and persist after introduction. Hence, the inclusion of reproductive traits of plants should therefore be included in risk assessments for future plant invaders.
- Full Text:
- Date Issued: 2016
- Authors: Thorne, Cara-Jayne
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/3683 , vital:20535
- Description: Baker’s rule predicts species capable of uniparental reproduction are more likely to establish after long distance dispersal (or introduction in the case of invasive plants), thus the ability to undergo autonomous self-pollination should promote colonization. An investigation into the reproductive biology of eleven invasive species in the Eastern Cape Province of South Africa between 2012 and 2014 showed strong support for Baker’s law. Breeding system results showed evidence of self-compatibility in eight species, ten species were capable of autonomous self-pollination, and only three species showed evidence of varying levels of self-incompatibility. These results provide evdence that autonomous self-pollination occurs more frequently among invasive species, self-compatible species more frequently become invasive compared with self-incompatible species and that autogamous species should have a larger invasive range. Co-opting suitable local pollinators may be problematic for invasive plants, especially those with highly specialized pollination systems. The species investigated appear to be largely independent of pollinators, mostly setting seed in the absence of pollinators. Despite this, all eleven invasive plant species are regularly visited by a variety of generalist pollinators including Apis mellifera, Xylocopa bees and Allodapini species. Pollinators all carried substantial pollen loads, even managing to extract pollen from more specialized plants, such as the poricidal anthers of Solanum species, and frequently came into contact with both anthers and stigmas. Considering most of theses species are capable of autonomous self-pollination, their reliance on pollinators may be low. Even the most self-incompatible species, Passiflora caerulea, appears to have successfully co-opted local pollinators (honeybees and carpenter bees), ensuring successful pollination and seed set. The ability for cross-pollination by local pollinators allows for some degree of genetic variation within invasive plant populations, especially for self-incompatible species. Inadequate pollen deposition by unreliable or inefficient pollinators, or reduced resource availability, can result in pollen limitation. Invasive plant species may be especially susceptible, with three of the plant species investiagted showing possible pollen limitation at the level of seed set, while the remaining nine invasive plant species showed no evidence of pollen limitation in South Africa. The ability to utilize uniparental reproduction (as Baker’s law predicted), and co-opt local pollinators has allowed invasive plants in the Eastern Cape to successfully establish and persist after introduction. Hence, the inclusion of reproductive traits of plants should therefore be included in risk assessments for future plant invaders.
- Full Text:
- Date Issued: 2016
Resolving the service delivery backlog at the Eastern Cape Department of Human Settlements
- Authors: Hlamandana, Zukiswa
- Date: 2016
- Subjects: Project management -- South Africa -- Eastern Cape , Public administration -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/5303 , vital:20831
- Description: The purpose of this study is resolving the service delivery backlog at the Eastern Cape Department of Human Settlements. The problem of service delivery backlogs is not one unique to South Africa but a problem faced by many developing nations. South African government in all spheres still faces a challenge of creating the good life for its citizen, even more on local Municipality as they are government closest to the people and interacts more closely with communities. It is two decades since South Africa became a democratic state and despite promises and efforts to improve service delivery to the public there still exist backlog in service delivery. In order to address the research problem and to fulfil the research objectives, an in-depth literature study was done on the current state and the role of the Department of Human settlements as well as the current backlog facing the department. Housing process and procedures, challenges, policies, finance, factors influencing housing allocation and delivery were also reviewed. Empirical studies were also performed by means of questionnaires with the community and officials in the Eastern Cape Department of Human Settlements. The literature and empirical study made it possible to identify causes, challenges and impact of service delivery backlog and to recommend possible solutions for resolving service delivery backlogs. These recommendations should be of value to the department and the country as a whole. In this study research methodology was focused on the research design, target population of study, sampling design and procedures, data collection instrument, data collection procedures, data presentation, analysis and interpretation. The major findings were identified in the study such as poor workmanship, delays in procurement processes, illegal acts, vandalism, poor planning, finance, project management and quality assurance. The study also offers recommendations such as revising procurement policy, source more funds from National, employ more qualified staff, involve community and all stakeholders in decision making in order to address the service delivery backlog successfully .All kinds of approaches that the government needs to employ in order to also improve its performance of delivering service to the public in South Africa were determined.
- Full Text:
- Date Issued: 2016
- Authors: Hlamandana, Zukiswa
- Date: 2016
- Subjects: Project management -- South Africa -- Eastern Cape , Public administration -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/5303 , vital:20831
- Description: The purpose of this study is resolving the service delivery backlog at the Eastern Cape Department of Human Settlements. The problem of service delivery backlogs is not one unique to South Africa but a problem faced by many developing nations. South African government in all spheres still faces a challenge of creating the good life for its citizen, even more on local Municipality as they are government closest to the people and interacts more closely with communities. It is two decades since South Africa became a democratic state and despite promises and efforts to improve service delivery to the public there still exist backlog in service delivery. In order to address the research problem and to fulfil the research objectives, an in-depth literature study was done on the current state and the role of the Department of Human settlements as well as the current backlog facing the department. Housing process and procedures, challenges, policies, finance, factors influencing housing allocation and delivery were also reviewed. Empirical studies were also performed by means of questionnaires with the community and officials in the Eastern Cape Department of Human Settlements. The literature and empirical study made it possible to identify causes, challenges and impact of service delivery backlog and to recommend possible solutions for resolving service delivery backlogs. These recommendations should be of value to the department and the country as a whole. In this study research methodology was focused on the research design, target population of study, sampling design and procedures, data collection instrument, data collection procedures, data presentation, analysis and interpretation. The major findings were identified in the study such as poor workmanship, delays in procurement processes, illegal acts, vandalism, poor planning, finance, project management and quality assurance. The study also offers recommendations such as revising procurement policy, source more funds from National, employ more qualified staff, involve community and all stakeholders in decision making in order to address the service delivery backlog successfully .All kinds of approaches that the government needs to employ in order to also improve its performance of delivering service to the public in South Africa were determined.
- Full Text:
- Date Issued: 2016
Risk analysis and management systems in South African construction project management practices
- Authors: Cook, Iain Murray
- Date: 2016
- Subjects: Construction projects -- Management , Construction industry -- Risk management , Project management -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/3469 , vital:20433
- Description: Risk management (RM) should be seen as one of the most important functions in the South African built environment. Without the effective management of the risks associated with the industry, the noble vision of a sector that is efficient, profitable, and sustainable cannot be achieved. By embracing tried and tested policies that successfully mitigate risk, industry stakeholders will achieve many project successes, and will outlast any competitors that choose to ignore, or are ignorant of the fact, that the negative impact risk has on projects is inversely proportional to the level of RM employed. Construction Project Management (CPM) practices, realising that there are excellent business opportunities across South Africa’s borders, and faced with a competitive South African market, are engaging with developers and government entities involved in cross border projects in the hope of securing these potentially lucrative African projects. With this move into Africa comes increased uncertainty and risk for these CPM practices, and other project stakeholders. Similarly, CPM practices that have made the strategic decision to remain operational only within South Africa’s borders, are faced with a competitive and complex built environment and industry, made increasingly challenging by a weakening economy, exacerbated by industrial strikes, infrastructure deficiencies and a decrease in industry skill levels. This study reports on Project Managers’ (PMs’) perceptions of project failures and inefficiencies resulting from inadequate RM on projects, including the RM methodologies currently being employed. The study focused on perceptions of PMs who operate within South Africa’s borders, PMs that operate across border into other African countries, as well as PMs who operate exclusively within South Africa’s built environment framework. A study was undertaken incorporating qualitative methodologies via a normative survey. The survey was split into three main phases. Phase one employed the use of a pilot survey executed with the objective of further investigating the main sub-problems to gain more insight into the related issues and challenges. For the pilot survey, PMs were selected based on their engagement in CPM activities within South Africa as well as across South Africa’s borders into other African countries. Phase two of the main survey, with the sample stratum being the Association of Construction Project Managers (ACPM), was aimed at PMs within the ACPM who have engaged, or are engaging, in CPM activities both within South Africa’s borders as well as across South Africa’s borders into other African countries. Phase 3 of the main survey, with the sample stratum being the ACPM, was aimed at PMs within the ACPM who have engaged, or are engaging, in CPM activities within South Africa’s borders only and have not engaged in cross border activities. Survey findings identified the commercial sector and value of the projects undertaken by the practices, the level of risk associated with different client typologies, the link between inadequate RM and project inefficiency and failure, and the importance of RM on projects. Findings also identified that RM methodologies are employed by CPM practices, and that CPM practices generally endeavour to create a culture of risk awareness amongst employees. Further findings indicated that CPM practices may not always understand the risks associated with new industry sectors, regions or countries that they are considering operating within, and that that there is room for improvement regarding the effectiveness of current RM systems. Survey findings also indicated that risk is not always transferred to the correct project stakeholder most suited to managing the risk, and CPM practices are not always able to accurately quantify the costs associated with project risk. Furthermore, it was identified that CPM practices do not always undertaken risk assessments (RAs) at the correct project stage resulting in inadequate risk contingencies allowances, regular risk reviews are not always undertaken for projects, project pre-mortems are seen as valuable tools by CPM practices as a method to reduce future risk, and project post-mortems relative to ‘lessons learnt’ are not always undertaken. Conclusions outline the link between effective RM, project inefficiencies and project failure, as well as the increase or decrease in risk relative to ineffective or effective use of risk identification and management methodologies for time, cost, and quality factors respectively. Conclusions also outline the fact that although CPM practices generally understand the link between RM and project success, they are not always able to fully comprehend the risks associated with new industry sectors, regions or cross border countries. This indicates that without the adequate identification of risk, the RM process or steps that follow the qualitative risk identification process will have little or no value. This is indicative of the requirement for professional associations to consolidate risk data for industry activities with the aim of improving the level of RM industry wide. Recommendations highlight the importance of the compiling of sector specific risk registers, compiled by the South African Council for the Project and Construction Management Professions (SACPCMP) with registered member input, made available to all PMs via the SACPCMPs online database. Further recommendations include: the engendering, by senior management of CPM practices; a healthy ‘risk aware’ culture, by promoting RM practices aligned with best practice methodologies; the implementation of well balanced and formal RM systems throughout the CPM practice, with the aim of achieving effective RM without overburdening PMs with unnecessary documentation or ‘paperwork’; the attendance of risk conferences and workshops by all CPM practices, aimed at specifically identifying challenges that exist with RM and methods that can be employed to improve the status quo; the attendance of formal risk training courses, by all CPM practices, aimed at improving the knowledge base of PMs relative to effective RM, and the appointment of risk professionals, driven by the monetary value and risk levels of the project, to undertake the RM process and unburden PMs from the task, allowing PMs to concentrate on the other project knowledge areas.
- Full Text:
- Date Issued: 2016
- Authors: Cook, Iain Murray
- Date: 2016
- Subjects: Construction projects -- Management , Construction industry -- Risk management , Project management -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/3469 , vital:20433
- Description: Risk management (RM) should be seen as one of the most important functions in the South African built environment. Without the effective management of the risks associated with the industry, the noble vision of a sector that is efficient, profitable, and sustainable cannot be achieved. By embracing tried and tested policies that successfully mitigate risk, industry stakeholders will achieve many project successes, and will outlast any competitors that choose to ignore, or are ignorant of the fact, that the negative impact risk has on projects is inversely proportional to the level of RM employed. Construction Project Management (CPM) practices, realising that there are excellent business opportunities across South Africa’s borders, and faced with a competitive South African market, are engaging with developers and government entities involved in cross border projects in the hope of securing these potentially lucrative African projects. With this move into Africa comes increased uncertainty and risk for these CPM practices, and other project stakeholders. Similarly, CPM practices that have made the strategic decision to remain operational only within South Africa’s borders, are faced with a competitive and complex built environment and industry, made increasingly challenging by a weakening economy, exacerbated by industrial strikes, infrastructure deficiencies and a decrease in industry skill levels. This study reports on Project Managers’ (PMs’) perceptions of project failures and inefficiencies resulting from inadequate RM on projects, including the RM methodologies currently being employed. The study focused on perceptions of PMs who operate within South Africa’s borders, PMs that operate across border into other African countries, as well as PMs who operate exclusively within South Africa’s built environment framework. A study was undertaken incorporating qualitative methodologies via a normative survey. The survey was split into three main phases. Phase one employed the use of a pilot survey executed with the objective of further investigating the main sub-problems to gain more insight into the related issues and challenges. For the pilot survey, PMs were selected based on their engagement in CPM activities within South Africa as well as across South Africa’s borders into other African countries. Phase two of the main survey, with the sample stratum being the Association of Construction Project Managers (ACPM), was aimed at PMs within the ACPM who have engaged, or are engaging, in CPM activities both within South Africa’s borders as well as across South Africa’s borders into other African countries. Phase 3 of the main survey, with the sample stratum being the ACPM, was aimed at PMs within the ACPM who have engaged, or are engaging, in CPM activities within South Africa’s borders only and have not engaged in cross border activities. Survey findings identified the commercial sector and value of the projects undertaken by the practices, the level of risk associated with different client typologies, the link between inadequate RM and project inefficiency and failure, and the importance of RM on projects. Findings also identified that RM methodologies are employed by CPM practices, and that CPM practices generally endeavour to create a culture of risk awareness amongst employees. Further findings indicated that CPM practices may not always understand the risks associated with new industry sectors, regions or countries that they are considering operating within, and that that there is room for improvement regarding the effectiveness of current RM systems. Survey findings also indicated that risk is not always transferred to the correct project stakeholder most suited to managing the risk, and CPM practices are not always able to accurately quantify the costs associated with project risk. Furthermore, it was identified that CPM practices do not always undertaken risk assessments (RAs) at the correct project stage resulting in inadequate risk contingencies allowances, regular risk reviews are not always undertaken for projects, project pre-mortems are seen as valuable tools by CPM practices as a method to reduce future risk, and project post-mortems relative to ‘lessons learnt’ are not always undertaken. Conclusions outline the link between effective RM, project inefficiencies and project failure, as well as the increase or decrease in risk relative to ineffective or effective use of risk identification and management methodologies for time, cost, and quality factors respectively. Conclusions also outline the fact that although CPM practices generally understand the link between RM and project success, they are not always able to fully comprehend the risks associated with new industry sectors, regions or cross border countries. This indicates that without the adequate identification of risk, the RM process or steps that follow the qualitative risk identification process will have little or no value. This is indicative of the requirement for professional associations to consolidate risk data for industry activities with the aim of improving the level of RM industry wide. Recommendations highlight the importance of the compiling of sector specific risk registers, compiled by the South African Council for the Project and Construction Management Professions (SACPCMP) with registered member input, made available to all PMs via the SACPCMPs online database. Further recommendations include: the engendering, by senior management of CPM practices; a healthy ‘risk aware’ culture, by promoting RM practices aligned with best practice methodologies; the implementation of well balanced and formal RM systems throughout the CPM practice, with the aim of achieving effective RM without overburdening PMs with unnecessary documentation or ‘paperwork’; the attendance of risk conferences and workshops by all CPM practices, aimed at specifically identifying challenges that exist with RM and methods that can be employed to improve the status quo; the attendance of formal risk training courses, by all CPM practices, aimed at improving the knowledge base of PMs relative to effective RM, and the appointment of risk professionals, driven by the monetary value and risk levels of the project, to undertake the RM process and unburden PMs from the task, allowing PMs to concentrate on the other project knowledge areas.
- Full Text:
- Date Issued: 2016
Risk management practices on public sector construction projects: Case studies in Lesotho
- Authors: Nketekete, Molefi
- Date: 2016
- Subjects: Construction industry -- Risk management Construction industry -- Lesotho Risk management -- Lesotho
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/11228 , vital:26900
- Description: Risk management (RM) is a knowledge area in project management (PM). The challenges of project complexity require astute RM. However, RM practices in Lesotho appear to lag behind international trends. Within the sub-Sahara African region, RM incompetence affects timely delivery of public projects owing to PM practices that do not address risks. This study, which adopts a case study approach, unravels the „how and why‟ of contemporary RM practices which are lacking in Lesotho, despite a poor record of project success in the construction industry. Through the reviewed literature and primary data collection, this study investigates three elements in order to determine the level of RM practice within Lesotho public sector construction projects. These elements were the basis of RM, the RM processes, and the peoples‟ perceptions which were essentially centred on the probability of risk and the impact thereof. The results from the study achieved through cross-case synthesis show that the level of RM practice in the Lesotho public sector construction projects is at variance with international practice. The notable gaps in practice include construction professionals who do not know about or who have not practiced project RM. The study thus propose that the Government of Lesotho (GoL) should invest in educating more people in the areas of construction project management or engage professionals with extensive project RM experience. The recommended initiatives should promote professionalism and accountability that are essential for bracing the RM practice in public sector construction projects.
- Full Text:
- Date Issued: 2016
- Authors: Nketekete, Molefi
- Date: 2016
- Subjects: Construction industry -- Risk management Construction industry -- Lesotho Risk management -- Lesotho
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/11228 , vital:26900
- Description: Risk management (RM) is a knowledge area in project management (PM). The challenges of project complexity require astute RM. However, RM practices in Lesotho appear to lag behind international trends. Within the sub-Sahara African region, RM incompetence affects timely delivery of public projects owing to PM practices that do not address risks. This study, which adopts a case study approach, unravels the „how and why‟ of contemporary RM practices which are lacking in Lesotho, despite a poor record of project success in the construction industry. Through the reviewed literature and primary data collection, this study investigates three elements in order to determine the level of RM practice within Lesotho public sector construction projects. These elements were the basis of RM, the RM processes, and the peoples‟ perceptions which were essentially centred on the probability of risk and the impact thereof. The results from the study achieved through cross-case synthesis show that the level of RM practice in the Lesotho public sector construction projects is at variance with international practice. The notable gaps in practice include construction professionals who do not know about or who have not practiced project RM. The study thus propose that the Government of Lesotho (GoL) should invest in educating more people in the areas of construction project management or engage professionals with extensive project RM experience. The recommended initiatives should promote professionalism and accountability that are essential for bracing the RM practice in public sector construction projects.
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- Date Issued: 2016