Phytoplankton of the Southern Agulhas Large Marine Ecosystem (sACLME)
- Authors: Sonnekus, Martinus Jakobus
- Date: 2020
- Subjects: Botanical chemistry
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/47646 , vital:40261
- Description: The southern Agulhas Large Marine Ecosystem (sACLME) consists of the greater Agulhas Current system, including the areas influenced by the Agulhas Current, the Agulhas Shelf, Agulhas Bank, Agulhas Retroflection as well as the Agulhas Return Current. Four biogeographical regions were identified within the sACLME and the composition of the phytoplankton communities and the associated physico-chemical variables in each were investigated. Water temperature and nitrate concentration were found to be the main drivers of the sACLME phytoplankton community. A total of 215 phytoplankton taxa were identified that were separated into two groups: the Agulhas Current group and the Southwest Indian Ocean Ridge group. The structure of the phytoplankton community was consistently homogeneous throughout the sACLME. Nutrient concentrations of the water varied, but nitrate was the most abundant source of nitrogen, especially in regions that were subjected to the upwelling of cold nutrient-rich water. The phytoplankton communities were significantly influenced by the availability and stoichiometry of the macronutrients nitrogen; phosphorus and silicon. The low mean N:P ratio of 5.5 is an indication that the waters of the sACLME are generally nitrogen limited, as is typical of oceanic systems. There is a change in phytoplankton cell size and functional groups within in the various water masses that are specific to certain biogeographical regions within the Agulhas Current system. It is clear that frontal systems may form barriers between phytoplankton communities.
- Full Text:
- Date Issued: 2020
- Authors: Sonnekus, Martinus Jakobus
- Date: 2020
- Subjects: Botanical chemistry
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/47646 , vital:40261
- Description: The southern Agulhas Large Marine Ecosystem (sACLME) consists of the greater Agulhas Current system, including the areas influenced by the Agulhas Current, the Agulhas Shelf, Agulhas Bank, Agulhas Retroflection as well as the Agulhas Return Current. Four biogeographical regions were identified within the sACLME and the composition of the phytoplankton communities and the associated physico-chemical variables in each were investigated. Water temperature and nitrate concentration were found to be the main drivers of the sACLME phytoplankton community. A total of 215 phytoplankton taxa were identified that were separated into two groups: the Agulhas Current group and the Southwest Indian Ocean Ridge group. The structure of the phytoplankton community was consistently homogeneous throughout the sACLME. Nutrient concentrations of the water varied, but nitrate was the most abundant source of nitrogen, especially in regions that were subjected to the upwelling of cold nutrient-rich water. The phytoplankton communities were significantly influenced by the availability and stoichiometry of the macronutrients nitrogen; phosphorus and silicon. The low mean N:P ratio of 5.5 is an indication that the waters of the sACLME are generally nitrogen limited, as is typical of oceanic systems. There is a change in phytoplankton cell size and functional groups within in the various water masses that are specific to certain biogeographical regions within the Agulhas Current system. It is clear that frontal systems may form barriers between phytoplankton communities.
- Full Text:
- Date Issued: 2020
Enumeration of insect viruses using microscopic and molecular analyses: South African isolate of cryotophlebia leucotreta granulovirus as a case study
- Authors: Dhladhla, Busisiwe I R
- Date: 2012
- Subjects: Baculoviruses , Insects -- Viruses , Molecular genetics , Microbial genomics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10318 , http://hdl.handle.net/10948/d1008395 , Baculoviruses , Insects -- Viruses , Molecular genetics , Microbial genomics
- Description: Baculoviruses have been used as biocontrol agents to control insect pests in agriculture since the 1970s. Out of the fifteen virus families known to infect insects, baculoviruses offer the greatest potential as insect biopesticides, due to their high host specificity which makes them extremely safe to humans, other vertebrates, plants and non-target microorganisms. They comprise of two genera: nucleopolyhedroviruses (NPVs) and granuloviruses (GVs). The South African isolate of Cryptophlebia leucotreta granulovirus (CrleGV-SA) which is infectious for the false codling moth (FCM), Thaumatotibia leucotreta, (Meyrick) (Lepidoptera: Tortricidae), has been successfully developed into two commercial biopesticides; Cryptogran® and Cryptex®, for the control of FCM in citrus crops. The current method of enumeration used for CrleGV-SA virus particles in routine experiments during the production of the GV as biopesticides, is dark field microscopy. However, due to the small size of GVs (300-500 nm in length), the technique is not easy to perform on these viruses, and no systemic comparison has been made of potential alternative methods. Therefore, the main objective of this study was to develop a quantitative enumeration method for CrleGV-SA occlusion bodies (OBs) which is accurate, reliable, and feasible, and compare the developed methods of enumeration to the current method. Purified and semi-purified CrleGV-SA viral stocks were prepared for enumeration studies using spectrophotometry, dark field microscopy, scanning electron microscopy (SEM) and real time qPCR. Spectrophotometry was found to be an unreliable method for enumeration of GVs in the production, standardisation, and quality control of biopesticides. Dark field microscopy and SEM were found to be accurate, and statistically comparable (p = 0.064) enumeration techniques. qPCR is currently being optimised for the enumeration of GVs. This technique was demonstrated to generate accurate standard curves for absolute quantification of virus particles for pure and semi-pure virus preparations. qPCR offers the greatest potential as an accurate enumeration method because it is not affected by contamination with non-biological contaminating debris, nor by other biological material due to the specificity of PCR primers. Further work is required to fully develop qPCR as an enumeration method for GVs. However, dark field microscopy has been successfully validated as an enumeration method. SEM, which has a high resolution compared to light microscopy, has an added advantage over dark field microscopy, which is to distinguish virus particles in semi-pure viral stock preparations during counting. Therefore, SEM currently provides the most unambiguous and feasible enumeration method for GVs in both purified and semi-purified virus samples.
- Full Text:
- Date Issued: 2012
- Authors: Dhladhla, Busisiwe I R
- Date: 2012
- Subjects: Baculoviruses , Insects -- Viruses , Molecular genetics , Microbial genomics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10318 , http://hdl.handle.net/10948/d1008395 , Baculoviruses , Insects -- Viruses , Molecular genetics , Microbial genomics
- Description: Baculoviruses have been used as biocontrol agents to control insect pests in agriculture since the 1970s. Out of the fifteen virus families known to infect insects, baculoviruses offer the greatest potential as insect biopesticides, due to their high host specificity which makes them extremely safe to humans, other vertebrates, plants and non-target microorganisms. They comprise of two genera: nucleopolyhedroviruses (NPVs) and granuloviruses (GVs). The South African isolate of Cryptophlebia leucotreta granulovirus (CrleGV-SA) which is infectious for the false codling moth (FCM), Thaumatotibia leucotreta, (Meyrick) (Lepidoptera: Tortricidae), has been successfully developed into two commercial biopesticides; Cryptogran® and Cryptex®, for the control of FCM in citrus crops. The current method of enumeration used for CrleGV-SA virus particles in routine experiments during the production of the GV as biopesticides, is dark field microscopy. However, due to the small size of GVs (300-500 nm in length), the technique is not easy to perform on these viruses, and no systemic comparison has been made of potential alternative methods. Therefore, the main objective of this study was to develop a quantitative enumeration method for CrleGV-SA occlusion bodies (OBs) which is accurate, reliable, and feasible, and compare the developed methods of enumeration to the current method. Purified and semi-purified CrleGV-SA viral stocks were prepared for enumeration studies using spectrophotometry, dark field microscopy, scanning electron microscopy (SEM) and real time qPCR. Spectrophotometry was found to be an unreliable method for enumeration of GVs in the production, standardisation, and quality control of biopesticides. Dark field microscopy and SEM were found to be accurate, and statistically comparable (p = 0.064) enumeration techniques. qPCR is currently being optimised for the enumeration of GVs. This technique was demonstrated to generate accurate standard curves for absolute quantification of virus particles for pure and semi-pure virus preparations. qPCR offers the greatest potential as an accurate enumeration method because it is not affected by contamination with non-biological contaminating debris, nor by other biological material due to the specificity of PCR primers. Further work is required to fully develop qPCR as an enumeration method for GVs. However, dark field microscopy has been successfully validated as an enumeration method. SEM, which has a high resolution compared to light microscopy, has an added advantage over dark field microscopy, which is to distinguish virus particles in semi-pure viral stock preparations during counting. Therefore, SEM currently provides the most unambiguous and feasible enumeration method for GVs in both purified and semi-purified virus samples.
- Full Text:
- Date Issued: 2012
An assessment of the in vitro neuroprotective potential of selected Algerian and South African medicinal plant extracts
- Authors: Fewell, William
- Date: 2015
- Subjects: Medicinal plants -- South Africa , Nervous system -- Alternative treatment -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/8608 , vital:26411
- Description: It is estimated by the World Health Organization (WHO) that by 2040 neurodegenerative disorders will collectively surpass cancer as the primary cause of death in industrialised countries (WHO,2006). Natural flora represents one of the most important therapeutic sources in modern drug discovery, however only a limited number of plant species have been screened for their neuroprotective value. The neuroprotective potential of eleven Algerian and two South African medicinal plant extracts were assessed in this study, aiming to identify promising candidates for future research. Neurodegenerative disorders such as Parkinson’s disease are characterised by distinct biochemical features, including protein misfolding/-aggregation, excessive oxidative stress and apoptotic cell death. As such, medicinal plant extracts were screened for biological properties directly relevant to neurodegeneration. The capacity to induce autophagy was also investigated as mounting evidence suggests that activation of this pathway may reduce abnormal protein aggregation and promote neuronal survival.
- Full Text: false
- Date Issued: 2015
- Authors: Fewell, William
- Date: 2015
- Subjects: Medicinal plants -- South Africa , Nervous system -- Alternative treatment -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/8608 , vital:26411
- Description: It is estimated by the World Health Organization (WHO) that by 2040 neurodegenerative disorders will collectively surpass cancer as the primary cause of death in industrialised countries (WHO,2006). Natural flora represents one of the most important therapeutic sources in modern drug discovery, however only a limited number of plant species have been screened for their neuroprotective value. The neuroprotective potential of eleven Algerian and two South African medicinal plant extracts were assessed in this study, aiming to identify promising candidates for future research. Neurodegenerative disorders such as Parkinson’s disease are characterised by distinct biochemical features, including protein misfolding/-aggregation, excessive oxidative stress and apoptotic cell death. As such, medicinal plant extracts were screened for biological properties directly relevant to neurodegeneration. The capacity to induce autophagy was also investigated as mounting evidence suggests that activation of this pathway may reduce abnormal protein aggregation and promote neuronal survival.
- Full Text: false
- Date Issued: 2015
Testing the application of coastal altimetry in two South-Eastern African bights: the relationship between mesoscale features and chlorophyll-a, cyclonic eddies in the Indian Ocean
- Authors: Ziegler, Lisa
- Date: 2018
- Subjects: Oceanography -- Remote sensing -- Indian Ocean
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/15225 , vital:28188
- Description: Enhanced coastal altimetry, adaptive Leading-Edge Subwaveform(ALES), was used to study wo well known eddies along the southeastern African coast, namely the Delagoa Bight Lee Eddy and the Durban Lee Eddy. I address a two part problem. Firstly, how well does the application of coastal altimetry techniques behave in the coastal region? Secondly, is there a relationship between the eddies’ presence and chlorophyll-a (chl-a). Sea level anomalies (SLA) were computed from the re-tracked ALES data of two satellite missions — Envisat (used for Delagoa Bight eddy) and Jason -2 (for the Durban eddy) with geophysical corrections removed. These datasets were compared with the original satellite, 1 Hz RADS, AND AVISO gridded data. Two regions were selected to see if there was a biophysical link. A centre region of the eddy and an outside region of the eddy were taken. Results indicate that coastal altimetrywas successful in delimiting both features. ALES was less noisey and able to recover more data that were missed by the 1 Hz RADS dataset. Hovmöller plots showed the Delagoa Bight eddy to be more of a transient feature than semi-permanent, as had previously been suggested. Results from the linear model indicate a negative correlation between SLA and chl-a. This influence could be through facilitation of chl-a in the bight or just retaining chla. This is hard to elucidate without in situ data. These results show a promising indication that coastal altimetry will be a useful and reliable product to further biophysical coupling research along the coast.
- Full Text:
- Date Issued: 2018
- Authors: Ziegler, Lisa
- Date: 2018
- Subjects: Oceanography -- Remote sensing -- Indian Ocean
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/15225 , vital:28188
- Description: Enhanced coastal altimetry, adaptive Leading-Edge Subwaveform(ALES), was used to study wo well known eddies along the southeastern African coast, namely the Delagoa Bight Lee Eddy and the Durban Lee Eddy. I address a two part problem. Firstly, how well does the application of coastal altimetry techniques behave in the coastal region? Secondly, is there a relationship between the eddies’ presence and chlorophyll-a (chl-a). Sea level anomalies (SLA) were computed from the re-tracked ALES data of two satellite missions — Envisat (used for Delagoa Bight eddy) and Jason -2 (for the Durban eddy) with geophysical corrections removed. These datasets were compared with the original satellite, 1 Hz RADS, AND AVISO gridded data. Two regions were selected to see if there was a biophysical link. A centre region of the eddy and an outside region of the eddy were taken. Results indicate that coastal altimetrywas successful in delimiting both features. ALES was less noisey and able to recover more data that were missed by the 1 Hz RADS dataset. Hovmöller plots showed the Delagoa Bight eddy to be more of a transient feature than semi-permanent, as had previously been suggested. Results from the linear model indicate a negative correlation between SLA and chl-a. This influence could be through facilitation of chl-a in the bight or just retaining chla. This is hard to elucidate without in situ data. These results show a promising indication that coastal altimetry will be a useful and reliable product to further biophysical coupling research along the coast.
- Full Text:
- Date Issued: 2018
An evaluation of the effectiveness of area-based conservation intervention in avoiding biodiversity loss in South Africa
- Authors: Van Straten, Maurice Oswald
- Date: 2023-04
- Subjects: Soil conservation -- South Africa , Livestock farms – South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61132 , vital:69765
- Description: Habitat degradation, livestock farming, crop cultivation, rangeland overutilization and veld mismanagement are among the factors causing biodiversity loss worldwide. Rangelands in arid and semi-arid environments are no exception, as they are under stress from conversion into cropland and pressure from livestock farming. In these arid areas, rainfall is unpredictable and plant recruitment levels low, resulting in veld rehabilitation being a potentially expensive and time-consuming undertaking for landowners. Landowners implement different rehabilitation methods to increase overall vegetation cover and prevent further soil and vegetation degradation. These rehabilitation methods may include the creation of micro-catchments, mulching, brushpacking, ripping, geotextiles, stone cobbling and erosion control fences, individually or in combination with the addition of reseeding, replanting, and use of manure or fertilizer to supplement land rehabilitation. This study investigated the significance of three rehabilitation methods (hollows, brush packing and a combination of these two methods) on water infiltration rates, soil moisture content, and vegetation canopy cover with associated growth form canopy cover over a period of 17 months (March 2021 to August 2022). This study showed that rehabilitation methods implemented had no significant impact on water infiltration rates and vegetation canopy cover. However, rehabilitation methods had a significant impact on soil moisture content. The use of a hollows is recommended when attempting to increase the soil moisture content percentage when performing rehabilitation. Overall vegetation canopy cover is influenced more by seasonal changes than by the rehabilitation methods implemented. This study indicated that the creation of micro-catchments is an effective rehabilitation method to use in an arid area, as it promotes vegetation establishment and growth. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Science and Management , 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Van Straten, Maurice Oswald
- Date: 2023-04
- Subjects: Soil conservation -- South Africa , Livestock farms – South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61132 , vital:69765
- Description: Habitat degradation, livestock farming, crop cultivation, rangeland overutilization and veld mismanagement are among the factors causing biodiversity loss worldwide. Rangelands in arid and semi-arid environments are no exception, as they are under stress from conversion into cropland and pressure from livestock farming. In these arid areas, rainfall is unpredictable and plant recruitment levels low, resulting in veld rehabilitation being a potentially expensive and time-consuming undertaking for landowners. Landowners implement different rehabilitation methods to increase overall vegetation cover and prevent further soil and vegetation degradation. These rehabilitation methods may include the creation of micro-catchments, mulching, brushpacking, ripping, geotextiles, stone cobbling and erosion control fences, individually or in combination with the addition of reseeding, replanting, and use of manure or fertilizer to supplement land rehabilitation. This study investigated the significance of three rehabilitation methods (hollows, brush packing and a combination of these two methods) on water infiltration rates, soil moisture content, and vegetation canopy cover with associated growth form canopy cover over a period of 17 months (March 2021 to August 2022). This study showed that rehabilitation methods implemented had no significant impact on water infiltration rates and vegetation canopy cover. However, rehabilitation methods had a significant impact on soil moisture content. The use of a hollows is recommended when attempting to increase the soil moisture content percentage when performing rehabilitation. Overall vegetation canopy cover is influenced more by seasonal changes than by the rehabilitation methods implemented. This study indicated that the creation of micro-catchments is an effective rehabilitation method to use in an arid area, as it promotes vegetation establishment and growth. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Science and Management , 2023
- Full Text:
- Date Issued: 2023-04
Comparison of mesozooplankton communities at three shallow seamounts in the South West Indian Ocean using size spectrum analysis
- Rasoloarijao, Zo, Huggett, Jenny
- Authors: Rasoloarijao, Zo , Huggett, Jenny
- Date: 2019
- Subjects: Seamounts
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/43012 , vital:36731
- Description: Seamounts influence ocean dynamics and consequently the surrounding ecosystem. Zooplankton communities associated with seamounts may be influenced by various mechanisms related to increased retention,such as Taylor columns and/or enhanced local productivity, leading to increased predation pressure. Through this study we investigated mesozooplankton distribution and community structure in the vicinity of three shallow seamounts in the South West Indian Ocean (SWIO) during September 2016, December 2016 and April/May 2017 at La Pérouse, MadRidge and Walters Shoal respectively. The water-column was profiled at 42 stations using a CTD-F equipped with a L-ADCP and mesozooplankton was sampled with a Bongo net or a Hydrobios Midi MultiNet, both fitted with 200 µm mesh. Walters Shoal had significantly lower mesozooplankton total abundance and biovolume compared to La Perouse and MadRidge. La Perouse and MadRidge showed similar mesozooplankton community structures with steep Normalised Biovolume Size Spectrum (NBSS) slopes, indicating higher productivity and dominance of small organisms, compared to Walters Shoal where the slopes were flatter. Total and per taxon abundances and biovolumes at locations “On” and “Off” the seamount were similar, as was the size diversity for MadRidge and Walter Shoal. None of the environmental parameters tested had a significant effect on variability of the mesozooplankton community structure at the stations overall.
- Full Text:
- Date Issued: 2019
- Authors: Rasoloarijao, Zo , Huggett, Jenny
- Date: 2019
- Subjects: Seamounts
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/43012 , vital:36731
- Description: Seamounts influence ocean dynamics and consequently the surrounding ecosystem. Zooplankton communities associated with seamounts may be influenced by various mechanisms related to increased retention,such as Taylor columns and/or enhanced local productivity, leading to increased predation pressure. Through this study we investigated mesozooplankton distribution and community structure in the vicinity of three shallow seamounts in the South West Indian Ocean (SWIO) during September 2016, December 2016 and April/May 2017 at La Pérouse, MadRidge and Walters Shoal respectively. The water-column was profiled at 42 stations using a CTD-F equipped with a L-ADCP and mesozooplankton was sampled with a Bongo net or a Hydrobios Midi MultiNet, both fitted with 200 µm mesh. Walters Shoal had significantly lower mesozooplankton total abundance and biovolume compared to La Perouse and MadRidge. La Perouse and MadRidge showed similar mesozooplankton community structures with steep Normalised Biovolume Size Spectrum (NBSS) slopes, indicating higher productivity and dominance of small organisms, compared to Walters Shoal where the slopes were flatter. Total and per taxon abundances and biovolumes at locations “On” and “Off” the seamount were similar, as was the size diversity for MadRidge and Walter Shoal. None of the environmental parameters tested had a significant effect on variability of the mesozooplankton community structure at the stations overall.
- Full Text:
- Date Issued: 2019
The development of novel cancer targeting agents
- Authors: Knoetze, Steyn
- Date: 2011
- Subjects: Cancer -- Research , Cancer -- Treatment
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:10397 , http://hdl.handle.net/10948/d1010636 , Cancer -- Research , Cancer -- Treatment
- Description: The search for the cure for cancer is currently a multi-billion dollar industry and the search for the elusive “magic bullet”, i.e. the perfect cancer drug that would interact therapeutically with cancerous tissues while having a minimal effect on healthy cells, is the topic of many research studies in the world today. A large number of novel drugs or drug complexes and conjugates are being synthesized and subjected to rigorous evaluation in the race to find the perfect cure. ECDG (Ethylene diCysteine DeoxyGlucose) seems to have promising cancer targeting ability. Even though this compound has been described in a few publications, we could not find any reference to the current use of ECDG in oncology clinics, either as a therapeutic agent, or as a diagnostic tool for imaging purposes. It was also not possible to purchase pure ECDG anywhere in the world. This prompted us to further investigate ECDG as a possible candidate for cancer targeting research, either as an imaging agent for cancer diagnosis or complexed with an anti-cancer agent for therapeutic purposes. Detailed investigations done in our laboratory can be divided into the following categories: - Development of a synthetic method for ECDG on a multigram scale ; - Purification of prepared ECDG not using the described dialysis method that only allows the purification of small quantities of ECDG (mg scale) ; Detailed investigation of the chemistry involved in the preparation of pure ECDG and its metal complexes ; - Investigation of the stability of ECDG and its metal complexes that is essential data required for any pharmaceutical agent ; - Preparation of ECDG complexes for use as a diagnostic tool, i.e. complexation with 99mTc ; Investigation of the bio distribution of ECDG-ReO complexes ; - Preparation of an ECDG kit as a diagnostic tool for use in oncology clinics. The development of novel aromatic ligands having similar characteristics compared to ECDG, containing an N2S2 chromophore as donor atoms, to further investigate their targeting capabilities, have also been investigated. All intermediates and final compounds were characterized mainly by ESI MS, in some cases IR and NMR whenever available. Successful preparation and purification of ECDG ands its metal complexes was achieved and extensively characterized and evaluated. Efforts directed towards the development of ECDG at NECSA, South Africa, were also rewarded with significant success. Furthermore, significant development regarding the synthesis of two novel compounds with ECDG-like characteristics was also completed.
- Full Text:
- Date Issued: 2011
- Authors: Knoetze, Steyn
- Date: 2011
- Subjects: Cancer -- Research , Cancer -- Treatment
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:10397 , http://hdl.handle.net/10948/d1010636 , Cancer -- Research , Cancer -- Treatment
- Description: The search for the cure for cancer is currently a multi-billion dollar industry and the search for the elusive “magic bullet”, i.e. the perfect cancer drug that would interact therapeutically with cancerous tissues while having a minimal effect on healthy cells, is the topic of many research studies in the world today. A large number of novel drugs or drug complexes and conjugates are being synthesized and subjected to rigorous evaluation in the race to find the perfect cure. ECDG (Ethylene diCysteine DeoxyGlucose) seems to have promising cancer targeting ability. Even though this compound has been described in a few publications, we could not find any reference to the current use of ECDG in oncology clinics, either as a therapeutic agent, or as a diagnostic tool for imaging purposes. It was also not possible to purchase pure ECDG anywhere in the world. This prompted us to further investigate ECDG as a possible candidate for cancer targeting research, either as an imaging agent for cancer diagnosis or complexed with an anti-cancer agent for therapeutic purposes. Detailed investigations done in our laboratory can be divided into the following categories: - Development of a synthetic method for ECDG on a multigram scale ; - Purification of prepared ECDG not using the described dialysis method that only allows the purification of small quantities of ECDG (mg scale) ; Detailed investigation of the chemistry involved in the preparation of pure ECDG and its metal complexes ; - Investigation of the stability of ECDG and its metal complexes that is essential data required for any pharmaceutical agent ; - Preparation of ECDG complexes for use as a diagnostic tool, i.e. complexation with 99mTc ; Investigation of the bio distribution of ECDG-ReO complexes ; - Preparation of an ECDG kit as a diagnostic tool for use in oncology clinics. The development of novel aromatic ligands having similar characteristics compared to ECDG, containing an N2S2 chromophore as donor atoms, to further investigate their targeting capabilities, have also been investigated. All intermediates and final compounds were characterized mainly by ESI MS, in some cases IR and NMR whenever available. Successful preparation and purification of ECDG ands its metal complexes was achieved and extensively characterized and evaluated. Efforts directed towards the development of ECDG at NECSA, South Africa, were also rewarded with significant success. Furthermore, significant development regarding the synthesis of two novel compounds with ECDG-like characteristics was also completed.
- Full Text:
- Date Issued: 2011
Bush clumps as indicators of thresholds of change in Arid Thicket mosaic piospheres
- Authors: Schmidt, Anton George
- Date: 2017
- Subjects: Biodiversity conservation Ecological processes
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/20811 , vital:29403
- Description: In the literature, Arid Thicket transformation by domestic meso-herbivores is purported to follow a state-and-transition model, whereby the ecosystem is initially resilient to herbivory until some threshold is crossed, where after there is a rapid shift to a new alternative stable state. My study represents a first attempt to verify this hypothesis by searching for evidence of stable ecosystem states separated by structural, functional and degradation thresholds in Pruim-Spekboomveld, a variation of Arid Thicket found in the southern Cape of South Africa. In this variation, thicket bush clumps ranging in size from approximately 1 m2 to 100 m2 are interspersed in a matrix of Succulent Karoo vegetation. I correlate structural and functional attributes of the thicket bush clumps and the soil environment beneath them (indicators of ecosystem function) to distance from artificial watering points in four piosphere treatments that have had a different rangeland management history. I mostly fit linear, exponential and sigmoid regression models to my data and use Akaike’s Information Criterion to select the best fitting model. When analysing data on changes in the variation of vegetation production with distance from water using the Normalized Difference Vegetation Index, I additionally fit Generalized Additive Models to the data to take into account more complex predicted patterns of change. Furthermore, I compare the end regions of my data in the piosphere treatments to each other and to similar data collected in a transformed and untransformed reference site. I use both the pattern and extent of transformation within and between the treatments and the reference sites, to verify the existence of stable states and structural, functional and degradation thresholds. I also subject my entire dataset to multivariate analysis using ordination and permutation procedures, in an attempt to corroborate my results from the univariate analysis and to assess the response of bush clump community composition to herbivory. My results indicate that at the scale of a bush clump, a threshold reduction in species richness, functional type diversity, succulent shrub redundancy and cover, palatable shrub cover and bush clump leaf mass below 1.5 m occurs in regions intensively used by domestic meso-herbivores. Furthermore, at the landscape scale there is a threshold reduction in canopy tree cover and bush clump density. In addition to these structural threshold changes, results from a Landscape Function Analysis indicate that soil nutrient cycling, soil water infiltration and soil stability thresholds are crossed at the landscape scale. The soil nutrient cycling threshold is affirmed by soil chemical analyses which indicate that the most rested treatment in the study area has low carbon and nitrogen levels. Furthermore, the keystone species, Portulacaria afra, is unable to re-establish itself in any of the treatments. High pH and potassium levels in all the treatments, relative to the untransformed reference site, indicate that Portulacaria afra (which prefers moderate soil conditions) is unlikely to re-establish in the study area. This finding suggests that all my treatments have crossed a degradation threshold and therefore represent an alternative stable state to the untransformed reference site. My multivariate analysis supports this finding and further indicates that the sampling zones within 25 m of the watering points in the most utilized treatments have crossed a second degradation threshold. This finding is supported by my results that indicate that structural and function thresholds (related to the size, density and ability of bush clumps to capture and retain soil resources) have been crossed. Furthermore, excessively high concentrations of base cations in these sampling zones, relative to the untransformed reference site, affirm the crossing of a degradation threshold. My results on the changes in the variation of vegetation production with distance from water using the Normalized Difference Vegetation Index, support the growing body of evidence in the literature that suggests that increases in the variance of ecosystem processes and services are important indicators of impending ecological thresholds. In general, my findings support the prediction in the literature that domestic meso-herbivore induced transformation of Arid Mosaic Thicket will follow a state-andtransition model.
- Full Text:
- Date Issued: 2017
- Authors: Schmidt, Anton George
- Date: 2017
- Subjects: Biodiversity conservation Ecological processes
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/20811 , vital:29403
- Description: In the literature, Arid Thicket transformation by domestic meso-herbivores is purported to follow a state-and-transition model, whereby the ecosystem is initially resilient to herbivory until some threshold is crossed, where after there is a rapid shift to a new alternative stable state. My study represents a first attempt to verify this hypothesis by searching for evidence of stable ecosystem states separated by structural, functional and degradation thresholds in Pruim-Spekboomveld, a variation of Arid Thicket found in the southern Cape of South Africa. In this variation, thicket bush clumps ranging in size from approximately 1 m2 to 100 m2 are interspersed in a matrix of Succulent Karoo vegetation. I correlate structural and functional attributes of the thicket bush clumps and the soil environment beneath them (indicators of ecosystem function) to distance from artificial watering points in four piosphere treatments that have had a different rangeland management history. I mostly fit linear, exponential and sigmoid regression models to my data and use Akaike’s Information Criterion to select the best fitting model. When analysing data on changes in the variation of vegetation production with distance from water using the Normalized Difference Vegetation Index, I additionally fit Generalized Additive Models to the data to take into account more complex predicted patterns of change. Furthermore, I compare the end regions of my data in the piosphere treatments to each other and to similar data collected in a transformed and untransformed reference site. I use both the pattern and extent of transformation within and between the treatments and the reference sites, to verify the existence of stable states and structural, functional and degradation thresholds. I also subject my entire dataset to multivariate analysis using ordination and permutation procedures, in an attempt to corroborate my results from the univariate analysis and to assess the response of bush clump community composition to herbivory. My results indicate that at the scale of a bush clump, a threshold reduction in species richness, functional type diversity, succulent shrub redundancy and cover, palatable shrub cover and bush clump leaf mass below 1.5 m occurs in regions intensively used by domestic meso-herbivores. Furthermore, at the landscape scale there is a threshold reduction in canopy tree cover and bush clump density. In addition to these structural threshold changes, results from a Landscape Function Analysis indicate that soil nutrient cycling, soil water infiltration and soil stability thresholds are crossed at the landscape scale. The soil nutrient cycling threshold is affirmed by soil chemical analyses which indicate that the most rested treatment in the study area has low carbon and nitrogen levels. Furthermore, the keystone species, Portulacaria afra, is unable to re-establish itself in any of the treatments. High pH and potassium levels in all the treatments, relative to the untransformed reference site, indicate that Portulacaria afra (which prefers moderate soil conditions) is unlikely to re-establish in the study area. This finding suggests that all my treatments have crossed a degradation threshold and therefore represent an alternative stable state to the untransformed reference site. My multivariate analysis supports this finding and further indicates that the sampling zones within 25 m of the watering points in the most utilized treatments have crossed a second degradation threshold. This finding is supported by my results that indicate that structural and function thresholds (related to the size, density and ability of bush clumps to capture and retain soil resources) have been crossed. Furthermore, excessively high concentrations of base cations in these sampling zones, relative to the untransformed reference site, affirm the crossing of a degradation threshold. My results on the changes in the variation of vegetation production with distance from water using the Normalized Difference Vegetation Index, support the growing body of evidence in the literature that suggests that increases in the variance of ecosystem processes and services are important indicators of impending ecological thresholds. In general, my findings support the prediction in the literature that domestic meso-herbivore induced transformation of Arid Mosaic Thicket will follow a state-andtransition model.
- Full Text:
- Date Issued: 2017
Environmental management of wetlands on an urban periphery: the case of Bay West
- Authors: Domoney, Nicola Leah
- Date: 2018
- Subjects: Wetland management -- South Africa -- Nelson Mandela Bay Municipality , Remote sensing Chlorophyll
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/30854 , vital:31183
- Description: South Africa is a semi-arid country and thus depends on sound management of its water resources. Wetlands, despite their importance to water resource storage and water quality, among their other ecological and social significance, remain the most threatened of South Africa’s ecosystems. One of their greatest threats is encroachment by urbanisation. This occurs because wetlands, and especially ephemeral urban periphery wetlands, are overlooked. This study’s main objective was to determine the water quality and health of the wetlands adjacent to the newly established Bay West development on the western urban periphery of Nelson Mandela Bay. Wetlands are difficult to access and it is time-consuming to assess them. Remote sensing, however, overcomes this challenge and is cost-effective and time-considerate. It was the aim of this study to assess the health of the peri-urban wetlands on the Bay West periphery in order to formulate an appropriate environmental management plan, and remote sensing was tested as an effective method for wetland health management. It was found that the wetlands closer to the urban residential area (Sherwood suburb) were far more impacted than the wetlands nearer to Bay West Mall. Wetlands Six to Eight were higher in all parameters of pH, total dissolved solutes (TDS), salinity, conductivity and chlorophyll a concentration than Wetlands One to Five located further away from the urban area. A correlation with distance away from the urban area found a strong inverse relationship with between distance and the water quality factor, yielding a correlation coefficient of (<-0.7) in 2017 and (<-0.9) in 2018 with regard to TDS, salinity and conductivity. This, therefore, suggests that the wetlands’ health deteriorates towards the urban area. TDS, salinity, pH and conductivity correlate highly with chlorophyll a concentration at (>0.70). There was significant difference in pH in the year 2017 between the Bay West wetlands and the reference wetland (p<0.05; df=19; f= 3.56; n=3) and in 2018 (p<0.01; df=22; f= 8.90; n=3). No significant difference was found between the wetlands for dissolved oxygen. TDS between the wetlands was found to be significantly different in the year 2017 (p<0.01; df=23; f= 44.16; n=3) and 2018 (p<0.05; df=22; f=2.62; n=3), where conductivity and salinity returned the same p value for 2017 and 2018 as TDS respectively. There was a significant difference in chlorophyll a between the Bay West wetlands in 2017 (p<0.05; df=20; f=3.29; n=3) and Wetland Seven measured eutrophic at 22.45 mg/L-1. Remote sensing red band values and the field sample absorption values were highly correlated at R2= 0.5. Chlorophyll a content of wetland water correlated with NDVI data at R2= 0.6. Thus, remote sensing proved to be a successful estimator for wetlands health analysis and a proxy for wetland management. These results yielded an environmental management plan where monitoring water quality via chlorophyll a indicated health levels of the wetlands via trophic state.
- Full Text:
- Date Issued: 2018
- Authors: Domoney, Nicola Leah
- Date: 2018
- Subjects: Wetland management -- South Africa -- Nelson Mandela Bay Municipality , Remote sensing Chlorophyll
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/30854 , vital:31183
- Description: South Africa is a semi-arid country and thus depends on sound management of its water resources. Wetlands, despite their importance to water resource storage and water quality, among their other ecological and social significance, remain the most threatened of South Africa’s ecosystems. One of their greatest threats is encroachment by urbanisation. This occurs because wetlands, and especially ephemeral urban periphery wetlands, are overlooked. This study’s main objective was to determine the water quality and health of the wetlands adjacent to the newly established Bay West development on the western urban periphery of Nelson Mandela Bay. Wetlands are difficult to access and it is time-consuming to assess them. Remote sensing, however, overcomes this challenge and is cost-effective and time-considerate. It was the aim of this study to assess the health of the peri-urban wetlands on the Bay West periphery in order to formulate an appropriate environmental management plan, and remote sensing was tested as an effective method for wetland health management. It was found that the wetlands closer to the urban residential area (Sherwood suburb) were far more impacted than the wetlands nearer to Bay West Mall. Wetlands Six to Eight were higher in all parameters of pH, total dissolved solutes (TDS), salinity, conductivity and chlorophyll a concentration than Wetlands One to Five located further away from the urban area. A correlation with distance away from the urban area found a strong inverse relationship with between distance and the water quality factor, yielding a correlation coefficient of (<-0.7) in 2017 and (<-0.9) in 2018 with regard to TDS, salinity and conductivity. This, therefore, suggests that the wetlands’ health deteriorates towards the urban area. TDS, salinity, pH and conductivity correlate highly with chlorophyll a concentration at (>0.70). There was significant difference in pH in the year 2017 between the Bay West wetlands and the reference wetland (p<0.05; df=19; f= 3.56; n=3) and in 2018 (p<0.01; df=22; f= 8.90; n=3). No significant difference was found between the wetlands for dissolved oxygen. TDS between the wetlands was found to be significantly different in the year 2017 (p<0.01; df=23; f= 44.16; n=3) and 2018 (p<0.05; df=22; f=2.62; n=3), where conductivity and salinity returned the same p value for 2017 and 2018 as TDS respectively. There was a significant difference in chlorophyll a between the Bay West wetlands in 2017 (p<0.05; df=20; f=3.29; n=3) and Wetland Seven measured eutrophic at 22.45 mg/L-1. Remote sensing red band values and the field sample absorption values were highly correlated at R2= 0.5. Chlorophyll a content of wetland water correlated with NDVI data at R2= 0.6. Thus, remote sensing proved to be a successful estimator for wetlands health analysis and a proxy for wetland management. These results yielded an environmental management plan where monitoring water quality via chlorophyll a indicated health levels of the wetlands via trophic state.
- Full Text:
- Date Issued: 2018
Vanadium-based catalysts for oxidation of organosulfur compounds: synthesis, catalysis and mechanistic studies
- Dembaremba, Tendai, Ogunlaja, Adeniyi
- Authors: Dembaremba, Tendai , Ogunlaja, Adeniyi
- Date: 2018
- Subjects: Organosulfur compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/30248 , vital:30909
- Description: A series of oxidovanadium(IV) complexes based on the ligand, 2-(2’-hydroxyphenyl)imidazole, with substituent groups of different electronegativities on the phenolic para position, were successfully synthesized, characterized and investigated for their catalytic activities in the oxidation of dibenzothiophene (DBT), a typical refractory sulfur compound found in fuel. It was observed from catalytic oxidation studies that the presence of an electron withdrawing group on the phenolic para position of the ligand results in higher catalytic activity. SC-XRD data and DFT studies were used to explain the trends in activity observed. The highest activity was observed with 6.5 nmol of the nitro derivative catalyst [VO(PIMNO2)2] when 100% of 100 mg (0.543 mmol) of DBT was converted to its sulfone derivative dibenzothiophene sulfoxide (DBTO2) using 2.0 mL (1.05 mmol) of t-BuOOH. Potential to immobilize the complex catalysts was demonstrated through the synthesis of oxidovanadium(IV) copolymer nanofibers. The oxidovanadium nanofibers were successfully employed in the oxidation of sulfur compounds in a real fuel sample (diesel 500) which were then removed through solvent extraction using acetonitrile to give clean fuel. SC-XRD, EPR and UV-Vis spectroscopy were instrumental in providing insight into the mechanism of the catalyzed reaction. Vanadium oxides were also investigated as a cheaper alternative for the catalytic oxidation reaction. Phases of different vanadium oxides were synthesized by calcining NH4VO3 in air at different temperatures with an intention to investigate them for their catalytic activities. The catalyst obtained from calcination at 600⁰C was predominantly the orthorhombic phase of V2O5. Potential to immobilize the vanadium oxides was demonstrated using a silica support where NH4VO3 was impregnated onto silica and calcined in air at 600⁰C. The catalyst showed good potential in the oxidation of DBT to DBTO2, with 10 mg (43.9 μmol) of catalyst successfully converting 100% of 100 mg (0.543 mmol) DBT to DBTO2 using 2.0 mL (1.05 mmol) of t-BuOOH. The catalyst was also employed for a real fuel sample (diesel 500) with good results. The mechanistic aspects of vanadium oxides were also investigated in this study.
- Full Text:
- Date Issued: 2018
- Authors: Dembaremba, Tendai , Ogunlaja, Adeniyi
- Date: 2018
- Subjects: Organosulfur compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/30248 , vital:30909
- Description: A series of oxidovanadium(IV) complexes based on the ligand, 2-(2’-hydroxyphenyl)imidazole, with substituent groups of different electronegativities on the phenolic para position, were successfully synthesized, characterized and investigated for their catalytic activities in the oxidation of dibenzothiophene (DBT), a typical refractory sulfur compound found in fuel. It was observed from catalytic oxidation studies that the presence of an electron withdrawing group on the phenolic para position of the ligand results in higher catalytic activity. SC-XRD data and DFT studies were used to explain the trends in activity observed. The highest activity was observed with 6.5 nmol of the nitro derivative catalyst [VO(PIMNO2)2] when 100% of 100 mg (0.543 mmol) of DBT was converted to its sulfone derivative dibenzothiophene sulfoxide (DBTO2) using 2.0 mL (1.05 mmol) of t-BuOOH. Potential to immobilize the complex catalysts was demonstrated through the synthesis of oxidovanadium(IV) copolymer nanofibers. The oxidovanadium nanofibers were successfully employed in the oxidation of sulfur compounds in a real fuel sample (diesel 500) which were then removed through solvent extraction using acetonitrile to give clean fuel. SC-XRD, EPR and UV-Vis spectroscopy were instrumental in providing insight into the mechanism of the catalyzed reaction. Vanadium oxides were also investigated as a cheaper alternative for the catalytic oxidation reaction. Phases of different vanadium oxides were synthesized by calcining NH4VO3 in air at different temperatures with an intention to investigate them for their catalytic activities. The catalyst obtained from calcination at 600⁰C was predominantly the orthorhombic phase of V2O5. Potential to immobilize the vanadium oxides was demonstrated using a silica support where NH4VO3 was impregnated onto silica and calcined in air at 600⁰C. The catalyst showed good potential in the oxidation of DBT to DBTO2, with 10 mg (43.9 μmol) of catalyst successfully converting 100% of 100 mg (0.543 mmol) DBT to DBTO2 using 2.0 mL (1.05 mmol) of t-BuOOH. The catalyst was also employed for a real fuel sample (diesel 500) with good results. The mechanistic aspects of vanadium oxides were also investigated in this study.
- Full Text:
- Date Issued: 2018
Ecological principles for honeybush (Cyclopia spp.) conservation and cultivation
- Authors: Beyers, Andrea
- Date: 2016
- Subjects: Fynbos -- South Africa , Rooibos tea industry -- South Africa , Herbal teas -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/5723 , vital:20975
- Description: Market demand for the fynbos-derived honeybush (Cyclopia spp.) tea is on the rise, and there is an urgent need for better conservation of wild Cyclopia populations and for a shift to sustainable cultivation. Rooibos is another popular fynbos product that underwent exponential market growth over the last two decades but this resulted in large-scale conversion of pristine mountain fynbos to intensively-used crop lands. Adopting a conservation agriculture approach in expanding indigenous products will help in conserving biodiversity and ecosystem processes in this global biodiversity hotspot. Conservation agriculture of indigenous fynbos products grown in the Cape Floristic Region (CFR) should follow five main principles in order to maximise biodiversity conservation alongside agriculture. These principles are: 1) maintain high diversity at all levels, 2) conserve soil structure and processes, 3) conserve and restore natural ecosystem processes, 4) promote ecosystem stability and self-perpetuation, and 5) maintain natural areas as sources of ecosystem components. Given the negative ecological consequences of the industrialisation of the rooibos industry, it would be in the interest of biodiversity conservation, and even of agriculture, to apply these principles to honeybush cultivation. In order to prevent further fynbos habitat loss, cultivation of honeybush could be catalysed on old fields rather than in ploughed or cleared fynbos. Here I compare germination, growth and survival of two species (Cyclopia intermedia E.Mey. and C. subternata Vogel) between different land use types (ploughed lands, old fields and intact fynbos) and treatments (cleared and uncleared) in the Langkloof, Eastern Cape, over one year. Plots of each land use type were subject to each of these two treatments, although the ploughed plot constituted only a cleared treatment. Growth was highest on ploughed land, while survival and growth were lowest in uncleared fynbos. Cleared fynbos had the lowest germination success in both species, with the other sites and treatments coming out roughly the same. These results show that although ploughed lands give highest yields, growth and survival on old fields without ploughing is comparable with that on ploughed lands and is therefore a feasible alternative. Understanding the recruitment dynamics of honeybush is imperative for adequate conservation of wild populations. Furthermore, understanding this ecological aspect of the genus will help in developing the honeybush industry as a sustainable, agroecological market that uses semi-natural populations for production. Although Cyclopia species are early-successional species that germinate after fire, recruitment of Cyclopia pubescens Eckl. & Zeyh. continues throughout the inter-fire period. Cyclopia pubescens populations near Port Elizabeth were described according to their age structure and plant densities to discern possible density-dependent recruitment effects. Results showed that dense stands for the most part do not support high post-fire recruitment. This gives insight into suitable planting densities for new or restore populations and into management guidelines for remnant populations of threatened species. This thesis highlights important issues facing the honeybush industry. Mainstreaming biodiversity conservation into honeybush production is achievable, given that the industry is still relatively young, but this will require further research and strong market leadership.
- Full Text:
- Date Issued: 2016
- Authors: Beyers, Andrea
- Date: 2016
- Subjects: Fynbos -- South Africa , Rooibos tea industry -- South Africa , Herbal teas -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/5723 , vital:20975
- Description: Market demand for the fynbos-derived honeybush (Cyclopia spp.) tea is on the rise, and there is an urgent need for better conservation of wild Cyclopia populations and for a shift to sustainable cultivation. Rooibos is another popular fynbos product that underwent exponential market growth over the last two decades but this resulted in large-scale conversion of pristine mountain fynbos to intensively-used crop lands. Adopting a conservation agriculture approach in expanding indigenous products will help in conserving biodiversity and ecosystem processes in this global biodiversity hotspot. Conservation agriculture of indigenous fynbos products grown in the Cape Floristic Region (CFR) should follow five main principles in order to maximise biodiversity conservation alongside agriculture. These principles are: 1) maintain high diversity at all levels, 2) conserve soil structure and processes, 3) conserve and restore natural ecosystem processes, 4) promote ecosystem stability and self-perpetuation, and 5) maintain natural areas as sources of ecosystem components. Given the negative ecological consequences of the industrialisation of the rooibos industry, it would be in the interest of biodiversity conservation, and even of agriculture, to apply these principles to honeybush cultivation. In order to prevent further fynbos habitat loss, cultivation of honeybush could be catalysed on old fields rather than in ploughed or cleared fynbos. Here I compare germination, growth and survival of two species (Cyclopia intermedia E.Mey. and C. subternata Vogel) between different land use types (ploughed lands, old fields and intact fynbos) and treatments (cleared and uncleared) in the Langkloof, Eastern Cape, over one year. Plots of each land use type were subject to each of these two treatments, although the ploughed plot constituted only a cleared treatment. Growth was highest on ploughed land, while survival and growth were lowest in uncleared fynbos. Cleared fynbos had the lowest germination success in both species, with the other sites and treatments coming out roughly the same. These results show that although ploughed lands give highest yields, growth and survival on old fields without ploughing is comparable with that on ploughed lands and is therefore a feasible alternative. Understanding the recruitment dynamics of honeybush is imperative for adequate conservation of wild populations. Furthermore, understanding this ecological aspect of the genus will help in developing the honeybush industry as a sustainable, agroecological market that uses semi-natural populations for production. Although Cyclopia species are early-successional species that germinate after fire, recruitment of Cyclopia pubescens Eckl. & Zeyh. continues throughout the inter-fire period. Cyclopia pubescens populations near Port Elizabeth were described according to their age structure and plant densities to discern possible density-dependent recruitment effects. Results showed that dense stands for the most part do not support high post-fire recruitment. This gives insight into suitable planting densities for new or restore populations and into management guidelines for remnant populations of threatened species. This thesis highlights important issues facing the honeybush industry. Mainstreaming biodiversity conservation into honeybush production is achievable, given that the industry is still relatively young, but this will require further research and strong market leadership.
- Full Text:
- Date Issued: 2016
Applying a systems analysis approach to support marine spatial planning in Algoa Bay, South Africa
- Authors: Vermeulen, Estee Ann
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/54121 , vital:46312
- Description: Ocean health provides the foundation for human health through the provisioning of ecosystem services. Increasing demands on ocean space and resources are, however, resulting in a decline in ocean health, with direct and indirect knock-on effects on marine uses and ultimately on human health. In response, there is a growing need to acknowledge and better manage complex human-ocean interactions. This has been recognised in global sustainable development goals and in integrated ocean management processes, leading to widespread endorsement of an ecosystem-based marine spatial planning (MSP) process, including in South Africa. In support of the national MSP process, significant progress has been made in understanding the spatial extent of marine activities and associated marine pressures, but the temporal dynamics of marine activities and interconnections with the marine environment are less well understood. To plan for the growth of marine activities and associated user conflicts, the drivers of these temporal dynamics and associated feedback effects need to be analysed and potential policy and management interventions identified and tested. To support South Africa’s national MSP process, this study adopts a systems analysis approach, using system dynamics modelling, to explore the temporal change in marine uses under alternative growth scenarios in Algoa Bay. Algoa Bay is an appropriate study area because it is experiencing a rapid expansion of marine activities, coupled with a growing uncertainty regarding marine sustainability outcomes. To assist future marine management decisions, the Algoa Marine Systems Analysis Tool (Algoa MSAT) was developed, comprising seven sub-models. Five of the sub-models represent selected marine uses in Algoa Bay, whereas the sixth and seventh integrate the outputs from each marine use in terms of sustainable management indicators (marine health, marine wealth and marine labour). Model development primarily adopted an expert-based model ling approach, although the involvement of stakeholders, through a collaborative modelling process, assisted in integrating knowledge on different marine sectors’ activities, impacts and planning visions into the model framework. Model results were generated under different scenarios to investigate changes in the growth of marine activities and marine sustainability indicators under different levels of ocean governance. Under the baseline (or business-as-usual) model scenario, marine activities were shown to grow increasingly within their respective management limits, with an increase in marine wealth and labour and a consequential decrease in marine health. This scenario particularly highlights that current ocean governance practices are ineffective in sustaining the projected growth of the marine uses, particularly for those that are vulnerable to negative changes in marine health. Conversely, sectors that hold more value in marine wealth and are more resilient to changes in marine health, may continue to grow regardless of negative knock-on effects of the health of the marine environment and on other uses in the bay. This emphasises that an alternative governance strategy is needed to achieve the long-term goal of an ecosystem-based MSP process, as required by South African MSP legislation. To achieve this will require multiple, adaptive cross-sectoral management interventions that are directed towards the ‘deeper leverage points’ that are able to maintain the growth of marine activities within appropriate limits defined by marine health. Using the model interface developed in this project, decision-makers and stakeholders can use the model to explore the temporal dynamics in marine activities under different governance scenarios. Although the model is limited to Algoa Bay, the model boundary can be adapted to assist in marine planning processes at national or trans-national scales. Such analytical assessments and tools are critical to progress the ecosystem-based management approach in MSP, as is required to achieve global sustainable development goals. , Thesis (PhD) -- Faculty of Science, Coastal and Marine Research Unit, 2021
- Full Text:
- Date Issued: 2021-12
- Authors: Vermeulen, Estee Ann
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/54121 , vital:46312
- Description: Ocean health provides the foundation for human health through the provisioning of ecosystem services. Increasing demands on ocean space and resources are, however, resulting in a decline in ocean health, with direct and indirect knock-on effects on marine uses and ultimately on human health. In response, there is a growing need to acknowledge and better manage complex human-ocean interactions. This has been recognised in global sustainable development goals and in integrated ocean management processes, leading to widespread endorsement of an ecosystem-based marine spatial planning (MSP) process, including in South Africa. In support of the national MSP process, significant progress has been made in understanding the spatial extent of marine activities and associated marine pressures, but the temporal dynamics of marine activities and interconnections with the marine environment are less well understood. To plan for the growth of marine activities and associated user conflicts, the drivers of these temporal dynamics and associated feedback effects need to be analysed and potential policy and management interventions identified and tested. To support South Africa’s national MSP process, this study adopts a systems analysis approach, using system dynamics modelling, to explore the temporal change in marine uses under alternative growth scenarios in Algoa Bay. Algoa Bay is an appropriate study area because it is experiencing a rapid expansion of marine activities, coupled with a growing uncertainty regarding marine sustainability outcomes. To assist future marine management decisions, the Algoa Marine Systems Analysis Tool (Algoa MSAT) was developed, comprising seven sub-models. Five of the sub-models represent selected marine uses in Algoa Bay, whereas the sixth and seventh integrate the outputs from each marine use in terms of sustainable management indicators (marine health, marine wealth and marine labour). Model development primarily adopted an expert-based model ling approach, although the involvement of stakeholders, through a collaborative modelling process, assisted in integrating knowledge on different marine sectors’ activities, impacts and planning visions into the model framework. Model results were generated under different scenarios to investigate changes in the growth of marine activities and marine sustainability indicators under different levels of ocean governance. Under the baseline (or business-as-usual) model scenario, marine activities were shown to grow increasingly within their respective management limits, with an increase in marine wealth and labour and a consequential decrease in marine health. This scenario particularly highlights that current ocean governance practices are ineffective in sustaining the projected growth of the marine uses, particularly for those that are vulnerable to negative changes in marine health. Conversely, sectors that hold more value in marine wealth and are more resilient to changes in marine health, may continue to grow regardless of negative knock-on effects of the health of the marine environment and on other uses in the bay. This emphasises that an alternative governance strategy is needed to achieve the long-term goal of an ecosystem-based MSP process, as required by South African MSP legislation. To achieve this will require multiple, adaptive cross-sectoral management interventions that are directed towards the ‘deeper leverage points’ that are able to maintain the growth of marine activities within appropriate limits defined by marine health. Using the model interface developed in this project, decision-makers and stakeholders can use the model to explore the temporal dynamics in marine activities under different governance scenarios. Although the model is limited to Algoa Bay, the model boundary can be adapted to assist in marine planning processes at national or trans-national scales. Such analytical assessments and tools are critical to progress the ecosystem-based management approach in MSP, as is required to achieve global sustainable development goals. , Thesis (PhD) -- Faculty of Science, Coastal and Marine Research Unit, 2021
- Full Text:
- Date Issued: 2021-12
A potential biological role for microcystin in photosynthesis in Microcystis Aeruginosa
- Authors: Phelan, Richard Reginald
- Date: 2009
- Subjects: Microcystis aeruginosa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10320 , http://hdl.handle.net/10948/1285 , Microcystis aeruginosa
- Description: Neither the ecological role nor the metabolic function of microcystin is known. Cellular microcystin concentrations correlate to cellular nitrogen status for a given environmental phosphorous concentration and specific growth rate. Microcystin production is enhanced when the rate of nitrogen accumulation exceeds the relative specific growth rate and/or when cellular N:C ratios exceed the Redfield ratio as a function of reduced carbon fixation, suggesting enhanced production of microcystin under carbon stress. Additionally, a strong correlation between medium phosphate and carbon fixation, and the negative correlation between medium phosphate and microcystin combined with the cellular localization of microcystin in thylakoids supports a possible role for microcystin in enhancement of photosynthesis. Batch cultures of both Microcystis aeruginosa PCC7806 and a mcyA- knockout mutant of PCC7806 were therefore cultured at different light intensities and media treatments, so as to vary cellular N:C ratios and concentrations, and sampled for analysis of microcystin concentration, cell numbers and residual medium nitrates. Inter-strain differences in photosynthetic electron transfer rates and levels were monitored using a Hansatech PEA fluorometer and compared to cellular microcystin concentrations. An enhanced survival was observed at high light, where the toxic strain survived while the nontoxic strain became chlorotic. A strong correlation (r2 = 0.907, p< 0.001, N=22) between microcystin concentration and growth rate was observed at high light conditions. No such advantage was observed at optimal or low-light conditions and media composition had no significant effect on the relationship between toxicity and survival at high light. PCC7806 showed elevated PI(abs) values compared to the mcyA knockout strain, which indicates an increased stability of PSII. A strong correlation between PI(abs) and microcystin (r = 0.88, p< 0.005, N=15) was observed for cultures grown in modified BG11 containing 25 mM under continuous illumination of 37 μmol of photons m-2.s-1. No correlation was observed between PI(abs) and microcystin for the other treatments. The toxin producer had significantly higher values for density of active reaction centers and ii quantum efficiency compared to the mutant. A decrease in F0 in the mutant suggests degradation of the phycobiliproteins, whereas PCC7806 didn’t show a significant decrease in F0 Data indicate that microcystins play a role in photosynthesis by preventing chlorosis in saturating light conditions either by enhancing the redox stability of the phycobiliproteins or PS II, thus preventing photooxidation.
- Full Text:
- Date Issued: 2009
- Authors: Phelan, Richard Reginald
- Date: 2009
- Subjects: Microcystis aeruginosa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10320 , http://hdl.handle.net/10948/1285 , Microcystis aeruginosa
- Description: Neither the ecological role nor the metabolic function of microcystin is known. Cellular microcystin concentrations correlate to cellular nitrogen status for a given environmental phosphorous concentration and specific growth rate. Microcystin production is enhanced when the rate of nitrogen accumulation exceeds the relative specific growth rate and/or when cellular N:C ratios exceed the Redfield ratio as a function of reduced carbon fixation, suggesting enhanced production of microcystin under carbon stress. Additionally, a strong correlation between medium phosphate and carbon fixation, and the negative correlation between medium phosphate and microcystin combined with the cellular localization of microcystin in thylakoids supports a possible role for microcystin in enhancement of photosynthesis. Batch cultures of both Microcystis aeruginosa PCC7806 and a mcyA- knockout mutant of PCC7806 were therefore cultured at different light intensities and media treatments, so as to vary cellular N:C ratios and concentrations, and sampled for analysis of microcystin concentration, cell numbers and residual medium nitrates. Inter-strain differences in photosynthetic electron transfer rates and levels were monitored using a Hansatech PEA fluorometer and compared to cellular microcystin concentrations. An enhanced survival was observed at high light, where the toxic strain survived while the nontoxic strain became chlorotic. A strong correlation (r2 = 0.907, p< 0.001, N=22) between microcystin concentration and growth rate was observed at high light conditions. No such advantage was observed at optimal or low-light conditions and media composition had no significant effect on the relationship between toxicity and survival at high light. PCC7806 showed elevated PI(abs) values compared to the mcyA knockout strain, which indicates an increased stability of PSII. A strong correlation between PI(abs) and microcystin (r = 0.88, p< 0.005, N=15) was observed for cultures grown in modified BG11 containing 25 mM under continuous illumination of 37 μmol of photons m-2.s-1. No correlation was observed between PI(abs) and microcystin for the other treatments. The toxin producer had significantly higher values for density of active reaction centers and ii quantum efficiency compared to the mutant. A decrease in F0 in the mutant suggests degradation of the phycobiliproteins, whereas PCC7806 didn’t show a significant decrease in F0 Data indicate that microcystins play a role in photosynthesis by preventing chlorosis in saturating light conditions either by enhancing the redox stability of the phycobiliproteins or PS II, thus preventing photooxidation.
- Full Text:
- Date Issued: 2009
Applications of complex functions on problems in Banach algebras
- Authors: Snyman, Jandré Dillon
- Date: 2019
- Subjects: Banach algebras , Functions of several complex variables
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48643 , vital:41055
- Description: In this dissertation, we provide applications of complex function theory to problems in Banach algebras. We discuss the structure of analytic functions f : D → A, where D is a domain of C and A is a Banach algebra as given by Aupetit in [3]: either the set {λ ∈ D : Sp(f(λ)) is finite} is of capacity zero, or there exists an integer n such that Sp(f(λ)) has exactly n elements, for every λ, except on a closed, discrete set of capacity zero, where the spectrum has at most n−1 elements. This deep result, which describes the structure of Sp(f(λ)) for all λ ∈ D, relies heavily on subharmonic techniques, which are also included in the dissertation. Let A and B be Banach algebras. A linear mapping φ : A → B is called a Jordan homomorphism if and only if φ(xy + yx) = φ(x)φ(y) + φ(y)φ(x) for every x, y ∈ A. This is equivalent to saying that φ(x 2 ) = φ(x) 2 for every x ∈ A. The following problem, due to I. Kaplansky, is still unsolved for the general Banach algebra case: Let A and B be unital Banach algebras and φ : A → B a unital, invertibility preserving linear mapping. Under what conditions of A and B is φ a Jordan homomorphism? The author’s honours project [24] served as an exposition of the GleasonKahane-Żelazko Theorem [7, Theorem 4], which provides an answer to Kaplansky’s problem in the case where B = C. In this dissertation we look at other special cases of Kaplansky’s problem, such as the case where A and B are von Neumann algberas, as solved by Aupetit [4, Theorem 1.3] and remark that his result holds for the more general case where A is any C ∗ -algebra that has the property that every self-adjoint element is the limit of a sequence of linear combinations of orthogonal idempotents in A, and B is a semi-simple Banach algebra. This result relies heavily on complex function theory, spectral theory and holomorphic functional calculus. We also provide detailed expositions of the work of Taylor [27] in which an operator calculus on undounded, closed linear operators is developed, and the work of Allan [1] in which a holomorphic functional calculus is defined for locally convex algebras.
- Full Text:
- Date Issued: 2019
- Authors: Snyman, Jandré Dillon
- Date: 2019
- Subjects: Banach algebras , Functions of several complex variables
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48643 , vital:41055
- Description: In this dissertation, we provide applications of complex function theory to problems in Banach algebras. We discuss the structure of analytic functions f : D → A, where D is a domain of C and A is a Banach algebra as given by Aupetit in [3]: either the set {λ ∈ D : Sp(f(λ)) is finite} is of capacity zero, or there exists an integer n such that Sp(f(λ)) has exactly n elements, for every λ, except on a closed, discrete set of capacity zero, where the spectrum has at most n−1 elements. This deep result, which describes the structure of Sp(f(λ)) for all λ ∈ D, relies heavily on subharmonic techniques, which are also included in the dissertation. Let A and B be Banach algebras. A linear mapping φ : A → B is called a Jordan homomorphism if and only if φ(xy + yx) = φ(x)φ(y) + φ(y)φ(x) for every x, y ∈ A. This is equivalent to saying that φ(x 2 ) = φ(x) 2 for every x ∈ A. The following problem, due to I. Kaplansky, is still unsolved for the general Banach algebra case: Let A and B be unital Banach algebras and φ : A → B a unital, invertibility preserving linear mapping. Under what conditions of A and B is φ a Jordan homomorphism? The author’s honours project [24] served as an exposition of the GleasonKahane-Żelazko Theorem [7, Theorem 4], which provides an answer to Kaplansky’s problem in the case where B = C. In this dissertation we look at other special cases of Kaplansky’s problem, such as the case where A and B are von Neumann algberas, as solved by Aupetit [4, Theorem 1.3] and remark that his result holds for the more general case where A is any C ∗ -algebra that has the property that every self-adjoint element is the limit of a sequence of linear combinations of orthogonal idempotents in A, and B is a semi-simple Banach algebra. This result relies heavily on complex function theory, spectral theory and holomorphic functional calculus. We also provide detailed expositions of the work of Taylor [27] in which an operator calculus on undounded, closed linear operators is developed, and the work of Allan [1] in which a holomorphic functional calculus is defined for locally convex algebras.
- Full Text:
- Date Issued: 2019
The synthesis of anastrazole intermediates using continuous flow systems
- Authors: Tanyi, Sam Tambi
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/54116 , vital:46304
- Description: In this study, the continuous flow synthesis of anastrozole intermediates were investigated using mesitylene as starting material. Anastrozole is an important drug used for the treatment of breast cancer. In the first step, mesitylene was brominated using N-bromosuccinimide to obtain 3,5-bis(bromomethyl)toluene. Selectivity became an issue due to the formation of two by-products; namely 1,3,5-tris(bromomethyl) benzene (the tribrominated by-product) and 1-(bromomethyl)-3,5-dimethylbenzene (the monobrominated by-product). Since the reaction parameters can be more precisely controlled in flow chemistry systems, we were able to optimize the formation the desired product 3,5-bis(bromomethyl)toluene. The reaction was initially optimized ina 15μLChemtrix glass micro reactor resulting in 100%conversion with 95%selectivity towards the desired product 3,5-bis(bromomethyl)toluenein 15 seconds, with a throughput of 0.006 g/h. The reaction was then scaled up in a 1.7 mLLTF reactor, equally yielding 100%conversion with 95%selectivityin 4minutes, with a throughput of2.01g/h. The bromination of mesitylene was also attempted in a homemade photochemical reactor consisting of a 3.02 polytetrafluoroethylene coil reactor and BLE-6T365 UV lamp. In this photochemical reactor, although 100%conversionwas again obtained only75%selectivity was achieved in 20minutes, with a throughput of 0.025g/h. This drop in selectivity was attributed to poorer mixing in the larger polytetrafluoroethylene coil reactor and possibly insufficient light penetration. The next step, involving the cyanation of 3,5-bis(bromomethyl)toluene to obtain 2,2'-(5-methyl-1,3-phenylene) diacetonitrilegave 100%conversion in 1 minute at 190 °C in a 1.7 mLLTFreactor, with a throughput of 5.2g/h. The subsequent methylation of 3,5-bis(cyanomethyl)toluene to obtain3,5-bis(1-cyano-1-methylethyl) toluene was investigated using a1mLpolytetrafluoroethylenecoil reactor, ultimatelyachieving99%conversionat40 °Cin 8minutes, with a throughput of 0.045g/h. Next, the bromination of3,5-bis(1-cyano-1-methylethyl)toluene using N-bromosuccinimideto yield 2,2'-(5-bromomethyl-1,3-phenylene)di(2-methyl propionitrile) gave 100%conversion at 120 °C in 4 minutes, with a throughput of 0.35g/h. Lastly, the multistep synthesis of 3,5-bis(cyanomethyl)toluene was done in two integrated 1.7 mLLTF reactors, using the predetermined optimum conditions to achieve 94%conversion towards 3,5-bis(cyanomethyl)toluene with a total r , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
- Full Text:
- Date Issued: 2021-12
- Authors: Tanyi, Sam Tambi
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/54116 , vital:46304
- Description: In this study, the continuous flow synthesis of anastrozole intermediates were investigated using mesitylene as starting material. Anastrozole is an important drug used for the treatment of breast cancer. In the first step, mesitylene was brominated using N-bromosuccinimide to obtain 3,5-bis(bromomethyl)toluene. Selectivity became an issue due to the formation of two by-products; namely 1,3,5-tris(bromomethyl) benzene (the tribrominated by-product) and 1-(bromomethyl)-3,5-dimethylbenzene (the monobrominated by-product). Since the reaction parameters can be more precisely controlled in flow chemistry systems, we were able to optimize the formation the desired product 3,5-bis(bromomethyl)toluene. The reaction was initially optimized ina 15μLChemtrix glass micro reactor resulting in 100%conversion with 95%selectivity towards the desired product 3,5-bis(bromomethyl)toluenein 15 seconds, with a throughput of 0.006 g/h. The reaction was then scaled up in a 1.7 mLLTF reactor, equally yielding 100%conversion with 95%selectivityin 4minutes, with a throughput of2.01g/h. The bromination of mesitylene was also attempted in a homemade photochemical reactor consisting of a 3.02 polytetrafluoroethylene coil reactor and BLE-6T365 UV lamp. In this photochemical reactor, although 100%conversionwas again obtained only75%selectivity was achieved in 20minutes, with a throughput of 0.025g/h. This drop in selectivity was attributed to poorer mixing in the larger polytetrafluoroethylene coil reactor and possibly insufficient light penetration. The next step, involving the cyanation of 3,5-bis(bromomethyl)toluene to obtain 2,2'-(5-methyl-1,3-phenylene) diacetonitrilegave 100%conversion in 1 minute at 190 °C in a 1.7 mLLTFreactor, with a throughput of 5.2g/h. The subsequent methylation of 3,5-bis(cyanomethyl)toluene to obtain3,5-bis(1-cyano-1-methylethyl) toluene was investigated using a1mLpolytetrafluoroethylenecoil reactor, ultimatelyachieving99%conversionat40 °Cin 8minutes, with a throughput of 0.045g/h. Next, the bromination of3,5-bis(1-cyano-1-methylethyl)toluene using N-bromosuccinimideto yield 2,2'-(5-bromomethyl-1,3-phenylene)di(2-methyl propionitrile) gave 100%conversion at 120 °C in 4 minutes, with a throughput of 0.35g/h. Lastly, the multistep synthesis of 3,5-bis(cyanomethyl)toluene was done in two integrated 1.7 mLLTF reactors, using the predetermined optimum conditions to achieve 94%conversion towards 3,5-bis(cyanomethyl)toluene with a total r , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
- Full Text:
- Date Issued: 2021-12
Upwelling over submarine canyons: an in-situ and modelling approach
- Authors: Rautenbach, Gustav
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Oceanography -- Research -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52078 , vital:43442
- Description: The iSimangaliso Wetland Park, located along the coastline of northern KwaZulu-Natal (KZN), hosts South Africa's only tropical coral reef system and is clustered with submarine canyons. These ecosystems support a flourishing diving and pelagic sportfishing industry in the area that contributes tens of millions of rand to the South African Gross Domestic Profit (GDP) annually as well as to provide income and job security for the majority of the local residents. Understanding the oceanographic dynamics, particularly upwelling events, will improve current knowledge of how the ecosystem works and may enhance conservation techniques. The upwelling events within the iSimangaliso Wetland Park results in the influx of cold and nutrient rich waters that supports biological productivity in the area. The complex oceanography, dominated by the Northern Agulhas Current and mesoscale eddies that stem from the Mozambique Channel and South East Madagascar Current (SEMC) is understudied and lacks understanding. This thesis aims to build upon the current knowledge of the upwelling events over the submarine canyons and the concurrent influence on the Mixed Layer Depth (MLD). At the submarine canyons, six anomalous cooling events were identified from surface and subsurface measurements extracted from the Operational Sea Surface Temperature and Ice Analysis (OSTIA) Sea Surface Temperature (SST) and from data collected using Underwater Temperature Recorders (UTRs) over a 12-month period. Depth-integrated lagged correlations showed a 2-to-7-hour lag period from the deep to shallow stations, suggesting that the anomalous cooling events are in fact upwelling events. Wind measurements from the Mbazwana Weather Station and snapshots of sea-level anomalies illustrated that the weaker and shorter upwelling events are driven either by alongshore wind stress or a cyclonic eddy event solely; whereas the stronger event was driven by the combination of both forcing mechanisms. An idealized canyon ocean model is used to interrogate the two forcing mechanisms more fully and showed that the most intense upwelling events are driven by the combined effect of upwelling-favourable alongshore wind stress and a cyclonic eddy which results in strong upward vertical velocity anomalies and the greatest shallowing (6.88 m) of the MLD. With the contribution of the in-situ measurements as a baseline study it is apparent that the idealised model does provide an improved understanding of the upwelling events and forcing mechanism over the submarine canyons within the iSimangaliso Wetland Park. , Thesis (MSc) -- Faculty of Science, Ocean Sciences, 2021
- Full Text: false
- Date Issued: 2021-04
- Authors: Rautenbach, Gustav
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Oceanography -- Research -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52078 , vital:43442
- Description: The iSimangaliso Wetland Park, located along the coastline of northern KwaZulu-Natal (KZN), hosts South Africa's only tropical coral reef system and is clustered with submarine canyons. These ecosystems support a flourishing diving and pelagic sportfishing industry in the area that contributes tens of millions of rand to the South African Gross Domestic Profit (GDP) annually as well as to provide income and job security for the majority of the local residents. Understanding the oceanographic dynamics, particularly upwelling events, will improve current knowledge of how the ecosystem works and may enhance conservation techniques. The upwelling events within the iSimangaliso Wetland Park results in the influx of cold and nutrient rich waters that supports biological productivity in the area. The complex oceanography, dominated by the Northern Agulhas Current and mesoscale eddies that stem from the Mozambique Channel and South East Madagascar Current (SEMC) is understudied and lacks understanding. This thesis aims to build upon the current knowledge of the upwelling events over the submarine canyons and the concurrent influence on the Mixed Layer Depth (MLD). At the submarine canyons, six anomalous cooling events were identified from surface and subsurface measurements extracted from the Operational Sea Surface Temperature and Ice Analysis (OSTIA) Sea Surface Temperature (SST) and from data collected using Underwater Temperature Recorders (UTRs) over a 12-month period. Depth-integrated lagged correlations showed a 2-to-7-hour lag period from the deep to shallow stations, suggesting that the anomalous cooling events are in fact upwelling events. Wind measurements from the Mbazwana Weather Station and snapshots of sea-level anomalies illustrated that the weaker and shorter upwelling events are driven either by alongshore wind stress or a cyclonic eddy event solely; whereas the stronger event was driven by the combination of both forcing mechanisms. An idealized canyon ocean model is used to interrogate the two forcing mechanisms more fully and showed that the most intense upwelling events are driven by the combined effect of upwelling-favourable alongshore wind stress and a cyclonic eddy which results in strong upward vertical velocity anomalies and the greatest shallowing (6.88 m) of the MLD. With the contribution of the in-situ measurements as a baseline study it is apparent that the idealised model does provide an improved understanding of the upwelling events and forcing mechanism over the submarine canyons within the iSimangaliso Wetland Park. , Thesis (MSc) -- Faculty of Science, Ocean Sciences, 2021
- Full Text: false
- Date Issued: 2021-04
The biota of the Swartkops Solar Saltworks and their potential for producing biofuels
- Authors: De Lauwere, Monique Simone
- Date: 2012
- Subjects: Organisms , Biomass energy
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10625 , http://hdl.handle.net/10948/d1011657 , Organisms , Biomass energy
- Description: The Swartkops and Missionvale salinas in Port Elizabeth on the east coast of South Africa are surrounding by large informal settlements. The runoff from these settlements contributes largely to the eutrophication of the solar saltworks which in turn has an effect on the biotic functioning of the systems, ultimately affecting the quantity and quality of the salt produced. Inorganic nutrients and organic composition, as well as important biological groups were examined within the brine with the aim of comparing the current condition of the same salinas to their condition twelve years ago. Comparisons between inorganic nutrient concentrations and biological groups showed significantly higher inorganic nutrients, with chlorophyll a concentrations in the Swartkops salina in 2011 being significantly higher than in 2012 and the 1999 and 2011 chlorophyll a concentrations being significantly higher than 2012 in the Missionvale salina. Microalgae found in the salinas were cultured in four different growth media. Cells were stained with Nile Red fluorescent dye in order to estimate the extent of lipids production. Five of the most promising lipid producing species were isolated into a monoculture and grown at different salinities to establish the growth and lipid production in response to salinity. Halamphora coffeaeformis and Navicula sp. were found to be the best candidate species. They grew best at salinities between 50 and 70 psu and produced lipid vesicles consuming approximately 10 percent of the cell.
- Full Text:
- Date Issued: 2012
- Authors: De Lauwere, Monique Simone
- Date: 2012
- Subjects: Organisms , Biomass energy
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10625 , http://hdl.handle.net/10948/d1011657 , Organisms , Biomass energy
- Description: The Swartkops and Missionvale salinas in Port Elizabeth on the east coast of South Africa are surrounding by large informal settlements. The runoff from these settlements contributes largely to the eutrophication of the solar saltworks which in turn has an effect on the biotic functioning of the systems, ultimately affecting the quantity and quality of the salt produced. Inorganic nutrients and organic composition, as well as important biological groups were examined within the brine with the aim of comparing the current condition of the same salinas to their condition twelve years ago. Comparisons between inorganic nutrient concentrations and biological groups showed significantly higher inorganic nutrients, with chlorophyll a concentrations in the Swartkops salina in 2011 being significantly higher than in 2012 and the 1999 and 2011 chlorophyll a concentrations being significantly higher than 2012 in the Missionvale salina. Microalgae found in the salinas were cultured in four different growth media. Cells were stained with Nile Red fluorescent dye in order to estimate the extent of lipids production. Five of the most promising lipid producing species were isolated into a monoculture and grown at different salinities to establish the growth and lipid production in response to salinity. Halamphora coffeaeformis and Navicula sp. were found to be the best candidate species. They grew best at salinities between 50 and 70 psu and produced lipid vesicles consuming approximately 10 percent of the cell.
- Full Text:
- Date Issued: 2012
Characterization of animal fibres
- Authors: Notayi, Mzwamadoda
- Date: 2014
- Subjects: Animal fibres , Textile fabrics , Animal science
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10552 , http://hdl.handle.net/10948/d1020426
- Description: Identification of fibres, particularly in blends, requires knowledge of their characteristics. Individual Identifying features between wool and mohair fibres were investigated in this study using a Scanning Electron Microscope (SEM), Fourier Transform Infrared-Attenuated Total Reflection (FTIR-ATR), Fourier Transform Raman and Atomic Force Microscope (AFM). This study confirmed that wool and mohair can be differentiated and identified in blends using the cuticle scale height (CSH) criterion, wool having an average CSH of 0.6 ± 0.1 μm and mohair having an average CSH of 0.4 ± 0.1 μm. The AFM provided highly reproducible CSH results, which also confirmed the SEM results that indeed wool and mohair could be differentiated using the CSH as criterion. The AFM gave a CSH value of 0.9 ± 0.2 μm for wool and 0.6 ± 0.2 μm for mohair, the difference between the two results being statistically significant according to the student t-test. It has been demonstrated that wool and mohair identification in blends is possible, by using the AFM to measure CSH, although the method is very time consuming and might be expensive. The FTIR-ATR showed similar spectra for wool and mohair fibres, confirming that the two fibre types consist of the same polymer material. Nevertheless, a difference was observed in the ratios of the relative intensities of the amide I (around 1630 cm-1) to the amide II (around 1515cm-1) absorption bands. The FT Raman provided similar spectra for the wool and mohair fibres, although a possible distinguishing feature between the two fibres could be the intensities of the alkyl side chains chemical band near 2940 cm-1 in the spectra of the two fibre types. According to the results obtained in this study, the FTIR-ATR and the FT Raman techniques may have potential for differentiating between wool and mohair but this requires further investigation.
- Full Text:
- Date Issued: 2014
- Authors: Notayi, Mzwamadoda
- Date: 2014
- Subjects: Animal fibres , Textile fabrics , Animal science
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10552 , http://hdl.handle.net/10948/d1020426
- Description: Identification of fibres, particularly in blends, requires knowledge of their characteristics. Individual Identifying features between wool and mohair fibres were investigated in this study using a Scanning Electron Microscope (SEM), Fourier Transform Infrared-Attenuated Total Reflection (FTIR-ATR), Fourier Transform Raman and Atomic Force Microscope (AFM). This study confirmed that wool and mohair can be differentiated and identified in blends using the cuticle scale height (CSH) criterion, wool having an average CSH of 0.6 ± 0.1 μm and mohair having an average CSH of 0.4 ± 0.1 μm. The AFM provided highly reproducible CSH results, which also confirmed the SEM results that indeed wool and mohair could be differentiated using the CSH as criterion. The AFM gave a CSH value of 0.9 ± 0.2 μm for wool and 0.6 ± 0.2 μm for mohair, the difference between the two results being statistically significant according to the student t-test. It has been demonstrated that wool and mohair identification in blends is possible, by using the AFM to measure CSH, although the method is very time consuming and might be expensive. The FTIR-ATR showed similar spectra for wool and mohair fibres, confirming that the two fibre types consist of the same polymer material. Nevertheless, a difference was observed in the ratios of the relative intensities of the amide I (around 1630 cm-1) to the amide II (around 1515cm-1) absorption bands. The FT Raman provided similar spectra for the wool and mohair fibres, although a possible distinguishing feature between the two fibres could be the intensities of the alkyl side chains chemical band near 2940 cm-1 in the spectra of the two fibre types. According to the results obtained in this study, the FTIR-ATR and the FT Raman techniques may have potential for differentiating between wool and mohair but this requires further investigation.
- Full Text:
- Date Issued: 2014
How does the ungulate community respond to predation risk from cheetah (Acinonyx jubatus) in Samara Private Game Reserve?
- Authors: Makin, Douglas Ferguson
- Date: 2012
- Subjects: Ungulates -- South Africa -- Eastern Cape , Predatory animals -- Ecology -- South Africa -- Eastern Cape , Predation (Biology) -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10722 , http://hdl.handle.net/10948/d1018461
- Description: Predator reintroductions are becoming increasingly more common for multiple reasons, including assisting with the conservation of a predator species, the restoration of ecosystem functions and the economic benefits of their reintroduction for ecotourism ventures. There remains however, little knowledge on prey species responses to these predator reintroductions. As such, the reintroduction of cheetah (Acinonyx jubatus) into Samara Private Game Reserve provided an opportunity to investigate prey responses to predator reintroduction across a range of spatial and temporal scales. More specifically, the aim of this study was to investigate the effect of cheetah predation risk on habitat use and behavioural responses of the resident ungulate community. Samara is divided into “predator present” and “predator absent” sections, providing the opportunity to conduct a comparative study investigating the effect of cheetah on prey responses. It was hypothesized that different ungulate species would respond differently to the presence of cheetah, depending on differences in perceived vulnerability to cheetah predation. To address this, shifts in habitat use, and behavioural responses of the ungulate community reflected at landscape and patch scale were investigated. Overall, ungulate species have not shifted habitat use since cheetah reintroduction, this was possibly related to life history strategy constraints and the need for individuals to obtain suitable forage and therefore remain in specific habitats. While no shift in habitat use was observed for the majority of ungulate species, a shift in behaviour was observed for kudu (Tragelaphus strepsiceros) at a landscape scale, where kudu dedicated more time to vigilance and less time to foraging within the predator section. In addition, individuals within smaller kudu groups were observed to be more vigilant than individuals within larger groups of kudu within the predator section. Although the other three ungulate species monitored did not increase time spent vigilant within the predator section, they still maintained relatively high levels of vigilance, potentially as a means of social monitoring. At a patch level, ungulate species responded strongly to a predator cue as a proxy for cheetah proximity, and increased time spent vigilant with a trade-off of lower foraging effort. This vigilant response was strongest for kudu. Differences in perceived predation risk were reflected within eland (Tragelaphus oryx) and kudu species demographic classes, with juvenile eland and kudu, adult female kudu and subadult female kudu spending more time vigilant within manipulated patches than respective males of each species. Kudu were also observed adopting fine-scale behavioural responses to minimize predation risk within patches. The asymmetrical prey species response to perceived predation risk from cheetah supports the hypothesis that different species respond differently to the presence of a predator. Furthermore, this study illustrated the importance of measuring prey responses to predation risk across multiple scales and highlighted the need to replicate this study for a number of different sites where predators have been reintroduced, to better understand the range of factors influencing these predator-prey interactions.
- Full Text:
- Date Issued: 2012
- Authors: Makin, Douglas Ferguson
- Date: 2012
- Subjects: Ungulates -- South Africa -- Eastern Cape , Predatory animals -- Ecology -- South Africa -- Eastern Cape , Predation (Biology) -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10722 , http://hdl.handle.net/10948/d1018461
- Description: Predator reintroductions are becoming increasingly more common for multiple reasons, including assisting with the conservation of a predator species, the restoration of ecosystem functions and the economic benefits of their reintroduction for ecotourism ventures. There remains however, little knowledge on prey species responses to these predator reintroductions. As such, the reintroduction of cheetah (Acinonyx jubatus) into Samara Private Game Reserve provided an opportunity to investigate prey responses to predator reintroduction across a range of spatial and temporal scales. More specifically, the aim of this study was to investigate the effect of cheetah predation risk on habitat use and behavioural responses of the resident ungulate community. Samara is divided into “predator present” and “predator absent” sections, providing the opportunity to conduct a comparative study investigating the effect of cheetah on prey responses. It was hypothesized that different ungulate species would respond differently to the presence of cheetah, depending on differences in perceived vulnerability to cheetah predation. To address this, shifts in habitat use, and behavioural responses of the ungulate community reflected at landscape and patch scale were investigated. Overall, ungulate species have not shifted habitat use since cheetah reintroduction, this was possibly related to life history strategy constraints and the need for individuals to obtain suitable forage and therefore remain in specific habitats. While no shift in habitat use was observed for the majority of ungulate species, a shift in behaviour was observed for kudu (Tragelaphus strepsiceros) at a landscape scale, where kudu dedicated more time to vigilance and less time to foraging within the predator section. In addition, individuals within smaller kudu groups were observed to be more vigilant than individuals within larger groups of kudu within the predator section. Although the other three ungulate species monitored did not increase time spent vigilant within the predator section, they still maintained relatively high levels of vigilance, potentially as a means of social monitoring. At a patch level, ungulate species responded strongly to a predator cue as a proxy for cheetah proximity, and increased time spent vigilant with a trade-off of lower foraging effort. This vigilant response was strongest for kudu. Differences in perceived predation risk were reflected within eland (Tragelaphus oryx) and kudu species demographic classes, with juvenile eland and kudu, adult female kudu and subadult female kudu spending more time vigilant within manipulated patches than respective males of each species. Kudu were also observed adopting fine-scale behavioural responses to minimize predation risk within patches. The asymmetrical prey species response to perceived predation risk from cheetah supports the hypothesis that different species respond differently to the presence of a predator. Furthermore, this study illustrated the importance of measuring prey responses to predation risk across multiple scales and highlighted the need to replicate this study for a number of different sites where predators have been reintroduced, to better understand the range of factors influencing these predator-prey interactions.
- Full Text:
- Date Issued: 2012
A structural study of Witteberg group rocks (Cape supergroup) in the Cape fold belt, Steytlerville district, Eastern Cape
- Authors: Brunsdon, Gideon
- Date: 2006
- Subjects: Geology, Structural|zSouth Africa|zEastern Cape , Faults (Geology)|zSouth Africa|zEastern Cape , Folds (Geology)|zSouth Africa|zEastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10666 , http://hdl.handle.net/10948/d1019682
- Description: A structural study of Witteberg Group Rocks was conducted along the Soutkloof River, approximately 14 km east of Steytlerville, Eastern Cape Province of South Africa. Here a north to south geotraverse was studied in an attempt at unravelling the structural geology of the rocks belonging to the Upper Devonian to Lower Carboniferous Witteberg Group (Upper Cape Supergroup). These rocks are mostly arenaceous and include quartzite, sandstone, siltstone and shale which have been folded, faulted and metamorphosed. Thrust, normal and strike-slip faulting occur in the area. Shallow south-dipping low-angle thrust fault planes are displaced by steep south-dipping thrust planes and subordinate north-dipping backthrusts. Displacement along thrust planes is predominantly northwards. Steeply dipping thrust fault planes are often reactivated as east-west striking normal faults. Strike-slip faulting postdates all observed structural features and displaces normal and thrust fault planes. Open to tight folds are present and are mostly northvergent and often steepened or truncated by steep south-dipping thrust fault planes. South-vergent folds are related to backthrusting and post-fold faulting. The study has revealed that the current geological map and the local stratigraphy were compiled without recognising major structural features such as thrust, normal and strike-slip faulting and their (the map and currently accepted stratigraphy) validity are therefore questioned. The presence of extensive faulting suggests that the conventional stratigraphic interpretation of the Witteberg Group should be revised.
- Full Text:
- Date Issued: 2006
- Authors: Brunsdon, Gideon
- Date: 2006
- Subjects: Geology, Structural|zSouth Africa|zEastern Cape , Faults (Geology)|zSouth Africa|zEastern Cape , Folds (Geology)|zSouth Africa|zEastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10666 , http://hdl.handle.net/10948/d1019682
- Description: A structural study of Witteberg Group Rocks was conducted along the Soutkloof River, approximately 14 km east of Steytlerville, Eastern Cape Province of South Africa. Here a north to south geotraverse was studied in an attempt at unravelling the structural geology of the rocks belonging to the Upper Devonian to Lower Carboniferous Witteberg Group (Upper Cape Supergroup). These rocks are mostly arenaceous and include quartzite, sandstone, siltstone and shale which have been folded, faulted and metamorphosed. Thrust, normal and strike-slip faulting occur in the area. Shallow south-dipping low-angle thrust fault planes are displaced by steep south-dipping thrust planes and subordinate north-dipping backthrusts. Displacement along thrust planes is predominantly northwards. Steeply dipping thrust fault planes are often reactivated as east-west striking normal faults. Strike-slip faulting postdates all observed structural features and displaces normal and thrust fault planes. Open to tight folds are present and are mostly northvergent and often steepened or truncated by steep south-dipping thrust fault planes. South-vergent folds are related to backthrusting and post-fold faulting. The study has revealed that the current geological map and the local stratigraphy were compiled without recognising major structural features such as thrust, normal and strike-slip faulting and their (the map and currently accepted stratigraphy) validity are therefore questioned. The presence of extensive faulting suggests that the conventional stratigraphic interpretation of the Witteberg Group should be revised.
- Full Text:
- Date Issued: 2006