List of Titles

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.
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Date Issued: 2018

The association of the bushclumps of Calcrete Bontveld with adjacent thicket

Authors: Carvalho, Shandon Luke
Date: 2018
Subjects: Plant ecology -- South Africa -- Eastern Cape , Biodiversity conservation Landscape ecology -- South Africa -- Eastern Cape
Language: English
Type: Thesis , Masters , MSc
Identifier: http://hdl.handle.net/10948/21949 , vital:29806
Description: The thicket mosaic vegetation type known as Calcrete Bontveld is now only found at three sites within the Eastern Cape Province. Consisting of thicket-like bushclumps scattered among grassy dwarf shrubland, this vegetation is isolated from other systems due to its unique geographical location and the surrounding Valley Thicket. A strong similarity between the bushclumps of Calcrete Bontveld and the adjacent Valley Thicket has led to the aim of this study, which was to demonstrate that an association exists between these two vegetation types. To investigate this, two sites, namely Grassridge (natural vegetation on a mine) and Shamwari (natural due to its status as a reserve), were selected. This provided a unique comparison of the functionality of the two vegetation types and identified key processes responsible for the existence of this association. In terms of edaphic variables, soil organic content and field capacity, values were similar between bushclumps and thicket while soil depth was the greatest in thicket at both sites. At both sites, life forms, diversity and similarity indices were similar for bushclumps and thicket. By utilizing the Island Biogeography Theory, these bushclumps show an island-type origin and the distance between them and the adjacent Valley Thicket (mainland-type), as well as their size, influenced the association between the two vegetation types. Commonality of species between thicket and bushclumps are postulated to be tied to their dispersal mechanisms and fruit types. Bushclump isolation on flat-topped ridges excluded thicket species dispersed by autochory and anemochory. Zoochorous dispersal (by birds and mammals) was the common factor in the transfer of species between thicket and bushclumps as the latter is a large resource patch for fauna. The size of the bushclumps and their distance from the thicket influenced zoochorous dispersal. Larger and closer bushclumps attracted more birds and mammals than the small or more distant ones. These effects differ at the two sites due to the complex animal interaction that occurs in the Shamwari Game Reserve as opposed to the reduced animal interaction at Grassridge. This study suggests that an association exists between the bushclumps of Calcrete Bontveld and the adjacent Valley Thicket, and is reliant on the natural zoochory that occurs at each site.
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Date Issued: 2018

The development of natural fibre reinforced composites roof sheet

Authors: Musikwa, Mufeba
Date: 2018
Subjects: Textile fibers -- Research , Textile fabrics Textile chemistry
Language: English
Type: Thesis , Masters , MSc
Identifier: http://hdl.handle.net/10948/32927 , vital:32398
Description: The study aims to develop natural fibre reinforced bio-epoxy composite for use as roof sheets, manufacturing and characterization to evaluate its suitability for building applications. In this study natural fibres such as flax and kenaf were selected to reinforce bio-epoxy matrix. Different weight ratios of flax and kenaf fibres were processed by needle-punching technique to produce nonwoven mats. The nonwoven mats and bio-epoxy matrix were prepared using vacuum assisted resin transfer moulding (VARTM) at room temperature until dry and cured. The effects of weathering and water aging on the static and dynamic mechanical properties of kenaf and flax composites were investigated. Flax fibre reinforced bio-epoxy composites were found to exhibit higher tensile strength at 25% fibre content of 41.5 MPa in comparison to the composites reinforced with kenaf fibres (33.0 MPa). With regards to the drop weight impact results, flax fibre reinforced bio-epoxy composites exhibited brittle failure. Water aging results showed that kenaf fibre reinforced bio-epoxy composites absorbed less water for all fibre contents in comparison to composites reinforced with flax fibres. The tensile strength and modulus of both the composites reinforced with flax and kenaf fibres were reduced after water aging. However, the composite reinforced with kenaf fibres showed the maximum reduction in tensile strength at 25% fibre content. After UV treatment both composites reinforced with flax and kenaf fibres showed a decrease in tensile strength of 6.25% and 30%, respectively. In comparison to kenaf, bioepoxy composites reinforced with flax fibres showed an increase in tensile modulus. Both composites reinforced with flax and kenaf fibres were found to be brittle and broke easily but no colour fading was observed after UV treatment. The dynamic mechanical analyses results showed that the incorporation of flax and kenaf fibres increases the storage modulus of the composites with the maximum storage modulus value exhibited by flax fibre reinforced bio-epoxy composite at 30% fibre content. The glass transition temperature of composites reinforced with both flax and kenaf fibres shifted to lower temperatures of 79 °C and 69 °C respectively, in comparison to 96 °C for bio-epoxy resin, with the incorporation of fibres.
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Date Issued: 2018

The development of rhenium(III) oxide nanoradiopharmaceuticals

Authors: Joseph, Sinelizwi Veronica
Date: 2018
Subjects: Radiopharmaceuticals , Radiopharmaceuticals Rhenium
Language: English
Type: Thesis , Masters , MSc
Identifier: http://hdl.handle.net/10948/30507 , vital:30955
Description: The study details the experimental work on the development of rhenium(III) oxide nanoradiopharmaceuticals for imaging and therapy of disease states. The nanoparticles (NPs) were capped with covalently linked tetraaminophthalocyanine-folate and ethylenediamine-folate to enhance their targeting ability. The capping agents were successfully synthesised and structurally characterised using Ultraviolet-Visible Spectroscopy (UV-Vis), Fourier Transform-Infrared Spectroscopy (FT-IR), Proton Nuclear Magnetic Resonance (1H-NMR), and Liquid Chromatography-Mass Spectroscopy (LC-MS). The nanoparticles were characterised using UV-Vis, spectrofluorimetry, Transmission Electron Microscopy (TEM), dynamic light scattering (DLS) and Zeta potential. Nanoparticles of sizes between 10 and 100 nm size were envisaged to be suitable for applications in biological systems. The preferred surface charge for the uptake of NPs must be between -30 and +30 mV, Re2O3 NPs capped with ethylenediamine were found to have a surface charge of -49 mV as compared with NPs capped with ethylenediamine-folate which gave -18.6 mV. The cytotoxicity studies of the nanoparticles were tested against four different cell lines: MDA-MB-468, MDA-MB-231, MCF-7, and MCF-10A. The cell survival rate after treatment was done with different capped rhenium(III) oxide nanoparticles obtained at a 10 μM concentration showed more than 80% cell viability. A comparison was conducted based on different nanoparticle sizes of capping agents across the four cell lines of varying folate receptor. All the cell lines were compared, and it was observed that MCF-7 had high percentage of cell viability especially with the cells treated with folate conjugated nanoparticles. Further investigation was done on the effects of folate conjugates and the effects of size. It was observed that the tetraaminophthalocyanine-folate favoured the MCF-7, for large-sized nanoparticles. However, further work is required to test the cancer cell internalisation of the nanoparticles using TEM as well as the correct size for endocytosis. Thereafter, the mice model study will be carried out for investigation of biodistribution of particles in tumour tissue using hot isotopes (186/188Re) and this will be done in a radiophamarceutical laboratory.
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Date Issued: 2018

The economic and ecological trade-offs of wetland conversion for development projects: the case of the Kampala–Mukono corridor

Authors: Wasswa, Hannington
Date: 2018
Subjects: Wetland ecology -- Uganda -- Kampala , Wetlands -- Uganda -- Kampala Wetland management -- Uganda -- Kampala Hydrogeology
Language: English
Type: Thesis , Doctoral , DPhil
Identifier: http://hdl.handle.net/10948/36409 , vital:33939
Description: Wetland diminution for development projects (DPs) in the Kampala–Mukono Corridor (KMC) continues to pose threats to the socio-economic and ecological benefits of wetlands because decision-makers and wetland users at various levels often have insufficient knowledge of these benefits. This situation has resulted in unsustainable development decisions that accord little weight to wetlands and have allocated many of them to DPs. In order to inform decision making for optimal development in the KMC, the present study analysed the spatial and temporal wetland loss to DPs, estimated the economic value of the KMC wetlands, and assessed the environmental consequences of wetland conversion for DPs. Sets of ortho-rectified and cloud-free multi-temporal Landsat MSS (1974) and Landsat TM/ETM+ images (30m) for 1986, 2006, and 2013 were analysed in a spatial and temporal framework. The 79m Landsat image (MSS) of 1974 was resampled and later filtered with subsequent 30m images using a majority filter method. An unsupervised classification approach was employed to characterize the wetlands and associated DPs. The classified DPs and wetland cover types were validated by reference to topographical maps (sheets) of 1974 at a scale of 1:50,000 obtained from Uganda Lands and Surveys, apriori knowledge and Google earth images corresponding to the same spatial and temporal frames. The IDRISI Selva-based Markov Chain model was employed to model future wetland loss to DPs. The Total Economic Valuation Approach (TEV) was employed to quantify selected use values of wetland economic benefits using the market price, replacement cost and contingent valuation techniques. The ecological implications of wetland loss focused on soil organic carbon (SOC) and hydrological impacts in the KMC wetlands. The estimated SOC was assessed with climatic data in order to infer the implication of SOC loss for local climate variability. The manual wet chemistry/oxidation method by Walkley-Black (1934) was adopted to estimate SOC in various wetland cover types. Hydrological impact assessments focused on water quality analysis in various wetland cover types, with major parameters being total nitrogen (TN), total phosphorous (TP) total dissolved solids – (TDS) and total suspended sediments (TSS). Hydrologic flow data parameters across the different wetland cover types in the KMC focused on water level, speed, stream width, and bed load. Results from analysis of the spatial-temporal wetland change revealed that by 2013 the KMC wetlands had lost almost half (47%) of their 1974 areal coverage, with 56% of this loss resulting from conversion to DPs. It is projected that 26% of the KMC wetlands will be lost to more DPs by 2040. Wetland loss is attributed to intensified economic activity and preference of Kampala as an industrial zone, weakness in the previous spatial planning of Kampala, and the general lack of information flow to various institutions involved in the establishment of DPs. The KMC wetlands provide a flow of economic benefits at a minimum approximated value of US$ 3,418 / ha / per year. It is revealed that a great deal of these economic benefits (88%) accrues to the local subsistence level in the form of livelihood products, incomes, and employment benefits. The 56% wetlands loss to DPs in the KMC by 2013 brings the minimum economic value lost to US$ 19,311,700 in the sampled wetlands, and projections of future wetland loss put the minimum economic loss at US$ 48,368,118 by 2040. Continuous degradation of these wetlands means serious economic costs to the government and local communities, as reflected in high replacement expenditures for wetland services, foregone incomes, subsistence livelihood support and alternative employment. The highest carbon (C) sinks were identified in forest swamps, palms, thickets and wetlands converted to agriculture, which accounted for 25% of the KMC wetlands by 2013, while the lowest total soil organic carbon (TSOC) range occurred in converted wetland cover types (converted wetlands to industrial and settlements) that occupied 47% of the study area. A general decrease in SOC sequestration from 1974 to 2013 across the KMC wetlands is identified, with the lowest C pool registered in 2013. The dwindling SOC banks are considered to be partly responsible for varying climate and related feedbacks on wetland benefits in the KMC. The hydrologic impacts of wetland loss are felt mainly in converted wetland cover types, in the form of compromised water quality, with increased nutrient pollution and TSS. These all create negative impacts on wetland hydrological services, particularly filtration, flood attenuation, recharge and discharge benefits, all of which have profound effects on biodiversity. There is an urgent need to reduce the scale of wetland diminution in the KMC. This will be achieved if mitigation and conservation measures are undertaken. Mitigation measures should include a revision of development plans, user sensitization on wetland economic values and enforcement of regulatory mechanisms. Conservation strategies should involve the use of economic incentives and disincentives which include: a revision of historic property rights to regulate wetland use, performance bonds or subsidies for environmentally friendly activities and taxes, fees or fines for unacceptable levels of degradation and tradable permits that utilise the concept of ‘wetland banks’ to ensure no further loss of the KMC wetlands to DPs. Future research should focus on modelling the response of wetland ecosystems to multiple threats and management interventions, and on a feasibility study of wetland restoration options and the implications for local people’s livelihoods in the KMC.
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Date Issued: 2018

The effect of casuarina trees on sea turtles nesting beaches throughout the Indian Ocean and South-East Asia regions: A beach vulnerability assessment

Authors: De Vos, Deidre
Date: 2018
Subjects: Conservation biology , Casuarina Sea turtles
Language: English
Type: Thesis , Masters , MSc
Identifier: http://hdl.handle.net/10948/22420 , vital:29968
Description: Rapid global change and anthropogenic modification of natural habitats are threatening ecosystems across the globe. Many of these threats and adverse impacts are concentrated on the world’s coastlines, with a large portion of the global population choosing to live next to the coast. To accommodate coastal populations and their related activities, the dynamic littoral active zone is often stabilized with hard engineering structures such as sea walls, which disrupt coastal ecological processes. Most natural coastal processes have since become natural disaster risks to the anthropogenically-modified coasts. Coastal stabilization has led to “coastal squeeze” with modified shorelines unable to respond naturally to changes in sea level. Furthermore, global change through global ‘warming’ exacerbates sea level rise. The combined impacts result in permanent/episodic inundation and coastal erosion, which may damage human settlements and degrade or destroy coastal habitat. As an alternative to hard armouring structures like sea walls, ‘soft’ options like large-scale plantations of trees as bio-shields are used as a ‘green’ option to protect developed coasts. Indeed, green shelter belts have rapidly increased since the December 2004 tsunami event in the Indian Ocean and South-East Asian (IOSEA) region. Extensive portions of the coastal habitat, including sensitive sea turtle nesting habitat, have been modified by planting exotic vegetation. Two invasive species, Casuarina equisetifolia and Casuarina glauca, are regularly used for coastal dune stabilization or as bio-shields because they are adapted to arid conditions, high salinity and low soil fertility typical of beach systems. The functionality of Casuarina trees as a ‘comprehensive’ coastal protection tool, however, has yet to be tested and the effects of Casuarina on sandy beach ecosystems remain largely unquantified. There is no empirical evidence to support the claim that Casuarina trees adequately function as a storm protection measure, and other studies have suggested that Casuarina species have adverse effects on sandy beach ecosystems, including the promotion of erosion in some instances and negative impacts on fauna, including sea turtles. This study investigated the potential value of non-native Casuarina trees as a coastal protection measure on sea turtle nesting beaches taking into consideration the potential impacts of global change. First, the study estimated local scale effects of Casuarina trees within the South African sea turtle nesting rookery in the iSimangaliso Wetland Park by measuring impacts on back-beach substrate characteristics and shape. A few metrics were unaffected, such as grain size, sand penetrability and sand moisture, but sand pH and sand temperature were significantly lower underneath Casuarina stands. A mean pH of 8.2 and a median temperature of 26 ± SD1.5oC were recorded under Casuarina trees and a pH of 9 and a median temperature of 27.2 ± SD1.9oC under native vegetation. The significantly lower, more stable average temperature underneath Casuarina trees may have significant implications for sex ratios of sea turtles as the sex of sea turtles is determined by temperature; Temperatures above 32°C will yield all females and temperatures below 28°C will produce only males, with a pivotal temperature at which a 1:1 sex ratio is developed is about 29°C. Furthermore, sand temperature underneath Casuarina trees is less likely to reach lethal temperatures (above ~33°C) that could lead to hatchling mortality than in areas with no vegetation. So, in terms of hatchling success, the thermal environment created by Casuarina trees might be favourable in extremely hot climate areas, especially when considering the effects of climate change. Casuarina trees, however, affect back-beach and dune dynamics by altering sand movement. Semi-quantitative and qualitative analyses of beach profiles suggested that Casuarina trees and shrubs result in wind scouring directly in front of the foredunes as evidenced by the concave shape in front of Casuarina stands at some sites. Sites with natural vegetation had mainly convex beach shapes, suggesting sand accretion. Either way, vegetation had an important effect on sand dynamics (both positive and negative) where areas with no vegetation (bare sand) only had a neutral/straight shape. There was, however, a significant interaction between vegetation type and site, indicating that vegetation type alone cannot account for all the differences in beach profile dynamics and that site-specific conditions like wave height, sand budget, precipitation and orientation differences among locations may also have an effect. The second part of the study had a regional perspective, investigating the effect of Casuarina trees on 50 sea turtle nesting beaches across the Indian Ocean South East Asia (IOSEA) region. The study first derived an appropriate (novel) beach vulnerability index using features that drive beach erosion. The index was then applied to 50 turtle rookeries in the presence/absence of Casuarina trees. The study noted the extensive distribution of exotic Casuarina trees throughout the IOSEA region and established that 28% of the 50 selected sea turtle nesting beaches had non-native Casuarina present. There was no significant difference in the erosion vulnerability of beaches with and without Casuarina based on the existing indicators. However, the study did show that seven important sea turtle rookeries were highly vulnerable to erosion, some with extensive exotic Casuarina stands. Olive ridley (Lepidochelys olivacea) nesting beaches in India, were dominated by Casuarina trees and were highly vulnerable to erosion. The study showed that the presence of Casuarina trees alone could not be viewed as an indicator of erosion but could be a contributing factor, as several other drivers like narrow back-beach width, absence of dunes and development on exposed coasts prone to storms, also contribute to the high erosion vulnerability of beaches. The study questions the use of exotic vegetation, such as Casuarina species, for coastal protection by demonstrating local scale effects on the back-beach environment and provides a comprehensive overview of the erosion potential of sea turtle nesting beaches throughout the IOSEA region.
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Date Issued: 2018

The effect of ER stress in INS-1E cells using IL-1β under hyperglycaemic conditions

Authors: Jackson, Simon
Date: 2018
Subjects: Diabetes -- Pathogenesis , Endoplasmic reticulum -- Pathophysiology Endoplasmic reticulum Diabetes
Language: English
Type: Thesis , Masters , MSc
Identifier: http://hdl.handle.net/10948/30397 , vital:30938
Description: Diabetes afflicts millions of individuals worldwide, and the statistics rise each year. It is associated with various ailments which reduce the quality of life and has been shown to be associated with seemingly unrelated diseases or conditions. One aspect of the pathogenesis of diabetes is endoplasmic reticulum (ER) stress, which is an imbalance in the protein loading and protein folding capacities of the ER of a cell. Under chronic hyperglycaemic conditions associated with the development of diabetes, excessive insulin production disrupts the ER homeostasis, leading to ER stress. If the ER stress is severe or chronic, cell death of pancreatic β-cells may occur, leading to the onset of diabetes. There is currently a gap in available models that closely resemble the pathogenesis of diabetes in insulinoma-1E (INS-1E) pancreatic β-cells to study ER stress under hyperglycaemic conditions. This study optimised various ER stress-inducing models and tested terpenoid treatments to investigate their potential in modulating ER stress. Using various cell viability assays, five models to induce ER stress were optimised (hyperglycaemic, interleukin-1β (IL-1β), tunicamycin (Tm), brefeldin-A (BFA) and thapsigargin (Tg)). The five models were shown to induce ER stress through the expression of the downstream ER stress marker CCAAT-enhancer binding protein (C/EBP) homologous protein (CHOP). The various models induced ER stress under different mechanisms. Insulin secretion analysis using enzyme-linked immunosorbent assays (ELISAs) demonstrated that low concentrations of IL-1β promoted insulin secretion. Several of the terpenoid treatments showed potential in alleviating different aspects of either ER stress or inflammation.
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Date Issued: 2018

The effects of environmental variability on the physiology and ecology of Cape stumpnose Rhabdosargus holubi (Steindachner, 1881) (Sparidae)

Authors: Kisten, Yanasivan
Date: 2018
Subjects: Freshwater fishes -- South Africa , Fishes -- Ecology Freshwater fishes -- Ecology Estuarine ecology -- South Africa Estuaries -- South Africa
Language: English
Type: Thesis , Doctoral , DPhil
Identifier: http://hdl.handle.net/10948/31424 , vital:31374
Description: Estuaries are important nursery areas for early stages of marine estuarine-dependent fishes, such as the sparid Rhabdosargus holubi. Estuaries provide food, shelter from predators and optimal habitats and environmental conditions for growth and development. However, estuaries are environmentally dynamic and resident organisms must be able to adapt to rapid changes. Such changes are potentially further exacerbated anthropogenically by water and land use practices such as freshwater abstraction, impoundment, pollution and anthropogenically driven climatic change. An effective approach to better understanding the current and future impacts of these kinds of changes, is by assessing the environmental adaptability of organisms, especially to extreme conditions such as droughts and resulting water shortages, which are prevalent in some parts of southern Africa. This thesis examines the effect of various environmental changes such as salinity, turbidity and temperature on the ecology and physiology of a South African common endemic fish species, the Cape stumpnose, R. holubi. Previous work on the species have investigated short term impacts on physiology while this study investigates medium to short term impacts. The specie’s wide distribution in South Africa and tolerance enabled a range of environmental, ecological and physiological relationships to be tested in the context of a changing world. These included: 1) determining the relationship between environmental variability and the distribution and abundance of R. holubi larvae in 25 estuaries along the temperate coast of South Africa; 2) determining the relationship between environmental variability and the movement of larvae and juveniles within two permanently open estuaries; 3) determining the impact of shock and acclimatization on R. holubi salinity tolerance ranges under hypersaline conditions; 4) II determining the impact of hypersalinity on the potential long term impacts growth and skeletal deformities of juvenile R. holubi in aquaria. The findings of these studies suggest that larval occurrence and density within estuaries is a function of salinity and turbidity, by proxy indicating a preference for high freshwater inflow especially in estuary types such as permanently open estuaries. The movement of larvae and juveniles within these estuaries is also mediated by salinity, turbidity and temperature, indicating the importance of seasonality along with environmental conditions and potential olfactory recruitment cues driven by freshwater flow. Tolerance experiments showed that slower acclimation to higher salinities can expand the previously reported tolerance range indicating the potential for adaptation. Physiological experiments showed negative impacts on respiration at salinities exceeding 45, indicating potential long-term physiological effects in hypersaline conditions. Further, living at high salinities for extended periods may have potentially negative effects on long term physiology, particularly growth and skeletal development. The overall results indicate that low salinity (5–18), high turbidity (20–30 NTU) and high temperature (5–22°C) are integral to the distribution and abundance of the species in permanently open estuaries. This conforms to the general rule that estuarine-associated marine fish have higher growth rates in salinities of 12-19. However, juveniles are also adapted to survive at higher salinities for long periods (2 months in the current thesis). This explains why R. holubi is one of the few species in the estuarine fish community that may persist during droughts. The predicted future changes in coastal temperatures and rainfall by climate change investigators, are likely to result in range shifts and changes in recruitment times of estuarine fish communities. The current work addresses novel aspects of the ecology and physiology of R. holubi and indicates that this species will play an increasingly important role within the estuaries of South Africa.
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Date Issued: 2018

The effects of frost on Albany subtropical thicket and nama-karoo shrubland in South Africa

Authors: Duker, Robert
Date: 2018
Subjects: Shrubland ecology , Desert ecology -- South Africa Ecological surveys -- South Africa
Language: English
Type: Thesis , Doctoral , DPhil
Identifier: http://hdl.handle.net/10948/29951 , vital:30799
Description: Numerous treeless shrublands exist in areas where climates should support tree growth. In South Africa, the predominantly lowland Albany Subtropical Thicket (thicket), and the predominantly upland Nama-Karoo semi-desert shrubland share a boundary that is often abrupt and analogous to a forest-shrubland alpine ‘treeline’. This boundary exists across similar climatic and edaphic conditions, and field observations and leaf-level experiments suggest that certain thicket component species have lower levels of frost tolerance than the Nama-Karoo shrubs. The hypothesis is that the occurrence of sub-zero temperatures and frost dictates the position of this boundary at both the local landscape and broader regional levels. I test this hypothesis by quantifying leaf-level and whole-plant freezing tolerance of thicket and Nama-Karoo shrubland species, in relation to their local- and regional-scale distribution, and by modelling the occurrence of frost in the mountainous areas of the coastal lowlands relation to 1) naturally occurring boundaries between these two vegetation types, and 2) levels of aboveground net primary productivity (NPP) of Portulacaria afra Jacq. (spekboom) cuttings (planted with the aim of restoring livestock-degraded thicket). I found that the observed and modelled occurrence of frost in the local landscape has significant negative influences on the photosynthetic health, survival and growth rates of thicket component species, and that leaf-level freezing tolerance of evergreen thicket and Nama-Karoo shrubland species is strongly related to their broader regional-scale distributional thresholds. These results support the hypothesis that the occurrence of sub-zero temperatures and frost play a major role in determining the local- and regional-scale distribution of thicket and Nama-Karoo shrubland species, via their reliance on frost-defined refugia at a variety of different scales, and that the once-widespread and regionally dominant thicket vegetation contracted into small climatic refugia during the Last Glacial Maximum (LGM). These results also have major implications for landscape- and regional-level planning of livestock-degraded thicket restoration efforts that use planting of spekboom as an ecosystem engineer, and for predicting boundary shifts under the predicted future warming of global climates.
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Date Issued: 2018

The extraction, quantification and application of high-value biological compounds from olive oil processing waste

Authors: Postma-Botha, Marthie
Date: 2018
Subjects: Organic compounds , Biochemistry , Biomass energy , Olive oil industry
Language: English
Type: Thesis , Doctoral , DPhil
Identifier: http://hdl.handle.net/10948/34383 , vital:33371
Description: Olive oil processing waste (pomace) as a by-product of the olive oil industry is regarded as a rich source of high-value biological compounds exhibiting antioxidant potential. The objective of the present work was to obtain a concentrated extract of high-value biological antioxidants from the pomace. The effect of extraction conditions on the concentration of the bioactive compounds in the extracts was investigated. The simultaneous recovery of both hydrophilic and lipophilic high-value biological compounds exhibiting antioxidant potential was achieved through a one-step extraction method under reduced pressure using a non-toxic solvent blend. A multilevel experimental design was implemented with the aim of optimising the recovery of selected compounds, namely, hydroxytyrosol, tyrosol, oleuropein, α-tocopherol and squalene from olive pomace by using solvent blends of n-heptane, d-limonene, ethanol and water. The factors considered were: extraction time, percentage composition of solvent blends and extraction temperature. The results suggested that a good recovery of the hydrophilic polyphenolic compounds, namely, hydroxytyrosol, tyrosol and oleuropein, as well as the lipophilic compounds, α-tocopherol and squalene may be achieved at a solvent temperature of 60°C at 400 mbar with a solvent blend of 30% n-heptane, 50% ethanol and 20% water and an extraction time of two hours. It was found that freeze-drying the pomace before extraction minimised production of artefacts, avoided degradation of biophenols, ensured long term stability of a reproducible sample and achieved better recovery of important hydrophilic and lipophilic bioactive compounds. Since the bioactive compounds are temperature sensitive, the extraction was performed under reduced pressure in order to reduce solvent reflux temperature and to improve extraction efficiency. The quantitative and qualitative determinations of the aforementioned high-value compounds were performed by high-performance liquid chromatography (HPLC), which revealed that the hydrophilic polyphenolic as well as the lipophilic α-tocopherol and squalene were present. In this study hydroxytyrosol, tyrosol, oleuropein, α-tocopherol and squalene were extracted from the pomace of two olive cultivars (Frantoio and Coratina). A comparison among the two cultivars showed quantitative differences between the two cultivars in all five high-value biological compounds and in the antioxidant capacity of the extracts evaluated by measuring the radical scavenging effect on 1,1-diphenyl-2- picrylhydrazyl (DPPH) free radical. Coratina cultivar was found to have a significantly higher antioxidant capacity than Frantoio due to the much greater oleuropein content in the Coratina compared to the Frantoio although Frantoio had a significantly greater amount of hydroxytyrosol. The stability of olive waste extracts stored at four temperatures was also investigated and the results show that increased temperatures caused greater extent of degradation of both the hydrophilic polyphenolic and lipophilic compounds. The proposed optimum storage condition for the olive pomace extracts was found to be at 5°C in the absence of light. The extracts were incorporated into two cosmetic formulations and were found, from a stability study, to be stable at room temperature and optimally stable at 5°C in the absence of light.
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Date Issued: 2018

The FAST fabric objective measurement properties of commercial worsted apparel fabrics available in South Africa

Authors: Das, Sweta
Date: 2018
Subjects: Textile fabrics -- Testing , Textile fabrics -- Measurement , Textile fibers -- Testing , Textile design
Language: English
Type: Thesis , Doctoral , PhD
Identifier: http://hdl.handle.net/10948/17814 , vital:28458
Description: In the last few decades, there has been a shift globally towards the objective measurement of these textile fibre, yarn and fabric properties which determine processing performance and product quality. This shift is also very apparent in the objective measurement of fabric properties, particularly those relating to handle and making-up into a garment. This study was motivated by the fact that the adoption of fabric objective measurement (FOM), specifically the FAST system, will benefit the South African worsted apparel sector, as it has done in various other countries which produce high quality worsted apparel fabrics and garments. FAST is robust and portable, yet inexpensive. The main objective of the study was to develop a FAST referencing system which can be used for benchmarking by the local apparel industry and, as a basis for encouraging and persuading the industry to adopt this system of fabric quality measurement and assurance and thereby improve their product quality and international competitiveness. To achieve the main objective, involved sourcing and FAST testing a representative cross-section of commercial worsted apparel fabrics with the emphasis on wool and wool blends from the local fabric and clothing manufacturing industry, and determining how the various FAST properties were affected by factors such as fabric weave, fibre blend and weight, since this could impact on the specific nature and validity of the referencing system. A total of some 394 worsted type commercial fabrics, mainly in wool and wool blends, were sourced from, and with the inputs of, local apparel fabric and clothing manufacturers so as to ensure the local fabric and garment representative of the sample population and after which the fabrics were tested on the FAST system. ANOVA (regression analysis) was carried out on each of the FAST parameters in order to determine whether fabric weight, weave, thickness and fibre composition (pure wool and wool blends) had a statistically significant effect on them, since this is an important aspect which needs to be clarified prior to the development of a envisaged meaningful FAST system.
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Date Issued: 2018

The foraging ecology of Wedge-tailed Shearwaters (Ardenna Pacifica) in the tropical Western Indian Ocean

Authors: Keys, Danielle Zuanda
Date: 2018
Subjects: Birds of prey -- Behavior -- South Africa -- Western Cape , Animal behavior , Wildlife conservation
Language: English
Type: Thesis , Masters , MSc
Identifier: http://hdl.handle.net/10948/31251 , vital:31348
Description: The distribution and abundance of prey largely influences how marine predators forage. Thus, understanding how marine predators respond to such changes becomes imperative when making decisions in marine spatial planning, especially in light of global climate change. Tropical marine systems are known for their relatively low productivity and high unpredictability of prey resources. Compared to higher latitudes, very few studies on seabirds have been implemented in the tropics. The Wedge-tailed Shearwater Ardenna pacifica is an Indo-Pacific tropical seabird with a wide distributional range. However, like many other seabirds, its population numbers are currently declining. Very little is known about the at-sea distribution of Wedge-tailed Shearwaters in the tropical western Indian Ocean. Therefore, this thesis investigates the foraging ecology of Wedge-tailed Shearwaters in the western Indian Ocean by tracking the fine scale movements of individuals at sea. This study was conducted in two different oceanic environments, namely D’Arros Island and Fouquet Island, St Joseph Atoll in the Amirantes Group in Seychelles archipelago as well as Réunion Island in the Mascarene archipelago during the Wedge-tailed Shearwaters breeding seasons. Here I aimed to investigate the foraging distribution of Wedge-tailed Shearwaters on Réunion Island in relation to different stages of the breeding period. I also compared the foraging ecology of all three populations, subjected to different abiotic and biotic factors. Furthermore, I investigated foraging site fidelity in individuals and repeatability within individual flight characteristics. To my knowledge, this is the first study to comprehensively investigate the foraging ecology of Wedge-tailed Shearwaters using global positioning system (GPS) loggers. This study demonstrated that the Wedge-tailed Shearwaters implement flexible foraging strategies throughout different stages of their breeding period and between different islands. In Réunion, during the shearwater breeding season, sexual segregation was prominent during early chick rearing and both sexes implemented dual foraging. As suggested by previous studies, it is likely that long trips were implemented for self-maintenance, whereas multiple short trips were implemented to meet the high energetic demands of the chicks. Several important foraging areas were identified for these Wedge-tailed Shearwaters. During incubation, shearwaters from Réunion faithfully foraged towards the south east of Madagascar near the East Madagascar Current and flew over large areas of the Mascarene Basin. During chick rearing, shearwaters significantly constricted their range closer to the colony and exploited deep waters on the south-west of Réunion Island. Shearwaters concentrated near oceanographic features such as the Pérouse Seamount (which is a known area of high productivity) as well as the Bourdonnais Ridge. There was no clear evidence for spatial or sexual segregation between individuals from the two study colonies in Seychelles during incubation and birds utilized a broader foraging range than birds from Réunion. This is likely to be the result of a large annual phytoplankton bloom which coincides with the shearwater breeding season in Seychelles, providing many foraging opportunities within the Seychelles Basin. The shearwaters from Seychelles exploited the Amirante Basin, East Somali Basin, and parts of the Seychelles archipelago. Shearwaters from D’Arros flew further east and foraged in the Mascarene Basin. Shearwaters from all populations foraged over deep, relatively unproductive waters with relatively high sea surface temperatures which are similar oceanographic features favoured by tuna. Foraging plasticity between individuals from different colonies was observed with varying flight bearings, flight durations and the maximum distances travelled from their respective colonies. Shearwaters displayed dissimilar levels of site fidelity, where shearwaters from Réunion faithfully foraged towards south east Madagascar, while shearwaters from Seychelles foraged over a wide range over the Seychelles Basin. Foraging effort for shearwaters from Fouquet was lower than shearwaters from Reunion and they spent less time at sea and foraged closer to their colony. These difference in behaviour responses between colonies may be advantageous to shearwaters, indicating that they may be able to respond to some level of environmental variability resulting from climate change and anthropogenic pressures. Lastly, during chick rearing, though shearwaters showed low levels of repeatability in flight characterising, foraging site fidelity was high amongst some of the individuals. Here we see that shearwaters continuously rely on permanent features, like seamounts and possibly fish aggregating devices, which are known to attract high abundances of tuna. Shearwaters may to some extent be relying on memory to find prey in a seemingly unpredictable environment. This study has helped us gain valuable insight about the foraging ecology of Wedge-tailed Shearwaters in the western Indian Ocean. Together with similar studies determining the at-sea behaviour of seabirds, better informed recommendations can be made to marine spatial planners as to where much needed pelagic marine protection should be implemented to preserve marine life in this fascinating part of the global ocean.
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Date Issued: 2018

The impact, on fibre quality, of changing from conventional cotton to genetically modified cotton

Authors: van Rensburg, Joané Jansen
Date: 2018
Subjects: Cotton -- Genetic engineering , Cotton -- Quality Cotton
Language: English
Type: Thesis , Masters , MSc
Identifier: http://hdl.handle.net/10948/30408 , vital:30940
Description: This study was aimed at investigating the impact, on cotton fibre quality, of changing from conventional (non-GM) to genetically modified (GM) cotton, in both South Africa and the United States of America (USA). The cotton quality data, pre- and post-GM, generated by Cotton SA and the USDA, respectively, using the HVI systems, were accessed for 25 years in South Africa, and 27 years in the U.S. The key cotton quality parameters evaluated were staple length, micronaire and strength. These quality parameters had been measured on the Uster® HVI system by the various classing facilities in South Africa and the USA, on each bale of cotton produced within the specific country. The data for South Africa covered the period from 1992 (six years before the introduction of GM cotton) to 2016, composing at least 90% GM cotton since 2007. Data for the USA covered the period from 1990 (five years before the introduction of GM cotton) to 2016, composing at least 90% GM cotton since 2010. The data accessed and compiled, from the respective databases of two different countries, had to be electronically captured, regrouped (according to standards provided by the USDA) and thereafter analysed. It was found that the introduction and phasing in of GM cotton in both South Africa and the USA had a beneficial impact on the overall quality (FQI) of cotton produced in these countries. These positive trends in FQI were mainly caused by an increase in staple length for both countries, due to the beneficial impact that the introduction and phasing in of GM cotton had on staple length. Certain of the fibre parameters, notably micronaire, tended to fluctuate from year to year, quite unrelated to the introduction and phasing in of GM cotton, this being ascribed to fluctuating climatic conditions, and the parameter’s extreme sensitivity to such conditions. Over the period covered, cotton fibre, strength, showed a different trend for each country, remaining largely constant in South Africa, while increasing in the USA, this being unrelated to the introduction of GM cotton per sé.
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Date Issued: 2018

The mangroves of Mozambique: pathways to conservation through integrated management

Authors: Macamo, Célia , Bandeira, Salomão
Date: 2018
Subjects: Mangrove ecology -- Mozambique , Mangrove conservation -- Mozambique
Language: English
Type: Thesis , Doctorate , Dphil
Identifier: http://hdl.handle.net/10948/30843 , vital:31182
Description: This study analyses the status and management of mangroves in Mozambique and how the management system addresses the threats to mangrove conservation. A comprehensive analysis of the country forest condition and management status was conducted based on a literature review and informal interviews with key informants. GIS and remote sensing techniques combined with groundtruthing were used to assess the impact of natural and human threats on mangroves based on changes in NDVI (Normalised Difference Vegetation Index) and cover area. These studies were conducted at the Save River and Cabo Delgado province, respectively. Structural data of the mangrove forest were collected during field visits to assess changes in structural parameters and compare impacts in different forests or locations within the same forest. Finally a community-based management system in Nhangau (Sofala province) was analysed in order to assess the efficacy as a management tool to meet mangrove conservation objectives. Mozambique has an estimated mangrove cover area of 3 054 km2. In general there is a trend of decrease in cover around major human settlements, while remote areas show an increase in cover as documented in Maputo Bay (175.96 km2, decreasing within Maputo town) and Zambezi Delta (370.34 km2, increasing), respectively. Mangroves are mostly used for wood resources, salt production and fishing grounds. However, urban development, saltpans, logging and natural phenomena such as floods and cyclones are a threat to these systems. Mozambique has 27% of its mangroves protected in conservation areas. At places like the Quirimbas National Park, this protection is not effective due to illegal cutting and poor enforcement. The Mozambican institutional and legal frameworks provide protection to mangroves at all levels and prohibit all forms of degradation and unsustainable use. However law enforcement and institutional functioning is weak. There is also a need to update the legislation by adding specific aspects related to mangroves, such as regulating invertebrate collection and defining customary use. At the Save River changes in NDVI indicated that 63.42 km2 of mangrove (47.8%) were affected by cyclone Eline. Field investigations 11 years after the cyclone showed that there was substantial recovery in the protected creek forest but changes in sedimentation prevented recovery in the seaward sites that are exposed to storm surges and wind. This study highlighted the necessity for field based investigations in addition to remote sensing as results showed site specific differences. The percentage of living trees at the creek forest ranged from 71 to 97% from the outer to inner forest. Also species density was higher at the creek sites from the outer (101 ± 63 tree/ha) to inner forest (488 ± 111 trees/ha) as was the complexity index (0.09 to 0.25 respectively). At the seaward forest the percentage of living trees increased from 0 to 79% from the outer to inner forest. Seedlings (up to 40 cm height) dominated the understory throughout the forest however the outer edge of the seaward forest had no regeneration at all. This forest recovered naturally from the cyclone, however it is important to maintain low exploitation levels to ensure forest resilience in case of similar future impacts. The frequency and intensity of cyclones is expected to increase with climate change and thus the results can contribute to management strategies and climate change adaptation plans. 3 Human impacts were investigated at a peri-urban, rural and island setting in Cabo Delgado province. It was hypothesized that peri-urban forests would be more impacted. However an analysis of LandSat images showed that mangrove cover at the peri-urban site actually increased by 22.7% between 1991 and 2013; while rural forests lost 23.2% of its area during the same period. Field studies showed that there was no significant difference between average tree density for the different sites (p= 0.16) and the low complexity indices indicated young disturbed forests. At the peri-urban and rural sites, the tree diameter class 5.1-8 cm was targeted for extraction, while at the rural island all size classes were targeted. The proportion of stump:living trees was 1:11 at the peri-urban site; 1:9 at the rural site and 1:4 at the rural island. Most of the standing trees were crooked and not suitable for building purposes. The small extractive use of mangroves at the peri-urban site could be related to the fact that the dominant ethnic group has kept its essentially agricultural habits while at the rural site the people are typically fishermen and marine invertebrate collectors that rely on mangroves and marine resources for their livelihoods. Proposed management measures for these sites include raising awareness at all sites and conducting mangrove restoration at the peri-urban (abandoned saltpans and aquaculture farm) and rural sites. A community-based management system at Nhangau (Sofala province) was analysed in order to assess how this has achieved management conservation objectives. After facing several impacts due to mangrove degradation, the community of Nhangau engaged in mangrove replanting and management. The main management actions were (1) reduction of extractive uses, (2) continuous awareness and mangrove planting and (3) law enforcement. The restoration interventions started in the late 1990s by the local government in partnership with the local community and NGOs. Currently (2018), most of the activities are led by the local Natural Resources Management Committee (NRMC). Ten hectares of mangrove were planted between 1996 and 2017, and according to the local community the restored areas are already providing important ecological services such as temperature regulation. There are several challenges such as, limited functionality of the NRMC and its interaction with other stakeholders, Government representatives and local NGOs. There is also a lack of alternative livelihoods for mangrove cutters and the wider Nhangau community. Improvements to the system include better integration of local government representative structures with the civil society organizations (NGO and NRMC), law enforcement, financing of the appropriate sustainable use practices, environmental awareness and education and the promotion of appropriate NRMC functionality and representation. With these improvements this community-based management system can be effective as a management tool to meet mangrove conservation objectives and serve as a replicable model for other parts of the country. In conclusion, this research has documented both anthropogenic and climate-related impacts on mangroves in Mozambique and highlighted options for mangrove management focusing at strengthening the community –based management of mangroves in rural sites. Mangrove management would improve significantly by strengthening the legislation on specific mangrove issues combined with law enforcement and better community organization and their training and sensitization to manage mangrove resources at the local level. Such actions will increase the resilience of forests, allowing sustainable use and faster recovery in case of impacts by either anthropogenic or natural factors such as cyclones.
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Date Issued: 2018

The spatial ecology and roost site selection of fledging Cape vultures (Gyps coprotheres) in the Eastern Cape, South Africa

Authors: Martens, Francis Rae , Downs, Colleen
Date: 2018
Subjects: Spatial ecology -- South Africa -- Easter , Gyps -- South Africa -- Eastern Cape Vultures -- South Africa -- Eastern Cape Birds -- Behavior -- South Africa -- Eastern Cape
Language: English
Type: Thesis , Masters , MSc
Identifier: http://hdl.handle.net/10948/15875 , vital:28284
Description: The Cape Vulture (Gyps coprotheres), a southern African endemic, is a species currently listed on the IUCN Red List as “Threatened” due to its 66-81% decline over the past 50 years. South Africa and Lesotho hold 90% of the global population, which are focused at two core areas, namely northern central South Africa and eastern South Africa. This species provides important ecological services yet faces numerous anthropogenic threats. An emerging threat in the south eastern part of South Africa is that of wind energy development. Understanding the movement and roosting behaviour of the Cape Vulture may mitigate potential collisions if areas of high use are avoided. Juvenile Cape Vultures, who naturally suffer high mortality rates, are known to forage extensively over a wider landscape and as a consequence may face a greater assortment of threats. The overall aim of this study therefore was to determine the ranging and roosting behaviour of juvenile Cape Vultures in the Eastern Cape Province, South Africa. In order to achieve this aim, i) the ranging behaviour and habitat use were determined and ii) roost sites and factors that influence roost site selection were determined. Using five juvenile Cape Vultures tagged with Global Positioning System (GPS/GSM) transmitters, home range sizes, distance travelled from the nest and habitat use were determined. Home range was determined through kernel density estimates and distance travelled from the nest was determined through the Euclidean distance. Habitat use was determined by overlaying the home range size onto a merged layer of all protected areas and the National Land Cover Database of South Africa. To determine roost sites, data from the tagged vultures were split into encamped and exploratory movements using a mixture model in a cluster analysis setting. Encamped movements were associated with roost sites. Roost density was determined around the natal colony using predetermined buffer sizes and a generalised linear mixed model (GLMM) fitted to the data. Conditions considered favourable for roost sites were based on previous research conducted on cliff-nesting species and a GLMM conducted. Juveniles increased their home range progressively for the first two months, then exhibited a rapid increase in size associated with dispersal from the colony. Distance from the nest increased rapidly following the dispersal period. Protected areas and woody vegetation were areas of preferred habitat. The highest density of roosts for juveniles was located within 20 km’s from the breeding colony and decreased further away. Roost sites that were favoured for juveniles and adult birds were those that were located close to colonies, had low accessibility to terrestrial predators and were in areas of high wind speed. The orientation of the cliff into the prevailing wind direction was also a determining factor. Roosting sites and foraging areas are important spatial determinants of Cape Vulture behaviour and the identification of such areas can help with conservation management. With the additional threat of wind development in areas highly utilised, wind farms located too close to colonies could have a devastating impact on the Cape Vulture population. Therefore, this study highlights the importance of conservation buffer zones as no-go areas for wind energy development around vulture colonies.
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Date Issued: 2018

The synthesis of functionalized carbon nanomaterial from waste tyre sourced carbon for chemosensing during purification processes

Authors: Du Plessis, Jacolien
Date: 2018
Subjects: Nanostructured materials , Nanotechnology
Language: English
Type: Thesis , Masters , MSc
Identifier: http://hdl.handle.net/10948/29925 , vital:30794
Description: The short lifetime of tyres causes great environmental harm due to their non-biodegradable nature resulting in land and water pollution. Exploration of novel uses for recycled tyres is therefore imperative. The use of recycled waste tyres as carbon source for the synthesis of fluorescent chemosensing carbon nanomaterial for the detection of harmful chemicals in water is proposed in this work. Three key problems are addressed in this study: i) re-using of waste tyre products, ii) synthesis of low-cost carbon nanomaterial, iii) detection of harmful compounds within environment systems. The fluorescent triazolyl-coumarin compound, 7-(diethylamino)-3-(4-(1-hydroxyethyl)-1H-1,2,3-triazol-1-yl)-2H-chromen-2-one, was synthesized in multiple steps from 4-diethylamino salicylaldehyde. The last step included the use of Cu(I)-catalyzed 1,3-dipolar azide-alkyne cycloaddition (“click-reaction”) to form a triazole ring. Carbon spheres were synthesized through catalytic chemical vapour deposition (CVD) from waste tyre pyrolysis oil (WTPO), as the carbon source, in the presence of a catalytic amount of ferrocene. The quality and quantity of the carbon spheres had an overall improvement as the synthesis temperatures increased from 800 oC to 950 oC. The diameter of the carbon spheres reduced from 1017 nm to 577 nm as seen in TEM and SEM imaging. TGA and XRD analysis indicated a direct relationship between an increase in synthesis temperatures with an increase in the crystallinity of the carbon spheres. Commercially available naphthenic oil was used as a reference to compare the impact of the starting carbon precursor on the morphology of the carbon nanomaterial under the same reaction conditions. Multi-walled carbon nanotubes were synthesized at the lower temperatures of 800-850 oC. Carbon fibres and carbon spheres were observed at the synthesis temperatures of 900-950 oC. The carbon source played a role in the morphology of the carbon nanomaterial as it could be seen between the complex natured WTPO and the pure naphthenic oil. The purified carbon spheres synthesized at 950 oC from WTPO were functionalized with the triazolyl-coumarin units on the surface through Steglich esterification using DCC/DMAP to yield fluorescent carbon spheres. Complexation studies of the functionalized carbon spheres were done using UV/Vis spectroscopy and fluorescence with a wide range of ions; Ag+, Al3+, Co2+, Cr3+, Cu2+, Fe3+, ii Hg2+, Li+, Ni2+, Pb2+ and Zn2+. The triazolyl-coumarin carbon spheres showed reasonable sensitivity and selectivity towards Fe3+ in water with a quenching effect in fluorescence. Titration studies with Fe3+ indicating an exponential decay of quenching in the fluorescence up to 68% with detection limit at 2.73 x 10-5 M.
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Date Issued: 2018

The use of a silica based coating to reduce moisture absorption of flax fibre reinforced composites

Authors: Bala, Sandisiwe
Date: 2018
Subjects: Chromatographic analysis , Nonwoven fabrics Nanocomposites (Materials)
Language: English
Type: Thesis , Masters , MSc
Identifier: http://hdl.handle.net/10948/23349 , vital:30534
Description: This study deals with the synthesis of silica particles, treatment of flax fabrics with silica, and the preparation and characterization of silica coated flax fibre reinforced phenolic composites treated with silica. Silica particles were successfully prepared by means of a hydrolytic sol-gel route. Two types of silica were prepared by employing either ammonium hydroxide solution as a base catalyst and acetic acid as an acid catalyst. The silica sols were then aged from three to five days in order to determine the effects of aging on the final properties of the silica. The chemical composition of the silica particles was evaluated by fourier transform infrared spectroscopy (FTIR), thermal stability was determined by using thermogravimetric analysis (TGA), and structural and physical properties of the silica particles prepared via two catalysts and aged at different time periods was investigated by x-ray diffraction (XRD). Silica sols, prepared at different conditions were then applied to treat flax fabrics (untreated/scoured) by use of the padding technique. The effects of the silica treatments on flax fabrics were evaluated by FTIR, XRD, determination of moisture content and mechanical properties. The FTIR revealed presence of silica groups on the silica treated flax fabrics, thus resulting in low moisture content for silica treated flax fabrics. XRD analysis revealed that aging the silica sols increases the crystallinity index. Silica treated flax fabrics showed enhanced tensile properties in the weft direction. The thermal, mechanical and water sorption properties of the composites were evaluated. TGA results revealed that the decomposition temperatures of the silica treated composites shifted to higher temperatures. Thus, silica treatments lead to an improvement in thermal stability for composites. A reduction in mechanical properties was also observed for silica treated composites and some composites showed a reduction in water absorption. It was quite evident from this study that the type of catalyst system used in silica preparation has a great influence on the final properties of the silica, which to a large extent changes the thermal, mechanical and water sorption properties of the composites.
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Date Issued: 2018

Tolerance of salt marsh ecotone species to salinity and inundation

Authors: Matabane, Rebotile
Date: 2018
Subjects: Geobiology , Plant ecology Plant ecophysiology
Language: English
Type: Thesis , Masters , MSc
Identifier: http://hdl.handle.net/10948/22409 , vital:29967
Description: Ecophysiology studies help understand and predict the response of coastal ecosystems to changes in environmental factors and complement modelling and mapping studies that often do not take into account the physiological tolerances of the biota. Along the South African coastline predicted sea level rise will shift the tidal front and result in larger submerged areas. The frequency and magnitude of inundation and subsequent salinity stress is expected to influence the survival and distribution of salt marsh. An understanding of the effects of sea level rise on plant growth and survival is required to predict, manage and adapt to climate change. The aim of this study was to investigate the response of the salt marsh ecotone species Disphyma crassifolium (L.) L. Bol. to salinity and submergence stress and to measure in situ spatial and temporal changes in vegetation cover and its environmental drivers in the Swartkops Estuary in South Africa.Three greenhouse experiments assessed morphological and physiological responses to salinity and inundation treatments on D. crassifolium. The first experiment used three inundation levels (dry, tidal and waterlogged) and five salinity treatments (0, 8, 18, 35 and 45 ppt) and ran for six weeks. The second experiment also had three inundation levels (dry, waterlogged and completely submerged) and five salinity treatments (0, 8, 18, 35 and 45 ppt) and ran for 12 weeks. The third experiment investigated the response of a narrower range of salinity treatments under dry conditions only; namely 0, 5, 10, 15, 20, 25, 30 and 35 ppt and ran for seven weeks. Experiment 1 showed that D. crassifolium growth decreased with an increase in salinity. Optimum growth occurred at lower salinity treatments of 0 to 18 ppt under dry conditions. Plant height and leaf succulence was the highest at 0 ppt (12.4 ± 1.2 cm and 94.9 ± 0.6 % respectively). The number of leaves produced were the highest at 0 ppt (47.7 ± 8.9 number of leaves) and 8 ppt (59.6 ± 6.3 number of leaves). The root/shoot ratio for dry treatment plants was significantly lower (p < 0.005, n=12) than that of waterlogged and tidal-treated plants. This was as a result of more leaves being produced in dry treatments. In Experiment 2 D. crassifolium plants died after one month of submergence regardless of the salinity. Once again optimum growth occurred at salinity of 0 to 18 ppt under the dry treatment. Within the waterlogged treatment, 0 and 8 ppt treated plants developed adventitious roots and started flowering after two weeks.The electrolyte leakage increased with salinity, however the waterlogged plants had significantly higher electrolyte leakage compare to the dry treated plants. Within the waterlogged treatment electrolyte leakage was at the highest at 18 ppt (36.5 ± 4.2 %) and lowest at 0 ppt (26.1 ± 3.3 %). Photosynthetic pigments showed significant difference across the two inundation states. However, chlorophyll and carotenoids concentrations did not differ significantly with an increase in salinity in each treatment. D. crassifolium tolerated stress through accumulation of solutes that increased in concentration with salinity treatment. The proline concentration ranged between 23.1 to 102 mM while the glycinebetaine concentration ranged between 36.6 and 120 mM. Experiment 3 showed that growth was highest at salinity < 20 ppt. The highest growth based on plant height was measured at 0 and 10 ppt. Spatial and temporal changes in the salt marsh terrestrial boundary was investigated in situ at two sites in the Swartkops Estuary using three line transects per site extending from the terrestrial boundary to the supratidal salt marsh. Plant cover abundance was measured seasonally along with sediment moisture content, electrical conductivity, redox potential, organic content and sediment particle size. There were five sampling trips between April 2016 to July 2017, representing autumn, winter and summer. The transects at Sites 1 and 2 were divided into three zones; a Drosanthemum zone (dominated by Drosanthemum parvifolium (Haw.) Schwantes at the beginning of the transect), a Sarcocornia zone (in the middle of the transect and dominated by Sarcocornia pillanssii (Moss) A.J. Scott) and a Disphyma zone at the end of the transect in the supratidal marsh (dominated by Disphyma crassifolium). There was no significant seasonal change in vegetation cover except in Site 1 during Winter 2016 when Isolepis sp. appeared and was dominant in the middle of the transects. Sediment assessed from each of the zones showed physicochemical ranges within the typical ecotone sediment characteristics. Moisture content ranged between 0.6 and 30.9 % at Site 1 and between 3 and 33.8 % at Site 2. Electrical conductivity ranged between 0.9 and 10.2 mS cm-1 at Site 1 and between 1.4 and 17.8 mS cm-1 at Site 2. Organic content ranged between 1.9 and 16 % at Site 1 and between 3.9 and 16.3 % at Site 2. Redox potential ranged between 208 and 406.7 mV at Site 1 and between 202.7 and 389.67 mV at Site 2. Sediment particle size consisted of sand (>70%), silt (>15%) and clay (<10%). The aim of this study was to provide insight on the effects of salinity and inundation on the morphology and physiology of D. crassifolium occurring in the salt marsh terrestrial boundary and to assess its spatial and temporal changes over time. The research suggests that D. crassifolium is more sensitive to inundation than salinity. Furthermore the succulent was found in the field to be dominant in conditions which the glasshouse experiments showed to be its optimum growth. That is, in dry sediments with salinity of < 18 ppt. Therefore, if these conditions change (sediment moisture and salinity), the cover abundance of D. crassifolium could significantly change in the field.
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Date Issued: 2018

Towards a community based conservation strategy for wetlands in Uganda

Authors: Barakagira, Alex
Date: 2018
Subjects: Conservation of natural resources , Wetland conservation -- Uganda Wetlands -- Uganda -- Management
Language: English
Type: Thesis , Doctoral , DPhil
Identifier: http://hdl.handle.net/10948/23902 , vital:30640
Description: Conservation of natural resources in Uganda focuses primarily on protected areas, including savannah national parks, mainly for conserving big game and forests, for controlling the harvest of commercially valuable timber resources, with less concern for wetlands. Later, policies and legislation in Uganda favoured agricultural production rather than the conservation of wetlands, a situation that culminated in their degradation. In a bid to counter the effects of wetlands degradation, Wetland Management Agencies were created. These agencies excluded the input of members of the local communities who reside in the wetlands environs. Local communities were not consulted on matters concerning management and conservation strategies, a situation that may have escalated the problem of wetlands degradation. Local knowledge is needed for the effective management and conservation of the wetlands and it is essential that local communities are included in decision making. This research study is more of an initiative for providing information that may be essential for the formulation of a community based conservation strategy for wetlands in Uganda. The study aimed to identify and characterize activities carried out by members of the local communities in wetlands found in central and western Uganda that are responsible for their progressive degradation; to assess the performance of existing Wetlands Management Institutions towards protection and conservation of wetlands in Uganda; to ascertain whether the acts and policies that have been promulgated for the protection of wetlands in Uganda have been adhered to by members of the local communities and to evaluate three community based conservation case studies with two vastly different outcomes in order to come up with the community-based conservation principles Ugandan communities may need to adopt to achieve sustainable utilisation and conservation of wetland resources. To achieve the objectives stated above, the researcher used a multi-disciplinary methodology that required several areas of expertise and sources of information. Hence, to accomplish the study, primary sources of data that included quantitative and qualitative data were collected from the study participants by means of a questionnaire survey, key informant interviews and direct observations. Secondary sources of data centred on published Ugandan acts and policies; textbooks; case study articles and journal articles. The study revealed a host of activities in which members of the local community are involved that have led to the degradation of the wetlands in Uganda. These include but are not limited to crop cultivation, dairy farming and unsustainable wetland resource harvesting. A number of other reasons for the degradation of the wetlands include unclear ownership of the wetlands, unclear wetland boundaries and a lack of awareness of the indirect benefits wetlands provide for members of the local communities. The study disclosed that wetlands management institutions have not been effective in the protection and conservation of wetlands in Uganda, mainly due to political interference and inadequate funding for the institutions’ conservation activities. The acts and policies that were promulgated for the protection and conservation of wetlands have been selectively implemented in some places and in others completely ignored, culminating in the degradation of the wetlands. The study revealed that effective community based conservation of wetlands in Uganda includes: initiation of the planning, implementation, monitoring and evaluation of all wetlands activities being borne by members of the local community; government introducing alternative income-generating activities aimed to reduce over-reliance on wetland resources and education of the local communities regarding the community-based projects’ objectives in order to garner their support. Recommendations emanating from this study are that the Land Act should be amended to specify a particular land tenure system, preferably freehold, which may promote the conservation of wetlands in Uganda; fertilizers (organic) should be introduced in the study area to fertilize the uplands that have reportedly become infertile in order to reduce the pressure the local community members are exerting on the wetlands for agriculture; wetlands management institutions should be empowered financially and political interference in activities aimed at conservation of wetlands in Uganda must cease. There should be uniform implementation of the rules and regulations stipulated in the acts and policies for all members of the public concerning wetlands protection. Lastly, essential community based conservation principles, as stated above, need to be applied carefully and adhered to if effective implementation of community-based conservation of wetlands is to be achieved in Uganda.
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Date Issued: 2018

Understanding the impacts of foliar insect pests on eucalyptus species growth and the development of appropriate management strategies

Authors: Dlamini, Lindokuhle Sithembiso
Date: 2018
Subjects: Eucalyptus -- South Africa , Trees -- Breeding Wood-pulp industry -- South Africa
Language: English
Type: Thesis , Masters , MSc
Identifier: http://hdl.handle.net/10948/29962 , vital:30801
Description: Within South Africa (SA), eucalypts contribute significantly to the commercial production of pulpwood, treated poles, wood chips and saw timber. Due to their rapid growth and desirable timber properties, 47% of the afforested area within SA is planted with various eucalypts and their hybrid combinations. Biotic and abiotic factors pose a risk to the productivity of eucalypts, with the most significant risk currently associated with the increased impacts of foliar insect pests on tree productivity, for example Leptocybe invasa Fisher & La Salle (Hymenoptera: Eulophidae); Gonipterus scutellatus Gyllenhal (Coleoptera; Curculionidae); Thaumastocoris peregrinus Carpintero and Dellape (Hemiptera: Thaumastocoridae); Glycaspis brimblecombei Moore (Hemiptera: Psyllidae) etc. Past and current research has focused more on the individual components of biological, cultural and chemical control, with limited research conducted on the practical integration of these management strategies. Although the combination of biological and cultural control methods for long-term management would be preferred, the use of environmentally acceptable insecticides can contribute to the short-term management of insect pests where necessary. Environmental constraints (associated with forest certification) around the use of insecticides, means that there are currently few insecticides available for controlling foliar insect pests of eucalypts within the SA forest industry. Due to the recent increased introduction of insect pests, there is also a lack of data related to their impacts on tree growth, as well as the success of any management methods used. To improve our understanding regarding these components, three groups of trials (five in total) were implemented in the summer rainfall region of SA to quantify the impacts of insect pests on eucalypt growth, test integrated management practices (chemical and cultural management), and test environmentally acceptable insecticides. In 2010, two insect exclusion trials were established at Palm Ridge and Teza plantations in KwaZulu-Natal to quantify the impact of insect pests on two Eucalyptus hybrids. The trial locations were selected adjacent to compartments for which the pests Gonipterus spp. and Thaumastocoris peregrinus were present. Each trial had an insecticide treatment with an active ingredient of alpha-cypermethrin at a rate of 100 g l-1 and a control treatment where trees were not sprayed. Insect pests were collected after every spraying event. A greater number of insect pests were collected from the Palm Ridge site. Gonipterus spp. were the predominant insect pests collected. No significant growth differences were recorded between treated and untreated trees at Teza. Measurements taken at Palm Ridge indicated that insecticide-treated trees had significantly greater tree growth than untreated trees. Final measurements showed a v 25% reduction in volume for the control treatment compared to the insecticide treatment. Results of this study indicate that timing and duration of insecticide application could hold larger and additive benefits for insect exclusion. Due to the lack of non-hazardous registered insecticides, and the susceptibility of many of the eucalypts grown within SA to L. invasa, a trial was initiated in 2011 in Zululand (KwaZulu-Natal). A 3 x 4 x 4 factorial combination of 48 treatments were replicated 3 trials and arranged in a split-split-plot design. The factors included insecticide type as the whole plot (fenvalerate, azadirachtin and imidacloprid), timing of insecticide application as a sub-plot (0, 3, 6 and 9 months) and type of hybrid as the sub-sub-plot (a susceptible and tolerant E. grandis x E. camaldulensis hybrid (GC_s and GC_t) and a susceptible and tolerant E. grandis x E. urophylla hybrid (GU_s and GU_t)). To determine insecticide efficacy, plots of untreated clones were included as control treatments within each replicate. The incidence and magnitude of L. invasa damage and tree performance were assessed for up to 5.5 years of age. L. invasa damage recorded over the trial period indicated that irrespective of treatment, damage was lower in the GU clones than the GC clones resulting in a 63.9 m3 ha-1 volume difference at 5.5 years. In addition, the difference between the GU_s and GU_t clones (3.2 m3 ha-1) was marginal when compared to the GC_s and GC_t clones (37.2 m3 ha-1). A decrease in GC stocking correlated with the period when there was a high damage incidence recorded for L. invasa. Although the three insecticides tested delayed the onset of L. invasa damage, they did not result in improved tree performance at 5.5 years. Results indicate that the planting of a tolerant species (hybrid in this trial) was the most viable option for the management of L. invasa. Two trials were implemented in the KwaZulu-Natal Midlands in October 2016 (at Ingwe and Balgowan plantations), to test the efficacy of eight different insecticides (synthetic and organic) for the management of foliar insect pests. The Ingwe trial was planted with Eucalyptus dunnii and the Balgowan trial was planted with Eucalyptus badjensis. The insecticides tested were azadirachtin, deltamethrin, imidacloprid (liquid and tablet), Beauveria bassiana, Bacillus thuringiensis, potassium silicate and a combination of plant oil extracts (garlic oil, soybean oil and capsicum oleoresin extract). The imidacloprid tablet, deltamethrin and an untreated control were implemented as additional treatments. The insecticides were tested at the recommended rate (single rate) and at double the recommended rate (double rate), except for the insecticides in the additional treatments which were only tested at the single rate. These insecticides were applied three times over a period of four months, and tree growth measurements (Gld/Dbh and Ht) were taken four times over a period of seven months. Gonipterus spp. vi was the only insect pest found in both these trials, thus the insecticides were tested for their efficacy in managing this specific insect pest. A higher population and damage of Gonipterus spp. was found in the E. dunnii trial and very little to no damage was observed in the E. badjensis trial. All insecticides tested were not effective in managing Gonipterus spp. in these specific sites. A low population of insect pests and incorrect timing and method of application of some of the insecticides could offer a plausible explanation of results. Results from these trials indicate that where foliar insect pests occur in high abundance, significant tree-growth reduction occurs. Although insecticides (deltamethrin - for G. scutellatus; imidacloprid for L. invasa) can be used for the short-term control of these insects, their commercial benefits may be reduced due to the number of repeat applications required and/or with high levels of infestation. Of the eight environmentally acceptable insecticides tested for foliar insect control, the low abundance of insect pests present in the trials meant that their efficacy could not be quantified. If an alternative insecticide were to be found, its application would need to be linked to the environmentally stimulated outbreaks of specific insects. Of the treatments implemented, the selection and planting of eucalypts with known resistance to specific insect pests currently remains the most viable management strategy. Breeding for increased tolerance within resistant eucalypts may also provide additional benefits. Although the above research showed the negative impacts of foliar insect pests on tree growth, it also indicated that no single control method is viable for all insect pests. Future research should look at the integration of different management methods while incorporating more insect pests and different seasons in the study.
Full Text:
Date Issued: 2018

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