Weight gain in hospitalised low birth weight (LBW) premature infants receiving breast milk or breast milk with human milk fortifier in the Nelson Mandela Bay Health District
- Authors: Wicomb, Ra-eesa
- Date: 2018
- Subjects: Premature infants -- South Africa -- Nelson Mandela Bay Municipality , Birth weight, Low -- South Africa -- Nelson Mandela Bay Municipality Birth weight -- South Africa -- Nelson Mandela Bay Municipality Infants -- Nutrition Children -- Nutrition -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/23327 , vital:30529
- Description: Rationale: Worldwide, hospitals with premature units have one generalised objective, i.e. to achieve postnatal growth and body composition similar to that of a normal foetus of similar gestational age. Optimal nutrition leads to optimal neurodevelopment and breastfeeding (BF) is known as the golden standard for infant nutrition. Human breast milk (BM) has significant value for preterm and term infants and is of special benefit to HIV infected mothers. Maternal supplementation is provided as part of the standard protocol in certain hospitals in the Eastern Cape province to those mothers who breastfeed their low birth weight (LBW) infants after delivery. human milk fortifier (HMF) is a nutritional supplement that is added to expressed breast milk for feeding preterm infants in order to meet their high energy and protein needs and therefore supporting the recommended growth velocity of 10g/kg/day-15g/kg/day. Some hospitals within South Africa provide HMF to preterm infants as part of their standard nutritional protocol in order for the infant to gain weight if BM only failed to produce adequate results. To date, little to no South African studies support or discourage the use of HMF for LBW infants. This study aimed to describe the effect of maternal supplementation compared with breast milk with HMF, or a combination of maternal supplementation and breast milk with HMF, on growth velocity in hospitalised LBW premature infants within the Nelson Mandela Bay health district. The proposed study design followed a longitudinal, observational, descriptive study in a cohort of LBW infants. The study was analytical using quantitative empirical data. Study participants were selected, by using convenience sampling, at Dora Nginza Hospital, Zwide between October 2015 and August 2016 (ethics approval: EC_2016RP27_564). Quantitative data on anthropometric measurements was collected from study participants. Primary care givers provided written informed consent. Registered nurses were trained and performed anthropometrical measurements according to standardised methods. A structured questionnaire was completed by the principal reasarcher as a source of data collection. Numerical data was described using means and standard deviations. Chi squares were used to describe the associations between maternal risk factors and birth weight outcomes. ANOVA was used to determine the relationship between growth velocity and the various supplementation groups. A sample size of 91 LBW preterm infants and mother pairs were entered into this study. The majority of mothers, 64% (n=58) fell in the age category of 20-35 years old. Of the total maternal sample (n=88), 35% (n=31) were classified in the at risk age category, i.e. <20years old and >36years old. Out of the total infant sample (n=91), 65% (n=59) was classified as VLBW, 22% was LBW and 22% (n=20) was ELBW. No statistically significant association was found between infant growth velocity and maternal risk factors. The group receiving BM with HMF had a mean growth velocity of 19.75 g/kg/day (SD=6.45) that was statistically significantly (p<0.05) more than the other groups. The maternal supplementation only group and the maternal supplementation and BM fortification group showed mean growth velocities of 12.26 g/kg/day (SD=5.41) and 12.29 g/kg/day (SD=6.97) respectively. A post hoc test was done between growth velocity in the supplementated groups and the length of hospital stay. These results reveal that the group receiving BM with HMF had a significantly (p<0.05) shorter mean length of hospital stay of 11.29 days (SD=7.02), compared with the group on the combination of maternal supplementation and BM with HMF. In this study, infants receiving HMF with BM showed the highest growth velocity with the shortest hospital stay before discharge. In this group, infants were already receiving an adequate BM intake of 150-180 ml/kg/day prior to participation in the study. This meant that the HMF group consisted of more stable preterm infants compared to the rest of the supplementated groups. However, a large proportion of participants in the maternal supplementation group also showed adequate to good growth velocity. The researcher recommends the implementation of maternal supplementation only, as standard of care for all hospitalised lactating women. Furthermore, timeous addition of HMF to expressed BM is necessary for infants with growth velocities <15 g/kg/day. This may save costs to the hospital as the use of HMF allowed for better weight gain and earlier discharge.
- Full Text:
- Date Issued: 2018
- Authors: Wicomb, Ra-eesa
- Date: 2018
- Subjects: Premature infants -- South Africa -- Nelson Mandela Bay Municipality , Birth weight, Low -- South Africa -- Nelson Mandela Bay Municipality Birth weight -- South Africa -- Nelson Mandela Bay Municipality Infants -- Nutrition Children -- Nutrition -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/23327 , vital:30529
- Description: Rationale: Worldwide, hospitals with premature units have one generalised objective, i.e. to achieve postnatal growth and body composition similar to that of a normal foetus of similar gestational age. Optimal nutrition leads to optimal neurodevelopment and breastfeeding (BF) is known as the golden standard for infant nutrition. Human breast milk (BM) has significant value for preterm and term infants and is of special benefit to HIV infected mothers. Maternal supplementation is provided as part of the standard protocol in certain hospitals in the Eastern Cape province to those mothers who breastfeed their low birth weight (LBW) infants after delivery. human milk fortifier (HMF) is a nutritional supplement that is added to expressed breast milk for feeding preterm infants in order to meet their high energy and protein needs and therefore supporting the recommended growth velocity of 10g/kg/day-15g/kg/day. Some hospitals within South Africa provide HMF to preterm infants as part of their standard nutritional protocol in order for the infant to gain weight if BM only failed to produce adequate results. To date, little to no South African studies support or discourage the use of HMF for LBW infants. This study aimed to describe the effect of maternal supplementation compared with breast milk with HMF, or a combination of maternal supplementation and breast milk with HMF, on growth velocity in hospitalised LBW premature infants within the Nelson Mandela Bay health district. The proposed study design followed a longitudinal, observational, descriptive study in a cohort of LBW infants. The study was analytical using quantitative empirical data. Study participants were selected, by using convenience sampling, at Dora Nginza Hospital, Zwide between October 2015 and August 2016 (ethics approval: EC_2016RP27_564). Quantitative data on anthropometric measurements was collected from study participants. Primary care givers provided written informed consent. Registered nurses were trained and performed anthropometrical measurements according to standardised methods. A structured questionnaire was completed by the principal reasarcher as a source of data collection. Numerical data was described using means and standard deviations. Chi squares were used to describe the associations between maternal risk factors and birth weight outcomes. ANOVA was used to determine the relationship between growth velocity and the various supplementation groups. A sample size of 91 LBW preterm infants and mother pairs were entered into this study. The majority of mothers, 64% (n=58) fell in the age category of 20-35 years old. Of the total maternal sample (n=88), 35% (n=31) were classified in the at risk age category, i.e. <20years old and >36years old. Out of the total infant sample (n=91), 65% (n=59) was classified as VLBW, 22% was LBW and 22% (n=20) was ELBW. No statistically significant association was found between infant growth velocity and maternal risk factors. The group receiving BM with HMF had a mean growth velocity of 19.75 g/kg/day (SD=6.45) that was statistically significantly (p<0.05) more than the other groups. The maternal supplementation only group and the maternal supplementation and BM fortification group showed mean growth velocities of 12.26 g/kg/day (SD=5.41) and 12.29 g/kg/day (SD=6.97) respectively. A post hoc test was done between growth velocity in the supplementated groups and the length of hospital stay. These results reveal that the group receiving BM with HMF had a significantly (p<0.05) shorter mean length of hospital stay of 11.29 days (SD=7.02), compared with the group on the combination of maternal supplementation and BM with HMF. In this study, infants receiving HMF with BM showed the highest growth velocity with the shortest hospital stay before discharge. In this group, infants were already receiving an adequate BM intake of 150-180 ml/kg/day prior to participation in the study. This meant that the HMF group consisted of more stable preterm infants compared to the rest of the supplementated groups. However, a large proportion of participants in the maternal supplementation group also showed adequate to good growth velocity. The researcher recommends the implementation of maternal supplementation only, as standard of care for all hospitalised lactating women. Furthermore, timeous addition of HMF to expressed BM is necessary for infants with growth velocities <15 g/kg/day. This may save costs to the hospital as the use of HMF allowed for better weight gain and earlier discharge.
- Full Text:
- Date Issued: 2018
Water quality, biomass and extracellular polymeric substances in an integrated algae pond system
- Authors: Jimoh, Taobat Adekilekun
- Date: 2018
- Subjects: Water -- Purification , Sewage -- Purification -- Anaerobic treatment , Sewage lagoons , Sewage disposal plants , ASPAM model (Acid mine drainage) , Integrated algae pond systems (IAPS)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/57307 , vital:26871
- Description: Integrated algae pond systems (IAPS) combine the use of anaerobic and aerobic bioprocesses to effect wastewater treatment. Although, IAPS as a technology process offers many advantages including efficient and simultaneous N and P removal, no requirement for additional chemicals, O2 generation, CO2 mitigation, and a biomass with potential for valorization, a lack of technological advancement and the need for large land area, has limited the reach of this technology at industrial scale. In mitigation, peroxonation was introduced as a tertiary treatment unit and its effect on COD and TSS of IAPS treated water investigated. An effort was made to characterize the soluble but persistent COD in IAPS treated water and, productivity of the HRAOP mixed liquor was investigated to gain insight into the potential use of this biomass. Results show that peroxone treatment effectively reduced COD, TSS, and nutrient load of IAPS water without any significant impact on land area requirement. Indeed, summary data describing the effect of peroxone on quality of IAPS-treated water confirmed that it complies with the general limit values for either irrigation or discharge into a water resource that is not a listed water resource for volumes up to 2 ML of treated wastewater on any given day. Extraction followed by FT-IR spectroscopy was used to confirm albeit tentatively, the identity of the soluble but persistent COD in IAPS treated water as MaB-floc EPS. Results show that MaB-flocs from HRAOPs are assemblages of microorganisms produced as discrete aggregates as a result of microbial EPS production. A relationship between photosynthesis and EPS production was established by quantification of the EPS following exposure of MaB-flocs to either continuous light or darkness. Several novel strains of bacteria were isolated from HRAOP mixed liquor and 16S ribosomal genomic sequence analysis resulted in the molecular characterization of Planococcus maitriensis strain ECCN 45b. This is the first report of Planococcus maitriensis from a wastewater treatment process. Productivity and change in MaB-flocs concentration, measured as mixed liquor suspended solids (MLSS) between morning and evening were monitored and revealed that MLSS is composed of microalgae and bacteria but not fungi. Concentration varied from 77 mg L-1 in September (winter) to 285 mg L-1 in November (spring); pond productivity increased from 5.8 g m-2 d-1 (winter) to 21.5 g m-2 d-1 (spring); and, irrespective of MLSS concentration in late afternoon, approximately 39% was lost overnight, which presumably occurred due to passive removal by the algae settling pond. The outcomes of this research are discussed in terms of the quality of treated water, and the further development of IAPS as a platform technology for establishing a biorefinery within the wastewater treatment sector.
- Full Text:
- Date Issued: 2018
- Authors: Jimoh, Taobat Adekilekun
- Date: 2018
- Subjects: Water -- Purification , Sewage -- Purification -- Anaerobic treatment , Sewage lagoons , Sewage disposal plants , ASPAM model (Acid mine drainage) , Integrated algae pond systems (IAPS)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/57307 , vital:26871
- Description: Integrated algae pond systems (IAPS) combine the use of anaerobic and aerobic bioprocesses to effect wastewater treatment. Although, IAPS as a technology process offers many advantages including efficient and simultaneous N and P removal, no requirement for additional chemicals, O2 generation, CO2 mitigation, and a biomass with potential for valorization, a lack of technological advancement and the need for large land area, has limited the reach of this technology at industrial scale. In mitigation, peroxonation was introduced as a tertiary treatment unit and its effect on COD and TSS of IAPS treated water investigated. An effort was made to characterize the soluble but persistent COD in IAPS treated water and, productivity of the HRAOP mixed liquor was investigated to gain insight into the potential use of this biomass. Results show that peroxone treatment effectively reduced COD, TSS, and nutrient load of IAPS water without any significant impact on land area requirement. Indeed, summary data describing the effect of peroxone on quality of IAPS-treated water confirmed that it complies with the general limit values for either irrigation or discharge into a water resource that is not a listed water resource for volumes up to 2 ML of treated wastewater on any given day. Extraction followed by FT-IR spectroscopy was used to confirm albeit tentatively, the identity of the soluble but persistent COD in IAPS treated water as MaB-floc EPS. Results show that MaB-flocs from HRAOPs are assemblages of microorganisms produced as discrete aggregates as a result of microbial EPS production. A relationship between photosynthesis and EPS production was established by quantification of the EPS following exposure of MaB-flocs to either continuous light or darkness. Several novel strains of bacteria were isolated from HRAOP mixed liquor and 16S ribosomal genomic sequence analysis resulted in the molecular characterization of Planococcus maitriensis strain ECCN 45b. This is the first report of Planococcus maitriensis from a wastewater treatment process. Productivity and change in MaB-flocs concentration, measured as mixed liquor suspended solids (MLSS) between morning and evening were monitored and revealed that MLSS is composed of microalgae and bacteria but not fungi. Concentration varied from 77 mg L-1 in September (winter) to 285 mg L-1 in November (spring); pond productivity increased from 5.8 g m-2 d-1 (winter) to 21.5 g m-2 d-1 (spring); and, irrespective of MLSS concentration in late afternoon, approximately 39% was lost overnight, which presumably occurred due to passive removal by the algae settling pond. The outcomes of this research are discussed in terms of the quality of treated water, and the further development of IAPS as a platform technology for establishing a biorefinery within the wastewater treatment sector.
- 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
Using action cameras to assess habitat use by Pseudobarbus afer and Sandelia capensis in the Swartkops River, Eastern Cape, South Africa
- Authors: Hannweg, Bianca
- Date: 2018
- Subjects: Freshwater biodiversity -- South Africa -- Eastern Cape , Freshwater biodiversity conservation -- South Africa -- Eastern Cape , Freshwater ecology -- South Africa -- Eastern Cape , Freshwater fishes -- South Africa -- Eastern Cape , Freshwater fishes -- Behavior -- South Africa -- Eastern Cape , Freshwater fishes -- Habitat -- South Africa -- Eastern Cape , Underwater videography , Anabantidae -- South Africa -- Eastern Cape , Cyprinidae -- South Africa -- Eastern Cape , Pseudobarbus afer , Sandelia capensis
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/62039 , vital:28098
- Description: Currently, freshwater systems are facing various threats, freshwater biota are declining and there is an increased need to monitor freshwater fauna and flora using non-invasive methods. This thesis aimed to evaluate the potential of using action cameras as a tool for the monitoring of freshwater fish populations and the collection of habitat utilisation data. This evaluation was conducted in headwater tributaries of the Swartkops River in South Africa, using two threatened species that have not been extensively studied, Pseudobarbus afer (Peters, 1864) and Sandelia capensis (Cuvier, 1831). The aims of this study were to: (1) assess the use of underwater video analysis (UWVA) using action cameras (videos and still photographs) in comparison to estimates derived from snorkel surveys, to estimate the abundance of P. afer in headwater streams; (2) use estimates derived from UWVA (videos and photographs) to assess the habitat use of two imperilled species, P. afer and S. capensis; and (3) assess habitat use by these two species in the presence of an artificial habitat. This work demonstrated that: (1) estimates derived from videos and photographs were strongly correlated to estimates derived from snorkel surveys, provided multiple cameras were used; (2) estimates derived from videos and photographs were not significantly different to estimates derived from snorkel surveys; (3) a filming period of 15 minutes was sufficient at detecting 0.9 of the cumulative mMaxN (mean MaxN) within one of the five habitats; and (4) still photographs, which are less time consuming to process than videos, could be used in preference to videos. Based on these findings, techniques using action cameras to assess habitat utilisation and behaviour in situ of the two-focal species, were developed using six habitat types (inflow, outflow, woody debris, fern root, middle and artificial) in four pools. It was demonstrated that: (1) there was a significant difference in proportional occupancies across habitats for both P. afer and S. capensis; (2) Pseudobarbus afer were mainly observed schooling in the middle of the pool and feeding on detritus material in fern root, woody debris and off the artificial structure; and (3) Sandelia capensis rapidly colonised the artificial structure and were observed utilising it for refuge. In conclusion, this work demonstrated that still photographs from action cameras can be used in place of videos to estimate the abundance of freshwater fishes and assess their habitat use and behaviour in clear headwater streams. This work also demonstrated how action cameras could be used to evaluate the effect of the introduction of artificial habitat as a restoration measure for headwater fish communities.
- Full Text:
- Date Issued: 2018
- Authors: Hannweg, Bianca
- Date: 2018
- Subjects: Freshwater biodiversity -- South Africa -- Eastern Cape , Freshwater biodiversity conservation -- South Africa -- Eastern Cape , Freshwater ecology -- South Africa -- Eastern Cape , Freshwater fishes -- South Africa -- Eastern Cape , Freshwater fishes -- Behavior -- South Africa -- Eastern Cape , Freshwater fishes -- Habitat -- South Africa -- Eastern Cape , Underwater videography , Anabantidae -- South Africa -- Eastern Cape , Cyprinidae -- South Africa -- Eastern Cape , Pseudobarbus afer , Sandelia capensis
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/62039 , vital:28098
- Description: Currently, freshwater systems are facing various threats, freshwater biota are declining and there is an increased need to monitor freshwater fauna and flora using non-invasive methods. This thesis aimed to evaluate the potential of using action cameras as a tool for the monitoring of freshwater fish populations and the collection of habitat utilisation data. This evaluation was conducted in headwater tributaries of the Swartkops River in South Africa, using two threatened species that have not been extensively studied, Pseudobarbus afer (Peters, 1864) and Sandelia capensis (Cuvier, 1831). The aims of this study were to: (1) assess the use of underwater video analysis (UWVA) using action cameras (videos and still photographs) in comparison to estimates derived from snorkel surveys, to estimate the abundance of P. afer in headwater streams; (2) use estimates derived from UWVA (videos and photographs) to assess the habitat use of two imperilled species, P. afer and S. capensis; and (3) assess habitat use by these two species in the presence of an artificial habitat. This work demonstrated that: (1) estimates derived from videos and photographs were strongly correlated to estimates derived from snorkel surveys, provided multiple cameras were used; (2) estimates derived from videos and photographs were not significantly different to estimates derived from snorkel surveys; (3) a filming period of 15 minutes was sufficient at detecting 0.9 of the cumulative mMaxN (mean MaxN) within one of the five habitats; and (4) still photographs, which are less time consuming to process than videos, could be used in preference to videos. Based on these findings, techniques using action cameras to assess habitat utilisation and behaviour in situ of the two-focal species, were developed using six habitat types (inflow, outflow, woody debris, fern root, middle and artificial) in four pools. It was demonstrated that: (1) there was a significant difference in proportional occupancies across habitats for both P. afer and S. capensis; (2) Pseudobarbus afer were mainly observed schooling in the middle of the pool and feeding on detritus material in fern root, woody debris and off the artificial structure; and (3) Sandelia capensis rapidly colonised the artificial structure and were observed utilising it for refuge. In conclusion, this work demonstrated that still photographs from action cameras can be used in place of videos to estimate the abundance of freshwater fishes and assess their habitat use and behaviour in clear headwater streams. This work also demonstrated how action cameras could be used to evaluate the effect of the introduction of artificial habitat as a restoration measure for headwater fish communities.
- Full Text:
- Date Issued: 2018
Use of recycled rubber tyres as an alternative ingredient in cementitious building materials
- Authors: Yuill, Robert Mark
- Date: 2018
- Subjects: Building materials , Building materials -- Environmental aspects Sustainable construction Recycled products
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/29783 , vital:30777
- Description: The need to incorporate recycled materials in building products is becoming more important than ever before. There is an abundance of waste rubber tyres which in turn results in a waste management issue. The use of waste rubber tyres in cementitious building material provides a possible solution to the problem (Kathomi, 2009:10). Previous research has shown the introduction of recycled rubber tyre crumb can improve the durability, thermal and acoustic performance in residential and commercial buildings. This could result in lives of dwellers in concrete block buildings in South Africa improving due to these characteristics whilst potentially creating a cost-effective, sustainable building material. A grading analysis, loose and compacted bulk densities and relative densities were determined to provide a mix design. Three tests were conducted for this study namely compressive strength, fire and thermal performance and acoustic performance. The testing was conducted on 100mmx100mm cubes at varying rubber replacement percentages. The replacement values were 10%, 20% and 30% tested against a control of ordinary concrete. The waste rubber crumb was a replacement for sand. The research of this study showed 20 % decrease of compression strength at 10 % rubber replacement compared to the control, 55 % decrease at 20 % rubber replacement and 75% decrease at 30 % rubber replacement. The thermal performance test showed a 24 % lower temperature for 10 % rubber replacement compared to the control, 39 % lower temperature at 20 % rubber replacement and 52 % lower temperature at 30 % rubber replacement. All rubber replacement % samples and the control performed adequately in the flame resistance test. The smoke density test showed that all rubber replacement % samples did not release a quantity of smoke which would be deemed dangerous. The acoustic performance test showed the values at 10% rubber replacement was 6 % lower; at 20% rubber replacement; 4% lower and at 30% rubber replacement 14 % lower. Based on these results, the acoustic performance regarding transmission increases with a rubber replacement % higher than 20 %.
- Full Text:
- Date Issued: 2018
- Authors: Yuill, Robert Mark
- Date: 2018
- Subjects: Building materials , Building materials -- Environmental aspects Sustainable construction Recycled products
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/29783 , vital:30777
- Description: The need to incorporate recycled materials in building products is becoming more important than ever before. There is an abundance of waste rubber tyres which in turn results in a waste management issue. The use of waste rubber tyres in cementitious building material provides a possible solution to the problem (Kathomi, 2009:10). Previous research has shown the introduction of recycled rubber tyre crumb can improve the durability, thermal and acoustic performance in residential and commercial buildings. This could result in lives of dwellers in concrete block buildings in South Africa improving due to these characteristics whilst potentially creating a cost-effective, sustainable building material. A grading analysis, loose and compacted bulk densities and relative densities were determined to provide a mix design. Three tests were conducted for this study namely compressive strength, fire and thermal performance and acoustic performance. The testing was conducted on 100mmx100mm cubes at varying rubber replacement percentages. The replacement values were 10%, 20% and 30% tested against a control of ordinary concrete. The waste rubber crumb was a replacement for sand. The research of this study showed 20 % decrease of compression strength at 10 % rubber replacement compared to the control, 55 % decrease at 20 % rubber replacement and 75% decrease at 30 % rubber replacement. The thermal performance test showed a 24 % lower temperature for 10 % rubber replacement compared to the control, 39 % lower temperature at 20 % rubber replacement and 52 % lower temperature at 30 % rubber replacement. All rubber replacement % samples and the control performed adequately in the flame resistance test. The smoke density test showed that all rubber replacement % samples did not release a quantity of smoke which would be deemed dangerous. The acoustic performance test showed the values at 10% rubber replacement was 6 % lower; at 20% rubber replacement; 4% lower and at 30% rubber replacement 14 % lower. Based on these results, the acoustic performance regarding transmission increases with a rubber replacement % higher than 20 %.
- Full Text:
- Date Issued: 2018
Understanding the impacts of foliar insect pests on eucalyptus species growth and the development of appropriate management strategies
- Dlamini, Lindokuhle Sithembiso
- 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
- 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
Understanding the extension capacity needs of the CapeNature Stewardship Programme in the Western Cape Province of South Africa
- Coetzee, Johannes Christiaan
- Authors: Coetzee, Johannes Christiaan
- Date: 2018
- Subjects: Conservation projects (Natural resources) , Psychometrics , Adaptive natural resource management , Biodiversity conservation , CapeNature Stewardship Programme
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/63220 , vital:28383
- Description: There is an increasing call for conservation programmes to provide sound evidence of effectiveness, and employing empirical evaluations can assist in the transition to evidence-based conservation practices. The objectives of this research were to develop a logic model for the CapeNature Stewardship Programme which would articulate the programme's theory of operation with respect to its Stewardship Programme landholders. The second major objective was to develop psychometric instruments for assessing the motivations and satisfactions of the programme's stewardship landholders. Both objectives included the aim to provide robust and repeatable instruments for exploring landholder's psychology, and developing a programme's theory of operation to understand the programme and improve with understanding the needs of the landowners. In this regard the processes and methodologies employed represent a major component of this research. A mixed methods approach was utilized, including stakeholder and volunteer surveys, conducted via mailing hardcopies and the internet, together with three focus groups held with the programme's management, extension staff and the stewardship landholders. Analysis of the data thus collected included both qualitative and quantitative approaches, specifically coding and content analysis, together with statistical tests of internal consistency, factor analysis and doubling correspondence analysis. Robust indices for example validity and internal consistency were developed for assessing landholder’s satisfaction with extension and level of satisfaction with the stewardship programme (Babbie 2007). These indices revealed that landholders in the Stewardship Programme are not satisfied with the programme, and exhibit behaviours suggesting they act as advocates for the programme. Demographic data and additional information provided further insights into the programme. The development of a method for articulating the programme's theory of operation is represented, together with four logic models which graphically illustrate this theory. This process and theory allowed for recommendations to be provided for the programme's improvement. A platform for adaptive management and further evaluations of this, and similar programmes, represents a major outcome of this research, understanding the extension capacity needs for the conservation of biodiversity in the CapeNature Stewardship Programme to function as a model for improving the implementation of the programme across the Western Cape, South Africa. This research feeds into an evaluation of CapeNature’s Biodiveristy Stewardship programme and demonstrates the importance of incorporating psychology into conservation interventions.
- Full Text:
- Date Issued: 2018
- Authors: Coetzee, Johannes Christiaan
- Date: 2018
- Subjects: Conservation projects (Natural resources) , Psychometrics , Adaptive natural resource management , Biodiversity conservation , CapeNature Stewardship Programme
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/63220 , vital:28383
- Description: There is an increasing call for conservation programmes to provide sound evidence of effectiveness, and employing empirical evaluations can assist in the transition to evidence-based conservation practices. The objectives of this research were to develop a logic model for the CapeNature Stewardship Programme which would articulate the programme's theory of operation with respect to its Stewardship Programme landholders. The second major objective was to develop psychometric instruments for assessing the motivations and satisfactions of the programme's stewardship landholders. Both objectives included the aim to provide robust and repeatable instruments for exploring landholder's psychology, and developing a programme's theory of operation to understand the programme and improve with understanding the needs of the landowners. In this regard the processes and methodologies employed represent a major component of this research. A mixed methods approach was utilized, including stakeholder and volunteer surveys, conducted via mailing hardcopies and the internet, together with three focus groups held with the programme's management, extension staff and the stewardship landholders. Analysis of the data thus collected included both qualitative and quantitative approaches, specifically coding and content analysis, together with statistical tests of internal consistency, factor analysis and doubling correspondence analysis. Robust indices for example validity and internal consistency were developed for assessing landholder’s satisfaction with extension and level of satisfaction with the stewardship programme (Babbie 2007). These indices revealed that landholders in the Stewardship Programme are not satisfied with the programme, and exhibit behaviours suggesting they act as advocates for the programme. Demographic data and additional information provided further insights into the programme. The development of a method for articulating the programme's theory of operation is represented, together with four logic models which graphically illustrate this theory. This process and theory allowed for recommendations to be provided for the programme's improvement. A platform for adaptive management and further evaluations of this, and similar programmes, represents a major outcome of this research, understanding the extension capacity needs for the conservation of biodiversity in the CapeNature Stewardship Programme to function as a model for improving the implementation of the programme across the Western Cape, South Africa. This research feeds into an evaluation of CapeNature’s Biodiveristy Stewardship programme and demonstrates the importance of incorporating psychology into conservation interventions.
- Full Text:
- Date Issued: 2018
Understanding and quantifying channel transmission loss processes in the Limpopo River Basin
- Authors: Mvandaba, Vuyelwa
- Date: 2018
- Subjects: Water-supply -- Management , Water-supply -- Limpopo River Watershed , Alluvium -- Limpopo River Watershed , Streamflow -- Limpopo River Watershed
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/63797 , vital:28490
- Description: Water availability is one of the major societal issues facing the world. The ability to understand and quantify the impact of key hydrological processes on the availability of water resources is therefore integral to ensuring equitable and sustainable resource management. A review of previous hydrological studies conducted in the Limpopo River Basin has revealed a gap in the understanding of surface water-groundwater interactions, particularly channel transmission loss processes. These earlier studies, focused largely on the Limpopo River’s main stem, have attributed the existence of these streamflow losses to the presence of significant alluvial aquifers and indicated that the losses account for about 30 percent (or 1000 Mm3 a-1) of the basin’s water balance. The work conducted in this dissertation reports on the delineation of alluvial aquifers across three sub-basins of the Limpopo River Basin namely, the Mokolo (South Africa), Motloutse (Botswana) and Mzingwane (Zimbabwe) sub-basins and the estimation of potential channel transmission losses based on the alluvial aquifer properties. Additionally, an assessment of the different approaches that can be applied to simulate these channel transmission losses in the Pitman Model is presented. To delineate alluvial aquifers, general land cover classes including alluvial aquifers were produced from Landsat-8 imagery through image classification. The areal extent of the delineated alluvial aquifers was calculated using ArcMap 10.3. To quantify channel transmission losses and determine the effects on regional water resources, three approaches using the Pitman model were applied. The three approaches include an explicit transmission loss function, the use of a wetland function to represent channel-floodplain storage exchanges and the use of a ‘dummy’ reservoir to represent floodplain storage and evapotranspiration losses. Results indicate that all three approaches were able to simulate channel transmission losses, although with differing magnitudes. Observed monthly flow data were used to as a means of validating loss simulations however for each sub-basin, medium and low flows were over-simulated which accounts for water uses that were inefficiently represented due to lack of data. Knowledge of the structure of the transmission loss function dictates that it is better at representing the dynamics of channel transmission losses, as it takes into account the contribution of losses to groundwater recharge whereas the other two functions simply store water and release it back to the channel. Overall, the hydrological modelling results demonstrate the potential of each approach in reproducing the dynamics of channel transmission losses between channel and alluvial aquifer within an existing sub-basin scale hydrological model. It is believed that better quantification of losses and more efficient qualitative determination of the function which best represents transmission losses, can be attained with more reliable observed data. In conclusion, a study of this nature can be beneficial to water resource estimation programmes as it highlights the uncertainties related with quantifying channel transmission loss processes in a semi-arid environment.
- Full Text:
- Date Issued: 2018
- Authors: Mvandaba, Vuyelwa
- Date: 2018
- Subjects: Water-supply -- Management , Water-supply -- Limpopo River Watershed , Alluvium -- Limpopo River Watershed , Streamflow -- Limpopo River Watershed
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/63797 , vital:28490
- Description: Water availability is one of the major societal issues facing the world. The ability to understand and quantify the impact of key hydrological processes on the availability of water resources is therefore integral to ensuring equitable and sustainable resource management. A review of previous hydrological studies conducted in the Limpopo River Basin has revealed a gap in the understanding of surface water-groundwater interactions, particularly channel transmission loss processes. These earlier studies, focused largely on the Limpopo River’s main stem, have attributed the existence of these streamflow losses to the presence of significant alluvial aquifers and indicated that the losses account for about 30 percent (or 1000 Mm3 a-1) of the basin’s water balance. The work conducted in this dissertation reports on the delineation of alluvial aquifers across three sub-basins of the Limpopo River Basin namely, the Mokolo (South Africa), Motloutse (Botswana) and Mzingwane (Zimbabwe) sub-basins and the estimation of potential channel transmission losses based on the alluvial aquifer properties. Additionally, an assessment of the different approaches that can be applied to simulate these channel transmission losses in the Pitman Model is presented. To delineate alluvial aquifers, general land cover classes including alluvial aquifers were produced from Landsat-8 imagery through image classification. The areal extent of the delineated alluvial aquifers was calculated using ArcMap 10.3. To quantify channel transmission losses and determine the effects on regional water resources, three approaches using the Pitman model were applied. The three approaches include an explicit transmission loss function, the use of a wetland function to represent channel-floodplain storage exchanges and the use of a ‘dummy’ reservoir to represent floodplain storage and evapotranspiration losses. Results indicate that all three approaches were able to simulate channel transmission losses, although with differing magnitudes. Observed monthly flow data were used to as a means of validating loss simulations however for each sub-basin, medium and low flows were over-simulated which accounts for water uses that were inefficiently represented due to lack of data. Knowledge of the structure of the transmission loss function dictates that it is better at representing the dynamics of channel transmission losses, as it takes into account the contribution of losses to groundwater recharge whereas the other two functions simply store water and release it back to the channel. Overall, the hydrological modelling results demonstrate the potential of each approach in reproducing the dynamics of channel transmission losses between channel and alluvial aquifer within an existing sub-basin scale hydrological model. It is believed that better quantification of losses and more efficient qualitative determination of the function which best represents transmission losses, can be attained with more reliable observed data. In conclusion, a study of this nature can be beneficial to water resource estimation programmes as it highlights the uncertainties related with quantifying channel transmission loss processes in a semi-arid environment.
- Full Text:
- Date Issued: 2018
Two-tissue stable isotope analysis to elucidate isotopic incorporation and trophic niche patterns for chubbyhead barb Enteromius anoplus
- Authors: Kambikambi, Manda Juliet
- Date: 2018
- Subjects: Food chains (Ecology) , Barbus -- South Africa -- Great Fish River Estuary , Stable isotopes , Freshwater fishes -- Feeding and feeds , Freshwater fishes -- Food , Fins (Anatomy) , Akaike Information Criterion , Freshwater fishes -- Conservation , Chubbyhead barb Enteromius anoplus
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/61906 , vital:28082
- Description: Knowledge of trophic ecology underpins conservation and management of threatened species. Stable isotope analysis has been widely used as a more objective approach for elucidating the trophic positions of freshwater fishes. Until recently, stable isotope analysis for trophic ecology studies in freshwater fishes largely utilised white muscle tissue. This sampling approach, however, involves either euthanasia or muscle biopsy procedures that may be inappropriate for small-sized and endangered fishes. These concerns raised the need to explore and validate the utility of non-lethal alternatives such as fin clips, mucus and scales. The present study investigated the use of caudal fin tissue as a potential non-lethal alternative to muscle tissue for trophic studies on the chubbyhead barb Enteromius anoplus. The chubbyhead barb was selected as a model taxon for the present study because it is closely related or comparable in body size to a number of highly threatened small-bodied minnows in southern Africa. The chubbyhead barb was also considered an ideal species for this study because it is widespread, abundant and classified as Least Concern on the IUCN list of threatened species. The study used a two-pronged approach based on laboratory and field experiments. A laboratory experiment was conducted to quantify isotopic turnover rates and diet-tissue discrimination factors (DTDFs/A) for both muscle and fin tissues. This involved feeding chubbyhead barb two diets with distinct carbon (δ13C) and nitrogen (δ15N) values, and monitoring the temporal isotopic incorporation patterns into the two tissues. These patterns were assessed by applying least squares non-linear one- and two-compartment isotopic kinetics models. Model comparisons, based on Akaike information criterion (AIC), revealed that one- compartment models described isotopic incorporation patterns better than two-compartment models for both muscle and fin tissues. For δ13C, relatively short and comparable turnover rates were observed for muscle and fin tissues, which suggests that fin tissue could potentially provide similar inference as muscle tissue when assessing short term dietary patterns for chubbyhead barb. In contrast to δ13C, turnover rates for δ15N between muscle and fin tissue were different for both diets. Specifically, stable isotope incorporation turnover rate was faster in muscle tissue for animals that were fed on isotopically enriched diets compared to fin tissue. Conversely, stable isotope incorporation into fin tissue was faster in animals fed on isotopically depleted diets compared to muscle tissue. This suggests that knowledge of animal diet is critical when inferring fin tissue δ15N turnover rates, particularly when extrapolating both short and long term dietary patterns. Diet-tissue discrimination factors were influenced by diet type, with the fish fed on isotopically enriched diet having lower DTDFs than animals fed on isotopically depleted diets. This variation may be explained by the protein quality hypothesis, which suggests that the DTDFs of consumers will decrease as protein quality increases. When A13C and A15N values were averaged across diets in muscle and fin tissue, the values were 0.74‰ and 0.64‰, respectively, for A13C, and 5.53‰ and 5.83 ‰, respectively, for A15N. This appeared to be consistent with studies on other taxa for A13C (0-1 ‰), but for A15N (3-5 ‰) the results of this study were higher than those reported for other taxa. These results suggest that investigating appropriate DTDFs for both muscle and fin tissues is important in trophic ecology studies of these minnows. A field-based study was conducted to investigate temporal dynamics in food web patterns for chubbyhead barb in the wild within the headwaters of the Koonap River, a tributary of the Great Fish River, in the Eastern Cape, South Africa. This was achieved by collecting and comparing stable isotope data for chubbyhead barb and its potential food sources on a seasonal scale. There was a discernible difference in both the composition of carbon and nitrogen isotope values for basal food sources and macroinvertebrate communities, which suggests that this headwater stream was subject to temporal changes in food web dynamics. For chubbyhead barb, comparison of its isotopic niche sizes on a temporal scale based on both muscle and fin tissue showed differences across seasons. Furthermore, isotopic niche sizes inferred from fin tissue were larger than those inferred from muscle tissue during winter and spring, whereas during summer and autumn the isotopic niche sizes inferred from muscle and fin tissue were generally comparable. This suggests the likely influence of different metabolic and physiological processes that these two tissues undergo on a temporal scale. Therefore, difference in tissue type, and their associated metabolic pathways should be considered when using fin tissue as a substitute for muscle tissue on broad temporal scales. The results from this study indicated that caudal fin tissue has the potential to be a substitute for muscle in trophic studies of chubbyhead barb Enteromius anoplus, as well as other related small bodied endangered minnow species from South Africa.
- Full Text:
- Date Issued: 2018
- Authors: Kambikambi, Manda Juliet
- Date: 2018
- Subjects: Food chains (Ecology) , Barbus -- South Africa -- Great Fish River Estuary , Stable isotopes , Freshwater fishes -- Feeding and feeds , Freshwater fishes -- Food , Fins (Anatomy) , Akaike Information Criterion , Freshwater fishes -- Conservation , Chubbyhead barb Enteromius anoplus
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/61906 , vital:28082
- Description: Knowledge of trophic ecology underpins conservation and management of threatened species. Stable isotope analysis has been widely used as a more objective approach for elucidating the trophic positions of freshwater fishes. Until recently, stable isotope analysis for trophic ecology studies in freshwater fishes largely utilised white muscle tissue. This sampling approach, however, involves either euthanasia or muscle biopsy procedures that may be inappropriate for small-sized and endangered fishes. These concerns raised the need to explore and validate the utility of non-lethal alternatives such as fin clips, mucus and scales. The present study investigated the use of caudal fin tissue as a potential non-lethal alternative to muscle tissue for trophic studies on the chubbyhead barb Enteromius anoplus. The chubbyhead barb was selected as a model taxon for the present study because it is closely related or comparable in body size to a number of highly threatened small-bodied minnows in southern Africa. The chubbyhead barb was also considered an ideal species for this study because it is widespread, abundant and classified as Least Concern on the IUCN list of threatened species. The study used a two-pronged approach based on laboratory and field experiments. A laboratory experiment was conducted to quantify isotopic turnover rates and diet-tissue discrimination factors (DTDFs/A) for both muscle and fin tissues. This involved feeding chubbyhead barb two diets with distinct carbon (δ13C) and nitrogen (δ15N) values, and monitoring the temporal isotopic incorporation patterns into the two tissues. These patterns were assessed by applying least squares non-linear one- and two-compartment isotopic kinetics models. Model comparisons, based on Akaike information criterion (AIC), revealed that one- compartment models described isotopic incorporation patterns better than two-compartment models for both muscle and fin tissues. For δ13C, relatively short and comparable turnover rates were observed for muscle and fin tissues, which suggests that fin tissue could potentially provide similar inference as muscle tissue when assessing short term dietary patterns for chubbyhead barb. In contrast to δ13C, turnover rates for δ15N between muscle and fin tissue were different for both diets. Specifically, stable isotope incorporation turnover rate was faster in muscle tissue for animals that were fed on isotopically enriched diets compared to fin tissue. Conversely, stable isotope incorporation into fin tissue was faster in animals fed on isotopically depleted diets compared to muscle tissue. This suggests that knowledge of animal diet is critical when inferring fin tissue δ15N turnover rates, particularly when extrapolating both short and long term dietary patterns. Diet-tissue discrimination factors were influenced by diet type, with the fish fed on isotopically enriched diet having lower DTDFs than animals fed on isotopically depleted diets. This variation may be explained by the protein quality hypothesis, which suggests that the DTDFs of consumers will decrease as protein quality increases. When A13C and A15N values were averaged across diets in muscle and fin tissue, the values were 0.74‰ and 0.64‰, respectively, for A13C, and 5.53‰ and 5.83 ‰, respectively, for A15N. This appeared to be consistent with studies on other taxa for A13C (0-1 ‰), but for A15N (3-5 ‰) the results of this study were higher than those reported for other taxa. These results suggest that investigating appropriate DTDFs for both muscle and fin tissues is important in trophic ecology studies of these minnows. A field-based study was conducted to investigate temporal dynamics in food web patterns for chubbyhead barb in the wild within the headwaters of the Koonap River, a tributary of the Great Fish River, in the Eastern Cape, South Africa. This was achieved by collecting and comparing stable isotope data for chubbyhead barb and its potential food sources on a seasonal scale. There was a discernible difference in both the composition of carbon and nitrogen isotope values for basal food sources and macroinvertebrate communities, which suggests that this headwater stream was subject to temporal changes in food web dynamics. For chubbyhead barb, comparison of its isotopic niche sizes on a temporal scale based on both muscle and fin tissue showed differences across seasons. Furthermore, isotopic niche sizes inferred from fin tissue were larger than those inferred from muscle tissue during winter and spring, whereas during summer and autumn the isotopic niche sizes inferred from muscle and fin tissue were generally comparable. This suggests the likely influence of different metabolic and physiological processes that these two tissues undergo on a temporal scale. Therefore, difference in tissue type, and their associated metabolic pathways should be considered when using fin tissue as a substitute for muscle tissue on broad temporal scales. The results from this study indicated that caudal fin tissue has the potential to be a substitute for muscle in trophic studies of chubbyhead barb Enteromius anoplus, as well as other related small bodied endangered minnow species from South Africa.
- Full Text:
- Date Issued: 2018
Towards understanding the effect of size variation on the aggressive and feeding behaviours of juvenile dusky kob Argyrosomus japonicus (Pisces: Sciaenidae)
- Authors: Babane, Siviwe Elvis
- Date: 2018
- Subjects: Argyrosomus -- Feeding and feeds , Aquaculture , Fishes -- Cannibalism , Fishes -- Feeding and feeds
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/59592 , vital:27629
- Description: Many studies have been conducted on the effect of size-grading in other fish species. However, there is a paucity of scientific information on the effects of size variation on cannibalism of juvenile dusky kob. Thus, a study focusing on the effect of size variation on juvenile dusky kob aggressive and feeding (browsing) behaviours was conducted. Three separate groups of hatchery-reared juvenile dusky kob of were obtained from Oceanwise (Pty) Ltd for use in a series of three experimental trials. In all trials, juvenile fish of the same age were size-graded and the COV-value was used to determine the size variation. The focal fish (largest fish) was exposed to groups of fish with different size variation for 30-min. behavioural observations before and after feeding in randomised trials. The first experimental trial (Chapter 2) quantified the effect of increasing size variation and observation time on the aggressive and browsing behaviours of juvenile dusky kob. On average, juvenile dusky kob weighed 3.60 ± 0.68 g fish-1 and measured 5.8 ± 0.41 mm. Each focal fish was observed (a) before feeding in the morning, (b) 2 h after feeding, (c) 6 h after feeding and (d) 12 h after feeding. Fish increased browsing behaviours (averaging 6.60 ± 0.56) and decreased intimidating aggressive behaviours (18.60 ± 1.39) 12 h after feeding. Other aggressive behaviours occurred but did not differ between observation times. Aggressive and browsing behaviours positively correlated with size variation variables, predominantly, 12 h after feeding. An average frequency of 19 chases were observed positively correlated with size variation, followed by average frequencies of 17 body bites and browses, and 11 tail bites per 30 min. Some behaviours including average frequencies of 0.2 chases, 4 tail bites, 2.4 intimidating and 0.3 browsing behaviours negatively correlated with the size variation, generally closer to the last meal. These preliminary observations thus showed that fish have become hungry approximately 6-12 h after feeding and substituted certain behaviours for others as time after feeding passed and as size variation increased. The second experimental trial (Chapter 3) consisted of the observations further testing the relationship between aggressive behaviours and size variation of juveniles of dusky kob averaging 0.43 ± 0.27 g fish-1. The focal fish was exposed to groups of fish of four size variation (COV) treatments for observations before and 12 h after feeding. Aggressive behaviours positively correlated with size variation both before and 12 h after feeding. An average frequency of 437 body bites positively correlated more often with COV, followed by average frequencies of 365 intimidating behaviours and 199 tail bites per 30 min., respectively, before and 12 h after feeding. The least often exhibited aggressive behaviours averaged 26 chases while positively correlating with size variation on the times specified. An average frequency of 311 intimidating behaviours before and after feeding including average of 28 tail bites after feeding negatively correlated with size variation. This may relate to shift of behaviours depending on the needs and capacity of the fish. Apparently, aggressive fish can change its behaviour as a function of COV-values rather than the mean size of the other fish. The third trial (Chapter 4) investigated the effect of the aggressor’s (focal fish) size in relation its aggressive and browsing behaviours to other fish (non-focal fish). Juvenile fish used for this trial, on average, weighed 30 ± 7.63 g fish-1. Aggressive and browsing behaviours were observed in four treatments of a) high COV and mean weight below, b) low COV and mean weight less, c) high COV and mean weight equivalent to and d) low COV and mean weight higher than that of the focal fish. Increased frequencies of aggressive and browsing behaviours per 30 min. occurred in treatment A, sharing similar frequencies in treatment C, compared to the other treatments (B and D) which shared certain frequencies. The intimidating behaviours predominated, followed by browsing, body bites, chases and tail bites, respectively. The results of the overall study suggest that the time passed after feeding and increasing size variation and differences facilitated aggressive and browsing behaviours in juvenile dusky kob. Dusky kob showed increasing aggressive behaviours as early as in the first two weeks after hatching, averaging 0.43 ± 0.27 g fish-1 with the frequency correlating with size differences. Consistent size-grading technique in the same-age fish should be used to manage size variation associated with aggressive behaviours. The period of about 4-6 h after feeding may explain the noticeable increased aggressive and browsing behaviours. Thus, fish should be fed immediately before or after evacuation of their guts to maintain less-aggressive behaviours of juvenile dusky kob. Fish generally increased aggressive and browsing acts before and long time after feeding than closer to after feeding. The study has provided the fundamental scientific groundwork for fish farmers and future researchers can further explore size variation, time after feeding and gut evacuation rate as critical components of aggressive behaviours. The scientific knowledge of aggressive and cannibalistic behaviours has essential application in farming management to achieve improved survival and growth rates in juvenile fish.
- Full Text:
- Date Issued: 2018
- Authors: Babane, Siviwe Elvis
- Date: 2018
- Subjects: Argyrosomus -- Feeding and feeds , Aquaculture , Fishes -- Cannibalism , Fishes -- Feeding and feeds
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/59592 , vital:27629
- Description: Many studies have been conducted on the effect of size-grading in other fish species. However, there is a paucity of scientific information on the effects of size variation on cannibalism of juvenile dusky kob. Thus, a study focusing on the effect of size variation on juvenile dusky kob aggressive and feeding (browsing) behaviours was conducted. Three separate groups of hatchery-reared juvenile dusky kob of were obtained from Oceanwise (Pty) Ltd for use in a series of three experimental trials. In all trials, juvenile fish of the same age were size-graded and the COV-value was used to determine the size variation. The focal fish (largest fish) was exposed to groups of fish with different size variation for 30-min. behavioural observations before and after feeding in randomised trials. The first experimental trial (Chapter 2) quantified the effect of increasing size variation and observation time on the aggressive and browsing behaviours of juvenile dusky kob. On average, juvenile dusky kob weighed 3.60 ± 0.68 g fish-1 and measured 5.8 ± 0.41 mm. Each focal fish was observed (a) before feeding in the morning, (b) 2 h after feeding, (c) 6 h after feeding and (d) 12 h after feeding. Fish increased browsing behaviours (averaging 6.60 ± 0.56) and decreased intimidating aggressive behaviours (18.60 ± 1.39) 12 h after feeding. Other aggressive behaviours occurred but did not differ between observation times. Aggressive and browsing behaviours positively correlated with size variation variables, predominantly, 12 h after feeding. An average frequency of 19 chases were observed positively correlated with size variation, followed by average frequencies of 17 body bites and browses, and 11 tail bites per 30 min. Some behaviours including average frequencies of 0.2 chases, 4 tail bites, 2.4 intimidating and 0.3 browsing behaviours negatively correlated with the size variation, generally closer to the last meal. These preliminary observations thus showed that fish have become hungry approximately 6-12 h after feeding and substituted certain behaviours for others as time after feeding passed and as size variation increased. The second experimental trial (Chapter 3) consisted of the observations further testing the relationship between aggressive behaviours and size variation of juveniles of dusky kob averaging 0.43 ± 0.27 g fish-1. The focal fish was exposed to groups of fish of four size variation (COV) treatments for observations before and 12 h after feeding. Aggressive behaviours positively correlated with size variation both before and 12 h after feeding. An average frequency of 437 body bites positively correlated more often with COV, followed by average frequencies of 365 intimidating behaviours and 199 tail bites per 30 min., respectively, before and 12 h after feeding. The least often exhibited aggressive behaviours averaged 26 chases while positively correlating with size variation on the times specified. An average frequency of 311 intimidating behaviours before and after feeding including average of 28 tail bites after feeding negatively correlated with size variation. This may relate to shift of behaviours depending on the needs and capacity of the fish. Apparently, aggressive fish can change its behaviour as a function of COV-values rather than the mean size of the other fish. The third trial (Chapter 4) investigated the effect of the aggressor’s (focal fish) size in relation its aggressive and browsing behaviours to other fish (non-focal fish). Juvenile fish used for this trial, on average, weighed 30 ± 7.63 g fish-1. Aggressive and browsing behaviours were observed in four treatments of a) high COV and mean weight below, b) low COV and mean weight less, c) high COV and mean weight equivalent to and d) low COV and mean weight higher than that of the focal fish. Increased frequencies of aggressive and browsing behaviours per 30 min. occurred in treatment A, sharing similar frequencies in treatment C, compared to the other treatments (B and D) which shared certain frequencies. The intimidating behaviours predominated, followed by browsing, body bites, chases and tail bites, respectively. The results of the overall study suggest that the time passed after feeding and increasing size variation and differences facilitated aggressive and browsing behaviours in juvenile dusky kob. Dusky kob showed increasing aggressive behaviours as early as in the first two weeks after hatching, averaging 0.43 ± 0.27 g fish-1 with the frequency correlating with size differences. Consistent size-grading technique in the same-age fish should be used to manage size variation associated with aggressive behaviours. The period of about 4-6 h after feeding may explain the noticeable increased aggressive and browsing behaviours. Thus, fish should be fed immediately before or after evacuation of their guts to maintain less-aggressive behaviours of juvenile dusky kob. Fish generally increased aggressive and browsing acts before and long time after feeding than closer to after feeding. The study has provided the fundamental scientific groundwork for fish farmers and future researchers can further explore size variation, time after feeding and gut evacuation rate as critical components of aggressive behaviours. The scientific knowledge of aggressive and cannibalistic behaviours has essential application in farming management to achieve improved survival and growth rates in juvenile fish.
- Full Text:
- Date Issued: 2018
Towards a collection of cost-effective technologies in support of the NIST cybersecurity framework
- Shackleton, Bruce Michael Stuart
- Authors: Shackleton, Bruce Michael Stuart
- Date: 2018
- Subjects: National Institute of Standards and Technology (U.S.) , Computer security , Computer networks Security measures , Small business Information technology Cost effectiveness , Open source software
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/62494 , vital:28199
- Description: The NIST Cybersecurity Framework (CSF) is a specific risk and cybersecurity framework. It provides guidance on controls that can be implemented to help improve an organisation’s cybersecurity risk posture. The CSF Functions consist of Identify, Protect, Detect, Respond, and Recover. Like most Information Technology (IT) frameworks, there are elements of people, processes, and technology. The same elements are required to successfully implement the NIST CSF. This research specifically focuses on the technology element. While there are many commercial technologies available for a small to medium sized business, the costs can be prohibitively expensive. Therefore, this research investigates cost-effective technologies and assesses their alignment to the NIST CSF. The assessment was made against the NIST CSF subcategories. Each subcategory was analysed to identify where a technology would likely be required. The framework provides a list of Informative References. These Informative References were used to create high- level technology categories, as well as identify the technical controls against which the technologies were measured. The technologies tested were either open source or proprietary. All open source technologies tested were free to use, or have a free community edition. Proprietary technologies would be free to use, or considered generally available to most organisations, such as components contained within Microsoft platforms. The results from the experimentation demonstrated that there are multiple cost-effective technologies that can support the NIST CSF. Once all technologies were tested, the NIST CSF was extended. Two new columns were added, namely high-level technology category, and tested technology. The columns were populated with output from the research. This extended framework begins an initial collection of cost-effective technologies in support of the NIST CSF.
- Full Text:
- Date Issued: 2018
- Authors: Shackleton, Bruce Michael Stuart
- Date: 2018
- Subjects: National Institute of Standards and Technology (U.S.) , Computer security , Computer networks Security measures , Small business Information technology Cost effectiveness , Open source software
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/62494 , vital:28199
- Description: The NIST Cybersecurity Framework (CSF) is a specific risk and cybersecurity framework. It provides guidance on controls that can be implemented to help improve an organisation’s cybersecurity risk posture. The CSF Functions consist of Identify, Protect, Detect, Respond, and Recover. Like most Information Technology (IT) frameworks, there are elements of people, processes, and technology. The same elements are required to successfully implement the NIST CSF. This research specifically focuses on the technology element. While there are many commercial technologies available for a small to medium sized business, the costs can be prohibitively expensive. Therefore, this research investigates cost-effective technologies and assesses their alignment to the NIST CSF. The assessment was made against the NIST CSF subcategories. Each subcategory was analysed to identify where a technology would likely be required. The framework provides a list of Informative References. These Informative References were used to create high- level technology categories, as well as identify the technical controls against which the technologies were measured. The technologies tested were either open source or proprietary. All open source technologies tested were free to use, or have a free community edition. Proprietary technologies would be free to use, or considered generally available to most organisations, such as components contained within Microsoft platforms. The results from the experimentation demonstrated that there are multiple cost-effective technologies that can support the NIST CSF. Once all technologies were tested, the NIST CSF was extended. Two new columns were added, namely high-level technology category, and tested technology. The columns were populated with output from the research. This extended framework begins an initial collection of cost-effective technologies in support of the NIST CSF.
- Full Text:
- 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.
- Full Text:
- Date Issued: 2018
- 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.
- Full Text:
- Date Issued: 2018
The use of building information modelling as a tool to improve informed design communication between student and lecturer during critique sessions
- Authors: Basson, Jean-Pierre
- Date: 2018
- Subjects: Building information modeling , Building -- Data processing Construction industry -- South Africa Construction projects -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/23680 , vital:30598
- Description: Within the design studio at the Department of Architecture, Nelson Mandela University, the timeous submission of design projects is a problem. After close inspection, it is noted that students spend weeks on conceptual design ideas with no progressions towards completion. The purpose of the study is thus to determine whether building information modelling (BIM), as opposed to the traditional method of design, can be used to improve informed design communication during conceptual design for the first-year master of architecture students and contribute to timeous design project submission. A cohort comparison rubric will be used as the method for looking at the qualitative attributes of design intention, function, aesthetics, and sustainability. The 2016 cohort made use of the traditional design method, whereas for the 2017 cohort the BIM course was introduced in the computer module with implementation in the design studio. The work of nine students from both cohorts was analysed and findings include the following: improved drawing type availability, accuracy, and quality; reduced time spent on redundant work; inclusive discussions compared to isolated critique sessions; reduced printing costs - and the establishment of “what if” scenarios early in the project. Based upon the research findings it can be concluded that BIM as a teaching strategy and process has the capability of improving the communication between student and lecturer in the conceptual stage, thereby leading to a more timeous submission. It is recommended that BIM education must be incorporated in the undergraduate programme thereby providing students with an appropriate platform for expressing conceptual ideas more effectively within the design course.
- Full Text:
- Date Issued: 2018
- Authors: Basson, Jean-Pierre
- Date: 2018
- Subjects: Building information modeling , Building -- Data processing Construction industry -- South Africa Construction projects -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/23680 , vital:30598
- Description: Within the design studio at the Department of Architecture, Nelson Mandela University, the timeous submission of design projects is a problem. After close inspection, it is noted that students spend weeks on conceptual design ideas with no progressions towards completion. The purpose of the study is thus to determine whether building information modelling (BIM), as opposed to the traditional method of design, can be used to improve informed design communication during conceptual design for the first-year master of architecture students and contribute to timeous design project submission. A cohort comparison rubric will be used as the method for looking at the qualitative attributes of design intention, function, aesthetics, and sustainability. The 2016 cohort made use of the traditional design method, whereas for the 2017 cohort the BIM course was introduced in the computer module with implementation in the design studio. The work of nine students from both cohorts was analysed and findings include the following: improved drawing type availability, accuracy, and quality; reduced time spent on redundant work; inclusive discussions compared to isolated critique sessions; reduced printing costs - and the establishment of “what if” scenarios early in the project. Based upon the research findings it can be concluded that BIM as a teaching strategy and process has the capability of improving the communication between student and lecturer in the conceptual stage, thereby leading to a more timeous submission. It is recommended that BIM education must be incorporated in the undergraduate programme thereby providing students with an appropriate platform for expressing conceptual ideas more effectively within the design course.
- Full Text:
- 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.
- Full Text:
- Date Issued: 2018
- 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.
- Full Text:
- Date Issued: 2018
The thermal physiology of Stenopelmus rufinasus and Neohydronomus affinis (Coleoptera: Curculionidae), biological control agents for the invasive alien aquatic weeds Azolla filiculoides and Pistia stratiotes respectively
- Authors: Mvandaba, Sisanda F
- Date: 2018
- Subjects: Beetles -- South Africa , Curculionidae -- South Africa , Azolla filiculoides -- South Africa , Water lettuce -- South Africa , Aquatic weeds -- Biological control -- South Africa , Stenopelmus rufinasus , Neohydronomus affinis
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/62362 , vital:28158
- Description: Water lettuce, Pistia stratiotes L. (Araceae), and red water fern, Azolla filiculoides Lam. (Azollaceae), are floating aquatic macrophytes that have become problematic invaders in numerous South African waterbodies. Two weevils, Neohydronomus affinis Hustache 1926 (Coleoptera: Curculionidae) and Stenopelmus rufinasus Gyllenhal 1936 (Coleoptera: Curculionidae), are successful biological control agents of these two species, respectively, in South Africa. However, nothing is known about the thermal physiology of these two species Therefore, the aim of this study was to investigate the thermal physiologies of these two species to explain their establishment, distribution and impact in the field. Laboratory based thermal physiology trials showed that both weevils were widely tolerant of cold and warm temperatures. The CTmin of N. affinis was determined to be 5.5 ± 0.312°C and the CTmax was 44 ± 0.697°C, while the CTmin of S. rufinasus was 5.4 ± 0.333°C and the CTmax was 44.5 ± 0.168°C. In addition, the lower lethal temperatures were -9.8 ± 0.053°C and -7.2 ± 0.19°C, and the upper lethal temperatures were 42.8 ± 0.053°C and 41.9 ± 0.19°C respectively. These results suggest that both species should not be limited by cold winter temperatures, as previously thought. This is evident in the field, where S. rufinasus has established widely on A. filiculoides, despite local cold climates in some areas of the plant’s distribution. Even though N. affinis has a similar thermal range, and should therefore theoretically reflect a similar distribution to S. rufinasus throughout South Africa, its distribution is limited by the range of its host, which is restricted to the warmer regions of the country, as is its biocontrol agent. Using the reduced major axis regression method, the development for N. affinis was described using the formulay=12.976x+435.24, while the development of S. rufinasus was described by y=13.6x+222.45. These results showed that S. rufinasus develops much faster, in fact almost twice as quickly, than N. affinis. Using these formulae and temperature data obtained from the South African Weather Service, N. affinis was predicted to complete between 4 and 9 generations per year in South Africa, while S. rufinasus was predicted to complete between 5 and 14 generations per year around the country. This study showed that although the native range of these two species is warm temperate to tropical, they possess sufficient thermal plasticity to not only establish, but also damage their respective host plants in far cooler climates. Thus, in South Africa N. affinis and S. rufinasus are limited by the distribution of their target weeds and not climate.
- Full Text:
- Date Issued: 2018
- Authors: Mvandaba, Sisanda F
- Date: 2018
- Subjects: Beetles -- South Africa , Curculionidae -- South Africa , Azolla filiculoides -- South Africa , Water lettuce -- South Africa , Aquatic weeds -- Biological control -- South Africa , Stenopelmus rufinasus , Neohydronomus affinis
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/62362 , vital:28158
- Description: Water lettuce, Pistia stratiotes L. (Araceae), and red water fern, Azolla filiculoides Lam. (Azollaceae), are floating aquatic macrophytes that have become problematic invaders in numerous South African waterbodies. Two weevils, Neohydronomus affinis Hustache 1926 (Coleoptera: Curculionidae) and Stenopelmus rufinasus Gyllenhal 1936 (Coleoptera: Curculionidae), are successful biological control agents of these two species, respectively, in South Africa. However, nothing is known about the thermal physiology of these two species Therefore, the aim of this study was to investigate the thermal physiologies of these two species to explain their establishment, distribution and impact in the field. Laboratory based thermal physiology trials showed that both weevils were widely tolerant of cold and warm temperatures. The CTmin of N. affinis was determined to be 5.5 ± 0.312°C and the CTmax was 44 ± 0.697°C, while the CTmin of S. rufinasus was 5.4 ± 0.333°C and the CTmax was 44.5 ± 0.168°C. In addition, the lower lethal temperatures were -9.8 ± 0.053°C and -7.2 ± 0.19°C, and the upper lethal temperatures were 42.8 ± 0.053°C and 41.9 ± 0.19°C respectively. These results suggest that both species should not be limited by cold winter temperatures, as previously thought. This is evident in the field, where S. rufinasus has established widely on A. filiculoides, despite local cold climates in some areas of the plant’s distribution. Even though N. affinis has a similar thermal range, and should therefore theoretically reflect a similar distribution to S. rufinasus throughout South Africa, its distribution is limited by the range of its host, which is restricted to the warmer regions of the country, as is its biocontrol agent. Using the reduced major axis regression method, the development for N. affinis was described using the formulay=12.976x+435.24, while the development of S. rufinasus was described by y=13.6x+222.45. These results showed that S. rufinasus develops much faster, in fact almost twice as quickly, than N. affinis. Using these formulae and temperature data obtained from the South African Weather Service, N. affinis was predicted to complete between 4 and 9 generations per year in South Africa, while S. rufinasus was predicted to complete between 5 and 14 generations per year around the country. This study showed that although the native range of these two species is warm temperate to tropical, they possess sufficient thermal plasticity to not only establish, but also damage their respective host plants in far cooler climates. Thus, in South Africa N. affinis and S. rufinasus are limited by the distribution of their target weeds and not climate.
- Full Text:
- 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.
- Full Text:
- Date Issued: 2018
- 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.
- Full Text:
- Date Issued: 2018
The spatial ecology of Albula glossodonta in the St. Joseph Atoll, Seychelles
- Authors: Moxham, Emily Jeanne
- Date: 2018
- Subjects: Bonefish -- Seychelles -- Amirante Islands , Albula -- Seychelles -- Amirante Islands , Bonefish fisheries -- Seychelles -- Amirante Islands , Small-scale fisheries -- Seychelles -- Amirante Islands -- Economic conditions , Underwater acoustic telemetry , Bonefish -- Behavior -- Seychelles -- Amirante Islands , Bonefish -- Home range -- Seychelles -- Amirante Islands , Bonefish -- Conservation -- Seychelles -- Amirante Islands , Predation (Biology) -- Seychelles -- Amirante Islands , Bonefishing
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/57863 , vital:26997
- Description: Bonefish (Albula spp.) support valuable recreational and artisanal fisheries worldwide. Declining stocks have been reported at multiple localities, potentially jeopardising numerous multimillion-dollar industries. In particular, tourism generated through bonefish fly fishing contributes considerably to the economies of many isolated tropical islands and atolls. However, despite their economic value, little is known about bonefish in the Indian Ocean. This study aimed to contribute to the understanding of bonefish ecology in the Indian Ocean by (1) reviewing the bonefish literature to identify knowledge gaps; (2) evaluating the postrelease survival of acoustically tagged bonefish and; (3) quantifying the spatial and temporal movements of bonefish at a near-pristine and predator rich atoll in the Seychelles. A review of published literature on bonefish indicated that despite considerable biological and ecological research in the Pacific and Atlantic oceans, virtually no research has been conducted in the Indian Ocean. To help address this research gap, an acoustic telemetry study was initiated at the remote St. Joseph Atoll, within an existing array of 88 automated datalogging acoustic receivers. Thirty Albula glossodonta were surgically implanted with Vemco V13 acoustic transmitters in May 2015 and tracked for a period of one year. Only 10% of the tagged bonefish were detected for more than two weeks. A comparison of the final 100 hours of movement data from fish that were detected for less than two weeks to fish detected for longer periods revealed distinct differences. These included differences in area use patterns and significant differences in the average daily distance moved, speed of movement and residency index. This suggested that mortality in the form of post-release predation was high (90%) with tagged fish detected for less than two weeks being preyed upon by sharks. The three surviving bonefish were tracked for 210 to 367 days. These individuals remained in the atoll and showed high use of the marginal habitats between the shallow sand flats and the deeper lagoon. Water temperature, diel cycle and tide were significant predictors of bonefish presence in the lagoon. The high post-release predation of bonefish has implications for the management of this and other Albula species. Despite these fisheries being catch-and-release, bonefish fishing may be unsustainable due to the high post-release mortality, particularly in areas that are rich in predators. Therefore, protected areas or limitations on fishing effort need to be considered.
- Full Text:
- Date Issued: 2018
- Authors: Moxham, Emily Jeanne
- Date: 2018
- Subjects: Bonefish -- Seychelles -- Amirante Islands , Albula -- Seychelles -- Amirante Islands , Bonefish fisheries -- Seychelles -- Amirante Islands , Small-scale fisheries -- Seychelles -- Amirante Islands -- Economic conditions , Underwater acoustic telemetry , Bonefish -- Behavior -- Seychelles -- Amirante Islands , Bonefish -- Home range -- Seychelles -- Amirante Islands , Bonefish -- Conservation -- Seychelles -- Amirante Islands , Predation (Biology) -- Seychelles -- Amirante Islands , Bonefishing
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/57863 , vital:26997
- Description: Bonefish (Albula spp.) support valuable recreational and artisanal fisheries worldwide. Declining stocks have been reported at multiple localities, potentially jeopardising numerous multimillion-dollar industries. In particular, tourism generated through bonefish fly fishing contributes considerably to the economies of many isolated tropical islands and atolls. However, despite their economic value, little is known about bonefish in the Indian Ocean. This study aimed to contribute to the understanding of bonefish ecology in the Indian Ocean by (1) reviewing the bonefish literature to identify knowledge gaps; (2) evaluating the postrelease survival of acoustically tagged bonefish and; (3) quantifying the spatial and temporal movements of bonefish at a near-pristine and predator rich atoll in the Seychelles. A review of published literature on bonefish indicated that despite considerable biological and ecological research in the Pacific and Atlantic oceans, virtually no research has been conducted in the Indian Ocean. To help address this research gap, an acoustic telemetry study was initiated at the remote St. Joseph Atoll, within an existing array of 88 automated datalogging acoustic receivers. Thirty Albula glossodonta were surgically implanted with Vemco V13 acoustic transmitters in May 2015 and tracked for a period of one year. Only 10% of the tagged bonefish were detected for more than two weeks. A comparison of the final 100 hours of movement data from fish that were detected for less than two weeks to fish detected for longer periods revealed distinct differences. These included differences in area use patterns and significant differences in the average daily distance moved, speed of movement and residency index. This suggested that mortality in the form of post-release predation was high (90%) with tagged fish detected for less than two weeks being preyed upon by sharks. The three surviving bonefish were tracked for 210 to 367 days. These individuals remained in the atoll and showed high use of the marginal habitats between the shallow sand flats and the deeper lagoon. Water temperature, diel cycle and tide were significant predictors of bonefish presence in the lagoon. The high post-release predation of bonefish has implications for the management of this and other Albula species. Despite these fisheries being catch-and-release, bonefish fishing may be unsustainable due to the high post-release mortality, particularly in areas that are rich in predators. Therefore, protected areas or limitations on fishing effort need to be considered.
- Full Text:
- Date Issued: 2018
The spatial ecology and roost site selection of fledging Cape vultures (Gyps coprotheres) in the Eastern Cape, South Africa
- Martens, Francis Rae, Downs, Colleen
- 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.
- Full Text:
- Date Issued: 2018
- 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.
- Full Text:
- Date Issued: 2018
The role of field and garden cultivation for food security under a changing climate: the case of Fairbairn and Ntloko villages, Eastern Cape
- Authors: Brooks, Haydn
- Date: 2018
- Subjects: Climatic changes -- Economic aspects -- Eastern Cape (South Africa) , Climatic changes -- Social aspects -- South Africa , Food -- Economic aspects -- South Africa , Food security -- South Africa -- Eastern Cape
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/58013 , vital:27019
- Description: The world is becoming more complex due to the increasing occurrence of social-ecological change. This is particularly evident in the developing world, especially on the African continent, where existing vulnerabilities (i.e. endemic poverty, weak governance, overpopulation and HIV/AIDS) are being exacerbated by the impact of climate change. Climate change poses a very real threat to millions of Africans, especially those who rely on the natural world for their livelihoods. The increasing variability of climate and rainfall patterns are said to have dire consequences on agricultural production which is the main livelihood activity of rural dwellers across the continent. The impacts of such change and variability include, changes in the frequency and intensity of droughts, flooding and heavy storms, leading to worsening soil conditions, desertification as well as disease and pest out-breaks which will likely result in reduced crop and livestock yields. A reduction in agricultural production will likely have a negative effect on the food security of millions of people. This study was conducted in the Eastern Cape of South Africa, in two rural villages, Fairbairn and Ntloko located in the former Ciskei homeland, with the purpose of exploring the nexus between climate change, cultivation and food security. This study combined social-ecological thinking with that of political ecology to create a robust lens, in which to analyse the complex interactions between humans and the environment. A mixed methods approach was used to gather the data which consisted of a household survey, using a structured questionnaire as well as semi-structured interviews with various respondents. Quantitative data were analysed using Excel and Statistica 13, whilst coding was used for qualitative data. The main aim of the study was to explore the extent and characteristics of cultivation in the two study sites, the role of household food production in food security as well as the challenges that local cultivator’s face with regards to climate change. In recent decades, there has been a decline in rural agricultural production with many fields that were previously cultivated, lying vacant and unused. However, as this study found, cultivation is still important as over 50% of sampled households cultivated a small area within the homestead. This was mainly done to supplement household food expenditure in order to save cash incomes. The results also found that although participants had perceived negative changes in climate and rainfall (amount, onset, duration), it was not considered the most important challenge for own production. Rather, lack of fencing and capital were seen as major hindrances to efficient own production. Understanding the complexity of own production and food security under a changing climate can help form better and more resilient policies and strategies for rural development, in addition to strengthening future livelihoods of rural people in an ever changing world.
- Full Text:
- Date Issued: 2018
- Authors: Brooks, Haydn
- Date: 2018
- Subjects: Climatic changes -- Economic aspects -- Eastern Cape (South Africa) , Climatic changes -- Social aspects -- South Africa , Food -- Economic aspects -- South Africa , Food security -- South Africa -- Eastern Cape
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/58013 , vital:27019
- Description: The world is becoming more complex due to the increasing occurrence of social-ecological change. This is particularly evident in the developing world, especially on the African continent, where existing vulnerabilities (i.e. endemic poverty, weak governance, overpopulation and HIV/AIDS) are being exacerbated by the impact of climate change. Climate change poses a very real threat to millions of Africans, especially those who rely on the natural world for their livelihoods. The increasing variability of climate and rainfall patterns are said to have dire consequences on agricultural production which is the main livelihood activity of rural dwellers across the continent. The impacts of such change and variability include, changes in the frequency and intensity of droughts, flooding and heavy storms, leading to worsening soil conditions, desertification as well as disease and pest out-breaks which will likely result in reduced crop and livestock yields. A reduction in agricultural production will likely have a negative effect on the food security of millions of people. This study was conducted in the Eastern Cape of South Africa, in two rural villages, Fairbairn and Ntloko located in the former Ciskei homeland, with the purpose of exploring the nexus between climate change, cultivation and food security. This study combined social-ecological thinking with that of political ecology to create a robust lens, in which to analyse the complex interactions between humans and the environment. A mixed methods approach was used to gather the data which consisted of a household survey, using a structured questionnaire as well as semi-structured interviews with various respondents. Quantitative data were analysed using Excel and Statistica 13, whilst coding was used for qualitative data. The main aim of the study was to explore the extent and characteristics of cultivation in the two study sites, the role of household food production in food security as well as the challenges that local cultivator’s face with regards to climate change. In recent decades, there has been a decline in rural agricultural production with many fields that were previously cultivated, lying vacant and unused. However, as this study found, cultivation is still important as over 50% of sampled households cultivated a small area within the homestead. This was mainly done to supplement household food expenditure in order to save cash incomes. The results also found that although participants had perceived negative changes in climate and rainfall (amount, onset, duration), it was not considered the most important challenge for own production. Rather, lack of fencing and capital were seen as major hindrances to efficient own production. Understanding the complexity of own production and food security under a changing climate can help form better and more resilient policies and strategies for rural development, in addition to strengthening future livelihoods of rural people in an ever changing world.
- Full Text:
- Date Issued: 2018
The role of ecological processes in structuring reef fish communities in the Agulhas Ecoregion, South Africa
- Authors: Dyer, Alexander
- Date: 2018
- Subjects: Reef fishes -- South Africa -- Agulhas, Cape (Cape) , Reef fishes -- Ecology -- South Africa -- Agulhas, Cape (Cape) , Marine biodiversity -- South Africa -- Agulhas, Cape (Cape) , Biotic communities -- South Africa -- Agulhas, Cape (Cape) , Sparidae -- South Africa -- Agulhas, Cape (Cape) , Reef fishes -- Size -- South Africa -- Agulhas, Cape (Cape) , Baited remote underwater stereo-video systems (stereo-BRUVs)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/63899 , vital:28504
- Description: Local, niche-based processes, which arise from the interplay between biotic interactions and abiotic constraints are considered to be important regulators of community structure. However, it is increasingly recognised that patterns of diversity can also be strongly influenced by dispersal-driven processes. While empirical research on the diversity of coral reef fishes on shallow tropical reefs has contributed greatly to the development of general concepts in ecology, there have been considerably fewer studies on the processes which shape the diversity of fish communities on shallow (10 - 30 m) and deep (30 - 75 m) rocky reefs. Consequently, it is less clear at which spatial scales niche partitioning and dispersal limitation contribute most strongly to the structure of reef-associated fish communities within rocky reef ecosystems. To address this caveat, research was conducted at four rocky reef complexes within the warm-temperate Agulhas Ecoregion, South Africa. The diversity of reef-associated fishes was sampled by baited remote underwater stereo-video systems (stereo-BRUVs) to incorporate the range of heterogeneous reef habitat in Tsitsikamma National Park Marine Protected Area (TNP MPA) and Algoa Bay (AB). To examine how niche-based and dispersal-driven processes influence patterns of diversity among species within the dominant family of resident fishes, the sparids (Sparidae), components of diversity were quantified at several spatial scales. Turnover in the number of species which locally co-occurred was found to be largely driven by the limited dispersal of species over hundreds of kilometres. When relative species abundances were taken into account, sparid communities were characterised by higher than expected rates of compositional turnover among local habitat patches separated by hundreds to thousands of metres of contiguous reef. Patterns of compositional turnover were associated with the spatial aggregation of conspecifics, particularly at scales which facilitate the post-settlement dispersal of fishes. Niche-based segregation of species along the depth gradient was found to be the primary driver of compositional turnover among both protected and exploited communities. However, spatial structuring within reefs, which was independent of variation in the environment, suggests that compositional differences among communities are also influenced by the limited post-settlement dispersal of resident fishes to adjacent areas during their ontogeny. Together, the results suggest that the diversity of reef-associated sparids is likely to depend both on an adequate diversity of suitable reef habitat and a sufficient degree of spatial connectivity to facilitate ontogenetic habitat shifts. Taxon-based descriptors of diversity do not adequately account for ecological difference among conspecifics within size-structured populations. To test whether differences in body size facilitated coexistence among sparid fishes, the number of species which coexisted at the local scale was related to variation in the size structure of communities. In communities which have been historically protected from fishing, local coexistence between a greater number of species was promoted by reduced levels of intraspecific variation in size of fishes. This suggests that, among species with similar trophic requirements, further niche segregation along a prey-size and body-size gradient is likely to mitigate the direct impacts of competition for shared food resources. Among exploited communities, size structure did not influence the number of species which coexisted at the local scale. This finding suggests that fishing-induced mortality of larger-bodied fishes is likely to remove some of the constraints to colonisation which arise from asymmetries in competitive fitness between small and large-bodied fishes. Together, these results highlight the importance of post-settlement processes and population size structure to the maintenance of reef-associated fish diversity within contiguous rocky reef habitats.
- Full Text:
- Date Issued: 2018
- Authors: Dyer, Alexander
- Date: 2018
- Subjects: Reef fishes -- South Africa -- Agulhas, Cape (Cape) , Reef fishes -- Ecology -- South Africa -- Agulhas, Cape (Cape) , Marine biodiversity -- South Africa -- Agulhas, Cape (Cape) , Biotic communities -- South Africa -- Agulhas, Cape (Cape) , Sparidae -- South Africa -- Agulhas, Cape (Cape) , Reef fishes -- Size -- South Africa -- Agulhas, Cape (Cape) , Baited remote underwater stereo-video systems (stereo-BRUVs)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/63899 , vital:28504
- Description: Local, niche-based processes, which arise from the interplay between biotic interactions and abiotic constraints are considered to be important regulators of community structure. However, it is increasingly recognised that patterns of diversity can also be strongly influenced by dispersal-driven processes. While empirical research on the diversity of coral reef fishes on shallow tropical reefs has contributed greatly to the development of general concepts in ecology, there have been considerably fewer studies on the processes which shape the diversity of fish communities on shallow (10 - 30 m) and deep (30 - 75 m) rocky reefs. Consequently, it is less clear at which spatial scales niche partitioning and dispersal limitation contribute most strongly to the structure of reef-associated fish communities within rocky reef ecosystems. To address this caveat, research was conducted at four rocky reef complexes within the warm-temperate Agulhas Ecoregion, South Africa. The diversity of reef-associated fishes was sampled by baited remote underwater stereo-video systems (stereo-BRUVs) to incorporate the range of heterogeneous reef habitat in Tsitsikamma National Park Marine Protected Area (TNP MPA) and Algoa Bay (AB). To examine how niche-based and dispersal-driven processes influence patterns of diversity among species within the dominant family of resident fishes, the sparids (Sparidae), components of diversity were quantified at several spatial scales. Turnover in the number of species which locally co-occurred was found to be largely driven by the limited dispersal of species over hundreds of kilometres. When relative species abundances were taken into account, sparid communities were characterised by higher than expected rates of compositional turnover among local habitat patches separated by hundreds to thousands of metres of contiguous reef. Patterns of compositional turnover were associated with the spatial aggregation of conspecifics, particularly at scales which facilitate the post-settlement dispersal of fishes. Niche-based segregation of species along the depth gradient was found to be the primary driver of compositional turnover among both protected and exploited communities. However, spatial structuring within reefs, which was independent of variation in the environment, suggests that compositional differences among communities are also influenced by the limited post-settlement dispersal of resident fishes to adjacent areas during their ontogeny. Together, the results suggest that the diversity of reef-associated sparids is likely to depend both on an adequate diversity of suitable reef habitat and a sufficient degree of spatial connectivity to facilitate ontogenetic habitat shifts. Taxon-based descriptors of diversity do not adequately account for ecological difference among conspecifics within size-structured populations. To test whether differences in body size facilitated coexistence among sparid fishes, the number of species which coexisted at the local scale was related to variation in the size structure of communities. In communities which have been historically protected from fishing, local coexistence between a greater number of species was promoted by reduced levels of intraspecific variation in size of fishes. This suggests that, among species with similar trophic requirements, further niche segregation along a prey-size and body-size gradient is likely to mitigate the direct impacts of competition for shared food resources. Among exploited communities, size structure did not influence the number of species which coexisted at the local scale. This finding suggests that fishing-induced mortality of larger-bodied fishes is likely to remove some of the constraints to colonisation which arise from asymmetries in competitive fitness between small and large-bodied fishes. Together, these results highlight the importance of post-settlement processes and population size structure to the maintenance of reef-associated fish diversity within contiguous rocky reef habitats.
- Full Text:
- Date Issued: 2018