A biochemical study of the antidiabetic and anticogulant effects of Tulbaghia Violacea
- Authors: Davison, Candice
- Date: 2010
- Subjects: Medicinal plants -- South Africa , Diabetes -- Alternative treatment -- South Africa , Violaceae -- Therapeutic use -- South Africa , Anticoagulants (Medicine) , Plants -- Analysis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10311 , http://hdl.handle.net/10948/1523 , Medicinal plants -- South Africa , Diabetes -- Alternative treatment -- South Africa , Violaceae -- Therapeutic use -- South Africa , Anticoagulants (Medicine) , Plants -- Analysis
- Description: Secondary metabolites derived from plants, especially those used by traditional healers, are at the forefront of new drug development in combating diseases such as cancer and diabetes. Garlic is employed in indigenous medicine all over the world for the treatment of a variety of diseases. Dietary garlic has been recognized for its beneficial health effects. In particular, garlic consumption has been correlated with (i) reduction of risk factors for cardiovascular diseases and cancer, (ii) stimulation of immune function, (iii) enhanced detoxification of foreign compounds, (iv) hepatoprotection, (v) antimicrobial effects, (vi) antioxidant effects, and most importantly (vii) its hypoglycemic and anticoagulant properties. Due to these beneficial properties, garlic and its closely related genera which includes Tulbaghia violacea, may be useful as coadjuvant therapy in the treatment of type 2 diabetes and some of its physiological complications. The aim of this study was to determine if T. violacea has antidiabetic and anticoagulant properties. This was performed in vitro using both aqueous and organic extracts of the roots, leaves and bulbs. An organic extract was able to improve glucose-stimulated insulin secretion (GSIS) in INS-1 pancreatic β-cells and glucose uptake in Chang liver cells. The BO extract had no effect on the glucose uptake in 3T3-L1 an adipose cell line and reduced glucose utilisation in C2C12, a skeletal muscle cell line. Some of the properties displayed by T. violacea in this study are consistent with those found in similar studies with garlic extracts. It was observed that the BO extract increased the membrane potential and Glut-2 expression in INS-1 cells cultured at hyperglycemic levels, however, at normoglycemic levels a reduction was observed. The oxygen consumption increased at both glycemic levels due to treatment with the BO extract. Platelets were exposed to the extracts to determine their effects upon platelet aggregation, adhesion and protein secretion. Since the BO extract displayed the highest potential at inhibiting platelet aggregation and adhesion. A rat model was used in ex vivo studies to determine if the extract exhibited the same effect in a physiological model. It was noted that the BO extract exhibited a higher degree of inhibition on platelet aggregation and adhesion than the positive control, aspirin. The BO extract reduced clotting times in the prothrombin time (PT) test, but prolonged the clotting time in the actived partial thromboplastin time (APTT) assay in the ex vivo model; however, it had no affect on these clotting assays in the in vitro model using human blood. The BO extract increased the D-dimer and Fibrinogen-C levels in the in vitro model, but had no effect on the D-dimer concentrations and lowered the Fibrinogen-C levels in the ex vivo model. The active compounds in the extract remain to be elucidated.
- Full Text:
- Date Issued: 2010
- Authors: Davison, Candice
- Date: 2010
- Subjects: Medicinal plants -- South Africa , Diabetes -- Alternative treatment -- South Africa , Violaceae -- Therapeutic use -- South Africa , Anticoagulants (Medicine) , Plants -- Analysis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10311 , http://hdl.handle.net/10948/1523 , Medicinal plants -- South Africa , Diabetes -- Alternative treatment -- South Africa , Violaceae -- Therapeutic use -- South Africa , Anticoagulants (Medicine) , Plants -- Analysis
- Description: Secondary metabolites derived from plants, especially those used by traditional healers, are at the forefront of new drug development in combating diseases such as cancer and diabetes. Garlic is employed in indigenous medicine all over the world for the treatment of a variety of diseases. Dietary garlic has been recognized for its beneficial health effects. In particular, garlic consumption has been correlated with (i) reduction of risk factors for cardiovascular diseases and cancer, (ii) stimulation of immune function, (iii) enhanced detoxification of foreign compounds, (iv) hepatoprotection, (v) antimicrobial effects, (vi) antioxidant effects, and most importantly (vii) its hypoglycemic and anticoagulant properties. Due to these beneficial properties, garlic and its closely related genera which includes Tulbaghia violacea, may be useful as coadjuvant therapy in the treatment of type 2 diabetes and some of its physiological complications. The aim of this study was to determine if T. violacea has antidiabetic and anticoagulant properties. This was performed in vitro using both aqueous and organic extracts of the roots, leaves and bulbs. An organic extract was able to improve glucose-stimulated insulin secretion (GSIS) in INS-1 pancreatic β-cells and glucose uptake in Chang liver cells. The BO extract had no effect on the glucose uptake in 3T3-L1 an adipose cell line and reduced glucose utilisation in C2C12, a skeletal muscle cell line. Some of the properties displayed by T. violacea in this study are consistent with those found in similar studies with garlic extracts. It was observed that the BO extract increased the membrane potential and Glut-2 expression in INS-1 cells cultured at hyperglycemic levels, however, at normoglycemic levels a reduction was observed. The oxygen consumption increased at both glycemic levels due to treatment with the BO extract. Platelets were exposed to the extracts to determine their effects upon platelet aggregation, adhesion and protein secretion. Since the BO extract displayed the highest potential at inhibiting platelet aggregation and adhesion. A rat model was used in ex vivo studies to determine if the extract exhibited the same effect in a physiological model. It was noted that the BO extract exhibited a higher degree of inhibition on platelet aggregation and adhesion than the positive control, aspirin. The BO extract reduced clotting times in the prothrombin time (PT) test, but prolonged the clotting time in the actived partial thromboplastin time (APTT) assay in the ex vivo model; however, it had no affect on these clotting assays in the in vitro model using human blood. The BO extract increased the D-dimer and Fibrinogen-C levels in the in vitro model, but had no effect on the D-dimer concentrations and lowered the Fibrinogen-C levels in the ex vivo model. The active compounds in the extract remain to be elucidated.
- Full Text:
- Date Issued: 2010
A framework for mobile SOA using compression
- Authors: Saunders, Evan
- Date: 2010
- Subjects: Service-oriented architecture (Computer science)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10459 , http://hdl.handle.net/10948/1500 , Service-oriented architecture (Computer science)
- Description: The widely accepted standards of Service-Oriented Architecture (SOA) have changed the way many organisations conduct their everyday business. The significant popularity of mobile devices has seen a rapid increase in the rate of mobile technology enhancements, which have become widely used for communication, as well as conducting everyday tasks. An increased requirement in many businesses is for staff not to be tied down to the office. Consequently, mobile devices play an important role in achieving the mobility and information access that people desire. Due to the popularity and increasing use of SOA and mobile devices, Mobile Service-Oriented Architecture (Mobile SOA) has become a new industry catch-phrase. Many challenges, however, exist within the Mobile SOA environment. These issues include limitations on mobile devices, such as a reduced screen size, lack of processing power, insufficient processing memory, limited battery life, poor storage capacity, unreliable network connections, limited bandwidth available and high transfer costs. This research aimed to provide an elegant solution to the issues of a mobile device, which hinders the performance of Mobile SOA. The main objective of this research was to improve the effectiveness and efficiency of Mobile SOA. In order to achieve this goal, a framework was proposed, which supported intelligent compression of files used within a Web Service. The proposed framework provided a set of guidelines that facilitate the quick development of a system. A proof-of-concept prototype was developed, based on these guidelines and the framework design principles. The prototype provided practical evidence of the effectiveness of implementing a system based on the proposed framework. An analytical evaluation was conducted to determine the effectiveness of the prototype within the Mobile SOA environment. A performance evaluation was conducted to determine efficiency it provides. Additionally, the performance evaluation highlighted the decrease in file transfer time, as well as the significant reduction in transfer costs. The analytical and performance evaluations demonstrated that the prototype optimises the effectiveness and efficiency of Mobile SOA. The framework could, thus, be used to facilitate efficient file transfer between a Server and (Mobile) Client.
- Full Text:
- Date Issued: 2010
- Authors: Saunders, Evan
- Date: 2010
- Subjects: Service-oriented architecture (Computer science)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10459 , http://hdl.handle.net/10948/1500 , Service-oriented architecture (Computer science)
- Description: The widely accepted standards of Service-Oriented Architecture (SOA) have changed the way many organisations conduct their everyday business. The significant popularity of mobile devices has seen a rapid increase in the rate of mobile technology enhancements, which have become widely used for communication, as well as conducting everyday tasks. An increased requirement in many businesses is for staff not to be tied down to the office. Consequently, mobile devices play an important role in achieving the mobility and information access that people desire. Due to the popularity and increasing use of SOA and mobile devices, Mobile Service-Oriented Architecture (Mobile SOA) has become a new industry catch-phrase. Many challenges, however, exist within the Mobile SOA environment. These issues include limitations on mobile devices, such as a reduced screen size, lack of processing power, insufficient processing memory, limited battery life, poor storage capacity, unreliable network connections, limited bandwidth available and high transfer costs. This research aimed to provide an elegant solution to the issues of a mobile device, which hinders the performance of Mobile SOA. The main objective of this research was to improve the effectiveness and efficiency of Mobile SOA. In order to achieve this goal, a framework was proposed, which supported intelligent compression of files used within a Web Service. The proposed framework provided a set of guidelines that facilitate the quick development of a system. A proof-of-concept prototype was developed, based on these guidelines and the framework design principles. The prototype provided practical evidence of the effectiveness of implementing a system based on the proposed framework. An analytical evaluation was conducted to determine the effectiveness of the prototype within the Mobile SOA environment. A performance evaluation was conducted to determine efficiency it provides. Additionally, the performance evaluation highlighted the decrease in file transfer time, as well as the significant reduction in transfer costs. The analytical and performance evaluations demonstrated that the prototype optimises the effectiveness and efficiency of Mobile SOA. The framework could, thus, be used to facilitate efficient file transfer between a Server and (Mobile) Client.
- Full Text:
- Date Issued: 2010
An evaluation of the impact of corruption, economic status and political influence on the Malawian construction industry
- Authors: Phiri, Mulima Anaclet
- Date: 2010
- Subjects: Construction industry -- Malawi
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:9688 , http://hdl.handle.net/10948/1155 , Construction industry -- Malawi
- Description: The key objectives of this MSc (Construction Management) dissertation are to evaluate the negative impact of: corruption; political influence, and the poor economy on the construction industry; in order to gain insight regarding the management of the sector to achieve the desired project deliverables, which are: • Achievement of a functional fit for purpose built environment, which is to the clients’ requirements; • Achievement of a Financially viable product in line with the clients’ budget; • Achievement of a successful and timely completion, and • Achievement of the required quality standard of the final product. To achieve the above mentioned project deliverables, the study entailed the following prominent findings: • There is a need to manage political greed in the distribution of development projects, and functionality of the product to suit the client / community; • There is a need to manage, mitigate and combat corruption in order to diminish the dominance of unscrupulous contractors over others, and to achieve clients’ desired quality standards; • There is a requirement to manage the construction policy formulation process and governance of laws and regulations to revamp the retrogression of the industry, and • There is a requirement to manage project cost to significantly boost the ailing economy. In conclusion, the study evaluates the Malawi construction industry status and improvements there on. The management of the industry’s phenomena and mind set is of paramount importance to the success of the findings in this study. Recommendations to improve the status quo relative to the findings are: to train all active stakeholders in construction management courses; a national initiative to sensitise the community regarding the powers granted to them, as an electorate of the stakeholders; to change the phenomenon of and mindset relative to bribes, and finally to derive a passion for construction and for the associated built environment.
- Full Text:
- Date Issued: 2010
- Authors: Phiri, Mulima Anaclet
- Date: 2010
- Subjects: Construction industry -- Malawi
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:9688 , http://hdl.handle.net/10948/1155 , Construction industry -- Malawi
- Description: The key objectives of this MSc (Construction Management) dissertation are to evaluate the negative impact of: corruption; political influence, and the poor economy on the construction industry; in order to gain insight regarding the management of the sector to achieve the desired project deliverables, which are: • Achievement of a functional fit for purpose built environment, which is to the clients’ requirements; • Achievement of a Financially viable product in line with the clients’ budget; • Achievement of a successful and timely completion, and • Achievement of the required quality standard of the final product. To achieve the above mentioned project deliverables, the study entailed the following prominent findings: • There is a need to manage political greed in the distribution of development projects, and functionality of the product to suit the client / community; • There is a need to manage, mitigate and combat corruption in order to diminish the dominance of unscrupulous contractors over others, and to achieve clients’ desired quality standards; • There is a requirement to manage the construction policy formulation process and governance of laws and regulations to revamp the retrogression of the industry, and • There is a requirement to manage project cost to significantly boost the ailing economy. In conclusion, the study evaluates the Malawi construction industry status and improvements there on. The management of the industry’s phenomena and mind set is of paramount importance to the success of the findings in this study. Recommendations to improve the status quo relative to the findings are: to train all active stakeholders in construction management courses; a national initiative to sensitise the community regarding the powers granted to them, as an electorate of the stakeholders; to change the phenomenon of and mindset relative to bribes, and finally to derive a passion for construction and for the associated built environment.
- Full Text:
- Date Issued: 2010
Artificial neural networks as simulators for behavioural evolution in evolutionary robotics
- Pretorius, Christiaan Johannes
- Authors: Pretorius, Christiaan Johannes
- Date: 2010
- Subjects: Neural networks (Computer science) , Robotics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10462 , http://hdl.handle.net/10948/1476 , Neural networks (Computer science) , Robotics
- Description: Robotic simulators for use in Evolutionary Robotics (ER) have certain challenges associated with the complexity of their construction and the accuracy of predictions made by these simulators. Such robotic simulators are often based on physics models, which have been shown to produce accurate results. However, the construction of physics-based simulators can be complex and time-consuming. Alternative simulation schemes construct robotic simulators from empirically-collected data. Such empirical simulators, however, also have associated challenges, such as that some of these simulators do not generalize well on the data from which they are constructed, as these models employ simple interpolation on said data. As a result of the identified challenges in existing robotic simulators for use in ER, this project investigates the potential use of Artificial Neural Networks, henceforth simply referred to as Neural Networks (NNs), as alternative robotic simulators. In contrast to physics models, NN-based simulators can be constructed without needing an explicit mathematical model of the system being modeled, which can simplify simulator development. Furthermore, the generalization capabilities of NNs suggest that NNs could generalize well on data from which these simulators are constructed. These generalization abilities of NNs, along with NNs’ noise tolerance, suggest that NNs could be well-suited to application in robotics simulation. Investigating whether NNs can be effectively used as robotic simulators in ER is thus the endeavour of this work. Since not much research has been done in employing NNs as robotic simulators, many aspects of the experimental framework on which this dissertation reports needed to be carefully decided upon. Two robot morphologies were selected on which the NN simulators created in this work were based, namely a differentially steered robot and an inverted pendulum robot. Motion tracking and robotic sensor logging were used to acquire data from which the NN simulators were constructed. Furthermore, custom code was written for almost all aspects of the study, namely data acquisition for NN training, the actual NN training process, the evolution of robotic controllers using the created NN simulators, as well as the onboard robotic implementations of evolved controllers. Experimental tests performed in order to determine ideal topologies for each of the NN simulators developed in this study indicated that different NN topologies can lead to large differences in training accuracy. After performing these tests, the training accuracy of the created simulators was analyzed. This analysis showed that the NN simulators generally trained well and could generalize well on data not presented during simulator construction. In order to validate the feasibility of the created NN simulators in the ER process, these simulators were subsequently used to evolve controllers in simulation, similar to controllers developed in related studies. Encouraging results were obtained, with the newly-evolved controllers allowing real-world experimental robots to exhibit obstacle avoidance and light-approaching behaviour with a reasonable degree of success. The created NN simulators furthermore allowed for the successful evolution of a complex inverted pendulum stabilization controller in simulation. It was thus clearly established that NN-based robotic simulators can be successfully employed as alternative simulation schemes in the ER process.
- Full Text:
- Date Issued: 2010
- Authors: Pretorius, Christiaan Johannes
- Date: 2010
- Subjects: Neural networks (Computer science) , Robotics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10462 , http://hdl.handle.net/10948/1476 , Neural networks (Computer science) , Robotics
- Description: Robotic simulators for use in Evolutionary Robotics (ER) have certain challenges associated with the complexity of their construction and the accuracy of predictions made by these simulators. Such robotic simulators are often based on physics models, which have been shown to produce accurate results. However, the construction of physics-based simulators can be complex and time-consuming. Alternative simulation schemes construct robotic simulators from empirically-collected data. Such empirical simulators, however, also have associated challenges, such as that some of these simulators do not generalize well on the data from which they are constructed, as these models employ simple interpolation on said data. As a result of the identified challenges in existing robotic simulators for use in ER, this project investigates the potential use of Artificial Neural Networks, henceforth simply referred to as Neural Networks (NNs), as alternative robotic simulators. In contrast to physics models, NN-based simulators can be constructed without needing an explicit mathematical model of the system being modeled, which can simplify simulator development. Furthermore, the generalization capabilities of NNs suggest that NNs could generalize well on data from which these simulators are constructed. These generalization abilities of NNs, along with NNs’ noise tolerance, suggest that NNs could be well-suited to application in robotics simulation. Investigating whether NNs can be effectively used as robotic simulators in ER is thus the endeavour of this work. Since not much research has been done in employing NNs as robotic simulators, many aspects of the experimental framework on which this dissertation reports needed to be carefully decided upon. Two robot morphologies were selected on which the NN simulators created in this work were based, namely a differentially steered robot and an inverted pendulum robot. Motion tracking and robotic sensor logging were used to acquire data from which the NN simulators were constructed. Furthermore, custom code was written for almost all aspects of the study, namely data acquisition for NN training, the actual NN training process, the evolution of robotic controllers using the created NN simulators, as well as the onboard robotic implementations of evolved controllers. Experimental tests performed in order to determine ideal topologies for each of the NN simulators developed in this study indicated that different NN topologies can lead to large differences in training accuracy. After performing these tests, the training accuracy of the created simulators was analyzed. This analysis showed that the NN simulators generally trained well and could generalize well on data not presented during simulator construction. In order to validate the feasibility of the created NN simulators in the ER process, these simulators were subsequently used to evolve controllers in simulation, similar to controllers developed in related studies. Encouraging results were obtained, with the newly-evolved controllers allowing real-world experimental robots to exhibit obstacle avoidance and light-approaching behaviour with a reasonable degree of success. The created NN simulators furthermore allowed for the successful evolution of a complex inverted pendulum stabilization controller in simulation. It was thus clearly established that NN-based robotic simulators can be successfully employed as alternative simulation schemes in the ER process.
- Full Text:
- Date Issued: 2010
Assessing the diet of the Cape leopard (panthera pardus) in the Cederberg and Gamka mountains, South Africa
- Authors: Rautenbach, Therèsè
- Date: 2010
- Subjects: Leopard -- South Africa , Animal feeding -- South Africa , Predation (Biology)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10699 , http://hdl.handle.net/10948/1078 , Leopard -- South Africa , Animal feeding -- South Africa , Predation (Biology)
- Description: As limited prey availability and persecution by humans in response to livestock predation are key conservation concerns for the Cape leopard (Martins & Martins 2006), the present study aimed to provide more information regarding their feeding habits. The first objective was to determine whether the Cape leopard was subject to a change in their prey base and how they responded to the change. This was established by comparison of their current diet in the Cederberg and Gamka Mountains, determined by using scat analysis techniques, with a previous dietary assessment (Norton et al. 1986). The second aim was to provide a preliminary assessment of the prey preference of the Cape leopard and examine the utility of camera trap surveys to determine leopard prey preference. Leopard diet in the Cederberg and Gamka Mountains consisted largely of small- (1-10 kg) and medium-sized (10-40 kg) mammals; rock hyraxes (Procavia capensis) and klipspringers (Oreotragus oreotragus) were key prey items. In terms of regional variation in leopard diet, there was a significant difference in the average weight of prey utilized in the Cederberg and Gamka Mountains. Despite the importance of prey availability of suitable size, their flexibility in terms of prey size utilization reflected their ability to switch to smaller prey to fulfil their dietary requirements, when prey is limited. The study suggested a dietary shift, with significant variation in prey species utilization in both regions. The shift did not appear to be in response to prey scarcity, but rather a reduction in key prey species, particularly the rock hyrax. The shift involved an increase in the number of species utilized, and only a very small increase in livestock predation in both areas. There was however no significant variation in prey size category utilization. This demonstrated their dietary flexibility, as well as the importance of suitable prey sizes rather than the presence of specific prey species to fulfil their dietary requirements. The camera trap survey revealed a strong correlation between the number of camera trap days and the number of photographs taken of identifiable species. Variation of this correlation between different habitats supported the notion that individual images are a better unit to determine sampling efficiency than trap days. The camera trap survey also showed that small rodent availability was underestimated by camera trap surveillance, which resulted in poor prey preference estimation. It was therefore suggested that camera trap surveys be restricted to the surveillance of larger prey species (> 1 kg). By excluding small rodents from the analysis, prey preference could be estimated for other species and prey size categories. Small- and medium-sized mammals were significantly preferred, whereas large mammals were significantly avoided by the Cape leopard.
- Full Text:
- Date Issued: 2010
- Authors: Rautenbach, Therèsè
- Date: 2010
- Subjects: Leopard -- South Africa , Animal feeding -- South Africa , Predation (Biology)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10699 , http://hdl.handle.net/10948/1078 , Leopard -- South Africa , Animal feeding -- South Africa , Predation (Biology)
- Description: As limited prey availability and persecution by humans in response to livestock predation are key conservation concerns for the Cape leopard (Martins & Martins 2006), the present study aimed to provide more information regarding their feeding habits. The first objective was to determine whether the Cape leopard was subject to a change in their prey base and how they responded to the change. This was established by comparison of their current diet in the Cederberg and Gamka Mountains, determined by using scat analysis techniques, with a previous dietary assessment (Norton et al. 1986). The second aim was to provide a preliminary assessment of the prey preference of the Cape leopard and examine the utility of camera trap surveys to determine leopard prey preference. Leopard diet in the Cederberg and Gamka Mountains consisted largely of small- (1-10 kg) and medium-sized (10-40 kg) mammals; rock hyraxes (Procavia capensis) and klipspringers (Oreotragus oreotragus) were key prey items. In terms of regional variation in leopard diet, there was a significant difference in the average weight of prey utilized in the Cederberg and Gamka Mountains. Despite the importance of prey availability of suitable size, their flexibility in terms of prey size utilization reflected their ability to switch to smaller prey to fulfil their dietary requirements, when prey is limited. The study suggested a dietary shift, with significant variation in prey species utilization in both regions. The shift did not appear to be in response to prey scarcity, but rather a reduction in key prey species, particularly the rock hyrax. The shift involved an increase in the number of species utilized, and only a very small increase in livestock predation in both areas. There was however no significant variation in prey size category utilization. This demonstrated their dietary flexibility, as well as the importance of suitable prey sizes rather than the presence of specific prey species to fulfil their dietary requirements. The camera trap survey revealed a strong correlation between the number of camera trap days and the number of photographs taken of identifiable species. Variation of this correlation between different habitats supported the notion that individual images are a better unit to determine sampling efficiency than trap days. The camera trap survey also showed that small rodent availability was underestimated by camera trap surveillance, which resulted in poor prey preference estimation. It was therefore suggested that camera trap surveys be restricted to the surveillance of larger prey species (> 1 kg). By excluding small rodents from the analysis, prey preference could be estimated for other species and prey size categories. Small- and medium-sized mammals were significantly preferred, whereas large mammals were significantly avoided by the Cape leopard.
- Full Text:
- Date Issued: 2010
Bioaccumulation and ecotoxicology of b-methylamino-l-alanine (BMAA) in model crop plants
- Niyonzima, Francois Niyongabo
- Authors: Niyonzima, Francois Niyongabo
- Date: 2010
- Subjects: Cyanobacteria , Environmental toxicology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10312 , http://hdl.handle.net/10948/1475 , Cyanobacteria , Environmental toxicology
- Description: Cyanobacteria are known to produce a variety of toxic compounds. β-N-methylamino-L-alanine (BMAA) is one of the neurotoxins produced by most cyanobacteria. BMAA has been implicated in amyotrophic lateral sclerosis / Parkinsonism dementia complex (ALS / PDC) and was suggested to contribute to this pathology after biomagnification and slow release of BMAA from a protein associated form. The uptake and accumulation of BMAA by the aquatic macrophyte Ceratophyllum demersum has recently been shown, but the consumption of aquatic macrophytes by humans is not typical. The uptake by, and accumulation in, crop plants (Nasturtium officinale and Daucus carota) was therefore investigated so as to establish the existence of any risk to humans from the consumption of plants irrigated with water from dams with high cyanobacterial biomass and therefore high BMAA levels. After the exposure to the BMAA through the growth medium, BMAA had no effect on growth and development of N. officinale and D. carota. The uptake and bioaccumulation of BMAA was observed in N. officinale and D. carota, and was found to be concentration-dependent. Both free and bound cellular BMAA was detected following BMAA exposure through the growth medium. The photosynthetic apparatus of N. officinale was not significantly damaged. The uptake and accumulation of BMAA in edible terrestrial plants may constitute another route of human exposure to BMAA; it may now be prudent to avoid spray irrigation of edible plants with waters from dams with high cyanobacterial biomass and therefore high BMAA levels. After uptake by plants, the cyanotoxins may induce oxidative stress. A recent study showed that BMAA has a significant inhibitory effect on the oxidative stress enzymes in C. demersum. Therefore, the toxicological effects on selected plants were investigated by a range of biochemical enzyme assays in order to establish the plant stress response to exogenous BMAA. The inhibition of antioxidant enzymes upon exposure of N. officinale to BMAA through the growth medium was observed. The inhibition of antioxidant defence enzymes by BMAA correlated with the BMAA bioaccumulation in N. officinale. Further investigations are needed to analyze the uptake, accumulation, and ecotoxicology of BMAA in other crop plants, and to examine the fate of BMAA in these plants particularly its distribution and metabolism.
- Full Text:
- Date Issued: 2010
- Authors: Niyonzima, Francois Niyongabo
- Date: 2010
- Subjects: Cyanobacteria , Environmental toxicology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10312 , http://hdl.handle.net/10948/1475 , Cyanobacteria , Environmental toxicology
- Description: Cyanobacteria are known to produce a variety of toxic compounds. β-N-methylamino-L-alanine (BMAA) is one of the neurotoxins produced by most cyanobacteria. BMAA has been implicated in amyotrophic lateral sclerosis / Parkinsonism dementia complex (ALS / PDC) and was suggested to contribute to this pathology after biomagnification and slow release of BMAA from a protein associated form. The uptake and accumulation of BMAA by the aquatic macrophyte Ceratophyllum demersum has recently been shown, but the consumption of aquatic macrophytes by humans is not typical. The uptake by, and accumulation in, crop plants (Nasturtium officinale and Daucus carota) was therefore investigated so as to establish the existence of any risk to humans from the consumption of plants irrigated with water from dams with high cyanobacterial biomass and therefore high BMAA levels. After the exposure to the BMAA through the growth medium, BMAA had no effect on growth and development of N. officinale and D. carota. The uptake and bioaccumulation of BMAA was observed in N. officinale and D. carota, and was found to be concentration-dependent. Both free and bound cellular BMAA was detected following BMAA exposure through the growth medium. The photosynthetic apparatus of N. officinale was not significantly damaged. The uptake and accumulation of BMAA in edible terrestrial plants may constitute another route of human exposure to BMAA; it may now be prudent to avoid spray irrigation of edible plants with waters from dams with high cyanobacterial biomass and therefore high BMAA levels. After uptake by plants, the cyanotoxins may induce oxidative stress. A recent study showed that BMAA has a significant inhibitory effect on the oxidative stress enzymes in C. demersum. Therefore, the toxicological effects on selected plants were investigated by a range of biochemical enzyme assays in order to establish the plant stress response to exogenous BMAA. The inhibition of antioxidant enzymes upon exposure of N. officinale to BMAA through the growth medium was observed. The inhibition of antioxidant defence enzymes by BMAA correlated with the BMAA bioaccumulation in N. officinale. Further investigations are needed to analyze the uptake, accumulation, and ecotoxicology of BMAA in other crop plants, and to examine the fate of BMAA in these plants particularly its distribution and metabolism.
- Full Text:
- Date Issued: 2010
Constraints and challenges faced by small, medium and micro enterprise contractors in Malawi
- Authors: Chilipunde, Rodrick Lengama
- Date: 2010
- Subjects: Small business -- Malawi -- Management , Contractors' operations -- Malawi , Small business -- Malawi -- Finance
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:9686 , http://hdl.handle.net/10948/1220 , Small business -- Malawi -- Management , Contractors' operations -- Malawi , Small business -- Malawi -- Finance
- Description: Small, medium and micro enterprises (SMMEs) are an important sector of any construction economy. The need for efficient SMMEs is well documented and cannot be over-emphasised. SMMEs are vital in their contribution to employment creation and value reorientation. However, their in process operations are not well understood and have rarely been addressed. The aim of this research was therefore to establish a base level of understanding of the operational core-face of SMMEs in Malawi. The methodology used included an extensive literature review and field survey conducted on 52 SMMEs. The field survey used the questionnaire instrument and random sampling. The critical findings from the literature were that there are binding constraints in the operations of SMMEs. The field survey confirmed the issues raised in the literature and posited the operational challenges as lack of finance, training and business skills; limited skills in Construction Information Technology (IT), and prevalence of unethical conduct amongst some of the stakeholders. The findings make an invaluable contribution to the search for solutions to the problems faced by construction SMMEs in Malawi and provide insight for further research in institutional weaknesses and policy issues regarding in this part of the world. The implications of the findings are that unless the limitations named above are resolved, SMMEs in Malawi will continue to experience poor growth and competitiveness. The recommendations include the developing of training programmes in business management, introduction of sector specific financing programmes and the provision of an appropriate regulatory and legislative framework. By establishing the core issues affecting the operations of SMMEs in the Malawian construction industry, the research has contributed to the enhancement of the understanding of this elusive subject.
- Full Text:
- Date Issued: 2010
- Authors: Chilipunde, Rodrick Lengama
- Date: 2010
- Subjects: Small business -- Malawi -- Management , Contractors' operations -- Malawi , Small business -- Malawi -- Finance
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:9686 , http://hdl.handle.net/10948/1220 , Small business -- Malawi -- Management , Contractors' operations -- Malawi , Small business -- Malawi -- Finance
- Description: Small, medium and micro enterprises (SMMEs) are an important sector of any construction economy. The need for efficient SMMEs is well documented and cannot be over-emphasised. SMMEs are vital in their contribution to employment creation and value reorientation. However, their in process operations are not well understood and have rarely been addressed. The aim of this research was therefore to establish a base level of understanding of the operational core-face of SMMEs in Malawi. The methodology used included an extensive literature review and field survey conducted on 52 SMMEs. The field survey used the questionnaire instrument and random sampling. The critical findings from the literature were that there are binding constraints in the operations of SMMEs. The field survey confirmed the issues raised in the literature and posited the operational challenges as lack of finance, training and business skills; limited skills in Construction Information Technology (IT), and prevalence of unethical conduct amongst some of the stakeholders. The findings make an invaluable contribution to the search for solutions to the problems faced by construction SMMEs in Malawi and provide insight for further research in institutional weaknesses and policy issues regarding in this part of the world. The implications of the findings are that unless the limitations named above are resolved, SMMEs in Malawi will continue to experience poor growth and competitiveness. The recommendations include the developing of training programmes in business management, introduction of sector specific financing programmes and the provision of an appropriate regulatory and legislative framework. By establishing the core issues affecting the operations of SMMEs in the Malawian construction industry, the research has contributed to the enhancement of the understanding of this elusive subject.
- Full Text:
- Date Issued: 2010
Customer profiling using a service-orientated architecture
- Authors: Ntawanga, Felix
- Date: 2010
- Subjects: Consumer profiling -- South Africa , Consumer behavior -- South Africa , Service-oriented architecture (Computer science) , Electronic commerce -- South Africa -- Computer programs
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10464 , http://hdl.handle.net/10948/1146 , Consumer profiling -- South Africa , Consumer behavior -- South Africa , Service-oriented architecture (Computer science) , Electronic commerce -- South Africa -- Computer programs
- Description: Customer profiling has recently gained much recognition in the e-commerce domain because of the benefits it is capable of bringing to online business. Customer profiling has been implemented in various systems development approaches such as in a client-server environment. Recently there has been an increase in the number of organisations adopting and implementing e-commerce systems using service-oriented architecture (SOA) principles. This research set out to determine how a customer profile can be implemented using open source SOA implementation tools, and how SOA-based customer profiles can be utilised to provide appropriate personalisation in an SOA environment. The research further endeavoured to complete a comparative study on customer profile implementation in two different architectures, namely SOA and client-server. An extensive literature review was conducted on SOA, customer profiling and e-commerce systems development. SOA enabling technologies, such as, web services, enterprise service bus (ESB) and open source Sun Java SOA implementation tools, for example, Open ESB, GlassFish application server and Netbeans IDE were analysed. A Java web services-based customer profiling system was prototyped following SOA design principles. An end-user evaluation survey was conducted using eye tracking with a sample of 30 participants. The evaluation was done on two e-commerce systems with the same interface but running on two different customer profile back-ends, SOA and client-server. The results show that participants did not experience significant difference between the two systems, however, eye tracking results showed a significant difference between the two systems. The research concluded that customer profiling using SOA offers more benefits than implementations using other architectures such as client-server. SOA component-based development proved to be easier to manage, develop, integrate and improves interoperability between different technologies. The research brought together necessary techniques and technologies that organisations can use to implement SOA. Using SOA, organisations can integrate and utilise different technologies seamlessly to achieve business goals.
- Full Text:
- Date Issued: 2010
- Authors: Ntawanga, Felix
- Date: 2010
- Subjects: Consumer profiling -- South Africa , Consumer behavior -- South Africa , Service-oriented architecture (Computer science) , Electronic commerce -- South Africa -- Computer programs
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10464 , http://hdl.handle.net/10948/1146 , Consumer profiling -- South Africa , Consumer behavior -- South Africa , Service-oriented architecture (Computer science) , Electronic commerce -- South Africa -- Computer programs
- Description: Customer profiling has recently gained much recognition in the e-commerce domain because of the benefits it is capable of bringing to online business. Customer profiling has been implemented in various systems development approaches such as in a client-server environment. Recently there has been an increase in the number of organisations adopting and implementing e-commerce systems using service-oriented architecture (SOA) principles. This research set out to determine how a customer profile can be implemented using open source SOA implementation tools, and how SOA-based customer profiles can be utilised to provide appropriate personalisation in an SOA environment. The research further endeavoured to complete a comparative study on customer profile implementation in two different architectures, namely SOA and client-server. An extensive literature review was conducted on SOA, customer profiling and e-commerce systems development. SOA enabling technologies, such as, web services, enterprise service bus (ESB) and open source Sun Java SOA implementation tools, for example, Open ESB, GlassFish application server and Netbeans IDE were analysed. A Java web services-based customer profiling system was prototyped following SOA design principles. An end-user evaluation survey was conducted using eye tracking with a sample of 30 participants. The evaluation was done on two e-commerce systems with the same interface but running on two different customer profile back-ends, SOA and client-server. The results show that participants did not experience significant difference between the two systems, however, eye tracking results showed a significant difference between the two systems. The research concluded that customer profiling using SOA offers more benefits than implementations using other architectures such as client-server. SOA component-based development proved to be easier to manage, develop, integrate and improves interoperability between different technologies. The research brought together necessary techniques and technologies that organisations can use to implement SOA. Using SOA, organisations can integrate and utilise different technologies seamlessly to achieve business goals.
- Full Text:
- Date Issued: 2010
Diet and population trends of warthog in the Addo Elephant National Park
- Authors: Mgqatsa, Nokubonga
- Date: 2010
- Subjects: Warthog -- South Africa -- Addo Elelphant National Park
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10693 , http://hdl.handle.net/10948/1277 , Warthog -- South Africa -- Addo Elelphant National Park
- Description: The common warthog (Phacochoerus africanus) has recently been recognised as an alien invasive species in the Eastern Cape and their population is increasing rapidly within the region. This then raises a concern as it is recorded that invasive species have negative impacts on both economic and ecological aspects of biodiversity in the receiving community. There are few studies that have documented the impacts of this species in the Eastern Cape. This study therefore seeks to determine the diet and population trends of this species in the Addo Elephant National Park (AENP) Main Camp and the results obtained can be correlated with previous studies and used to quantify the impacts of this species in the Eastern Cape. Warthogs are specialized grazers, it was therefore hypothesized that they will have potential impacts on grazing resources in the AENP Main Camp. The diet of common warthogs in the AENP Main Camp was determined through microhistological analysis of faecal material of samples collected seasonally. Population trends of common warthogs were determined in relation to the effects of predation on the population growth and population age structure of these animals within the AENP Main Camp. The results were compared with the findings for common warthog population growth and population age structure of Great Fish River Nature Reserve (GFRNR), a predator free population. It was hypothesized that the population growth rate of common warthogs in the AENP Main Camp before the introduction of lions and hyaenas in the AENP would not differ from the population growth rate of common warthogs in GFRNR. Secondly, the post-lion/hyaena common warthog population in the AENP Main Camp would differ from both the AENP Main Camp pre-lion/hyaena and GFRNR common warthog populations due to the presence of large predators in the AENP Main Camp. For population age structure it was hypothesized that the two populations, AENP Main Camp and GFRNR would differ because of predators increasing mortality. The diet of common warthogs was dominated by grass (87.4 percent), with Cynodon dactylon being the dominant grass species. Common warthogs in the AENP Main Camp should be properly managed because they have potential impact on grasses. The population growth of common warthogs in the AENP Main Camp showed no effect of predation, with population growth not differing from that of GFRNR. Predation had an effect on common warthog population age structure with AENP Main Camp and GFRNR populations differing, particularly in terms of adult structure. Thus, population growth of common warthogs in the AENP Main Camp is not determined by the presence of predators. These findings highlight the status of common warthog as an invasive species in the AENP Main Camp and potentially impacting on grass species and show little effects of top-down population regulation. These results show a need of monitoring common warthog population as well as their potential impacts in the area.
- Full Text:
- Date Issued: 2010
- Authors: Mgqatsa, Nokubonga
- Date: 2010
- Subjects: Warthog -- South Africa -- Addo Elelphant National Park
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10693 , http://hdl.handle.net/10948/1277 , Warthog -- South Africa -- Addo Elelphant National Park
- Description: The common warthog (Phacochoerus africanus) has recently been recognised as an alien invasive species in the Eastern Cape and their population is increasing rapidly within the region. This then raises a concern as it is recorded that invasive species have negative impacts on both economic and ecological aspects of biodiversity in the receiving community. There are few studies that have documented the impacts of this species in the Eastern Cape. This study therefore seeks to determine the diet and population trends of this species in the Addo Elephant National Park (AENP) Main Camp and the results obtained can be correlated with previous studies and used to quantify the impacts of this species in the Eastern Cape. Warthogs are specialized grazers, it was therefore hypothesized that they will have potential impacts on grazing resources in the AENP Main Camp. The diet of common warthogs in the AENP Main Camp was determined through microhistological analysis of faecal material of samples collected seasonally. Population trends of common warthogs were determined in relation to the effects of predation on the population growth and population age structure of these animals within the AENP Main Camp. The results were compared with the findings for common warthog population growth and population age structure of Great Fish River Nature Reserve (GFRNR), a predator free population. It was hypothesized that the population growth rate of common warthogs in the AENP Main Camp before the introduction of lions and hyaenas in the AENP would not differ from the population growth rate of common warthogs in GFRNR. Secondly, the post-lion/hyaena common warthog population in the AENP Main Camp would differ from both the AENP Main Camp pre-lion/hyaena and GFRNR common warthog populations due to the presence of large predators in the AENP Main Camp. For population age structure it was hypothesized that the two populations, AENP Main Camp and GFRNR would differ because of predators increasing mortality. The diet of common warthogs was dominated by grass (87.4 percent), with Cynodon dactylon being the dominant grass species. Common warthogs in the AENP Main Camp should be properly managed because they have potential impact on grasses. The population growth of common warthogs in the AENP Main Camp showed no effect of predation, with population growth not differing from that of GFRNR. Predation had an effect on common warthog population age structure with AENP Main Camp and GFRNR populations differing, particularly in terms of adult structure. Thus, population growth of common warthogs in the AENP Main Camp is not determined by the presence of predators. These findings highlight the status of common warthog as an invasive species in the AENP Main Camp and potentially impacting on grass species and show little effects of top-down population regulation. These results show a need of monitoring common warthog population as well as their potential impacts in the area.
- Full Text:
- Date Issued: 2010
Effective management of machinery in government-operated hospitals
- Authors: Gatang'i, Peter Gatheru
- Date: 2010
- Subjects: Machinery -- Maintenance and repair , Plant maintenance -- Management , Hospitals -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:9664 , http://hdl.handle.net/10948/1237 , Machinery -- Maintenance and repair , Plant maintenance -- Management , Hospitals -- South Africa -- Eastern Cape
- Description: The methodology and the processes that are followed in the maintenance of government-operated district hospitals in the Eastern Cape Province of South Africa are outlined while the strategies that are employed to roll-out the maintenance plan have been investigated. The challenges in managing hospital maintenance are identified so that it can be improved and advice be given on the strategies currently being used. The objectives of the research were to determine the effectiveness of machinery maintenance in government-operated district hospitals. The study has been carried out by investigating 50 district hospitals within the Eastern Cape Province, with the aim of obtaining knowledge of practices in relation to the strategic plans and best practices in the maintenance industry. The following factors identified by the maintenance staff were found to be most important in maintenance management practices; realistic budgets, adherence to occupational health and safety regulations, engagement of qualified and skilled maintenance staff, good record management in relation to the equipment under maintenance, availability of tools and materials and keeping abreast with the latest technologies and trends of machinery advancement. The study also revealed that the majority of the hospitals use a combination of in-house and outsourced personnel during maintenance, the outsourced part being under contract from the National Department of Public Works Repair and Maintenance Plan (RAMP) projects. Service kits and recommended replacement parts for machinery are rarely stocked on the hospital premises while only minor spare parts that include replacement bulbs, electrical fittings, plumbing fittings and paint are readily available. In addition, the maintenance staff members have little or no input in maintenance budgeting, this aspect is controlled by hospital management. For maintenance to be effective, strategic planning that takes into account carefully thought-out maintenance management systems is the first step in the direction of setting out definite tangible objectives and goals. The real challenge lies in the implementation and sustainability of the maintenance management system and the monitoring thereof.
- Full Text:
- Date Issued: 2010
- Authors: Gatang'i, Peter Gatheru
- Date: 2010
- Subjects: Machinery -- Maintenance and repair , Plant maintenance -- Management , Hospitals -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:9664 , http://hdl.handle.net/10948/1237 , Machinery -- Maintenance and repair , Plant maintenance -- Management , Hospitals -- South Africa -- Eastern Cape
- Description: The methodology and the processes that are followed in the maintenance of government-operated district hospitals in the Eastern Cape Province of South Africa are outlined while the strategies that are employed to roll-out the maintenance plan have been investigated. The challenges in managing hospital maintenance are identified so that it can be improved and advice be given on the strategies currently being used. The objectives of the research were to determine the effectiveness of machinery maintenance in government-operated district hospitals. The study has been carried out by investigating 50 district hospitals within the Eastern Cape Province, with the aim of obtaining knowledge of practices in relation to the strategic plans and best practices in the maintenance industry. The following factors identified by the maintenance staff were found to be most important in maintenance management practices; realistic budgets, adherence to occupational health and safety regulations, engagement of qualified and skilled maintenance staff, good record management in relation to the equipment under maintenance, availability of tools and materials and keeping abreast with the latest technologies and trends of machinery advancement. The study also revealed that the majority of the hospitals use a combination of in-house and outsourced personnel during maintenance, the outsourced part being under contract from the National Department of Public Works Repair and Maintenance Plan (RAMP) projects. Service kits and recommended replacement parts for machinery are rarely stocked on the hospital premises while only minor spare parts that include replacement bulbs, electrical fittings, plumbing fittings and paint are readily available. In addition, the maintenance staff members have little or no input in maintenance budgeting, this aspect is controlled by hospital management. For maintenance to be effective, strategic planning that takes into account carefully thought-out maintenance management systems is the first step in the direction of setting out definite tangible objectives and goals. The real challenge lies in the implementation and sustainability of the maintenance management system and the monitoring thereof.
- Full Text:
- Date Issued: 2010
Effects of salinity on the growth and lipid production of ten species of microalgae from the Swartkops saltworks : a biodiesel perspective
- Authors: Sonnekus, Martinus Jakobus
- Date: 2010
- Subjects: Microalgae -- South Africa -- Swartkops , Salinity -- South Africa -- Swartkops , Biodiesel fuels
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10618 , http://hdl.handle.net/10948/1097 , Microalgae -- South Africa -- Swartkops , Salinity -- South Africa -- Swartkops , Biodiesel fuels
- Description: Biodiesel from microalgae is a viable alternative for replacing the global demand for petro-diesel. High biomass and lipid production are key desirable characteristics needed in a species to be used for biodiesel production. It has been demonstrated in literature that the increase in salinity can increase the lipid content of microalgae, but lower the growth rate of a species. Therefore the effect that salinity has on the growth and lipid content of ten microalgal species, isolated from a warm temperate solar saltworks, was investigated. The microalgae were cultivated at a temperature of 22°C and at salinities ranging from 17 to 70 psu. It was found that growth and lipid production for all species were influenced to some degree by the salinity. Growth rates greater than 0.6 d-1 showed a decrease with higher salinity. Most (71 percent) of the growth rates that exceeded 0.6 per day were exhibited by cultures exposed to normal salinity (35 psu). This shift is a good indication that salinity inhibits/slows down growth and that the species in general prefer lower salinity conditions. Growth rates ranged from 0.17 ± 0.05 to 1.19 ± 0.17 d-1. Lipid content for the diatoms (2.78 ± 0.36 to 10.86 ± 4.59 percent DW) were lower than expected, whereas the lipid content for the green flagellates (3.10 ± 1.56 to 22.64 ± 1.19 percent DW) was on par with that reported in literature. To bring results into perspective a production model was developed to simulate a production scenario at the Swartkops Saltworks. Lipid and productivity results obtained in this study were used to estimate how much oil and biomass can be produced within the ponds of the Swartkops Saltworks. The model showed that although microalgae cultivation for biodiesel is technically feasible, at present it is not economically viable to do so.
- Full Text:
- Date Issued: 2010
- Authors: Sonnekus, Martinus Jakobus
- Date: 2010
- Subjects: Microalgae -- South Africa -- Swartkops , Salinity -- South Africa -- Swartkops , Biodiesel fuels
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10618 , http://hdl.handle.net/10948/1097 , Microalgae -- South Africa -- Swartkops , Salinity -- South Africa -- Swartkops , Biodiesel fuels
- Description: Biodiesel from microalgae is a viable alternative for replacing the global demand for petro-diesel. High biomass and lipid production are key desirable characteristics needed in a species to be used for biodiesel production. It has been demonstrated in literature that the increase in salinity can increase the lipid content of microalgae, but lower the growth rate of a species. Therefore the effect that salinity has on the growth and lipid content of ten microalgal species, isolated from a warm temperate solar saltworks, was investigated. The microalgae were cultivated at a temperature of 22°C and at salinities ranging from 17 to 70 psu. It was found that growth and lipid production for all species were influenced to some degree by the salinity. Growth rates greater than 0.6 d-1 showed a decrease with higher salinity. Most (71 percent) of the growth rates that exceeded 0.6 per day were exhibited by cultures exposed to normal salinity (35 psu). This shift is a good indication that salinity inhibits/slows down growth and that the species in general prefer lower salinity conditions. Growth rates ranged from 0.17 ± 0.05 to 1.19 ± 0.17 d-1. Lipid content for the diatoms (2.78 ± 0.36 to 10.86 ± 4.59 percent DW) were lower than expected, whereas the lipid content for the green flagellates (3.10 ± 1.56 to 22.64 ± 1.19 percent DW) was on par with that reported in literature. To bring results into perspective a production model was developed to simulate a production scenario at the Swartkops Saltworks. Lipid and productivity results obtained in this study were used to estimate how much oil and biomass can be produced within the ponds of the Swartkops Saltworks. The model showed that although microalgae cultivation for biodiesel is technically feasible, at present it is not economically viable to do so.
- Full Text:
- Date Issued: 2010
Integer optimisation for the selection of a fantasy league cricket team
- Authors: Brettenny, Warren James
- Date: 2010
- Subjects: Sports -- Research -- Methodology , Teamwork (Sports) , Cricket players
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10565 , http://hdl.handle.net/10948/1230 , Sports -- Research -- Methodology , Teamwork (Sports) , Cricket players
- Description: Sports fans often scrutinise the team selection strategies employed by their favourite team's coach or selection panel. Many of these fans believe that they can perform the selection process far better than those tasked with the responsibility. Fantasy leagues, provide a platform for fans to test their hand at this selection procedure. Twenty20 cricket is a new and exciting form of cricket and has become very popular in recent years. This research focuses on bringing these concepts together by proposing a binary integer program to determine a team selection strategy for fantasy league cricket. This is done in a Twenty20 setting. The approach used in this study focuses on evaluating the effectiveness of previously developed performance measures in a fantasy league setting. Adjustments to these measures are made and new measures are proposed. These measures are then used to select a fantasy league team using a prospective approach. This is done to provide fantasy league participants with a mathematical procedure for fantasy league team selection.
- Full Text:
- Date Issued: 2010
- Authors: Brettenny, Warren James
- Date: 2010
- Subjects: Sports -- Research -- Methodology , Teamwork (Sports) , Cricket players
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10565 , http://hdl.handle.net/10948/1230 , Sports -- Research -- Methodology , Teamwork (Sports) , Cricket players
- Description: Sports fans often scrutinise the team selection strategies employed by their favourite team's coach or selection panel. Many of these fans believe that they can perform the selection process far better than those tasked with the responsibility. Fantasy leagues, provide a platform for fans to test their hand at this selection procedure. Twenty20 cricket is a new and exciting form of cricket and has become very popular in recent years. This research focuses on bringing these concepts together by proposing a binary integer program to determine a team selection strategy for fantasy league cricket. This is done in a Twenty20 setting. The approach used in this study focuses on evaluating the effectiveness of previously developed performance measures in a fantasy league setting. Adjustments to these measures are made and new measures are proposed. These measures are then used to select a fantasy league team using a prospective approach. This is done to provide fantasy league participants with a mathematical procedure for fantasy league team selection.
- Full Text:
- Date Issued: 2010
Investigating the effect of various film-forming polymers on the evaporation rate of a volatile component in a cosmetic formulation
- Authors: Barnard, Carla
- Date: 2010
- Subjects: Cosmetic delivery systems , Controlled release preparations , Cosmetics , Polymers , Drugs -- Controlled release
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10377 , http://hdl.handle.net/10948/1498 , Cosmetic delivery systems , Controlled release preparations , Cosmetics , Polymers , Drugs -- Controlled release
- Description: The topical application of many substances, including drugs, enzymes, moisturizers and fragrances, contributes largely to the cosmetic and pharmaceutical industries. These components are often volatile in nature and dissipate in a matter of hours. When considering the different types of slow release systems, an overwhelming variety of these systems is available. Each one of the systems is unique in a way, and is designed to perform a particular function, whether it facilitates the controlled release of an active into the body via the skin surface (transdermal delivery) or whether it reduces the rate of loss of an active from the skin surface to the surrounding environment. For the purpose of this study, a previously existing fixative formulation which is believed to reduce the rate of loss of an active component to the environment, through film formation on the skin surface, was investigated. Alternative ingredients or components were incorporated together with the original fixative formulation ingredients into an experimental design which investigates the effect of each group of the components present. 18 formulations with various concentrations of the components within the groups and specified upper and lower limits for each component were formulated. The fixative properties of the formulations were analysed through the incorporation of a fixed amount of a simple fragrance molecule, 4- methoxybenzaldehyde, into each formulation and evaporation studies were conducted in an environmental room at 28±1° C over a period of 5 hours followed by gas chromatography analysis and finally data analyses using statistical methods. The most efficient fixative formulation was established using regression analysis. The fragrance compound in this formulation was found to evaporate at a rate of 0.47 g/L per hour. The least efficient fixative formulation lead to the loss of 0.78 g/L of the fragrance component per hour. From the calculated fragrance concentrations, the rate constant for each individual fixative formulation could be calculated and response surface 8 modelling by backward regression was used in order to determine how each component contributes to the rate of loss of the fragrance compound. Since the sum of the original ingredient and its alternative was constant, each of the original ingredients was coupled directly to its alternative and no conclusion could be made about the contribution of individual components. By increasing the concentration of Hydroxypropylcellulose (HPC) 100K and its alternative HPC 140K, while keeping the effects of the other components constant, a decrease in the rate of fragrance loss was observed. The same conclusion could be made when increasing the concentrations of PEG-12 Dimethicone and its alternative cetyl dimethicone (decreases the evaporation rate). An interaction took place between HPC 100K and PEG-12 dimethicone and their alternatives. The negative effect was, however, not as strong as the combined positive effect on the rate of fragrance loss of the individual components HPC and PEG-12 dimethicone. Evidence suggested that the removal of the components polyvinylpyrrolidone and its alternative, polyurethane-32 (Baycusan® C1003), would improve the effectiveness of the fixative formulation in terms of its slow release properties. A confirmation experiment established that the exclusion of these components from the fixative formulation does improve the “slow release” properties thereof. A larger, more intricate design is required to investigate the effect of each one of the individual components and where the sum of the components (original and its alternative) is not constant.
- Full Text:
- Date Issued: 2010
- Authors: Barnard, Carla
- Date: 2010
- Subjects: Cosmetic delivery systems , Controlled release preparations , Cosmetics , Polymers , Drugs -- Controlled release
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10377 , http://hdl.handle.net/10948/1498 , Cosmetic delivery systems , Controlled release preparations , Cosmetics , Polymers , Drugs -- Controlled release
- Description: The topical application of many substances, including drugs, enzymes, moisturizers and fragrances, contributes largely to the cosmetic and pharmaceutical industries. These components are often volatile in nature and dissipate in a matter of hours. When considering the different types of slow release systems, an overwhelming variety of these systems is available. Each one of the systems is unique in a way, and is designed to perform a particular function, whether it facilitates the controlled release of an active into the body via the skin surface (transdermal delivery) or whether it reduces the rate of loss of an active from the skin surface to the surrounding environment. For the purpose of this study, a previously existing fixative formulation which is believed to reduce the rate of loss of an active component to the environment, through film formation on the skin surface, was investigated. Alternative ingredients or components were incorporated together with the original fixative formulation ingredients into an experimental design which investigates the effect of each group of the components present. 18 formulations with various concentrations of the components within the groups and specified upper and lower limits for each component were formulated. The fixative properties of the formulations were analysed through the incorporation of a fixed amount of a simple fragrance molecule, 4- methoxybenzaldehyde, into each formulation and evaporation studies were conducted in an environmental room at 28±1° C over a period of 5 hours followed by gas chromatography analysis and finally data analyses using statistical methods. The most efficient fixative formulation was established using regression analysis. The fragrance compound in this formulation was found to evaporate at a rate of 0.47 g/L per hour. The least efficient fixative formulation lead to the loss of 0.78 g/L of the fragrance component per hour. From the calculated fragrance concentrations, the rate constant for each individual fixative formulation could be calculated and response surface 8 modelling by backward regression was used in order to determine how each component contributes to the rate of loss of the fragrance compound. Since the sum of the original ingredient and its alternative was constant, each of the original ingredients was coupled directly to its alternative and no conclusion could be made about the contribution of individual components. By increasing the concentration of Hydroxypropylcellulose (HPC) 100K and its alternative HPC 140K, while keeping the effects of the other components constant, a decrease in the rate of fragrance loss was observed. The same conclusion could be made when increasing the concentrations of PEG-12 Dimethicone and its alternative cetyl dimethicone (decreases the evaporation rate). An interaction took place between HPC 100K and PEG-12 dimethicone and their alternatives. The negative effect was, however, not as strong as the combined positive effect on the rate of fragrance loss of the individual components HPC and PEG-12 dimethicone. Evidence suggested that the removal of the components polyvinylpyrrolidone and its alternative, polyurethane-32 (Baycusan® C1003), would improve the effectiveness of the fixative formulation in terms of its slow release properties. A confirmation experiment established that the exclusion of these components from the fixative formulation does improve the “slow release” properties thereof. A larger, more intricate design is required to investigate the effect of each one of the individual components and where the sum of the components (original and its alternative) is not constant.
- Full Text:
- Date Issued: 2010
Macrobenthic community structure across an inter- and subtidal gradient in a mangrove estuary
- Authors: Groenewald, Christoff J
- Date: 2010
- Subjects: Mangrove ecology -- South Africa -- Mngazana Estuary , Estuarine ecology -- South Africa -- Mngazana Estuary , Benthos -- South Africa -- Mngazana Estuary
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10695 , http://hdl.handle.net/10948/1240 , Mangrove ecology -- South Africa -- Mngazana Estuary , Estuarine ecology -- South Africa -- Mngazana Estuary , Benthos -- South Africa -- Mngazana Estuary
- Description: Macrozoobenthic community structure and composition was investigated along a subtidal-intertidal gradient in the Mngazana Estuary. Six transects were sampled between the spring high water mark (HWST) and the bottom of the river channel in the lower estuary. Fifteen replicate samples were collected along each transect using a Van Veen type grab (211 cm2 bite) during each of three sampling sessions. Samples were sieved through a 500 μm mesh bag and the invertebrates stored in bottles for further analysis in the laboratory. Additional grab samples were collected for sediment particle size analysis and organic matter. Physical variables measured at each transect included: salinity, temperature, dissolved oxygen, depth, pH, percentage mud, organic content and turbidity. Sediment compactness was measured at all intertidal transects and additional sediment samples were collected at mid shore and high shore transects for percentage water content analysis. A total of 104 species were recorded along the intertidal-subtidal gradient in the sampling area. Species richness was higher in the subtidal zone compared to the intertidal zone and polychaetes numerically dominated the macrozoobenthic community at most transects, during all three sessions. At high shore transects the community was characterised by having fewer species, consisting mostly of brachyurans, polychaetes and gastropods. Shannon diversity index (H’) was generally higher for subtidal transects (x¯ = 2.3; range: 2.8 to 1) than for intertidal transects (x¯ = 1.4; range: 2.2 to 0.6) indicating that the distribution of individuals among species in the intertidal zone experienced greater variability. Results for Hill’s numbers followed the same trend as Shannon diversity with subtidal communities mostly consisting of abundant species followed by very abundant species. Intertidal communities generally exhibited lower numbers of abundant and very abundant species. Sedimentary characteristics played a major role in structuring benthic communities in comparison to other physico-chemical variables. Organic content and mud content of the substrate were identified as important factors influencing community patterns observed along the subtidal-intertidal gradient. In addition, sediment compactness and water content of the substrate was found to influence intertidal community structure. Subtidal community structure possibly had a greater dependence on seasonal variations in abiotic and/or biotic factors. Cluster dendrograms used in conjunction with MDS ordination mapping revealed that macrozoobenthic communities were generally distinct between high shore intertidal transects iii and subtidal transects. Most species exhibited a broad spatial distribution along the subtidal-intertidal gradient with mid and high shore transects being the exception. Most species also exhibited marked shifts in abundance and this was especially noticeable at the transition between the subtidal and intertidal zone. Two polychaete species, Prionospio sexoculata and Capitella capitata, were very abundant species and featured amongst the most numerically dominant species collected during each sampling session.
- Full Text:
- Date Issued: 2010
- Authors: Groenewald, Christoff J
- Date: 2010
- Subjects: Mangrove ecology -- South Africa -- Mngazana Estuary , Estuarine ecology -- South Africa -- Mngazana Estuary , Benthos -- South Africa -- Mngazana Estuary
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10695 , http://hdl.handle.net/10948/1240 , Mangrove ecology -- South Africa -- Mngazana Estuary , Estuarine ecology -- South Africa -- Mngazana Estuary , Benthos -- South Africa -- Mngazana Estuary
- Description: Macrozoobenthic community structure and composition was investigated along a subtidal-intertidal gradient in the Mngazana Estuary. Six transects were sampled between the spring high water mark (HWST) and the bottom of the river channel in the lower estuary. Fifteen replicate samples were collected along each transect using a Van Veen type grab (211 cm2 bite) during each of three sampling sessions. Samples were sieved through a 500 μm mesh bag and the invertebrates stored in bottles for further analysis in the laboratory. Additional grab samples were collected for sediment particle size analysis and organic matter. Physical variables measured at each transect included: salinity, temperature, dissolved oxygen, depth, pH, percentage mud, organic content and turbidity. Sediment compactness was measured at all intertidal transects and additional sediment samples were collected at mid shore and high shore transects for percentage water content analysis. A total of 104 species were recorded along the intertidal-subtidal gradient in the sampling area. Species richness was higher in the subtidal zone compared to the intertidal zone and polychaetes numerically dominated the macrozoobenthic community at most transects, during all three sessions. At high shore transects the community was characterised by having fewer species, consisting mostly of brachyurans, polychaetes and gastropods. Shannon diversity index (H’) was generally higher for subtidal transects (x¯ = 2.3; range: 2.8 to 1) than for intertidal transects (x¯ = 1.4; range: 2.2 to 0.6) indicating that the distribution of individuals among species in the intertidal zone experienced greater variability. Results for Hill’s numbers followed the same trend as Shannon diversity with subtidal communities mostly consisting of abundant species followed by very abundant species. Intertidal communities generally exhibited lower numbers of abundant and very abundant species. Sedimentary characteristics played a major role in structuring benthic communities in comparison to other physico-chemical variables. Organic content and mud content of the substrate were identified as important factors influencing community patterns observed along the subtidal-intertidal gradient. In addition, sediment compactness and water content of the substrate was found to influence intertidal community structure. Subtidal community structure possibly had a greater dependence on seasonal variations in abiotic and/or biotic factors. Cluster dendrograms used in conjunction with MDS ordination mapping revealed that macrozoobenthic communities were generally distinct between high shore intertidal transects iii and subtidal transects. Most species exhibited a broad spatial distribution along the subtidal-intertidal gradient with mid and high shore transects being the exception. Most species also exhibited marked shifts in abundance and this was especially noticeable at the transition between the subtidal and intertidal zone. Two polychaete species, Prionospio sexoculata and Capitella capitata, were very abundant species and featured amongst the most numerically dominant species collected during each sampling session.
- Full Text:
- Date Issued: 2010
Macrophyte phenology in a temporarily open/closed Estuary compared with a permanently open Estuary
- Authors: Vromans, Deborah Claire
- Date: 2010
- Subjects: Estuarine ecology -- South Africa -- East Kleinemonde Estuary , Aquatic plants -- South Africa -- East Kleinemonde Estuary
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10612 , http://hdl.handle.net/10948/1393 , Estuarine ecology -- South Africa -- East Kleinemonde Estuary , Aquatic plants -- South Africa -- East Kleinemonde Estuary
- Description: Temporarily open/closed estuaries (TOCEs) are unpredictable environments that change in response to mouth condition, which is influenced by freshwater flooding or sea storm surges. The aim of the study was to determine whether macrophyte phenology in a TOCE was event driven rather than cyclically predictable and if it differed from permanently open estuaries (POEs). Macrophyte growth and flowering phenology in response to environmental conditions was investigated in the East Kleinemonde Estuary (TOCE) and the Kowie Estuary (POE) along the eastern coastline of South Africa. The lack of freshwater flooding due to low rainfall coupled with several overwash events resulted in a prolonged period of mouth closure from September 2008 to the end of this study period in 2010. This in turn caused the inundation of the supratidal and intertidal habitats, high water level (> 1.57 m amsl) and high salinity (30 - 42 ppt) in the TOCE. Principle Components Analysis showed that high water level and reduced sediments were the most significant environmental factors affecting macrophyte phenology. Macrophyte phenology in the POE was primarily driven by temperature, sediment redox potential and salinity. The saline high water level and reduced sediment significantly reduced macrophyte cover in all habitats in the TOCE. Macrophytes in the POE maintained high cover abundance due to seasonal re-growth compared to the TOCE where cover declined over the sampling period due to the high water level. Subsequent to water level dropping by as little as 11 - 20 cm in the TOCE, the intertidal species Sarcocornia tegetaria and Salicornia meyeriana completed their life-cycles and produced viable seeds within four and three months of germinating respectively. In contrast, the Sarcocornia hybrid and S. meyeriana in the POE took longer to complete their life-cycles, namely seven and nine months respectively, while S. tegataria did not germinate in situ but reproduced vegetatively despite producing seed. In the TOCE, the submerged species Ruppia cirrhosa and Chara vulgaris completed their life-cycles within five and three months and produced a maximum of 26 242 and 196 998 seeds m-2 respectively. Due to high water level and prolonged inundation, the reproductive periods were shorter for the intertidal and reed and sedge species in the TOCE compared to the POE. Seed output during the two reproduction periods varied between the two estuaries. Sarcocornia decumbens and S. tegetaria produced a substantially higher number of seeds in the TOCE compared to the POE, namely 0 - 102 847 versus 20 661 - 48 576 seeds m-²; and 7 001 - 45 542 versus 1 587 – 16 958 seeds m-² respectively. Seed output in the TOCE was significantly higher in S. tegetaria during the second reproduction period despite the significantly lower plant cover, which may be a function of the stressful environment in the TOCE. Seed production of S. meyeriana was significantly higher in the POE compared to the TOCE, with 264 224 - 640 292 compared with 24 050 - 27 643 seeds m-², due to higher plant cover in the POE. The research suggests that macrophyte phenology in the TOCE was significantly influenced by mouth condition. Further, macrophytes were able to demonstrate considerable phenotypic plasticity in response to changing and unfavourable environmental conditions. These data can be used in mouth management plans and freshwater requirement studies in TOCEs to ensure that macrophytes can complete their life-cycles and produce viable seeds for the safeguarding of habitat persistence and ecological processes. In impacted estuaries where artificial mouth opening is practised and the macrophytes have been severely degraded or extirpated, management should ensure that the intertidal and supratidal habitats are not inundated during peak flowering and seed production periods i.e. late spring to early autumn (November to March).
- Full Text:
- Date Issued: 2010
- Authors: Vromans, Deborah Claire
- Date: 2010
- Subjects: Estuarine ecology -- South Africa -- East Kleinemonde Estuary , Aquatic plants -- South Africa -- East Kleinemonde Estuary
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10612 , http://hdl.handle.net/10948/1393 , Estuarine ecology -- South Africa -- East Kleinemonde Estuary , Aquatic plants -- South Africa -- East Kleinemonde Estuary
- Description: Temporarily open/closed estuaries (TOCEs) are unpredictable environments that change in response to mouth condition, which is influenced by freshwater flooding or sea storm surges. The aim of the study was to determine whether macrophyte phenology in a TOCE was event driven rather than cyclically predictable and if it differed from permanently open estuaries (POEs). Macrophyte growth and flowering phenology in response to environmental conditions was investigated in the East Kleinemonde Estuary (TOCE) and the Kowie Estuary (POE) along the eastern coastline of South Africa. The lack of freshwater flooding due to low rainfall coupled with several overwash events resulted in a prolonged period of mouth closure from September 2008 to the end of this study period in 2010. This in turn caused the inundation of the supratidal and intertidal habitats, high water level (> 1.57 m amsl) and high salinity (30 - 42 ppt) in the TOCE. Principle Components Analysis showed that high water level and reduced sediments were the most significant environmental factors affecting macrophyte phenology. Macrophyte phenology in the POE was primarily driven by temperature, sediment redox potential and salinity. The saline high water level and reduced sediment significantly reduced macrophyte cover in all habitats in the TOCE. Macrophytes in the POE maintained high cover abundance due to seasonal re-growth compared to the TOCE where cover declined over the sampling period due to the high water level. Subsequent to water level dropping by as little as 11 - 20 cm in the TOCE, the intertidal species Sarcocornia tegetaria and Salicornia meyeriana completed their life-cycles and produced viable seeds within four and three months of germinating respectively. In contrast, the Sarcocornia hybrid and S. meyeriana in the POE took longer to complete their life-cycles, namely seven and nine months respectively, while S. tegataria did not germinate in situ but reproduced vegetatively despite producing seed. In the TOCE, the submerged species Ruppia cirrhosa and Chara vulgaris completed their life-cycles within five and three months and produced a maximum of 26 242 and 196 998 seeds m-2 respectively. Due to high water level and prolonged inundation, the reproductive periods were shorter for the intertidal and reed and sedge species in the TOCE compared to the POE. Seed output during the two reproduction periods varied between the two estuaries. Sarcocornia decumbens and S. tegetaria produced a substantially higher number of seeds in the TOCE compared to the POE, namely 0 - 102 847 versus 20 661 - 48 576 seeds m-²; and 7 001 - 45 542 versus 1 587 – 16 958 seeds m-² respectively. Seed output in the TOCE was significantly higher in S. tegetaria during the second reproduction period despite the significantly lower plant cover, which may be a function of the stressful environment in the TOCE. Seed production of S. meyeriana was significantly higher in the POE compared to the TOCE, with 264 224 - 640 292 compared with 24 050 - 27 643 seeds m-², due to higher plant cover in the POE. The research suggests that macrophyte phenology in the TOCE was significantly influenced by mouth condition. Further, macrophytes were able to demonstrate considerable phenotypic plasticity in response to changing and unfavourable environmental conditions. These data can be used in mouth management plans and freshwater requirement studies in TOCEs to ensure that macrophytes can complete their life-cycles and produce viable seeds for the safeguarding of habitat persistence and ecological processes. In impacted estuaries where artificial mouth opening is practised and the macrophytes have been severely degraded or extirpated, management should ensure that the intertidal and supratidal habitats are not inundated during peak flowering and seed production periods i.e. late spring to early autumn (November to March).
- Full Text:
- Date Issued: 2010
Microalgal biomass and distribution in the Mngazi and Mngazana Estuaries
- Ngesi, Hlekani Ntombizakithi
- Authors: Ngesi, Hlekani Ntombizakithi
- Date: 2010
- Subjects: Microalgae -- South Africa -- Mngazi Estuary , Algae -- South Africa -- Mngazi Estuary , Algae -- South Africa -- Mngazana Estuary , Estuarine ecology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10610 , http://hdl.handle.net/10948/1591 , Microalgae -- South Africa -- Mngazi Estuary , Algae -- South Africa -- Mngazi Estuary , Algae -- South Africa -- Mngazana Estuary , Estuarine ecology -- South Africa
- Description: The present study was undertaken in the temporarily open/closed Mngazi and permanently open Mngazana estuaries, located on the subtropical east coast of South Africa. The results from this research will assist decision makers in the freshwater management of these systems. Intertidal and subtidal benthic chlorophyll a concentrations, water column chlorophyll a, nutrients and several physico-chemical parameters were measured between June 2002 and November 2003. The objective of this study was to determine if the presence of freshwater in the estuaries had an effect on the microalgae of both estuaries. Five sites were sampled in the Mngazi Estuary and 14 sites were sampled in the Mngazana Estuary. The average water column chlorophyll a was significantly higher (p<0.05) in the Mngazana Estuary (surface 7.8 ± 0.7 μg.l-1, bottom 6.4 ± 0.7 μg.l-1) compared to the Mngazi Estuary (surface 4.9 ± 1.2 μg.l-1, bottom 7.3 ± 1.5 μg.l-1). There was no evidence of an REI (river-estuary interface) zone in areas where the water column chlorophyll a concentrations were high even during open mouth conditions in the Mngazi Estuary. The REI is that area where salinity is less than 10 ppt and is characterized by high water column productivity. Even though both systems received some freshwater during the summer periods, this was not enough to stimulate phytoplankton growth and nutrient availability seems to be the major factor limiting phytoplankton in these systems. Flagellates and diatoms were the dominant phytoplankton groups in both estuaries during the entire sampling session. The relative abundance of the different phytoplankton groups did not show differences between sites. The relative abundance of flagellates was in most cases greater than 60% and diatoms made up the remainder. The average benthic chlorophyll a was higher in the Mngazana Estuary (intertidal 24 ± 6 μg.g-1 subtidal 15.2 ± 3 μg.g-1) compared to the Mngazi Estuary (intertidal 15.3 ± 4.3 μg.g-1 subtidal 5.4 ± 1.6 μg.g-1). Regions with high benthic chlorophyll a concentrations had high sediment organic content. Sediment organic content was higher in the Mngazana Estuary (1 percent - 8 percent) compared to the Mngazi Estuary (4 percent – 6.8 percent). The sites situated on the Main Channel had on average significantly higher (p<0.05) benthic chlorophyll a biomass compared to Creek 1 and Creek 2 in the Mngazana Estuary. Peaks in benthic chlorophyll a concentrations occurred in the intertidal sediments in Creek 1 (50.4 ± 13.4 μg.g-1) and Creek 2 (57.4 ± 1.4 μg.g-1) in the Mngazana Estuary, the peaks occurred in winter during a period of low freshwater inflow into the estuary. Microphytobenthic biomass measured in the Mngazi Estuary is among the lowest values reported in the literature for temporarily open/closed estuaries. Statistical 4 analysis showed no significant difference between benthic chlorophyll a during the different mouth conditions and sampling sessions in the Mngazi Estuary. Microalgal responses in the Mngazana Estuary were similar to those observed in other permanently open marine dominated estuaries. In the temporarily open/closed Mngazi Estuary microalgal characteristics were different to that of other temporarily open/closed estuaries probably because the estuary was only sampled in the open and semi-closed state.
- Full Text:
- Date Issued: 2010
- Authors: Ngesi, Hlekani Ntombizakithi
- Date: 2010
- Subjects: Microalgae -- South Africa -- Mngazi Estuary , Algae -- South Africa -- Mngazi Estuary , Algae -- South Africa -- Mngazana Estuary , Estuarine ecology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10610 , http://hdl.handle.net/10948/1591 , Microalgae -- South Africa -- Mngazi Estuary , Algae -- South Africa -- Mngazi Estuary , Algae -- South Africa -- Mngazana Estuary , Estuarine ecology -- South Africa
- Description: The present study was undertaken in the temporarily open/closed Mngazi and permanently open Mngazana estuaries, located on the subtropical east coast of South Africa. The results from this research will assist decision makers in the freshwater management of these systems. Intertidal and subtidal benthic chlorophyll a concentrations, water column chlorophyll a, nutrients and several physico-chemical parameters were measured between June 2002 and November 2003. The objective of this study was to determine if the presence of freshwater in the estuaries had an effect on the microalgae of both estuaries. Five sites were sampled in the Mngazi Estuary and 14 sites were sampled in the Mngazana Estuary. The average water column chlorophyll a was significantly higher (p<0.05) in the Mngazana Estuary (surface 7.8 ± 0.7 μg.l-1, bottom 6.4 ± 0.7 μg.l-1) compared to the Mngazi Estuary (surface 4.9 ± 1.2 μg.l-1, bottom 7.3 ± 1.5 μg.l-1). There was no evidence of an REI (river-estuary interface) zone in areas where the water column chlorophyll a concentrations were high even during open mouth conditions in the Mngazi Estuary. The REI is that area where salinity is less than 10 ppt and is characterized by high water column productivity. Even though both systems received some freshwater during the summer periods, this was not enough to stimulate phytoplankton growth and nutrient availability seems to be the major factor limiting phytoplankton in these systems. Flagellates and diatoms were the dominant phytoplankton groups in both estuaries during the entire sampling session. The relative abundance of the different phytoplankton groups did not show differences between sites. The relative abundance of flagellates was in most cases greater than 60% and diatoms made up the remainder. The average benthic chlorophyll a was higher in the Mngazana Estuary (intertidal 24 ± 6 μg.g-1 subtidal 15.2 ± 3 μg.g-1) compared to the Mngazi Estuary (intertidal 15.3 ± 4.3 μg.g-1 subtidal 5.4 ± 1.6 μg.g-1). Regions with high benthic chlorophyll a concentrations had high sediment organic content. Sediment organic content was higher in the Mngazana Estuary (1 percent - 8 percent) compared to the Mngazi Estuary (4 percent – 6.8 percent). The sites situated on the Main Channel had on average significantly higher (p<0.05) benthic chlorophyll a biomass compared to Creek 1 and Creek 2 in the Mngazana Estuary. Peaks in benthic chlorophyll a concentrations occurred in the intertidal sediments in Creek 1 (50.4 ± 13.4 μg.g-1) and Creek 2 (57.4 ± 1.4 μg.g-1) in the Mngazana Estuary, the peaks occurred in winter during a period of low freshwater inflow into the estuary. Microphytobenthic biomass measured in the Mngazi Estuary is among the lowest values reported in the literature for temporarily open/closed estuaries. Statistical 4 analysis showed no significant difference between benthic chlorophyll a during the different mouth conditions and sampling sessions in the Mngazi Estuary. Microalgal responses in the Mngazana Estuary were similar to those observed in other permanently open marine dominated estuaries. In the temporarily open/closed Mngazi Estuary microalgal characteristics were different to that of other temporarily open/closed estuaries probably because the estuary was only sampled in the open and semi-closed state.
- Full Text:
- Date Issued: 2010
Nest site fidelity and nest site selection of loggerhead, Caretta Caretta, and leatherback, dermochelys coriacea, turtles in KwaZulu-Natal, South Africa
- Authors: Botha, Marié
- Date: 2010
- Subjects: Sea turtles -- South Africa -- KwaZulu-Natal , Loggerhead turtle -- South Africa -- KwaZulu-Natal , Leatherback turtle -- South Africa -- KwaZulu-Natal , Nest building , Turtles -- Habitat
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10696 , http://hdl.handle.net/10948/1233 , Sea turtles -- South Africa -- KwaZulu-Natal , Loggerhead turtle -- South Africa -- KwaZulu-Natal , Leatherback turtle -- South Africa -- KwaZulu-Natal , Nest building , Turtles -- Habitat
- Description: Loggerhead and leatherback sea turtles nest on the beaches of the north-eastern portion of Kwazulu-Natal within the iSimangaliso Wetland Park. Loggerheads place ~60 percent of all nests within an 8 km stretch of beach, whereas leatherbacks tend to space their nests more evenly along the entire length of the monitoring area. The study aimed to determine nest site fidelity of loggerheads and leatherbacks (using four decades of nesting data housed by Ezemvelo KZN Wildlife) and the factors that influence nest site selection of both species within the 56 km of turtle monitoring area (32N to 100S) and the 5 km area of high-density loggerhead nesting (0N to 12N). The effectiveness of nest site selection was then determined through the hatching success of loggerheads over the 5km area (0N to 12N). Results showed that loggerheads show a high degree of nest site fidelity (~3 km) with nest site fidelity of individuals increasing over subsequent seasons of nesting, as well as these individuals using the same stretches of beach for nesting (the most popular area being 1N to 4N for repeat nesters). Leatherbacks displayed nest site fidelity of ~9 km and this did not increase over successive seasons of nesting. In terms of nest site selection, loggerheads and leatherbacks both avoided areas where low shore rock was present, whereas both species preferred nesting on beaches of intermediate morphodynamic state. Leatherback nesting was significantly higher in areas with wider surf zones. Both species were able to surpass the high water mark when nesting as nests below this point would be almost certainly doomed. Hatching success of loggerheads was comparative to high (83 %) relative to other studies, however, nest success varied across the beach from beacon 1N to 12N. Areas where highest nest success was observed were not areas of highest nest density presumably due to artificial lighting. Results from this study increase our understanding of the evolutionary biology of loggerhead and leatherback turtles in South Africa and the effectiveness of loggerhead nest site selection through hatching success.
- Full Text:
- Date Issued: 2010
- Authors: Botha, Marié
- Date: 2010
- Subjects: Sea turtles -- South Africa -- KwaZulu-Natal , Loggerhead turtle -- South Africa -- KwaZulu-Natal , Leatherback turtle -- South Africa -- KwaZulu-Natal , Nest building , Turtles -- Habitat
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10696 , http://hdl.handle.net/10948/1233 , Sea turtles -- South Africa -- KwaZulu-Natal , Loggerhead turtle -- South Africa -- KwaZulu-Natal , Leatherback turtle -- South Africa -- KwaZulu-Natal , Nest building , Turtles -- Habitat
- Description: Loggerhead and leatherback sea turtles nest on the beaches of the north-eastern portion of Kwazulu-Natal within the iSimangaliso Wetland Park. Loggerheads place ~60 percent of all nests within an 8 km stretch of beach, whereas leatherbacks tend to space their nests more evenly along the entire length of the monitoring area. The study aimed to determine nest site fidelity of loggerheads and leatherbacks (using four decades of nesting data housed by Ezemvelo KZN Wildlife) and the factors that influence nest site selection of both species within the 56 km of turtle monitoring area (32N to 100S) and the 5 km area of high-density loggerhead nesting (0N to 12N). The effectiveness of nest site selection was then determined through the hatching success of loggerheads over the 5km area (0N to 12N). Results showed that loggerheads show a high degree of nest site fidelity (~3 km) with nest site fidelity of individuals increasing over subsequent seasons of nesting, as well as these individuals using the same stretches of beach for nesting (the most popular area being 1N to 4N for repeat nesters). Leatherbacks displayed nest site fidelity of ~9 km and this did not increase over successive seasons of nesting. In terms of nest site selection, loggerheads and leatherbacks both avoided areas where low shore rock was present, whereas both species preferred nesting on beaches of intermediate morphodynamic state. Leatherback nesting was significantly higher in areas with wider surf zones. Both species were able to surpass the high water mark when nesting as nests below this point would be almost certainly doomed. Hatching success of loggerheads was comparative to high (83 %) relative to other studies, however, nest success varied across the beach from beacon 1N to 12N. Areas where highest nest success was observed were not areas of highest nest density presumably due to artificial lighting. Results from this study increase our understanding of the evolutionary biology of loggerhead and leatherback turtles in South Africa and the effectiveness of loggerhead nest site selection through hatching success.
- Full Text:
- Date Issued: 2010
New platinum and palladium complexes: their anticancer application
- Authors: Louw, Marissa
- Date: 2010
- Subjects: Complex compounds -- Synthesis , Ligands (Biochemistry) , Antineoplastic antibiotics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10424 , http://hdl.handle.net/10948/d1016218
- Description: Novel non-leaving groups were employed in this dissertation to synthesize platinum complexes which can assist in the understanding or improvement of anticancer action. Emphasis was placed on (NS)-chelate and (NN)-chelate platinum complexes. Bidentate (NS)-donor ligands were used as non-leaving ligands in the synthesis of platinum(II) complexes with iodo, chloro, bromo and oxalato groups as leaving groups. These complexes were synthesized and studied since many questions regarding the interaction of sulfur-donors and platinum still exist. These relate to thermodynamic and kinetic factors and their influence on anticancer action. In this dissertation the properties of novel platinum(II) complexes of a bidentate ligand having an aromatic nitrogen-donor atom in combination with a thioethereal sulfur atom capable of forming a five-membered ring with platinum(II) were studied. The general structure of the (NS)-ligands used was 2-((alkylthio)methyl)pyridine. Alkyl groups used were methyl, ethyl, propyl, benzyl and phenyl. Amine complexes of platinum have been studied extensively in the past. However, attention was given to novel aspects of substituted pyridine and imidazole ligands and their corresponding complexes. Amongst these are 2-(2-methylaminoethyl)pyridine, 1-methyl-2-methylaminoethylimidazole and 1-methyl-2-methylaminobenzylimidazole. The leaving groups included chloro, bromo and oxalato. Mononitroplatinum(IV) complexes were prepared using novel synthetic methods. Selected platinum(II) amine complexes were used as starting materials for this synthesis. Some of these compounds exhibit promising anticancer behaviour. (Trans-(R,R)-1,2-diaminocyclohexane)(oxalato)(mononitrochloro)platinum(IV) is a particularly good anticancer agent and has been patented internationally. All these complexes were characterized using mass spectrometry, chromatography, thermogravimetric analysis, kinetic aspects such as ligand exchange rates and finally their anticancer action against three different cancer cell lines was evaluated via cytotoxicity assays. Some of the compounds exhibited particularly good anticancer potential.
- Full Text:
- Date Issued: 2010
- Authors: Louw, Marissa
- Date: 2010
- Subjects: Complex compounds -- Synthesis , Ligands (Biochemistry) , Antineoplastic antibiotics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10424 , http://hdl.handle.net/10948/d1016218
- Description: Novel non-leaving groups were employed in this dissertation to synthesize platinum complexes which can assist in the understanding or improvement of anticancer action. Emphasis was placed on (NS)-chelate and (NN)-chelate platinum complexes. Bidentate (NS)-donor ligands were used as non-leaving ligands in the synthesis of platinum(II) complexes with iodo, chloro, bromo and oxalato groups as leaving groups. These complexes were synthesized and studied since many questions regarding the interaction of sulfur-donors and platinum still exist. These relate to thermodynamic and kinetic factors and their influence on anticancer action. In this dissertation the properties of novel platinum(II) complexes of a bidentate ligand having an aromatic nitrogen-donor atom in combination with a thioethereal sulfur atom capable of forming a five-membered ring with platinum(II) were studied. The general structure of the (NS)-ligands used was 2-((alkylthio)methyl)pyridine. Alkyl groups used were methyl, ethyl, propyl, benzyl and phenyl. Amine complexes of platinum have been studied extensively in the past. However, attention was given to novel aspects of substituted pyridine and imidazole ligands and their corresponding complexes. Amongst these are 2-(2-methylaminoethyl)pyridine, 1-methyl-2-methylaminoethylimidazole and 1-methyl-2-methylaminobenzylimidazole. The leaving groups included chloro, bromo and oxalato. Mononitroplatinum(IV) complexes were prepared using novel synthetic methods. Selected platinum(II) amine complexes were used as starting materials for this synthesis. Some of these compounds exhibit promising anticancer behaviour. (Trans-(R,R)-1,2-diaminocyclohexane)(oxalato)(mononitrochloro)platinum(IV) is a particularly good anticancer agent and has been patented internationally. All these complexes were characterized using mass spectrometry, chromatography, thermogravimetric analysis, kinetic aspects such as ligand exchange rates and finally their anticancer action against three different cancer cell lines was evaluated via cytotoxicity assays. Some of the compounds exhibited particularly good anticancer potential.
- Full Text:
- Date Issued: 2010
Reactivity of Rhenium (iii) and Rhenium (V) with multidentate NN-and no-donor ligands
- Yumata, Nonzaliseko Christine
- Authors: Yumata, Nonzaliseko Christine
- Date: 2010
- Subjects: Rhenium , Ligands
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10373 , http://hdl.handle.net/10948/1085 , Rhenium , Ligands
- Description: The reaction of the potentially tridentate Schiff-base chelate Hhaep [Haep = N’-(1- (2-hydroxyphenyl)ethylidene)benzohydrazide] with [ReCl3(benzil)(PPh3)] and trans-[ReOCl3(PPh3)2] produced the neutral oxorhenium(V) complexes cis- [ReOCl2(mep)] [Hmep = 2-(1-iminoethyl)phenol] and cis-[ReOCI2(meb)(PPh3)] [Hmeb = N’-(propan-2-ylidene)benzohydrazide] in ethanol and acetone respectively. In both reactions the Hhaep molecule cleaves to give different coordinated bidentate NO-donor chelates coordinated to the rhenium(V) centers. The X-ray studies reveal that mep is present as a bidentate, monoanionic Schiffbase coordinating through the neutral imino nitrogen and the deprotonated phenolate oxygen in cis-[ReOCl2(mep)]. The bond distances and angles in cis- [ReOCI2(meb)(PPh3)] confirm that meb coordinates to the metal in the enolate form. The distorted octahedral complex fac-[ReCl3(dpa)(PPh3)] was prepared by the reaction of trans-[ReCl3(MeCN)(PPh3)2] with a twofold molar excess of dpa in acetonitrile under a nitrogen atmosphere. The compound dpa.HCl.2H2O was obtained as a by-product in the reaction of dpa with trans-[ReCI3(MeCN)(PPh3)2] in acetonitrile. The reaction of trans-[ReCl3(MeCN)(PPh3)2] with a twofold molar excess of 6- amino-3-methyl-1-phenyl-4-azahept-2-ene-1-one (Hamp) in acetonitrile led to the isolation of cis-[ReCl2(bat)(PPh3)2]. On complexation to the metal center Hamp decomposed to give the coordinated benzoylacetone (bat). Bat is present as a monoanionic bidentate chelate. The complexes [ReVOCI(had)] and [ReIVCl(had)(PPh3)](ReO4) were prepared from the reaction of trans-[ReCl3(MeCN)(PPh3)2] with N,N-bis((2-hydroxybenzyl)-2- aminoethyl)dimethylamine (H2had) in ethanol under various reaction conditions. The treatment of [ReCl3(benzil)(PPh3)] with 2-[((2- pyridinylmethyl)amino)methyl]phenol (Hham) in a 2:1 molar ratio in acetonitrile led to the isolation of the hydrogen-bonded dimer [ReOCl2(ham)]2. The distorted octahedral complex [ReOCl(hap)] [H2hap = N,N-bis(2- hydroxybenzyl)aminomethylpyridine] was prepared from the reaction of trans- [ReCl3(MeCN)(PPh3)2] with a twofold molar excess of H2hap in acetonitrile. The X-ray crystal structure analysis shows that the chloride is coordinated trans to the tripodal tertiary amino nitrogen, with a phenolate oxygen trans to the oxo oxygen.
- Full Text:
- Date Issued: 2010
- Authors: Yumata, Nonzaliseko Christine
- Date: 2010
- Subjects: Rhenium , Ligands
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10373 , http://hdl.handle.net/10948/1085 , Rhenium , Ligands
- Description: The reaction of the potentially tridentate Schiff-base chelate Hhaep [Haep = N’-(1- (2-hydroxyphenyl)ethylidene)benzohydrazide] with [ReCl3(benzil)(PPh3)] and trans-[ReOCl3(PPh3)2] produced the neutral oxorhenium(V) complexes cis- [ReOCl2(mep)] [Hmep = 2-(1-iminoethyl)phenol] and cis-[ReOCI2(meb)(PPh3)] [Hmeb = N’-(propan-2-ylidene)benzohydrazide] in ethanol and acetone respectively. In both reactions the Hhaep molecule cleaves to give different coordinated bidentate NO-donor chelates coordinated to the rhenium(V) centers. The X-ray studies reveal that mep is present as a bidentate, monoanionic Schiffbase coordinating through the neutral imino nitrogen and the deprotonated phenolate oxygen in cis-[ReOCl2(mep)]. The bond distances and angles in cis- [ReOCI2(meb)(PPh3)] confirm that meb coordinates to the metal in the enolate form. The distorted octahedral complex fac-[ReCl3(dpa)(PPh3)] was prepared by the reaction of trans-[ReCl3(MeCN)(PPh3)2] with a twofold molar excess of dpa in acetonitrile under a nitrogen atmosphere. The compound dpa.HCl.2H2O was obtained as a by-product in the reaction of dpa with trans-[ReCI3(MeCN)(PPh3)2] in acetonitrile. The reaction of trans-[ReCl3(MeCN)(PPh3)2] with a twofold molar excess of 6- amino-3-methyl-1-phenyl-4-azahept-2-ene-1-one (Hamp) in acetonitrile led to the isolation of cis-[ReCl2(bat)(PPh3)2]. On complexation to the metal center Hamp decomposed to give the coordinated benzoylacetone (bat). Bat is present as a monoanionic bidentate chelate. The complexes [ReVOCI(had)] and [ReIVCl(had)(PPh3)](ReO4) were prepared from the reaction of trans-[ReCl3(MeCN)(PPh3)2] with N,N-bis((2-hydroxybenzyl)-2- aminoethyl)dimethylamine (H2had) in ethanol under various reaction conditions. The treatment of [ReCl3(benzil)(PPh3)] with 2-[((2- pyridinylmethyl)amino)methyl]phenol (Hham) in a 2:1 molar ratio in acetonitrile led to the isolation of the hydrogen-bonded dimer [ReOCl2(ham)]2. The distorted octahedral complex [ReOCl(hap)] [H2hap = N,N-bis(2- hydroxybenzyl)aminomethylpyridine] was prepared from the reaction of trans- [ReCl3(MeCN)(PPh3)2] with a twofold molar excess of H2hap in acetonitrile. The X-ray crystal structure analysis shows that the chloride is coordinated trans to the tripodal tertiary amino nitrogen, with a phenolate oxygen trans to the oxo oxygen.
- Full Text:
- Date Issued: 2010
Sandy beach food webs and trophic linkages with estuaries: a stable light isotope approach
- Authors: Bezuidenhout, Karien
- Date: 2010
- Subjects: Stable isotopes in ecological research -- South Africa -- Eastern Cape , Food chains (Ecology) -- South Africa -- Eastern Cape , Estuaries -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10694 , http://hdl.handle.net/10948/1269 , Stable isotopes in ecological research -- South Africa -- Eastern Cape , Food chains (Ecology) -- South Africa -- Eastern Cape , Estuaries -- South Africa -- Eastern Cape
- Description: Two pocket sandy beaches, Eastern Cape, South Africa, were investigated, to determine whether these beaches were subsidised by an adjacent mangrove estuary, by using stable light isotope (δ 13C and δ 15N) analyses. The trophodynamics and macrofaunal food webs of these two beaches, situated between the Mgazi and Mgazana estuaries (in a warm-temperate/subtropical transition zone,), were described. Two to 2.5 trophic levels were identified for the macrobenthic community, with suspension feeders and omnivorous scavengers as the primary consumers, and carnivores as the secondary consumers. Mangrove material and terrigenous inputs were not driving the sandy beach food webs. Instead, marine allochthonous inputs (carrion, macroalgae), possibly phytoplankton, sediment organic matter, and resident macroinfauna were the dominant food sources. Cattle dung could have been the only important terrigenous food source utilised by the beach benthos. The macroinfauna displayed generalist/omnivorous feeding strategies, but within the limits of predominantly marine food sources. There was evidence that carnivores actively preyed on resident beach fauna. Omnivory and intraguild feeding might also be important biological processes in these communities. Seasonal and spatial variability in stable isotope composition of the fauna was observed, but few patterns were evident. There was a general trend of more enriched δ 15N and δ 13C composition of animal tissues in summer as opposed to winter. This was accompanied by a general decrease in C:N ratios in summer. It was hypothesised that these isotopic and biochemical changes were in response to increased food availability during summer. Although mangrove material appeared not to play an important role in the nutrition of these sandy beach communities, it was suggested that a high retention time of particles in the bay could enhance bacterial decay of particulate mangrove material, which could then act as fine, bacterial-enriched particulate food to the macrobenthos. This remains to be tested.
- Full Text:
- Date Issued: 2010
- Authors: Bezuidenhout, Karien
- Date: 2010
- Subjects: Stable isotopes in ecological research -- South Africa -- Eastern Cape , Food chains (Ecology) -- South Africa -- Eastern Cape , Estuaries -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10694 , http://hdl.handle.net/10948/1269 , Stable isotopes in ecological research -- South Africa -- Eastern Cape , Food chains (Ecology) -- South Africa -- Eastern Cape , Estuaries -- South Africa -- Eastern Cape
- Description: Two pocket sandy beaches, Eastern Cape, South Africa, were investigated, to determine whether these beaches were subsidised by an adjacent mangrove estuary, by using stable light isotope (δ 13C and δ 15N) analyses. The trophodynamics and macrofaunal food webs of these two beaches, situated between the Mgazi and Mgazana estuaries (in a warm-temperate/subtropical transition zone,), were described. Two to 2.5 trophic levels were identified for the macrobenthic community, with suspension feeders and omnivorous scavengers as the primary consumers, and carnivores as the secondary consumers. Mangrove material and terrigenous inputs were not driving the sandy beach food webs. Instead, marine allochthonous inputs (carrion, macroalgae), possibly phytoplankton, sediment organic matter, and resident macroinfauna were the dominant food sources. Cattle dung could have been the only important terrigenous food source utilised by the beach benthos. The macroinfauna displayed generalist/omnivorous feeding strategies, but within the limits of predominantly marine food sources. There was evidence that carnivores actively preyed on resident beach fauna. Omnivory and intraguild feeding might also be important biological processes in these communities. Seasonal and spatial variability in stable isotope composition of the fauna was observed, but few patterns were evident. There was a general trend of more enriched δ 15N and δ 13C composition of animal tissues in summer as opposed to winter. This was accompanied by a general decrease in C:N ratios in summer. It was hypothesised that these isotopic and biochemical changes were in response to increased food availability during summer. Although mangrove material appeared not to play an important role in the nutrition of these sandy beach communities, it was suggested that a high retention time of particles in the bay could enhance bacterial decay of particulate mangrove material, which could then act as fine, bacterial-enriched particulate food to the macrobenthos. This remains to be tested.
- Full Text:
- Date Issued: 2010