Composition and phenology of insect pests of Capsicum (Solanaceae) cultivated in the Makana District, Eastern Cape Province, South Africa
- Authors: Hepburn, Colleen
- Date: 2008
- Subjects: Insects -- South Africa -- Eastern Cape -- Composition Insects -- South Africa -- Eastern Cape -- Phenology Agricultural pests -- South Africa -- Eastern Cape Peppers -- Diseases and pests -- South Africa -- Eastern Cape Solanaceae -- Diseases and pests -- South Africa -- Eastern Cape Insect pests -- South Africa -- Eastern Cape Insect pests -- Biological control -- South Africa -- Eastern Cape Insect pests -- Control -- Methods -- South Africa -- Eastern Cape Insects -- Host plants -- South Africa -- Eastern Cape Insect-plant relationships -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5656 , http://hdl.handle.net/10962/d1005339
- Description: Capsicum baccatum var. pendulum was first grown in the Makana District in 2005. Extremely little was known about best practices for cultivation or the insects and diseases associated with the crop in this area. The study was conducted during the second year of production, November 2005 and November 2006, in an attempt to identify the composition and phenology of insects occurring on C. baccatum. In the more rural parts of the Eastern Cape, and more particularly in Grahamstown, there are very few industries. With the advent of this new agricultural venture, a processing factory has been opened in Grahamstown creating more than 600 seasonal jobs in the factory and 1000 seasonal jobs on farms for local people. This business enterprise has not only brought about the creation of jobs, but also training and skills development and empowerment, generating much-needed income in this area. An extensive literature review yielded limited information on insect pests associated with Capsicum. Data from a pilot sampling trial undertaken were statistically analyzed to establish the number of plants to be scouted per site and the most effective scouting techniques to use. Based on the data available and insects collected during the pilot sampling trial, a surveillance programme was designed. Five different types of monitoring traps were placed in each of the eight study sites. Collection of trap catches and scouting of fifteen individual plants per site was undertaken on a weekly basis over the 52-week study period. The most commonly occurring potential insect pests were African Bollworm Helicoverpa armigera (Hübner), False Codling Moth Thaumatotibia leucotreta (= Cryptophlebia leucotreta) (Meyrick), Mediterranean Fruit Fly Ceratitis capitata (Wiedemann) and several species of thrips. Population densities of these pests and their phenology on Capsicum were determined. Statistical analyses established the efficacy of the monitoring traps for each pest, tested for differences among and between study sites, calculated an estimate of the number of pods damaged and a measure of plant damage.The results show that the majority of damage caused to the Capsicum baccatum cropping system was due to Mediterranean Fruit Fly populations. It was established that, although African Bollworm and False Codling Moth were present during the study period, their numbers were negligible and only nominal damage was caused by these pests. Damage caused by thrips species was apparent but not quantifiable. Intervention strategies using an Integrated Pest Management approach, are discussed.
- Full Text:
- Date Issued: 2008
- Authors: Hepburn, Colleen
- Date: 2008
- Subjects: Insects -- South Africa -- Eastern Cape -- Composition Insects -- South Africa -- Eastern Cape -- Phenology Agricultural pests -- South Africa -- Eastern Cape Peppers -- Diseases and pests -- South Africa -- Eastern Cape Solanaceae -- Diseases and pests -- South Africa -- Eastern Cape Insect pests -- South Africa -- Eastern Cape Insect pests -- Biological control -- South Africa -- Eastern Cape Insect pests -- Control -- Methods -- South Africa -- Eastern Cape Insects -- Host plants -- South Africa -- Eastern Cape Insect-plant relationships -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5656 , http://hdl.handle.net/10962/d1005339
- Description: Capsicum baccatum var. pendulum was first grown in the Makana District in 2005. Extremely little was known about best practices for cultivation or the insects and diseases associated with the crop in this area. The study was conducted during the second year of production, November 2005 and November 2006, in an attempt to identify the composition and phenology of insects occurring on C. baccatum. In the more rural parts of the Eastern Cape, and more particularly in Grahamstown, there are very few industries. With the advent of this new agricultural venture, a processing factory has been opened in Grahamstown creating more than 600 seasonal jobs in the factory and 1000 seasonal jobs on farms for local people. This business enterprise has not only brought about the creation of jobs, but also training and skills development and empowerment, generating much-needed income in this area. An extensive literature review yielded limited information on insect pests associated with Capsicum. Data from a pilot sampling trial undertaken were statistically analyzed to establish the number of plants to be scouted per site and the most effective scouting techniques to use. Based on the data available and insects collected during the pilot sampling trial, a surveillance programme was designed. Five different types of monitoring traps were placed in each of the eight study sites. Collection of trap catches and scouting of fifteen individual plants per site was undertaken on a weekly basis over the 52-week study period. The most commonly occurring potential insect pests were African Bollworm Helicoverpa armigera (Hübner), False Codling Moth Thaumatotibia leucotreta (= Cryptophlebia leucotreta) (Meyrick), Mediterranean Fruit Fly Ceratitis capitata (Wiedemann) and several species of thrips. Population densities of these pests and their phenology on Capsicum were determined. Statistical analyses established the efficacy of the monitoring traps for each pest, tested for differences among and between study sites, calculated an estimate of the number of pods damaged and a measure of plant damage.The results show that the majority of damage caused to the Capsicum baccatum cropping system was due to Mediterranean Fruit Fly populations. It was established that, although African Bollworm and False Codling Moth were present during the study period, their numbers were negligible and only nominal damage was caused by these pests. Damage caused by thrips species was apparent but not quantifiable. Intervention strategies using an Integrated Pest Management approach, are discussed.
- Full Text:
- Date Issued: 2008
Conceptualisations of 'the community' and 'community knowledge' among community radio volunteers in Katutura, Namibia
- Authors: Ellis, Hugh
- Date: 2008
- Subjects: Katutura Community Radio Community radio -- Namibia Radio broadcasting -- Namibia Radio stations -- Namibia Radio journalism -- Namibia Volunteers -- Namibia Radio in community development -- Namibia Mass media -- Social aspects -- Namibia
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3428 , http://hdl.handle.net/10962/d1002882
- Description: Community radio typically relies on volunteers to produce and present stations’ programming. Volunteers are generally drawn from stations’ target communities and are seen as “representatives” of those communities. It is with such volunteers and their role as representatives of stations’ target communities that this study is concerned. It poses the question: “what are the central concepts that typically inform volunteers’ knowledge of their target community, and how do these concepts impact on their perception of how they have gained this knowledge, and how they justify their role as representatives of this community?” The dissertation teases out the implications of these conceptualisations for a volunteer team’s ability to contribute to the establishment of a media environment that operates as a Habermasian ‘critical public sphere’. It argues that this can only be achieved if volunteers have detailed and in-depth knowledge of their target community. In order to acquire this knowledge, volunteers should make use of systematic ways of learning about the community, rather than relying solely on knowledge obtained by living there. In a case study of Katutura Community Radio (KCR), one of the bestknown community radio stations in Namibia, the study identifies key differences in the way in which different groups of volunteers conceptualise “the community”. The study focuses, in particular, on such difference as it applies to those who are volunteers in their personal capacity and those who represent non-governmental and community-based organisations at the station. It is argued that two strategies would lead to significant improvement in such a station’s ability to serve as a public sphere. Firstly, the station would benefit from an approach in which different sections of the volunteer team share knowledge of the target community with each other. Secondly, volunteers should undertake further systematic research into their target community. It is also argued that in order to facilitate such processes, radio stations such as KCR should recognise the inevitability of differences between different versions of “community knowledge”.
- Full Text:
- Date Issued: 2008
- Authors: Ellis, Hugh
- Date: 2008
- Subjects: Katutura Community Radio Community radio -- Namibia Radio broadcasting -- Namibia Radio stations -- Namibia Radio journalism -- Namibia Volunteers -- Namibia Radio in community development -- Namibia Mass media -- Social aspects -- Namibia
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3428 , http://hdl.handle.net/10962/d1002882
- Description: Community radio typically relies on volunteers to produce and present stations’ programming. Volunteers are generally drawn from stations’ target communities and are seen as “representatives” of those communities. It is with such volunteers and their role as representatives of stations’ target communities that this study is concerned. It poses the question: “what are the central concepts that typically inform volunteers’ knowledge of their target community, and how do these concepts impact on their perception of how they have gained this knowledge, and how they justify their role as representatives of this community?” The dissertation teases out the implications of these conceptualisations for a volunteer team’s ability to contribute to the establishment of a media environment that operates as a Habermasian ‘critical public sphere’. It argues that this can only be achieved if volunteers have detailed and in-depth knowledge of their target community. In order to acquire this knowledge, volunteers should make use of systematic ways of learning about the community, rather than relying solely on knowledge obtained by living there. In a case study of Katutura Community Radio (KCR), one of the bestknown community radio stations in Namibia, the study identifies key differences in the way in which different groups of volunteers conceptualise “the community”. The study focuses, in particular, on such difference as it applies to those who are volunteers in their personal capacity and those who represent non-governmental and community-based organisations at the station. It is argued that two strategies would lead to significant improvement in such a station’s ability to serve as a public sphere. Firstly, the station would benefit from an approach in which different sections of the volunteer team share knowledge of the target community with each other. Secondly, volunteers should undertake further systematic research into their target community. It is also argued that in order to facilitate such processes, radio stations such as KCR should recognise the inevitability of differences between different versions of “community knowledge”.
- Full Text:
- Date Issued: 2008
Connection management applications for high-speed audio networking
- Authors: Sibanda, Phathisile
- Date: 2008 , 2008-03-12
- Subjects: Flash (Computer file) , Computer networks , Computer networks -- Management , Digital communications , Computer sound processing , Sound -- Recording and reproducing -- Digital techniques , Broadcast data systems , C# (Computer program language) , C++ (Computer program language) , ActionScript (Computer program language)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4634 , http://hdl.handle.net/10962/d1006532 , Flash (Computer file) , Computer networks , Computer networks -- Management , Digital communications , Computer sound processing , Sound -- Recording and reproducing -- Digital techniques , Broadcast data systems , C# (Computer program language) , C++ (Computer program language) , ActionScript (Computer program language)
- Description: Traditionally, connection management applications (referred to as patchbays) for high-speed audio networking, are predominantly developed using third-generation languages such as C, C# and C++. Due to the rapid increase in distributed audio/video network usage in the world today, connection management applications that control signal routing over these networks have also evolved in complexity to accommodate more functionality. As the result, high-speed audio networking application developers require a tool that will enable them to develop complex connection management applications easily and within the shortest possible time. In addition, this tool should provide them with the reliability and flexibility required to develop applications controlling signal routing in networks carrying real-time data. High-speed audio networks are used for various purposes that include audio/video production and broadcasting. This investigation evaluates the possibility of using Adobe Flash Professional 8, using ActionScript 2.0, for developing connection management applications. Three patchbays, namely the Broadcast patchbay, the Project studio patchbay, and the Hospitality/Convention Centre patchbay were developed and tested for connection management in three sound installation networks, namely the Broadcast network, the Project studio network, and the Hospitality/Convention Centre network. Findings indicate that complex connection management applications can effectively be implemented using the Adobe Flash IDE and ActionScript 2.0.
- Full Text:
- Date Issued: 2008
- Authors: Sibanda, Phathisile
- Date: 2008 , 2008-03-12
- Subjects: Flash (Computer file) , Computer networks , Computer networks -- Management , Digital communications , Computer sound processing , Sound -- Recording and reproducing -- Digital techniques , Broadcast data systems , C# (Computer program language) , C++ (Computer program language) , ActionScript (Computer program language)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4634 , http://hdl.handle.net/10962/d1006532 , Flash (Computer file) , Computer networks , Computer networks -- Management , Digital communications , Computer sound processing , Sound -- Recording and reproducing -- Digital techniques , Broadcast data systems , C# (Computer program language) , C++ (Computer program language) , ActionScript (Computer program language)
- Description: Traditionally, connection management applications (referred to as patchbays) for high-speed audio networking, are predominantly developed using third-generation languages such as C, C# and C++. Due to the rapid increase in distributed audio/video network usage in the world today, connection management applications that control signal routing over these networks have also evolved in complexity to accommodate more functionality. As the result, high-speed audio networking application developers require a tool that will enable them to develop complex connection management applications easily and within the shortest possible time. In addition, this tool should provide them with the reliability and flexibility required to develop applications controlling signal routing in networks carrying real-time data. High-speed audio networks are used for various purposes that include audio/video production and broadcasting. This investigation evaluates the possibility of using Adobe Flash Professional 8, using ActionScript 2.0, for developing connection management applications. Three patchbays, namely the Broadcast patchbay, the Project studio patchbay, and the Hospitality/Convention Centre patchbay were developed and tested for connection management in three sound installation networks, namely the Broadcast network, the Project studio network, and the Hospitality/Convention Centre network. Findings indicate that complex connection management applications can effectively be implemented using the Adobe Flash IDE and ActionScript 2.0.
- Full Text:
- Date Issued: 2008
Contextual obstacles to the delivery of effective psychological treatment of PTSD in a South African community setting
- Authors: Swartz, Kerry
- Date: 2008
- Subjects: Post-traumatic stress disorder -- Treatment -- South Africa Rape victims -- Counseling of -- South Africa Psychic trauma -- Treatment HIV infections -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3068 , http://hdl.handle.net/10962/d1002577
- Description: The present study presents three individual cases; all three clients had endured a traumatic event, namely rape, and all three met the criteria for PTSD. Despite the fact that each of the clients was initially assessed as being a suitable candidate for psychological treatment, none of the cases proceeded to the therapy phase of treatment. A number of obstacles, both personal and contextual, were encountered during treatment implementation, preventing or limiting a successful outcome of psychological treatment in each case. An examination of these cases highlights a few of the many obstacles frequently faced when delivering psychological treatment to the South African context. In so doing, this research provides an opportunity to consider the possible reasons for the limited documentation of treatment efficacy within the South African context, as well as to enhance our understanding of and sensitivity towards the cultural and contextual factors playing a role in psychological treatment.
- Full Text:
- Date Issued: 2008
- Authors: Swartz, Kerry
- Date: 2008
- Subjects: Post-traumatic stress disorder -- Treatment -- South Africa Rape victims -- Counseling of -- South Africa Psychic trauma -- Treatment HIV infections -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3068 , http://hdl.handle.net/10962/d1002577
- Description: The present study presents three individual cases; all three clients had endured a traumatic event, namely rape, and all three met the criteria for PTSD. Despite the fact that each of the clients was initially assessed as being a suitable candidate for psychological treatment, none of the cases proceeded to the therapy phase of treatment. A number of obstacles, both personal and contextual, were encountered during treatment implementation, preventing or limiting a successful outcome of psychological treatment in each case. An examination of these cases highlights a few of the many obstacles frequently faced when delivering psychological treatment to the South African context. In so doing, this research provides an opportunity to consider the possible reasons for the limited documentation of treatment efficacy within the South African context, as well as to enhance our understanding of and sensitivity towards the cultural and contextual factors playing a role in psychological treatment.
- Full Text:
- Date Issued: 2008
Corporeal identification in selected works by Berni Searle
- Authors: Taggart, Emma
- Date: 2008
- Subjects: Searle, Berni Lacan, Jacques, 1901-1981 -- Criticism and interpretation Merleau-Ponty, Maurice, 1908-1961 -- Criticism and interpretation Women artists -- South Africa Body art -- South Africa Self-portraits
- Language: English
- Type: Thesis , Masters , MFA
- Identifier: vital:2434 , http://hdl.handle.net/10962/d1004576
- Description: Through a detailed analysis of a selection of works produced between 1999 and 2003 by the South African artist Berni Searle, this thesis explores the need to theorise a corporeal viewer in the process of interpreting art works. Such an approach is particularly necessary when dealing with an artist such as Searle because her work, which deals predominantly with the theme of identity, appeals not only to conceptual but also to experiential and corporeal understandings of identity. Searle incorporates the viewer into an experience of her own identity through a physical identification that the viewer feels in relation to her work. For viewers this means that they are made aware of how their own identity in the moment of interpretation is contingent on visual, mental and physical components. In order to develop this argument the work of psychoanalyst Jacques Lacan and the phenomenologist Maurice Merleau-Ponty is drawn on. These two theorists are very useful for an argument of this nature because both interpret identity as a construction involving an enfolding between the mind and, via the act of vision, the body of the subject. Through an inclusion of the corporeal element in interpretation, this thesis also offers a critique of interpretive theories that would reduce analysis to an interaction between eye and mind by analyzing how the viewer's body participates in the act of looking.
- Full Text:
- Date Issued: 2008
- Authors: Taggart, Emma
- Date: 2008
- Subjects: Searle, Berni Lacan, Jacques, 1901-1981 -- Criticism and interpretation Merleau-Ponty, Maurice, 1908-1961 -- Criticism and interpretation Women artists -- South Africa Body art -- South Africa Self-portraits
- Language: English
- Type: Thesis , Masters , MFA
- Identifier: vital:2434 , http://hdl.handle.net/10962/d1004576
- Description: Through a detailed analysis of a selection of works produced between 1999 and 2003 by the South African artist Berni Searle, this thesis explores the need to theorise a corporeal viewer in the process of interpreting art works. Such an approach is particularly necessary when dealing with an artist such as Searle because her work, which deals predominantly with the theme of identity, appeals not only to conceptual but also to experiential and corporeal understandings of identity. Searle incorporates the viewer into an experience of her own identity through a physical identification that the viewer feels in relation to her work. For viewers this means that they are made aware of how their own identity in the moment of interpretation is contingent on visual, mental and physical components. In order to develop this argument the work of psychoanalyst Jacques Lacan and the phenomenologist Maurice Merleau-Ponty is drawn on. These two theorists are very useful for an argument of this nature because both interpret identity as a construction involving an enfolding between the mind and, via the act of vision, the body of the subject. Through an inclusion of the corporeal element in interpretation, this thesis also offers a critique of interpretive theories that would reduce analysis to an interaction between eye and mind by analyzing how the viewer's body participates in the act of looking.
- Full Text:
- Date Issued: 2008
Corporeal tales : an investigation into narrative form in contemporary South African dance and choreography
- Authors: Parker, Alan Charles
- Date: 2008
- Subjects: Sichel, Adrienne Krouse, Matthew Dance -- South Africa Choreography -- South Africa Choreographers -- South Africa Dance criticism -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2157 , http://hdl.handle.net/10962/d1007658
- Description: In the years following the fall of Apartheid in South Africa, dance and choreography have undergone considerable transformation. This investigation stems from one observation relative to this change that has been articulated by two of South Africa's most respected dance critics, Adrienne Sichel and Matthew Krouse. Both critics have noted a growing concern for narrative in South African contemporary choreography, coupled with an apparent propensity for narratives of a distinctly personal and 'autobiographical' nature. In Part One: 'Just after the beginning', the proposed preoccupation with narrative in South African contemporary choreography is discussed in light of the relationship between narrative and the notion of personal identity. The use of the performed narrative as a medium to explore questions about identity is offered as one explanation underpinning this increased proclivity, where the interrogation of the form of the danced narrative provides a site for exploration of personal identity. Part Two: 'Somewhere in the middle' interrogates the notion of form through an in-depth discussion of the experimentation with form within theatrical and antitheatrical dance traditions over the last fifty years. Specific works by three selected South African choreographers (Ginslov, Maqoma and Sabbagha) are discussed in terms of their general approach to narrative form. This provides an illustration of some of the approaches to narrative form emergent in contemporary South African choreographic practices. Part Three: 'Nearing the end' offers Acty Tang's Chaste (2007) as a case study to illustrate the practical application of the dance narrative as a means to interrogate questions relating to personal identity. A detailed analysis of Tang's particular approach to forming the narrative of Chaste is conducted, exposing the intertextual, multimedia and multidisciplinary approach to creating the danced narrative.
- Full Text:
- Date Issued: 2008
- Authors: Parker, Alan Charles
- Date: 2008
- Subjects: Sichel, Adrienne Krouse, Matthew Dance -- South Africa Choreography -- South Africa Choreographers -- South Africa Dance criticism -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2157 , http://hdl.handle.net/10962/d1007658
- Description: In the years following the fall of Apartheid in South Africa, dance and choreography have undergone considerable transformation. This investigation stems from one observation relative to this change that has been articulated by two of South Africa's most respected dance critics, Adrienne Sichel and Matthew Krouse. Both critics have noted a growing concern for narrative in South African contemporary choreography, coupled with an apparent propensity for narratives of a distinctly personal and 'autobiographical' nature. In Part One: 'Just after the beginning', the proposed preoccupation with narrative in South African contemporary choreography is discussed in light of the relationship between narrative and the notion of personal identity. The use of the performed narrative as a medium to explore questions about identity is offered as one explanation underpinning this increased proclivity, where the interrogation of the form of the danced narrative provides a site for exploration of personal identity. Part Two: 'Somewhere in the middle' interrogates the notion of form through an in-depth discussion of the experimentation with form within theatrical and antitheatrical dance traditions over the last fifty years. Specific works by three selected South African choreographers (Ginslov, Maqoma and Sabbagha) are discussed in terms of their general approach to narrative form. This provides an illustration of some of the approaches to narrative form emergent in contemporary South African choreographic practices. Part Three: 'Nearing the end' offers Acty Tang's Chaste (2007) as a case study to illustrate the practical application of the dance narrative as a means to interrogate questions relating to personal identity. A detailed analysis of Tang's particular approach to forming the narrative of Chaste is conducted, exposing the intertextual, multimedia and multidisciplinary approach to creating the danced narrative.
- Full Text:
- Date Issued: 2008
Cranial ontogeny of the sole, dagetichthys marginatus (soleidae), with considerations on the feeding ability of larvae and early juveniles
- Ende, Stephan Siegfried Werner
- Authors: Ende, Stephan Siegfried Werner
- Date: 2008
- Subjects: Soleidae , Fishes -- Larvae -- Food , Flatfishes -- Nutrition , Artemia
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5250 , http://hdl.handle.net/10962/d1005093 , Soleidae , Fishes -- Larvae -- Food , Flatfishes -- Nutrition , Artemia
- Description: The overall aim of this study was to gain a better understanding of the feeding mechanisms of the larvae and early juveniles of the sole, Dagetichthys marginatus (Soleidae), with which to assess the suitability of current feeding protocols and to facilitate the development of an appropriate pelleted feed. This was achieved by examining the ontogeny of the cranium of laboratory reared sole, with particular emphasis on those elements associated with feeding and by comparing the cranium of juvenile fish with that of adult fish. At 4 dah (days after hatch) Dagetichthys marginatus larvae develop the first rudimentary branchial arches that facilitates the capture and ingestion of food items. Subsequent development of cranial structures, such as the oral jaws, suspensorium, neurocranium, hyoid and branchial arches and the opercular apparatus enables the larvae, at 16 dah, to switch from ram feeding to suction feeding on live prey. The use of live Artemia nauplii from 4 to 16 dah is therefore appropriate. The first morphological asymmetries developed at 16 dah in the dentaries and at 22 dah the maxillae and the premaxillae began to show asymmetries. Teeth were present only on the blind side of the oral jaw elements and during this period (16 to 22 dah) the existing elements began to ossify. From 16 to 35 dah the standard feeding protocol consists of a combination of pelagic (Artemia metanauplii) and benthic prey (dead, frozen Artemia nauplii) and from 25 dah onwards a sinking pellet is provided. The time (dah) at which frozen Artemia and sinking pellets were provided, appropriately corresponded to the initiation of benthic feeding behaviour. However at this stage the use of pelagic Artemia metanauplii is inappropriate and unnecessary. At 31 dah the cranial morphology resembled that of adult fish. Adult D. marginatus display extreme asymmetries among the elements of the oral jaws, the suspensorium and certain elements of the neurocranium. Elements on the blind side are larger and more robust than those on the ocular side and are adapted for feeding, while those on the ocular side appear to have a respiratory function. From 31 dah the cranial elements are identical to those of adult fish, suggesting that no further feeding behavioural changes occurred and that a sinking pellet, of which the nutrient composition meets the requirements of the fish, would be appropriate for ongrowing.
- Full Text:
- Date Issued: 2008
- Authors: Ende, Stephan Siegfried Werner
- Date: 2008
- Subjects: Soleidae , Fishes -- Larvae -- Food , Flatfishes -- Nutrition , Artemia
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5250 , http://hdl.handle.net/10962/d1005093 , Soleidae , Fishes -- Larvae -- Food , Flatfishes -- Nutrition , Artemia
- Description: The overall aim of this study was to gain a better understanding of the feeding mechanisms of the larvae and early juveniles of the sole, Dagetichthys marginatus (Soleidae), with which to assess the suitability of current feeding protocols and to facilitate the development of an appropriate pelleted feed. This was achieved by examining the ontogeny of the cranium of laboratory reared sole, with particular emphasis on those elements associated with feeding and by comparing the cranium of juvenile fish with that of adult fish. At 4 dah (days after hatch) Dagetichthys marginatus larvae develop the first rudimentary branchial arches that facilitates the capture and ingestion of food items. Subsequent development of cranial structures, such as the oral jaws, suspensorium, neurocranium, hyoid and branchial arches and the opercular apparatus enables the larvae, at 16 dah, to switch from ram feeding to suction feeding on live prey. The use of live Artemia nauplii from 4 to 16 dah is therefore appropriate. The first morphological asymmetries developed at 16 dah in the dentaries and at 22 dah the maxillae and the premaxillae began to show asymmetries. Teeth were present only on the blind side of the oral jaw elements and during this period (16 to 22 dah) the existing elements began to ossify. From 16 to 35 dah the standard feeding protocol consists of a combination of pelagic (Artemia metanauplii) and benthic prey (dead, frozen Artemia nauplii) and from 25 dah onwards a sinking pellet is provided. The time (dah) at which frozen Artemia and sinking pellets were provided, appropriately corresponded to the initiation of benthic feeding behaviour. However at this stage the use of pelagic Artemia metanauplii is inappropriate and unnecessary. At 31 dah the cranial morphology resembled that of adult fish. Adult D. marginatus display extreme asymmetries among the elements of the oral jaws, the suspensorium and certain elements of the neurocranium. Elements on the blind side are larger and more robust than those on the ocular side and are adapted for feeding, while those on the ocular side appear to have a respiratory function. From 31 dah the cranial elements are identical to those of adult fish, suggesting that no further feeding behavioural changes occurred and that a sinking pellet, of which the nutrient composition meets the requirements of the fish, would be appropriate for ongrowing.
- Full Text:
- Date Issued: 2008
Cross-cultural normative indicators on the Wechsler Memory Scale (WMS) associate learning and visual reproduction subtests
- Authors: Fike, Lauren
- Date: 2008
- Subjects: Wechsler Memory Scale -- Cross-cultural studies Memory -- Testing Memory -- Cross-cultural studies Memory Assessment Scales Short-term memory -- Testing Long-term memory -- Testing
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2975 , http://hdl.handle.net/10962/d1002484
- Description: A comprehensive battery of commonly used neuropsychological tests, including the WMS Associate Learning and Visual Reproduction subtests, forming the focus of this study, were administered to a southern African sample (n = 33, age range 18-40). This sample composed of black South African, IsiXhosa speakers with an educational level of Grade 11 and 12, derived through DET and former DET schooling. The gender demographics were as follows; females n = 21 and males n = 12. This sample was purposefully selected based on current cross-cultural research which suggests that individuals matching these above-mentioned demographics are significantly disadvantaged when compared to available neuropsychological norms. This is due to the fact that current norms have been created in contexts with socio-cultural influences; including culture, language and quantity and quality of education distinctly dissimilar to individuals like that composed in the sample. Hence the purpose of this study was fourfold namely; 1) Describe and consider socio-cultural factors and the influence on test performance 2) Provide descriptive and preliminary normative data on this neuropsychologically underrepresented population 3) Compare test performance between age and gender through stratification of the sample and finally to 4) Evaluate the current norms of the two WMS subtests and assess their validity for black South Africans with DET and former DET schooling with comparisons to the results found in the study. Information derived from the statistical analyses indicated that a higher performance in favour of the younger group over the older age range was consistently found for both WMS subtests. With regards to gender, some higher means were evident for the male population in the sample than was produced by the female group. Lastly, due to the fact that most scores derived from the sample were considerably lower when compared to the available norms, it is felt that socio-cultural factors prevalent to this population are a significant cause of lower test performance and thus warrant the development of appropriate normative indicators.
- Full Text:
- Date Issued: 2008
- Authors: Fike, Lauren
- Date: 2008
- Subjects: Wechsler Memory Scale -- Cross-cultural studies Memory -- Testing Memory -- Cross-cultural studies Memory Assessment Scales Short-term memory -- Testing Long-term memory -- Testing
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2975 , http://hdl.handle.net/10962/d1002484
- Description: A comprehensive battery of commonly used neuropsychological tests, including the WMS Associate Learning and Visual Reproduction subtests, forming the focus of this study, were administered to a southern African sample (n = 33, age range 18-40). This sample composed of black South African, IsiXhosa speakers with an educational level of Grade 11 and 12, derived through DET and former DET schooling. The gender demographics were as follows; females n = 21 and males n = 12. This sample was purposefully selected based on current cross-cultural research which suggests that individuals matching these above-mentioned demographics are significantly disadvantaged when compared to available neuropsychological norms. This is due to the fact that current norms have been created in contexts with socio-cultural influences; including culture, language and quantity and quality of education distinctly dissimilar to individuals like that composed in the sample. Hence the purpose of this study was fourfold namely; 1) Describe and consider socio-cultural factors and the influence on test performance 2) Provide descriptive and preliminary normative data on this neuropsychologically underrepresented population 3) Compare test performance between age and gender through stratification of the sample and finally to 4) Evaluate the current norms of the two WMS subtests and assess their validity for black South Africans with DET and former DET schooling with comparisons to the results found in the study. Information derived from the statistical analyses indicated that a higher performance in favour of the younger group over the older age range was consistently found for both WMS subtests. With regards to gender, some higher means were evident for the male population in the sample than was produced by the female group. Lastly, due to the fact that most scores derived from the sample were considerably lower when compared to the available norms, it is felt that socio-cultural factors prevalent to this population are a significant cause of lower test performance and thus warrant the development of appropriate normative indicators.
- Full Text:
- Date Issued: 2008
Curriculum recontextualising using gardens for the health promotion in the life orientation learning area of the senior phase
- Authors: Jenkins, Msawenkosi Wiseman
- Date: 2008
- Subjects: Environmental education -- South Africa -- Eastern Cape -- Case studies School gardens -- South Africa -- Eastern Cape Gardening -- Study and teaching (Secondary) -- South Africa -- Eastern Cape Environmental education -- Curricula -- South Africa -- Eastern Cape Environmental education -- Curricula -- Case studies Environmental policy -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1487 , http://hdl.handle.net/10962/d1003368
- Description: With a view to understanding how curriculum is interpreted at classroom practice level, the study examined three stories of how the environmental discourse of the National Curriculum Statements (R-9) was recontextualised using school gardens in the Life Orientation Learning Area for the Senior Phase. To understand how the curriculum is recontextualised, I used Bernstein's theory of recontexutalisation where he explained how official pedagogic discourse (OPD) (in this case the environmental discourse is first delocated once it is transferred from the field of production (FOP) and relocated in the recontextualising field (where teacher educators and departmental officials mediate the discourse) and in the field of reproduction (FOR) which is the classroom and school. Bernstein explained that as the discourse is delocated and relocated it undergoes transformation. This transformation is influenced by practitioners' prior-knowledge, experience, culture and beliefs and other factors. To understand how transformation of the environmental discourse takes place, Bernstein's conceptual constructs of selective appropriation and ideological transformation were applied to an interpretation of three lesson processes, to explain how the discourse was changed. Each lesson was reviewed in terms of the selective appropriations and ideological transformations which took place. All three of the lessons observed took place in one school, and as such the study is designed as an interpretive case study where I have tried to make meaning from a rich, thick description of a specific case context. The school is located in Bizana, one of the villages in the O.R. Tambo District Municipality in the Eastern Cape Province,, and is currently in the process of implementing South Africa’s new National Curriculum Statement (NCS) like all other schools in South Africa. In conducting the research I observed lessons, interviewed the learners and teachers, and a community member and the manager of the SANBI greening project, and I also analysed documents which included the NCS for Life Orientation, and teachers planning documents and learners work produced in the lessons. I started the study by conducting a document analysis of the NCS, through which I identified dimensions of the Official Pedagogic Discourse. This was used as a framework to review the lessons to understand how the OPD was being recontextualised. The study concludes by discussing the key findings of the study in the form of a set of analytical statements. Some of the findings indicate that teachers have not been given adequate training for understanding and implementing the NCS which affects the recontextualisation process. The study shows that there is a dire need for professional development if the OPD is to be interpreted adequately by teachers so that its implementation at the meso and micro- levels becomes clear and effective.
- Full Text:
- Date Issued: 2008
- Authors: Jenkins, Msawenkosi Wiseman
- Date: 2008
- Subjects: Environmental education -- South Africa -- Eastern Cape -- Case studies School gardens -- South Africa -- Eastern Cape Gardening -- Study and teaching (Secondary) -- South Africa -- Eastern Cape Environmental education -- Curricula -- South Africa -- Eastern Cape Environmental education -- Curricula -- Case studies Environmental policy -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1487 , http://hdl.handle.net/10962/d1003368
- Description: With a view to understanding how curriculum is interpreted at classroom practice level, the study examined three stories of how the environmental discourse of the National Curriculum Statements (R-9) was recontextualised using school gardens in the Life Orientation Learning Area for the Senior Phase. To understand how the curriculum is recontextualised, I used Bernstein's theory of recontexutalisation where he explained how official pedagogic discourse (OPD) (in this case the environmental discourse is first delocated once it is transferred from the field of production (FOP) and relocated in the recontextualising field (where teacher educators and departmental officials mediate the discourse) and in the field of reproduction (FOR) which is the classroom and school. Bernstein explained that as the discourse is delocated and relocated it undergoes transformation. This transformation is influenced by practitioners' prior-knowledge, experience, culture and beliefs and other factors. To understand how transformation of the environmental discourse takes place, Bernstein's conceptual constructs of selective appropriation and ideological transformation were applied to an interpretation of three lesson processes, to explain how the discourse was changed. Each lesson was reviewed in terms of the selective appropriations and ideological transformations which took place. All three of the lessons observed took place in one school, and as such the study is designed as an interpretive case study where I have tried to make meaning from a rich, thick description of a specific case context. The school is located in Bizana, one of the villages in the O.R. Tambo District Municipality in the Eastern Cape Province,, and is currently in the process of implementing South Africa’s new National Curriculum Statement (NCS) like all other schools in South Africa. In conducting the research I observed lessons, interviewed the learners and teachers, and a community member and the manager of the SANBI greening project, and I also analysed documents which included the NCS for Life Orientation, and teachers planning documents and learners work produced in the lessons. I started the study by conducting a document analysis of the NCS, through which I identified dimensions of the Official Pedagogic Discourse. This was used as a framework to review the lessons to understand how the OPD was being recontextualised. The study concludes by discussing the key findings of the study in the form of a set of analytical statements. Some of the findings indicate that teachers have not been given adequate training for understanding and implementing the NCS which affects the recontextualisation process. The study shows that there is a dire need for professional development if the OPD is to be interpreted adequately by teachers so that its implementation at the meso and micro- levels becomes clear and effective.
- Full Text:
- Date Issued: 2008
Designing and implementing a new pulsar timer for the Hartebeesthoek Radio Astronomy Observatory
- Authors: Youthed, Andrew David
- Date: 2008
- Subjects: Astronomical observatories , Radio astronomy , Pulsars , Astronomical instruments , Reduced instruction set computers , Random access memory
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5458 , http://hdl.handle.net/10962/d1005243 , Astronomical observatories , Radio astronomy , Pulsars , Astronomical instruments , Reduced instruction set computers , Random access memory
- Description: This thesis outlines the design and implementation of a single channel, dual polarization pulsar timing instrument for the Hartebeesthoek Radio Astronomy Observatory (HartRAO). The new timer is designed to be an improved, temporary replacement for the existing device which has been in operation for over 20 years. The existing device is no longer reliable and is di±cult to maintain. The new pulsar timer is designed to provide improved functional- ity, higher sampling speed, greater pulse resolution, more °exibility and easier maintenance over the existing device. The new device is also designed to keeping changes to the observation system to a minimum until a full de-dispersion timer can be implemented at theobservatory. The design makes use of an 8-bit Reduced Instruction Set Computer (RISC) micro-processor with external Random Access Memory (RAM). The instrument includes an IEEE-488 subsystem for interfacing the pulsar timer to the observation computer system. The microcontroller software is written in assembler code to ensure optimal loop execution speed and deterministic code execution for the system. The design path is discussed and problems encountered during the design process are highlighted. Final testing of the new instrument indicates an improvement in the sam- pling rate of 13.6 times and a significant reduction in 60Hz interference over the existing instrument.
- Full Text:
- Date Issued: 2008
- Authors: Youthed, Andrew David
- Date: 2008
- Subjects: Astronomical observatories , Radio astronomy , Pulsars , Astronomical instruments , Reduced instruction set computers , Random access memory
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5458 , http://hdl.handle.net/10962/d1005243 , Astronomical observatories , Radio astronomy , Pulsars , Astronomical instruments , Reduced instruction set computers , Random access memory
- Description: This thesis outlines the design and implementation of a single channel, dual polarization pulsar timing instrument for the Hartebeesthoek Radio Astronomy Observatory (HartRAO). The new timer is designed to be an improved, temporary replacement for the existing device which has been in operation for over 20 years. The existing device is no longer reliable and is di±cult to maintain. The new pulsar timer is designed to provide improved functional- ity, higher sampling speed, greater pulse resolution, more °exibility and easier maintenance over the existing device. The new device is also designed to keeping changes to the observation system to a minimum until a full de-dispersion timer can be implemented at theobservatory. The design makes use of an 8-bit Reduced Instruction Set Computer (RISC) micro-processor with external Random Access Memory (RAM). The instrument includes an IEEE-488 subsystem for interfacing the pulsar timer to the observation computer system. The microcontroller software is written in assembler code to ensure optimal loop execution speed and deterministic code execution for the system. The design path is discussed and problems encountered during the design process are highlighted. Final testing of the new instrument indicates an improvement in the sam- pling rate of 13.6 times and a significant reduction in 60Hz interference over the existing instrument.
- Full Text:
- Date Issued: 2008
Development of a novel in situ CPRG-based biosensor and bioprobe for monitoring coliform β-D-Galactosidase in water polluted by faecal matter
- Authors: Wutor, Victor Collins
- Date: 2008
- Subjects: Biosensors Molecular probes Enterobacteriaceae Feces -- Microbiology Water -- Pollution -- Environmental aspects Environmental monitoring Chromogenic compounds
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3944 , http://hdl.handle.net/10962/d1004003
- Description: The ultimate objective of this work was to develop a real-time method for detecting and monitoring β-D-galactosidase as a suitable indicator of the potential presence of total coliform bacteria in water environments. Preliminary comparison of the chromogenic substrate, chlorophenol red β-D-galactopyranoside and the fluorogenic substrate, MuGAL, revealed unreliable results with the fluorogenic technique due to interference from compounds commonly found in environmental water samples. Thus, the chromogenic assay was further explored. Hydrolysis of the chromogenic substrate chlorophenol red β-D-galactopyranoside by β-D-galactosidase to yield chlorophenol red was the basis of this assay. Fundamental studies with chlorophenol red β-Dgalactopyranoside showed that β-D-galactosidase occurs extracellularly and in low concentrations in the polluted water environment. A direct correlation between enzyme activity and an increase in environmental water sample volume, as well as enzyme activity with total coliform colony forming unit counts were observed. Spectrophotometric detection was achieved within a maximum period of 24 h with a limit of detection level of 1 colony forming unit 100 ml[superscript -1]. This enzyme also exhibited physical and kinetic properties different from those of the pure commercially available β-D-galactosidase. Cell permeabilisation was not required for releasing enzymes into the extracellular environment. PEG 20 000 offered the best option for concentrating β-D-galactosidase. The source of β-D-galactosidase in the polluted environmental water samples was confirmed as Escherichia coli through SDS-PAGE, tryptic mapping and MALDI-TOF, thus justifying the further use of this method for detecting and/or monitoring total coliforms. Several compounds and metal ions commonly found in environmental water samples (as well as those used in water treatment processes) did have an effect on β-D-galactosidase. All the divalent cations except Mg [superscript 2+], at the concentrations studied, inhibited the relative activity of β-D-galactosidase in both commercial β-D-galactosidase and environmental samples. Immobilisation of chlorophenol red β-D-galactopyranoside onto a solid support material for the development of a strip bioprobe was unsuccessful, even though the nylon support material yielded some positive results. A monthly (seasonal) variation in β-Dgalactosidase activity from the environmental water samples was observed, with the highest activity coinciding with the highest monthly temperatures. Electro-oxidative detection and/or monitoring of chlorophenol red was possible. Chlorophenol red detection was linear over a wide range of concentrations (0.001-0.01 μg ml[superscript -1]). Interference by chlorophenol red β-D-galactopyranoside in the reduction window affected analysis. A range of phthalocyanine metal complexes were studied in an attempt to reduce fouling and/or increase the sensitivity of the biosensor. The selected phthalocyanine metal complexes were generally sensitive to changes in pH with a reduction in sensitivity from acidic pH to alkaline pH. The tetrasulphonated phthalocyanine metal complex of copper was, however, more stable with a minimum change of sensitivity. The phthalocyanine metal complexes were generally stable to changes in temperature. While only two consecutive scans were possible with the unmodified glassy carbon electrode, 77 consecutive scans were performed successfully with the CuPc-modified glassy carbon electrode. Among the phthalocyanine metal complexes studied, the CuPc-modified glassy carbon electrode therefore provided excellent results for the development of a biosensor. The CuPc modified-glassy carbon electrode detected 1 colony forming unit 100 ml[superscript -1] in 15 minutes, while the plain unmodified glassy carbon electrode required 6 hours to detect the equivalent number of colony forming units. CoPc, ZnPc and CuTSPc required 2, 2.25 and 1.75 h, respectively, to detect the same numbers of colony forming units. The CuPcmodified glassy carbon electrode detected 40 colony forming units 100 ml[superscript -1] instantly. In general, a direct correlation between colony forming units and current generated in the sensor was observed (R2=0.92). A higher correlation coefficient of 0.99 for 0-30 coliform colony forming units 100 ml[superscript -1] was determined. Current was detected in some water samples which did not show any colony forming units on the media, probably due to the phenomenon of viable but non-culturable bacteria, which is the major disadvantage encountered in the use of media for detecting indicator microorganisms. This novel biosensor therefore presents a very robust and sensitive technique for the detection and/or monitoring of coliform bacterial activity in water.
- Full Text:
- Date Issued: 2008
- Authors: Wutor, Victor Collins
- Date: 2008
- Subjects: Biosensors Molecular probes Enterobacteriaceae Feces -- Microbiology Water -- Pollution -- Environmental aspects Environmental monitoring Chromogenic compounds
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3944 , http://hdl.handle.net/10962/d1004003
- Description: The ultimate objective of this work was to develop a real-time method for detecting and monitoring β-D-galactosidase as a suitable indicator of the potential presence of total coliform bacteria in water environments. Preliminary comparison of the chromogenic substrate, chlorophenol red β-D-galactopyranoside and the fluorogenic substrate, MuGAL, revealed unreliable results with the fluorogenic technique due to interference from compounds commonly found in environmental water samples. Thus, the chromogenic assay was further explored. Hydrolysis of the chromogenic substrate chlorophenol red β-D-galactopyranoside by β-D-galactosidase to yield chlorophenol red was the basis of this assay. Fundamental studies with chlorophenol red β-Dgalactopyranoside showed that β-D-galactosidase occurs extracellularly and in low concentrations in the polluted water environment. A direct correlation between enzyme activity and an increase in environmental water sample volume, as well as enzyme activity with total coliform colony forming unit counts were observed. Spectrophotometric detection was achieved within a maximum period of 24 h with a limit of detection level of 1 colony forming unit 100 ml[superscript -1]. This enzyme also exhibited physical and kinetic properties different from those of the pure commercially available β-D-galactosidase. Cell permeabilisation was not required for releasing enzymes into the extracellular environment. PEG 20 000 offered the best option for concentrating β-D-galactosidase. The source of β-D-galactosidase in the polluted environmental water samples was confirmed as Escherichia coli through SDS-PAGE, tryptic mapping and MALDI-TOF, thus justifying the further use of this method for detecting and/or monitoring total coliforms. Several compounds and metal ions commonly found in environmental water samples (as well as those used in water treatment processes) did have an effect on β-D-galactosidase. All the divalent cations except Mg [superscript 2+], at the concentrations studied, inhibited the relative activity of β-D-galactosidase in both commercial β-D-galactosidase and environmental samples. Immobilisation of chlorophenol red β-D-galactopyranoside onto a solid support material for the development of a strip bioprobe was unsuccessful, even though the nylon support material yielded some positive results. A monthly (seasonal) variation in β-Dgalactosidase activity from the environmental water samples was observed, with the highest activity coinciding with the highest monthly temperatures. Electro-oxidative detection and/or monitoring of chlorophenol red was possible. Chlorophenol red detection was linear over a wide range of concentrations (0.001-0.01 μg ml[superscript -1]). Interference by chlorophenol red β-D-galactopyranoside in the reduction window affected analysis. A range of phthalocyanine metal complexes were studied in an attempt to reduce fouling and/or increase the sensitivity of the biosensor. The selected phthalocyanine metal complexes were generally sensitive to changes in pH with a reduction in sensitivity from acidic pH to alkaline pH. The tetrasulphonated phthalocyanine metal complex of copper was, however, more stable with a minimum change of sensitivity. The phthalocyanine metal complexes were generally stable to changes in temperature. While only two consecutive scans were possible with the unmodified glassy carbon electrode, 77 consecutive scans were performed successfully with the CuPc-modified glassy carbon electrode. Among the phthalocyanine metal complexes studied, the CuPc-modified glassy carbon electrode therefore provided excellent results for the development of a biosensor. The CuPc modified-glassy carbon electrode detected 1 colony forming unit 100 ml[superscript -1] in 15 minutes, while the plain unmodified glassy carbon electrode required 6 hours to detect the equivalent number of colony forming units. CoPc, ZnPc and CuTSPc required 2, 2.25 and 1.75 h, respectively, to detect the same numbers of colony forming units. The CuPcmodified glassy carbon electrode detected 40 colony forming units 100 ml[superscript -1] instantly. In general, a direct correlation between colony forming units and current generated in the sensor was observed (R2=0.92). A higher correlation coefficient of 0.99 for 0-30 coliform colony forming units 100 ml[superscript -1] was determined. Current was detected in some water samples which did not show any colony forming units on the media, probably due to the phenomenon of viable but non-culturable bacteria, which is the major disadvantage encountered in the use of media for detecting indicator microorganisms. This novel biosensor therefore presents a very robust and sensitive technique for the detection and/or monitoring of coliform bacterial activity in water.
- Full Text:
- Date Issued: 2008
Drought responses of C3 and C4 (NADP-ME) Panicoid grasses
- Authors: Frole, Kristen Marie
- Date: 2008
- Subjects: Botany -- Research , Grasses -- Physiology -- South Africa , Grasses -- Effect of drought on , Grasses -- Drought tolerance , Plant-water relationships
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4193 , http://hdl.handle.net/10962/d1003762 , Botany -- Research , Grasses -- Physiology -- South Africa , Grasses -- Effect of drought on , Grasses -- Drought tolerance , Plant-water relationships
- Description: The success of C₄ plants lies in their ability to concentrate CO₂ at the site of Rubisco thereby conferring greater efficiencies of light, water and nitrogen. Such characteristics should advantage C₄ plants in arid, hot environments. However, not all C₄ subtypes are drought tolerant. The relative abundance of NADP-ME species declines with increasing aridity. Furthermore, selected species have been demonstrated as being susceptible to severe drought showing metabolic limitations of photosynthesis. However there is a lack of phylogenetic control with many of these studies. The aims of this study were to determine whether the NADP-ME subtype was inherently susceptible to drought by comparing six closely related C₃ and C₄ (NADP-ME) Panicoid grasses. Gas exchange measurements were made during a natural rainless period and a controlled drought / rewatering event. Prior to water stress, the C₄ species had higher assimilation rates (A), and water use efficiencies (WUE[subscript leaf]) than the C₃ species, while transpiration rates (E) and stomatal conductances (g[subscript s]) were similar. At low soil water content, the C₃ species reduced gs by a greater extent than the C₄ species, which maintained higher E during the driest periods. The C₄ species showed proportionally greater reductions in A than the C₃ species and hence lost their WUE[subscript leaf] and photosynthetic advantage. CO₂ response curves showed that metabolic limitation was responsible for a greater decrease in A in the C₄ type than the C₃ type during progressive drought. Upon re-watering, photosynthetic recovery was quicker in the C species than the C₄ species. Results from whole plant measurements showed that the C₄ type had a significant whole plant water use efficiency advantage over the C₃ type under well-watered conditions that was lost during severe drought due to a greater loss of leaf area through leaf mortality rather than reductions in plant level transpiration rates. The C₃ type had xylem characteristics that enhanced water-conducting efficiency, but made them vulnerable to drought. This is in contrast to the safer xylem qualities of the C₄ type, which permitted the endurance of more negative leaf water potentials than the C₃ type during low soil water content. Thus, the vulnerability of photosynthesis to severe drought in NADP-ME species potentially explains why NADP-ME species abundance around the world decreases with decreasing rainfall.
- Full Text:
- Date Issued: 2008
- Authors: Frole, Kristen Marie
- Date: 2008
- Subjects: Botany -- Research , Grasses -- Physiology -- South Africa , Grasses -- Effect of drought on , Grasses -- Drought tolerance , Plant-water relationships
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4193 , http://hdl.handle.net/10962/d1003762 , Botany -- Research , Grasses -- Physiology -- South Africa , Grasses -- Effect of drought on , Grasses -- Drought tolerance , Plant-water relationships
- Description: The success of C₄ plants lies in their ability to concentrate CO₂ at the site of Rubisco thereby conferring greater efficiencies of light, water and nitrogen. Such characteristics should advantage C₄ plants in arid, hot environments. However, not all C₄ subtypes are drought tolerant. The relative abundance of NADP-ME species declines with increasing aridity. Furthermore, selected species have been demonstrated as being susceptible to severe drought showing metabolic limitations of photosynthesis. However there is a lack of phylogenetic control with many of these studies. The aims of this study were to determine whether the NADP-ME subtype was inherently susceptible to drought by comparing six closely related C₃ and C₄ (NADP-ME) Panicoid grasses. Gas exchange measurements were made during a natural rainless period and a controlled drought / rewatering event. Prior to water stress, the C₄ species had higher assimilation rates (A), and water use efficiencies (WUE[subscript leaf]) than the C₃ species, while transpiration rates (E) and stomatal conductances (g[subscript s]) were similar. At low soil water content, the C₃ species reduced gs by a greater extent than the C₄ species, which maintained higher E during the driest periods. The C₄ species showed proportionally greater reductions in A than the C₃ species and hence lost their WUE[subscript leaf] and photosynthetic advantage. CO₂ response curves showed that metabolic limitation was responsible for a greater decrease in A in the C₄ type than the C₃ type during progressive drought. Upon re-watering, photosynthetic recovery was quicker in the C species than the C₄ species. Results from whole plant measurements showed that the C₄ type had a significant whole plant water use efficiency advantage over the C₃ type under well-watered conditions that was lost during severe drought due to a greater loss of leaf area through leaf mortality rather than reductions in plant level transpiration rates. The C₃ type had xylem characteristics that enhanced water-conducting efficiency, but made them vulnerable to drought. This is in contrast to the safer xylem qualities of the C₄ type, which permitted the endurance of more negative leaf water potentials than the C₃ type during low soil water content. Thus, the vulnerability of photosynthesis to severe drought in NADP-ME species potentially explains why NADP-ME species abundance around the world decreases with decreasing rainfall.
- Full Text:
- Date Issued: 2008
Ecological role of free-living bacteria in the microbial food web of the temporarily open/closed East Kleinemonde Estuary, South Africa
- Authors: Allan, Elizabeth Louise
- Date: 2008
- Subjects: Bacterial growth -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape , Estuaries -- South Africa -- Eastern Cape , Microbial ecology -- South Africa -- Eastern Cape , Nutrient cycles -- South Africa -- Eastern Cape , Food chains (Ecology)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5666 , http://hdl.handle.net/10962/d1005351 , Bacterial growth -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape , Estuaries -- South Africa -- Eastern Cape , Microbial ecology -- South Africa -- Eastern Cape , Nutrient cycles -- South Africa -- Eastern Cape , Food chains (Ecology)
- Description: The main aim of this study was to assess the “top-down” and “bottom-up” control of bacterial production in the small temporarily open/closed East Kleinemonde Estuary, situated on the south-eastern coastline of southern Africa. Spatial and temporal patterns in bacterial abundance, biomass and production and the importance of abiotic and biotic factors were investigated over the period May 2006 to April 2007. The trophic interactions between bacteria, phytoplankton, nanoflagellates (< 20 μm), microzooplankton (< 200 μm) and mesozooplankton (< 2 000 μm) were investigated during winter and summer. Bacterial abundance, biomass and production ranged between 1.00 × 10⁹ and 4.93 × 10⁹ cells 1⁻¹, 32.4 and 109 μg C 1⁻¹ and 0.01 and 1.99 μg C 1⁻¹ h⁻¹, respectively. With a few exceptions there were no spatial patterns in the values. Bacterial abundance, biomass and production, however, demonstrated a distinct temporal pattern with the lowest values consistently recorded during the winter months. Nanoflagellate and bacterial abundances were significantly correlated to one another (lower reaches: r = 0.818, p < 0.001; middle reaches: r = 0.628, p < 0.001; upper reaches: r = 0.484, p < 0.05) suggesting a strong predator-prey relationship. The frequency of visibly infected bacterial cells and the mean number of virus particles within each bacterial cell during this study demonstrated no temporal or spatial patterns and ranged from 0.5 to 6.1 % and 12.0 to 37.5 virus particles per bacterium, respectively. Viral infection and lysis was thus a constant source of bacterial mortality throughout the year. The estimated percentage of bacterial production removed by viral lysis ranged between 7.8 and 88.9% of the total which suggests that viral lysis represented a very important source of bacterial mortality during this study. The biological interactions between the selected components of the plankton community demonstrated that among the heterotrophic components of the plankton, the nanoflagellates were identified as the most important consumers of bacteria and small phytoplankton cells (< 20 μm). In the presence of microzooplankton the impact of the nanoflagellates on both the bacteria and phytoplankton was reduced, indicating that larger heterotrophs were preying upon the nanoflagellates. Mesozooplankton, however, appeared to exert the greatest impact on nanoflagellates. In the cascading experiments, the data suggest that mesozooplankton consume nanoflagellates, which resulted in a decrease in the predation impact of these organisms on the bacteria. This result is consistent with predator-prey cascades. The presence of the larger heterotrophs therefore, mediates the interactions between the primary bacterivores, the nanoflagellates, and the bacteria within the temporarily open/closed East Kleinemonde Estuary.
- Full Text:
- Date Issued: 2008
- Authors: Allan, Elizabeth Louise
- Date: 2008
- Subjects: Bacterial growth -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape , Estuaries -- South Africa -- Eastern Cape , Microbial ecology -- South Africa -- Eastern Cape , Nutrient cycles -- South Africa -- Eastern Cape , Food chains (Ecology)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5666 , http://hdl.handle.net/10962/d1005351 , Bacterial growth -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape , Estuaries -- South Africa -- Eastern Cape , Microbial ecology -- South Africa -- Eastern Cape , Nutrient cycles -- South Africa -- Eastern Cape , Food chains (Ecology)
- Description: The main aim of this study was to assess the “top-down” and “bottom-up” control of bacterial production in the small temporarily open/closed East Kleinemonde Estuary, situated on the south-eastern coastline of southern Africa. Spatial and temporal patterns in bacterial abundance, biomass and production and the importance of abiotic and biotic factors were investigated over the period May 2006 to April 2007. The trophic interactions between bacteria, phytoplankton, nanoflagellates (< 20 μm), microzooplankton (< 200 μm) and mesozooplankton (< 2 000 μm) were investigated during winter and summer. Bacterial abundance, biomass and production ranged between 1.00 × 10⁹ and 4.93 × 10⁹ cells 1⁻¹, 32.4 and 109 μg C 1⁻¹ and 0.01 and 1.99 μg C 1⁻¹ h⁻¹, respectively. With a few exceptions there were no spatial patterns in the values. Bacterial abundance, biomass and production, however, demonstrated a distinct temporal pattern with the lowest values consistently recorded during the winter months. Nanoflagellate and bacterial abundances were significantly correlated to one another (lower reaches: r = 0.818, p < 0.001; middle reaches: r = 0.628, p < 0.001; upper reaches: r = 0.484, p < 0.05) suggesting a strong predator-prey relationship. The frequency of visibly infected bacterial cells and the mean number of virus particles within each bacterial cell during this study demonstrated no temporal or spatial patterns and ranged from 0.5 to 6.1 % and 12.0 to 37.5 virus particles per bacterium, respectively. Viral infection and lysis was thus a constant source of bacterial mortality throughout the year. The estimated percentage of bacterial production removed by viral lysis ranged between 7.8 and 88.9% of the total which suggests that viral lysis represented a very important source of bacterial mortality during this study. The biological interactions between the selected components of the plankton community demonstrated that among the heterotrophic components of the plankton, the nanoflagellates were identified as the most important consumers of bacteria and small phytoplankton cells (< 20 μm). In the presence of microzooplankton the impact of the nanoflagellates on both the bacteria and phytoplankton was reduced, indicating that larger heterotrophs were preying upon the nanoflagellates. Mesozooplankton, however, appeared to exert the greatest impact on nanoflagellates. In the cascading experiments, the data suggest that mesozooplankton consume nanoflagellates, which resulted in a decrease in the predation impact of these organisms on the bacteria. This result is consistent with predator-prey cascades. The presence of the larger heterotrophs therefore, mediates the interactions between the primary bacterivores, the nanoflagellates, and the bacteria within the temporarily open/closed East Kleinemonde Estuary.
- Full Text:
- Date Issued: 2008
Education in the wetlands and wetlands in the education: a case of contextualizing primary/basic education in Tanzania
- Authors: Hogan, Alice Rosemary
- Date: 2008
- Subjects: Education -- Tanzania Environmental education -- Tanzania Education, Rural -- Tanzania Education -- Curricula -- Tanzania Community and school -- Tanzania
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1504 , http://hdl.handle.net/10962/d1003386
- Description: This dissertation describes an action research case study carried out at a sub-village school at Nyamakurukuru, Utete, Rufiji District, Tanzania. The study was a fully independent research activity funded and led by a female Irish environmental and community specialist who has fifteen years experience of working in rural Tanzania, five of which were in Rufiji District. The aim of the action research was to engage a community of villagers, teachers, students and district officers in a participatory process to adapt a module of a school curriculum to the local context, and teach it in order to describe one way in which contextualization, using local and indigenous knowledge and active discovery teaching-learning processes, can be done. The major research question, which I wished to answer for one specific case, was: Does integrating local environmental cultural knowledge into formal schooling contribute to curriculum relevance? If so, in what way? This document describes the background and context of the research, the motivation and the theoretical basis for the work, the methodology and methods, and the action research process itself. The results are interpreted and discussed in the light of current theoretical perspectives on education and environmental education. The main findings within the case are that: Contextualization improved relevance of education and thus its quality by: • breaking through traditional frames/barriers between teachers and students, students and elders and community and teachers, • allowing formal education to take place outside of the school, • necessitating a change in pedagogy1 to more learner-centered, discovery methods, • allowing indigenous knowledge to come into the classroom, • stimulating creativity and increased confidence, and • bringing local socio-political environmental issues into the classroom. This study provides a case example of how education processes, when engaging local cultural knowledge, can improve the relevance, and thus an aspect of the quality of teaching and learning in school-community contexts, while providing a conduit for integrating environmental education into the formal school curriculum. It provides insights into the key issue of relevance which currently faces educators of children in wetlands in Tanzania. Recommendations were made for the case studied and may be useful beyond the boundaries of the case: • Give more explicit government policy and strategic support for community involvement in educational content–epistemologies and pedagogies. • Weaken framing (hierarchical power positions) to encourage greater partnership between school, home and community to improve relevance. • Investigate the provision of education beyond schools. • Provide practical teacher and community training on use of learner-centered, discovery and active pedagogies. • Provide teacher and community education on biodiversity and the environment. • Provide relevant reference texts and research data on the ecology, biodiversity, vegetation, hydrology, agriculture, sociology, history and other relevant subjects. • Officially nurture a culture that learning should be enjoyable. • Allow the curriculum freedom, in these times of increasing risk for rural tropical wetland communities, to make the curriculum fit the local issues rather than vice versa. • Nurture critical analysis of the curriculum in local pedagogic discourse i.e., at the local contextualization level of the home, community and school.
- Full Text:
- Date Issued: 2008
- Authors: Hogan, Alice Rosemary
- Date: 2008
- Subjects: Education -- Tanzania Environmental education -- Tanzania Education, Rural -- Tanzania Education -- Curricula -- Tanzania Community and school -- Tanzania
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1504 , http://hdl.handle.net/10962/d1003386
- Description: This dissertation describes an action research case study carried out at a sub-village school at Nyamakurukuru, Utete, Rufiji District, Tanzania. The study was a fully independent research activity funded and led by a female Irish environmental and community specialist who has fifteen years experience of working in rural Tanzania, five of which were in Rufiji District. The aim of the action research was to engage a community of villagers, teachers, students and district officers in a participatory process to adapt a module of a school curriculum to the local context, and teach it in order to describe one way in which contextualization, using local and indigenous knowledge and active discovery teaching-learning processes, can be done. The major research question, which I wished to answer for one specific case, was: Does integrating local environmental cultural knowledge into formal schooling contribute to curriculum relevance? If so, in what way? This document describes the background and context of the research, the motivation and the theoretical basis for the work, the methodology and methods, and the action research process itself. The results are interpreted and discussed in the light of current theoretical perspectives on education and environmental education. The main findings within the case are that: Contextualization improved relevance of education and thus its quality by: • breaking through traditional frames/barriers between teachers and students, students and elders and community and teachers, • allowing formal education to take place outside of the school, • necessitating a change in pedagogy1 to more learner-centered, discovery methods, • allowing indigenous knowledge to come into the classroom, • stimulating creativity and increased confidence, and • bringing local socio-political environmental issues into the classroom. This study provides a case example of how education processes, when engaging local cultural knowledge, can improve the relevance, and thus an aspect of the quality of teaching and learning in school-community contexts, while providing a conduit for integrating environmental education into the formal school curriculum. It provides insights into the key issue of relevance which currently faces educators of children in wetlands in Tanzania. Recommendations were made for the case studied and may be useful beyond the boundaries of the case: • Give more explicit government policy and strategic support for community involvement in educational content–epistemologies and pedagogies. • Weaken framing (hierarchical power positions) to encourage greater partnership between school, home and community to improve relevance. • Investigate the provision of education beyond schools. • Provide practical teacher and community training on use of learner-centered, discovery and active pedagogies. • Provide teacher and community education on biodiversity and the environment. • Provide relevant reference texts and research data on the ecology, biodiversity, vegetation, hydrology, agriculture, sociology, history and other relevant subjects. • Officially nurture a culture that learning should be enjoyable. • Allow the curriculum freedom, in these times of increasing risk for rural tropical wetland communities, to make the curriculum fit the local issues rather than vice versa. • Nurture critical analysis of the curriculum in local pedagogic discourse i.e., at the local contextualization level of the home, community and school.
- Full Text:
- Date Issued: 2008
Effect of salinity on oxygen consumption and growth of juvenile white steenbras, litohognathus lithognathus
- Authors: Kandjou, Kaunahama
- Date: 2008
- Subjects: Lithognathus -- Growth , Salinity
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5275 , http://hdl.handle.net/10962/d1005119 , Lithognathus -- Growth , Salinity
- Description: A stress-induced increase in metabolic rate of fish consumes energy within the metabolic scope of a fish that could otherwise be used for such functions as growth and reproduction. By estimating the degree of the metabolic response under given salinity levels and sudden changes thereof, it could be tested whether growth under given culture conditions could be predicted. Using intermittent respirometers, this study investigated the metabolic response of juvenile Lithognathus lithognathus following gradual acclimation to 5, 25 and 35‰ and, as a result of abrupt change from 35‰ to 5‰ or from 35‰ to 25‰ at 20˚C. The main aim of the study was to establish whether the magnitude of such responses could be used to predict growth of juvenile L. lithognathus under culture conditions. Hence, in addition to the respirometry study, two growth studies were conducted at 5, 10, 25 and 35‰ salinities. The baseline metabolic rates of juvenile L. lithognathus were also determined. Oxygen consumption measurements over 24-hours showed that most fish exhibited a diurnal peak in metabolic rates. The standard and active metabolic rates calculated from juvenile L. lithognathus with a diurnal peak in oxygen consumption were 0.06±0.001mgO₂g⁻¹h⁻¹ (mean±SEM, n = 5), and 0.11±0.01mg O₂g⁻¹h⁻¹, respectively. The standard and active metabolic rates of juvenile L lithognathus showing a nocturnal peak in metabolic activities were 0.04±0.001mgO₂g-1h-1 (n = 1), and 0.12±0.003 mg O₂g⁻¹ h⁻¹, respectively. Routine metabolic rate of these fish calculated over a 3-h measurement period was 0.09±0.005mgO₂g⁻¹h⁻¹ (n = 6). Juvenile L. lithognathus showed a relationship between metabolic rate (mo₂) and body weight (W) following the equation: mo₂ = 0.62 W⁻°·⁵³.
- Full Text:
- Date Issued: 2008
- Authors: Kandjou, Kaunahama
- Date: 2008
- Subjects: Lithognathus -- Growth , Salinity
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5275 , http://hdl.handle.net/10962/d1005119 , Lithognathus -- Growth , Salinity
- Description: A stress-induced increase in metabolic rate of fish consumes energy within the metabolic scope of a fish that could otherwise be used for such functions as growth and reproduction. By estimating the degree of the metabolic response under given salinity levels and sudden changes thereof, it could be tested whether growth under given culture conditions could be predicted. Using intermittent respirometers, this study investigated the metabolic response of juvenile Lithognathus lithognathus following gradual acclimation to 5, 25 and 35‰ and, as a result of abrupt change from 35‰ to 5‰ or from 35‰ to 25‰ at 20˚C. The main aim of the study was to establish whether the magnitude of such responses could be used to predict growth of juvenile L. lithognathus under culture conditions. Hence, in addition to the respirometry study, two growth studies were conducted at 5, 10, 25 and 35‰ salinities. The baseline metabolic rates of juvenile L. lithognathus were also determined. Oxygen consumption measurements over 24-hours showed that most fish exhibited a diurnal peak in metabolic rates. The standard and active metabolic rates calculated from juvenile L. lithognathus with a diurnal peak in oxygen consumption were 0.06±0.001mgO₂g⁻¹h⁻¹ (mean±SEM, n = 5), and 0.11±0.01mg O₂g⁻¹h⁻¹, respectively. The standard and active metabolic rates of juvenile L lithognathus showing a nocturnal peak in metabolic activities were 0.04±0.001mgO₂g-1h-1 (n = 1), and 0.12±0.003 mg O₂g⁻¹ h⁻¹, respectively. Routine metabolic rate of these fish calculated over a 3-h measurement period was 0.09±0.005mgO₂g⁻¹h⁻¹ (n = 6). Juvenile L. lithognathus showed a relationship between metabolic rate (mo₂) and body weight (W) following the equation: mo₂ = 0.62 W⁻°·⁵³.
- Full Text:
- Date Issued: 2008
Effects of coastal topography on physiology, behaviour and genetics of indigenous (Perna perna) and invasive (Mytilus galloprovincialis) mussels
- Authors: Nicastro, Katy R
- Date: 2008
- Subjects: Mussels -- Ecology -- South Africa , Perna -- Physiology -- South Africa , Perna -- Behavior -- South Africa , Mussels -- Behavior -- Environmental factors -- South Africa , Mussels -- Habitat -- South Africa , Mytilus galloprovincialis , Mytilus galloprovincialis -- Physiology -- South Africa , Mytilus galloprovincialis -- Behavior -- South Africa , Mytilus galloprovincialis -- Genetics -- South Africa , Coastal ecology -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5833 , http://hdl.handle.net/10962/d1008262
- Description: Organisms inhabit environments that have many dimensions, each of which can vary temporally and spatially. The spatial-temporal variations of environmental stressors and disturbances may have major but different effects on indigenous and invasive species, favouring either of them at different times and places. The invasive mussel Mytilus galloprovincialis invaded the South African coast 30 years ago and, on the south coast of South Africa, it now competes and co-exists with the indigenous Perna perna in the lower eulittoral zone (referred to here as the mussel zone) The invasive and indigenous species dominate the upper and the lower mussel zones respectively, while the two co-exist in the mid-zone. My results show that intertidal mussels experience, and respond to, spatial and temporal fluctuations of several biotic and abiotic stressors. The invasive and the indigenous species adopt different strategies when reacting to environmental factors and their physiological and behavioural responses vary in time and in different habitats as different pressures become of overriding importance. Attachment strength of both species decreased in summer and increased in winter, and was higher on the open coast than in bays for both species, showing a strong positive correlation with wave force in time and space. P. perna had significantly higher attachment strength than M. galloprovincialis but, contrary to previous studies, the difference in gonad index between the two species varied according to the habitat. In bay habitats, M. galloprovincialis had a higher maximum reproductive effort than P. perna, however, on the open coast, there was no significant difference between the two species, suggesting that for the invasive species wave action is a limiting factor not only in terms of the attachment strength but also of energy availability for reproductive tissue development. Major spawning events occurred during periods of low wave action while minor spawning coincided with periods of intense hydrodynamic stress. On the open coast, gonad index was negatively correlated with attachment strength for both species while, in bays, there was no correlation between these two factors for either. The two species also showed different behaviour. In the field, M. galloprovincialis moved significantly more than P. perna over a period of six months. The higher mobility of the invasive species was also confirmed in the laboratory where, in general, M. galloprovincialis formed clumps more readily than P. perna. Taken collectively, these results suggest that channelling more energy into attachment strength limits reproductive tissue development and that, while the indigenous species invests more in byssal production, the invasive species adopts a more dynamic strategy looking for aggregation or a safer arrangement. Higher endolithic infestation and a greater expression of heat shock proteins (Hsps) in mussel populations on the open coast than in bays indicate that this habitat is a more stressful environment not only in terms of wave action. Endolith damaged mussels had significantly lower attachment strengths and condition indices than clean mussels, probably due to the need to channel energy into shell repair. The constant shell repair and expression of Hsps typical of open coast populations are energetically demanding processes. These observations suggest that on the open coast, mussels are subjected to more severe energetic constraints than in bay habitats. Wave and sand stress fluctuated seasonally with the former having a greater effect on mussel mortality on the open coast and the latter a higher impact on bay populations. Overall, mussel mortality rates were higher on the open coast than in bays. My results show that populations on the open coast had fewer private haplotypes and less genetic endemism than those inside bays. Gene flow analysis showed the relatively stable bay habitats act as source populations with greater genetic migration rates out of bays than into them. These differences in genetic structure on scales of las of kilometers show that coastal configuration strongly affects selection, larval dispersal and haplotype diversity. Environmental gradients that are key factors in species distribution over large geographical scales can also be responsible for micro-scale distributions. My results show that M. galloprovincialis colonizes the upper mussel zone where temperature is high, but is less tolerant to this stressor and has to maintain a high expression of Hsps. This suggests that temperature is probably a limiting factor in its invasion towards the sub-tropical east coast. There are inter- and intra-specific differences in responses to the environment which highlight the efforts of M. galloprovincialis and P. perna to optimize resource utilization for survival and reproduction. Determining these differences is crucial to understanding patterns of co-existence between competing indigenous and invasive species.
- Full Text:
- Date Issued: 2008
- Authors: Nicastro, Katy R
- Date: 2008
- Subjects: Mussels -- Ecology -- South Africa , Perna -- Physiology -- South Africa , Perna -- Behavior -- South Africa , Mussels -- Behavior -- Environmental factors -- South Africa , Mussels -- Habitat -- South Africa , Mytilus galloprovincialis , Mytilus galloprovincialis -- Physiology -- South Africa , Mytilus galloprovincialis -- Behavior -- South Africa , Mytilus galloprovincialis -- Genetics -- South Africa , Coastal ecology -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5833 , http://hdl.handle.net/10962/d1008262
- Description: Organisms inhabit environments that have many dimensions, each of which can vary temporally and spatially. The spatial-temporal variations of environmental stressors and disturbances may have major but different effects on indigenous and invasive species, favouring either of them at different times and places. The invasive mussel Mytilus galloprovincialis invaded the South African coast 30 years ago and, on the south coast of South Africa, it now competes and co-exists with the indigenous Perna perna in the lower eulittoral zone (referred to here as the mussel zone) The invasive and indigenous species dominate the upper and the lower mussel zones respectively, while the two co-exist in the mid-zone. My results show that intertidal mussels experience, and respond to, spatial and temporal fluctuations of several biotic and abiotic stressors. The invasive and the indigenous species adopt different strategies when reacting to environmental factors and their physiological and behavioural responses vary in time and in different habitats as different pressures become of overriding importance. Attachment strength of both species decreased in summer and increased in winter, and was higher on the open coast than in bays for both species, showing a strong positive correlation with wave force in time and space. P. perna had significantly higher attachment strength than M. galloprovincialis but, contrary to previous studies, the difference in gonad index between the two species varied according to the habitat. In bay habitats, M. galloprovincialis had a higher maximum reproductive effort than P. perna, however, on the open coast, there was no significant difference between the two species, suggesting that for the invasive species wave action is a limiting factor not only in terms of the attachment strength but also of energy availability for reproductive tissue development. Major spawning events occurred during periods of low wave action while minor spawning coincided with periods of intense hydrodynamic stress. On the open coast, gonad index was negatively correlated with attachment strength for both species while, in bays, there was no correlation between these two factors for either. The two species also showed different behaviour. In the field, M. galloprovincialis moved significantly more than P. perna over a period of six months. The higher mobility of the invasive species was also confirmed in the laboratory where, in general, M. galloprovincialis formed clumps more readily than P. perna. Taken collectively, these results suggest that channelling more energy into attachment strength limits reproductive tissue development and that, while the indigenous species invests more in byssal production, the invasive species adopts a more dynamic strategy looking for aggregation or a safer arrangement. Higher endolithic infestation and a greater expression of heat shock proteins (Hsps) in mussel populations on the open coast than in bays indicate that this habitat is a more stressful environment not only in terms of wave action. Endolith damaged mussels had significantly lower attachment strengths and condition indices than clean mussels, probably due to the need to channel energy into shell repair. The constant shell repair and expression of Hsps typical of open coast populations are energetically demanding processes. These observations suggest that on the open coast, mussels are subjected to more severe energetic constraints than in bay habitats. Wave and sand stress fluctuated seasonally with the former having a greater effect on mussel mortality on the open coast and the latter a higher impact on bay populations. Overall, mussel mortality rates were higher on the open coast than in bays. My results show that populations on the open coast had fewer private haplotypes and less genetic endemism than those inside bays. Gene flow analysis showed the relatively stable bay habitats act as source populations with greater genetic migration rates out of bays than into them. These differences in genetic structure on scales of las of kilometers show that coastal configuration strongly affects selection, larval dispersal and haplotype diversity. Environmental gradients that are key factors in species distribution over large geographical scales can also be responsible for micro-scale distributions. My results show that M. galloprovincialis colonizes the upper mussel zone where temperature is high, but is less tolerant to this stressor and has to maintain a high expression of Hsps. This suggests that temperature is probably a limiting factor in its invasion towards the sub-tropical east coast. There are inter- and intra-specific differences in responses to the environment which highlight the efforts of M. galloprovincialis and P. perna to optimize resource utilization for survival and reproduction. Determining these differences is crucial to understanding patterns of co-existence between competing indigenous and invasive species.
- Full Text:
- Date Issued: 2008
Effects of temperature on the development, behaviour and geography of blowflies in a forensic context
- Authors: Richards, Cameron Spencer
- Date: 2008
- Subjects: Blowflies Blowflies -- South Africa Diptera -- South Africa Insects -- Development Insects -- Behavior Forensic entomology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5683 , http://hdl.handle.net/10962/d1005369
- Description: The development of immature insects is commonly employed in forensic investigations to estimate time of death, or postmortem interval (PMI), of a corpse on which they are feeding. The bulk of this thesis focuses on factors influencing the accuracy of developmental data, and exploring how and why developmental data differ between studies involving the same species, and between different species. Because carrion feeding insects are ectotherms, temperature may be expected to significantly influence their behaviour, development and distribution, and the remainder of the thesis therefore focuses on the thermal biology and geographical distribution of seven forensically important blowflies. The species include Chrysomya albiceps, C. putoria, C. chloropyga, C. megacephala, C. marginalis, C. inclinata and Calliphora croceipalpis. A robust experimental design for estimating developmental models is outlined and tested. It is recommended that forensic entomologists should involve at least six constant temperatures, starting at about 7°C above the relevant developmental zero (D0) and going to about 10°C above the upper critical temperature, and a temporal sampling interval with a relative precision of about 10%. Using this design, focused experiments consistently provided the most reliable developmental data, while data pooled from different studies yielded inconsistent results. Similarly, developmental data from closely related species differed significantly, and surprisingly so did developmental data from different populations of the same species. Possible explanations for the latter lay in the different methods of data collection but only temporal sampling resolution had a direct influence on the accuracy of developmental data. Consequently, disparities in such data were primarily ascribed to genetic differences and phenotypic plasticity. Comparisons between numerous thermal thresholds of larvae, pupae and adults support this conclusion and suggest a phylogenetic component to the thermal biology of blowflies. Further comparisons were made between these temperature thresholds and the distributions of blowfly species present on two rhinoceros carcasses. These comparisons suggest that blowfly larvae with high upper lethal temperature thresholds dominate in interspecific competition in favorable thermal environments by raising maggot mass temperature above the thresholds of other carrion-feeding blowflies, through maggot-generated heat. Bioclimatic modeling using maximum entropy analysis provided a successful means of predicting whether a species is likely to occur in an area, and whether it would therefore be expected in a local carcass community. It also showed that temperature was less important than moisture in shaping the geographical distribution of African carrion blowflies. Based on these results, several recommendations are made for the practice of forensic entomology.
- Full Text:
- Date Issued: 2008
- Authors: Richards, Cameron Spencer
- Date: 2008
- Subjects: Blowflies Blowflies -- South Africa Diptera -- South Africa Insects -- Development Insects -- Behavior Forensic entomology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5683 , http://hdl.handle.net/10962/d1005369
- Description: The development of immature insects is commonly employed in forensic investigations to estimate time of death, or postmortem interval (PMI), of a corpse on which they are feeding. The bulk of this thesis focuses on factors influencing the accuracy of developmental data, and exploring how and why developmental data differ between studies involving the same species, and between different species. Because carrion feeding insects are ectotherms, temperature may be expected to significantly influence their behaviour, development and distribution, and the remainder of the thesis therefore focuses on the thermal biology and geographical distribution of seven forensically important blowflies. The species include Chrysomya albiceps, C. putoria, C. chloropyga, C. megacephala, C. marginalis, C. inclinata and Calliphora croceipalpis. A robust experimental design for estimating developmental models is outlined and tested. It is recommended that forensic entomologists should involve at least six constant temperatures, starting at about 7°C above the relevant developmental zero (D0) and going to about 10°C above the upper critical temperature, and a temporal sampling interval with a relative precision of about 10%. Using this design, focused experiments consistently provided the most reliable developmental data, while data pooled from different studies yielded inconsistent results. Similarly, developmental data from closely related species differed significantly, and surprisingly so did developmental data from different populations of the same species. Possible explanations for the latter lay in the different methods of data collection but only temporal sampling resolution had a direct influence on the accuracy of developmental data. Consequently, disparities in such data were primarily ascribed to genetic differences and phenotypic plasticity. Comparisons between numerous thermal thresholds of larvae, pupae and adults support this conclusion and suggest a phylogenetic component to the thermal biology of blowflies. Further comparisons were made between these temperature thresholds and the distributions of blowfly species present on two rhinoceros carcasses. These comparisons suggest that blowfly larvae with high upper lethal temperature thresholds dominate in interspecific competition in favorable thermal environments by raising maggot mass temperature above the thresholds of other carrion-feeding blowflies, through maggot-generated heat. Bioclimatic modeling using maximum entropy analysis provided a successful means of predicting whether a species is likely to occur in an area, and whether it would therefore be expected in a local carcass community. It also showed that temperature was less important than moisture in shaping the geographical distribution of African carrion blowflies. Based on these results, several recommendations are made for the practice of forensic entomology.
- Full Text:
- Date Issued: 2008
Evaluation of the pharmaceutical availability of erythromycin from topical formulations
- Authors: Mandimika, Nyaradzo
- Date: 2008
- Subjects: Pharmacy -- Research Chromatographic analysis Gel permeation chromatography Gels (Pharmacy) Chemistry, analytic Acne -- Treatment Sebaceous glands -- Diseases -- Treatment Drugs -- Testing Erythromycin -- Bioavailability
- Language: English
- Type: Thesis , Masters , MPharm
- Identifier: vital:3771 , http://hdl.handle.net/10962/d1003249
- Description: Erythromycin (ERY) is a macrolide antibiotic which is used in the treatment of acne vulgaris.Acne is a common skin condition that occurs when the sebaceous glands and hair shafts become infected by the bacteria Propionibacterium acnes. Acne is a chronic condition that may last for years and the severity of the effects of the disease on patients is often undermined especially in third world countries where more emphasis is placed on other more life-threatening diseases. It may cause considerable physical and emotional distress to sufferers along with the possibility of permanent scarring. Although use of topical ERY formulations is not the first line of treatment it has proven to be effective in treating inflammation of skin and skin structures cause by the responsible bacteria. To-date there are a variety of vehicles which are used in preparing topical ERY formulations namely ointment and gel bases, alcoholic solutions and pledgets. All the gel formulations on the market contain hydroxypropyl cellulose, alcohol and water along with the active ingredient(s). However, some gel formulations contain propylene glycol in addition to these excipients an example being Emgel®. Propylene glycol has been shown to affect the penetration of topically applied drugs through the skin suggesting that it would be highly likely that those formulations which contain propylene glycol may release more ERY into the skin following application. With this in mind, two ERY gel formulations were produced which contained different percentages of propylene glycol. According to the FDA guidelines, pharmacokinetic measurements in blood, plasma and/or urine of topical dermatological drug products are not feasible to document bioequivalence since the active ingredient(s) in topical formulations is/are not intended to be absorbed into the systemic circulation and in addition, concentrations in extracutaneous biological tissues would generally not be measurable. This limits determination of bioavailability and assessment of bioequivalence of such products to pharmacodynamic measurements, clinical trials and dermatopharmacokinetic (DPK) measurements such as tape stripping (TS) and microdialysis (MD).TS is a sampling technique which involves sequential removal of layers of the stratum corneum using strips of adhesive tape. This technique has found increasing use in DPK studies for investigation of drug kinetics in the skin following the application of a topical formulation. The technique has also been used as a diagnostic tool in assessing the quality of the stratum corneum in diseased skin. In the current research study, the tape stripping technique was used to investigate the pharmaceutical/biological availability of topical gel formulations containing ERY. MD is another DPK sampling technique which has been used to determine the amount of a topically applied drug that penetrates through the stratum corneum to reach deeper tissues of the skin. The in vivo sampling technique involves the insertion of microdialysis probes beneath the skin surface in the dermal tissue and allows for real-time sampling of the analyte at its target site. Recently in vitro MD has also been successfully used to assess the pharmaceutical availability of a topical corticosteroid, mometesone furoate, from topical formulations. Based on this work, microdialysis was used to determine the pharmaceutical availability of ERY from gel formulations which were developed for use in this research. The results of the pharmaceutical availability of ERY from in vivo tape stripping studies and the in vitro microdialysis studies were compared to establish correlation between the data. Pharmaceutical equivalence and bioequivalence data obtained from the respective studies on the gel formulations were investigated by statistical analysis of the data generated from both the in vitro and in vivo experiments. In summary the objectives of this research were: 1. To develop and validate a high performance liquid chromatography method suitable to analyse ERY concentrations obtained from in vitro microdialysis studies and in vivo tape stripping studies. 2. To prepare two different ERY gel formulations with different percentage content of propylene glycol. 3. To determine the pharmaceutical availability of ERY from two different gel formulations using in vitro microdialysis. 4. To develop and validate a tape stripping technique which could be used to determine percutaneous penetration and bioequivalence of the gel formulations. 5. To compare in vitro microdialysis and in vivo tape stripping data and attempt to establish a correlation between the two different approaches.
- Full Text:
- Date Issued: 2008
- Authors: Mandimika, Nyaradzo
- Date: 2008
- Subjects: Pharmacy -- Research Chromatographic analysis Gel permeation chromatography Gels (Pharmacy) Chemistry, analytic Acne -- Treatment Sebaceous glands -- Diseases -- Treatment Drugs -- Testing Erythromycin -- Bioavailability
- Language: English
- Type: Thesis , Masters , MPharm
- Identifier: vital:3771 , http://hdl.handle.net/10962/d1003249
- Description: Erythromycin (ERY) is a macrolide antibiotic which is used in the treatment of acne vulgaris.Acne is a common skin condition that occurs when the sebaceous glands and hair shafts become infected by the bacteria Propionibacterium acnes. Acne is a chronic condition that may last for years and the severity of the effects of the disease on patients is often undermined especially in third world countries where more emphasis is placed on other more life-threatening diseases. It may cause considerable physical and emotional distress to sufferers along with the possibility of permanent scarring. Although use of topical ERY formulations is not the first line of treatment it has proven to be effective in treating inflammation of skin and skin structures cause by the responsible bacteria. To-date there are a variety of vehicles which are used in preparing topical ERY formulations namely ointment and gel bases, alcoholic solutions and pledgets. All the gel formulations on the market contain hydroxypropyl cellulose, alcohol and water along with the active ingredient(s). However, some gel formulations contain propylene glycol in addition to these excipients an example being Emgel®. Propylene glycol has been shown to affect the penetration of topically applied drugs through the skin suggesting that it would be highly likely that those formulations which contain propylene glycol may release more ERY into the skin following application. With this in mind, two ERY gel formulations were produced which contained different percentages of propylene glycol. According to the FDA guidelines, pharmacokinetic measurements in blood, plasma and/or urine of topical dermatological drug products are not feasible to document bioequivalence since the active ingredient(s) in topical formulations is/are not intended to be absorbed into the systemic circulation and in addition, concentrations in extracutaneous biological tissues would generally not be measurable. This limits determination of bioavailability and assessment of bioequivalence of such products to pharmacodynamic measurements, clinical trials and dermatopharmacokinetic (DPK) measurements such as tape stripping (TS) and microdialysis (MD).TS is a sampling technique which involves sequential removal of layers of the stratum corneum using strips of adhesive tape. This technique has found increasing use in DPK studies for investigation of drug kinetics in the skin following the application of a topical formulation. The technique has also been used as a diagnostic tool in assessing the quality of the stratum corneum in diseased skin. In the current research study, the tape stripping technique was used to investigate the pharmaceutical/biological availability of topical gel formulations containing ERY. MD is another DPK sampling technique which has been used to determine the amount of a topically applied drug that penetrates through the stratum corneum to reach deeper tissues of the skin. The in vivo sampling technique involves the insertion of microdialysis probes beneath the skin surface in the dermal tissue and allows for real-time sampling of the analyte at its target site. Recently in vitro MD has also been successfully used to assess the pharmaceutical availability of a topical corticosteroid, mometesone furoate, from topical formulations. Based on this work, microdialysis was used to determine the pharmaceutical availability of ERY from gel formulations which were developed for use in this research. The results of the pharmaceutical availability of ERY from in vivo tape stripping studies and the in vitro microdialysis studies were compared to establish correlation between the data. Pharmaceutical equivalence and bioequivalence data obtained from the respective studies on the gel formulations were investigated by statistical analysis of the data generated from both the in vitro and in vivo experiments. In summary the objectives of this research were: 1. To develop and validate a high performance liquid chromatography method suitable to analyse ERY concentrations obtained from in vitro microdialysis studies and in vivo tape stripping studies. 2. To prepare two different ERY gel formulations with different percentage content of propylene glycol. 3. To determine the pharmaceutical availability of ERY from two different gel formulations using in vitro microdialysis. 4. To develop and validate a tape stripping technique which could be used to determine percutaneous penetration and bioequivalence of the gel formulations. 5. To compare in vitro microdialysis and in vivo tape stripping data and attempt to establish a correlation between the two different approaches.
- Full Text:
- Date Issued: 2008
Excavating the 'critique' : an investigation into disjunctions between the espoused and the practiced within a Fine Art studio practice curriculum
- Authors: Belluigi, Dina Zoe
- Date: 2008
- Subjects: Art -- Study and teaching (Higher) Postmodernism and education Universities and colleges -- Philosophy Universities and colleges -- Curricula Education, Higher -- Political aspects Creative thinking -- Study and teaching Discourse analysis -- Methodology Critical pedagogy
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1531 , http://hdl.handle.net/10962/d1003413
- Description: This report presents the findings of a case study excavating the event of the ‘Critique’ (crit), the formative assessment method within a Fine Art Studio Practice curriculum. Arguments informed by critical postmodernism, education theories and contemporary art criticism are utilised to construct a dialectic of higher education, contemporary art and fine art studio practice. An emphasis is placed on the importance of agency, expressed through intentionality and critical thinking, with a recognition of the relationship between ‘the self’ and ‘the other’. Using critical discourse analysis, the disjunctions between the espoused and practiced curriculum are explored. The researcher analyses how the assessment practices of the case studied are influenced by unexamined agentic factors, such as inter-departmental relations, lecturers’ assumptions and prior learning, and structural determinants, such as the medium-specific Bachelor of Fine Art degree structure and prevailing artistic traditions. The research findings indicate that these are underpinned by tensions between two orientations, the espoused curriculum’s discourse-interest informed by critical theory, and the theory-in-use. The latter is shown to have unexamined modernist leanings towards formalism and a master-apprentice relationship between lecturer and students, which encourages reproduction rather than critical, creative thinking. The dominant discourses in the case studied construct a negative dialectic of the artist-student that can be seen to deny student agency and authorial responsibility. Findings suggest that students experience this as alienating, to the extent that to preserve their sense of self, they adopted surface and strategic approaches to learning. An argument is made for lecturers’ critically reflexive engagement with their teaching practice, and thereby to model ethical relationships between ‘self’ and ‘other’ during ‘crits’. In addition, emphasis is placed on how assessment practices should be more aligned with the espoused curriculum, so that the importance of a reflexive relationship between form and content, process and product, intentionality and interpretation is acknowledged.
- Full Text:
- Date Issued: 2008
- Authors: Belluigi, Dina Zoe
- Date: 2008
- Subjects: Art -- Study and teaching (Higher) Postmodernism and education Universities and colleges -- Philosophy Universities and colleges -- Curricula Education, Higher -- Political aspects Creative thinking -- Study and teaching Discourse analysis -- Methodology Critical pedagogy
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1531 , http://hdl.handle.net/10962/d1003413
- Description: This report presents the findings of a case study excavating the event of the ‘Critique’ (crit), the formative assessment method within a Fine Art Studio Practice curriculum. Arguments informed by critical postmodernism, education theories and contemporary art criticism are utilised to construct a dialectic of higher education, contemporary art and fine art studio practice. An emphasis is placed on the importance of agency, expressed through intentionality and critical thinking, with a recognition of the relationship between ‘the self’ and ‘the other’. Using critical discourse analysis, the disjunctions between the espoused and practiced curriculum are explored. The researcher analyses how the assessment practices of the case studied are influenced by unexamined agentic factors, such as inter-departmental relations, lecturers’ assumptions and prior learning, and structural determinants, such as the medium-specific Bachelor of Fine Art degree structure and prevailing artistic traditions. The research findings indicate that these are underpinned by tensions between two orientations, the espoused curriculum’s discourse-interest informed by critical theory, and the theory-in-use. The latter is shown to have unexamined modernist leanings towards formalism and a master-apprentice relationship between lecturer and students, which encourages reproduction rather than critical, creative thinking. The dominant discourses in the case studied construct a negative dialectic of the artist-student that can be seen to deny student agency and authorial responsibility. Findings suggest that students experience this as alienating, to the extent that to preserve their sense of self, they adopted surface and strategic approaches to learning. An argument is made for lecturers’ critically reflexive engagement with their teaching practice, and thereby to model ethical relationships between ‘self’ and ‘other’ during ‘crits’. In addition, emphasis is placed on how assessment practices should be more aligned with the espoused curriculum, so that the importance of a reflexive relationship between form and content, process and product, intentionality and interpretation is acknowledged.
- Full Text:
- Date Issued: 2008
Floating sulphur biofilms structure, function and biotechnology
- Molwantwa, Jennifer Balatedi
- Authors: Molwantwa, Jennifer Balatedi
- Date: 2008
- Subjects: Biofilms Sulfur Acid mine drainage -- South Africa Mine water -- Purification -- Biological treatment Microbial ecology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3958 , http://hdl.handle.net/10962/d1004017
- Description: Mine wastewaters generated during active production operations, and decanting streams following mine closure have major environmental impacts, and volumes requiring treatment are expected to increase substantially as the South African mining industry matures. Biological treatment of mine waters has been the subject of increasing interest, where sulphate reducing bacteria are employed for the reduction of sulphate to sulphide, precipitation of metals and the production of alkalinity. However, the sulphide if not removed from the system can be oxidised back to sulphate. As a result there have been limitations especially in the provision of technological options that are sustainable over the long-term, where the total sulphur (in its different forms) can be removed from the system. These, however, are the subject of a number of constraints including, importantly, the process capability to remove reduced sulphur from the treated stream, in one of its oxidation states, and thus linearise the biological sulphur cycle. This remains a major bottleneck in the development of biological wastewater treatment technology. Floating sulphur biofilms are observed as surface layers in numerous aquatic sulphide-rich environments, and it has been suggested that they play a role in the biological cycling of sulphur. The use of sulphur biofilms for the removal of elemental sulphur was identified in this study as a possible means for addressing the technological bottleneck, especially in passive wastewater treatment systems. There is, however, little documented information in the literature on the structure of floating sulphur biofilms, the microbial species responsible for their occurrence or bio-process applications of the system. A linear flow channel reactor was developed to simulate natural conditions and enabled the study of floating sulphur biofilm under controlled laboratory conditions. It was observed that these biofilms developed through three distinct stages termed Thin, Sticky and Brittle films. A microprobe study showed the presence of a steep Redox gradient established across (260 to 380 μm) depth of the floating sulphur biofilm of ~ 0 to -200 mV (top to bottom), which correlated with pH and sulphide gradients across the system. Structural investigations embedded in an exopolymeric matrix containing clearly defined channels and pores. Sulphur crystals were found to develop within the biofilm and above a certain size these disengaged and then settled in the liquid phase below the biofilm. These features, together with the ability of the biofilm to remain suspended at the air/water interface thus provide the surface requirement, and indicate that these structures may be understood as “true” biofilms. In order to study an apparent functional differentiation within the floating sulphur biofilm system, a method was developed to expand its various components over a 13 cm length of agarose tube and across which an oxygen/sulphide gradient was established. This was done by inserting a sulphide plug in the bottom of the tube, overlaying this with the biofilm mixed and suspended in agarose and leaving the tube to open air. After allowing for growth, the different components of the microbial population occurring at various levels across the oxygen/sulphide gradient were sampled. The microbial population was found to resort in distinct functional layers. Aerobes including Acidithiobacillus and Azoarcus, Acidithiobacillus, Thiothrix, Thiovirga and Sulfurimonas were found in the upper oxidised layer. Aerobe and facultative anaerobes such as Chryseobacterium, Bacteroides and Planococcus were found in the middle and heterotrophic anaerobes such as Brevundimonas and uncultured anaerobes were found in the bottom anoxic layer. This enabled the development of a first descriptive structural/functional model accounting for the performance of floating sulphur biofilms. The potential of the floating sulphur biofilm for use as a bioprocess unit operation for sulphide removal in lignocellulose-based low-flow passive systems for acid mine drainage wastewater treatment was investigated. The linear flow channel reactor was scaled up and it was shown that the optimum sulphide removal of 74 % and sulphur recovery of 60 % could be achieved at 20 °C. In a further scale up of the linear channel reactor, the floating sulphur biofilm reactor was developed and operated. Sulphide removal and sulphur recovery of 65 and 56 % respectively was measured in the process. An understanding of the nature and function of floating sulphur biofilms and the further development of their potential application in sulphide removal in aquatic systems may provide a useful contribution to the treatment of acid mine drainage and other sulphidic wastewaters.
- Full Text:
- Date Issued: 2008
- Authors: Molwantwa, Jennifer Balatedi
- Date: 2008
- Subjects: Biofilms Sulfur Acid mine drainage -- South Africa Mine water -- Purification -- Biological treatment Microbial ecology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3958 , http://hdl.handle.net/10962/d1004017
- Description: Mine wastewaters generated during active production operations, and decanting streams following mine closure have major environmental impacts, and volumes requiring treatment are expected to increase substantially as the South African mining industry matures. Biological treatment of mine waters has been the subject of increasing interest, where sulphate reducing bacteria are employed for the reduction of sulphate to sulphide, precipitation of metals and the production of alkalinity. However, the sulphide if not removed from the system can be oxidised back to sulphate. As a result there have been limitations especially in the provision of technological options that are sustainable over the long-term, where the total sulphur (in its different forms) can be removed from the system. These, however, are the subject of a number of constraints including, importantly, the process capability to remove reduced sulphur from the treated stream, in one of its oxidation states, and thus linearise the biological sulphur cycle. This remains a major bottleneck in the development of biological wastewater treatment technology. Floating sulphur biofilms are observed as surface layers in numerous aquatic sulphide-rich environments, and it has been suggested that they play a role in the biological cycling of sulphur. The use of sulphur biofilms for the removal of elemental sulphur was identified in this study as a possible means for addressing the technological bottleneck, especially in passive wastewater treatment systems. There is, however, little documented information in the literature on the structure of floating sulphur biofilms, the microbial species responsible for their occurrence or bio-process applications of the system. A linear flow channel reactor was developed to simulate natural conditions and enabled the study of floating sulphur biofilm under controlled laboratory conditions. It was observed that these biofilms developed through three distinct stages termed Thin, Sticky and Brittle films. A microprobe study showed the presence of a steep Redox gradient established across (260 to 380 μm) depth of the floating sulphur biofilm of ~ 0 to -200 mV (top to bottom), which correlated with pH and sulphide gradients across the system. Structural investigations embedded in an exopolymeric matrix containing clearly defined channels and pores. Sulphur crystals were found to develop within the biofilm and above a certain size these disengaged and then settled in the liquid phase below the biofilm. These features, together with the ability of the biofilm to remain suspended at the air/water interface thus provide the surface requirement, and indicate that these structures may be understood as “true” biofilms. In order to study an apparent functional differentiation within the floating sulphur biofilm system, a method was developed to expand its various components over a 13 cm length of agarose tube and across which an oxygen/sulphide gradient was established. This was done by inserting a sulphide plug in the bottom of the tube, overlaying this with the biofilm mixed and suspended in agarose and leaving the tube to open air. After allowing for growth, the different components of the microbial population occurring at various levels across the oxygen/sulphide gradient were sampled. The microbial population was found to resort in distinct functional layers. Aerobes including Acidithiobacillus and Azoarcus, Acidithiobacillus, Thiothrix, Thiovirga and Sulfurimonas were found in the upper oxidised layer. Aerobe and facultative anaerobes such as Chryseobacterium, Bacteroides and Planococcus were found in the middle and heterotrophic anaerobes such as Brevundimonas and uncultured anaerobes were found in the bottom anoxic layer. This enabled the development of a first descriptive structural/functional model accounting for the performance of floating sulphur biofilms. The potential of the floating sulphur biofilm for use as a bioprocess unit operation for sulphide removal in lignocellulose-based low-flow passive systems for acid mine drainage wastewater treatment was investigated. The linear flow channel reactor was scaled up and it was shown that the optimum sulphide removal of 74 % and sulphur recovery of 60 % could be achieved at 20 °C. In a further scale up of the linear channel reactor, the floating sulphur biofilm reactor was developed and operated. Sulphide removal and sulphur recovery of 65 and 56 % respectively was measured in the process. An understanding of the nature and function of floating sulphur biofilms and the further development of their potential application in sulphide removal in aquatic systems may provide a useful contribution to the treatment of acid mine drainage and other sulphidic wastewaters.
- Full Text:
- Date Issued: 2008