Pro-active visualization of cyber security on a National Level : a South African case study
- Authors: Swart, Ignatius Petrus
- Date: 2015
- Subjects: Internet -- Security measures -- South Africa , Computer security -- Government policy -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4718 , http://hdl.handle.net/10962/d1017940
- Description: The need for increased national cyber security situational awareness is evident from the growing number of published national cyber security strategies. Governments are progressively seen as responsible for cyber security, but at the same time increasingly constrained by legal, privacy and resource considerations. Infrastructure and services that form part of the national cyber domain are often not under the control of government, necessitating the need for information sharing between governments and commercial partners. While sharing of security information is necessary, it typically requires considerable time to be implemented effectively. In an effort to decrease the time and effort required for cyber security situational awareness, this study considered commercially available data sources relating to a national cyber domain. Open source information is typically used by attackers to gather information with great success. An understanding of the data provided by these sources can also afford decision makers the opportunity to set priorities more effectively. Through the use of an adapted Joint Directors of Laboratories (JDL) fusion model, an experimental system was implemented that visualized the potential that open source intelligence could have on cyber situational awareness. Datasets used in the validation of the model contained information obtained from eight different data sources over a two year period with a focus on the South African .co.za sub domain. Over a million infrastructure devices were examined in this study along with information pertaining to a potential 88 million vulnerabilities on these devices. During the examination of data sources, a severe lack of information regarding the human aspect in cyber security was identified that led to the creation of a novel Personally Identifiable Information detection sensor (PII). The resultant two million records pertaining to PII in the South African domain were incorporated into the data fusion experiment for processing. The results of this processing are discussed in the three case studies. The results offered in this study aim to highlight how data fusion and effective visualization can serve to move national cyber security from a primarily reactive undertaking to a more pro-active model.
- Full Text:
- Authors: Swart, Ignatius Petrus
- Date: 2015
- Subjects: Internet -- Security measures -- South Africa , Computer security -- Government policy -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4718 , http://hdl.handle.net/10962/d1017940
- Description: The need for increased national cyber security situational awareness is evident from the growing number of published national cyber security strategies. Governments are progressively seen as responsible for cyber security, but at the same time increasingly constrained by legal, privacy and resource considerations. Infrastructure and services that form part of the national cyber domain are often not under the control of government, necessitating the need for information sharing between governments and commercial partners. While sharing of security information is necessary, it typically requires considerable time to be implemented effectively. In an effort to decrease the time and effort required for cyber security situational awareness, this study considered commercially available data sources relating to a national cyber domain. Open source information is typically used by attackers to gather information with great success. An understanding of the data provided by these sources can also afford decision makers the opportunity to set priorities more effectively. Through the use of an adapted Joint Directors of Laboratories (JDL) fusion model, an experimental system was implemented that visualized the potential that open source intelligence could have on cyber situational awareness. Datasets used in the validation of the model contained information obtained from eight different data sources over a two year period with a focus on the South African .co.za sub domain. Over a million infrastructure devices were examined in this study along with information pertaining to a potential 88 million vulnerabilities on these devices. During the examination of data sources, a severe lack of information regarding the human aspect in cyber security was identified that led to the creation of a novel Personally Identifiable Information detection sensor (PII). The resultant two million records pertaining to PII in the South African domain were incorporated into the data fusion experiment for processing. The results of this processing are discussed in the three case studies. The results offered in this study aim to highlight how data fusion and effective visualization can serve to move national cyber security from a primarily reactive undertaking to a more pro-active model.
- Full Text:
Production of Cydia pomonella granulovirus (CpGV) in a heteralogous host, Thaumatotibia Leucotreta (Meyrick) (False codling moth)
- Authors: Chambers, Craig Brian
- Date: 2015
- Subjects: Cryptophlebia leucotreta -- South Africa , Codling moth -- South Africa , Apples -- Diseases and pests -- South Africa , Codling moth -- Biological control -- South Africa , Insect pests -- Biological control -- South Africa , Biological pest control agents -- South Africa , Baculoviruses -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5935 , http://hdl.handle.net/10962/d1017906
- Description: Cydia pomonella (Linnaeus) (Family: Tortricidae), the codling moth, is considered one of the most significant pests of apples and pears worldwide, causing up to 80% crop loss in orchards if no control measures are applied. Cydia pomonella is oligophagous feeding on a number of alternate hosts including quince, walnuts, apricots, peaches, plums and nectarines. Historically the control of this pest has been achieved with the use of various chemical control strategies which have maintained pest levels below the economic threshold at a relatively low cost to the grower. However, there are serious concerns surrounding the use of chemical insecticides including the development of resistance in insect populations, the banning of various insecticides, regulations for lowering of the maximum residue level and employee and consumer safety. For this reason, alternate measures of control are slowly being adopted by growers such as mating disruption, cultural methods and the use of baculovirus biopesticides as part of integrated pest management programmes. The reluctance of growers to accept baculovirus or other biological control products in the past has been due to questionable product quality and inconsistencies in their field performance. Moreover, the development and application of biological control products is more costly than the use of chemical alternatives. Baculoviruses are arthropod specific viruses that are highly virulent to a number of lepidopteran species. Due to the virulence and host specificity of baculoviruses, Cydia pomonella granulovirus has been extensively and successfully used as part of integrated pest management systems for the control of C. pomonella in Europe and around the world, including South Africa. Commercial formulations have been typically based on the Mexican strain of CpGV. However due to long-term multiple applications of CpGV and the reliance on CpGV in organic farming practices in Europe, resistance to the CpGV-M strain has developed in a number of field populations of C. pomonella. This study aimed to identify and characterize novel isolates of CpGV in South Africa and compare their virulence with the commercial standard CpGV-M. Secondly, since C. pomonella is difficult to culture on a large scale, an alternate method of CpGV production was investigated in order to determine if CpGV could be produced more efficiently and at a reduced cost without negatively impacting the quality of the product. Several isolates of CpGV were recovered either from field collected larvae or from a laboratory-reared C. pomonella colony. Characterisation of DNA profiles using a variety of restriction enzymes revealed that only a single isolate, CpGV-SA, was genetically different from the Mexican strain of the virus used in the commercially available CpGV based products in South Africa. In dose-response bioassays using CpGV-SA, LC₅₀ and LC₉₀ values for neonate C. pomonella larvae were 3.18 x 10³ OBs/ml and 7.33 x 10⁴ respectively. A comparison of these values with those of CpGV-M indicated no significant difference in the virulence of the two isolates under laboratory conditions. This is a first report of a genetically distinct CpGV isolate in South Africa. The biological activity and novelty of CpGV-SA makes this isolate a potentially important tool for CpGV resistance management in South Africa. In order to justify production of CpGV in an alternative host, studies on the comparative biological performance of C. pomonella and T. leucotreta based on oviposition, time to hatch, larval developmental times and rearing efficiency as well as production costs were performed. Thaumatotibia leucotreta was found to be more fecund and to have significantly shorter egg and larval developmental times. In addition, larval production per unit of artificial diet was significantly higher than for C. pomonella. This resulted in T. leucotreta being more cost effective to produce with implications for reduced insectary space, sanitation practices as well as the labour component of production. Virus yield data generated by inoculation both C. pomonella and T. leucotreta with nine concentrations of CpGV resulted in comparable virus yields, justifying the continuation of the research into production of CpGV in T. leucotreta. It was important to determine the LC and LT values required for mass production of CpGV in late instar T. leucotreta larvae. Dose- and time-response bioassays with CpGV-M were conducted on artificial diet to determine these values. Fourth instar LC₅₀ and LC₉₀ values were 5.96 x 10³ OBs/ml and 1.64 x 10⁵ OBs/ml respectively. LT50 and LT90 values were 81.10 hours and 88.58 hours respectively. Fifth instar LC₅₀ and LC₉₀ values were 6.88 x 10⁴ OBs/ml and 9.78 x 10⁶ OBs/ml respectively. LT₅₀ and LT₉₀ values were 111.56 hours and 137.57 hours respectively. Virus produced in fourth instar T. leucotreta larvae was bioassayed against C. pomonella neonate larvae and compared to CpGV-M to establish if production in the heterologous host negatively affected the virulence of the isolate. No significant difference in virulence was observed between virus produced in T. leucotreta and that produced in C. pomonella. The data generated in the bioassays was used in CpGV mass production trials to evaluate production. All production methods tested produced acceptable virus yields. To examine the quality of the virus product, genomic DNA was extracted from larval cadavers and subjected to REN analysis with HindIII. The resulting DNA profiles indicated that the virus product was contaminated with the homologous virus, CrleGV. Based on the above results, the use of T. leucotreta as an alternate host for the in vivo production of CpGV on a commercial basis is not at this stage viable and requires further investigation before this production methodology can be reliable used to produce CpGV. However, this study has shown that CpGV can be produced in a homologous host, T. leucotreta and significant strides have been made towards developing a set of quality control standards that are essential for further development of successful production methodology. Finally a novel isolate of CpGV has been identified with comparable virulence to the CpGV-M. This is an important finding as it has broad reaching implications for resistance management of CpGV products in South Africa.
- Full Text:
- Authors: Chambers, Craig Brian
- Date: 2015
- Subjects: Cryptophlebia leucotreta -- South Africa , Codling moth -- South Africa , Apples -- Diseases and pests -- South Africa , Codling moth -- Biological control -- South Africa , Insect pests -- Biological control -- South Africa , Biological pest control agents -- South Africa , Baculoviruses -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5935 , http://hdl.handle.net/10962/d1017906
- Description: Cydia pomonella (Linnaeus) (Family: Tortricidae), the codling moth, is considered one of the most significant pests of apples and pears worldwide, causing up to 80% crop loss in orchards if no control measures are applied. Cydia pomonella is oligophagous feeding on a number of alternate hosts including quince, walnuts, apricots, peaches, plums and nectarines. Historically the control of this pest has been achieved with the use of various chemical control strategies which have maintained pest levels below the economic threshold at a relatively low cost to the grower. However, there are serious concerns surrounding the use of chemical insecticides including the development of resistance in insect populations, the banning of various insecticides, regulations for lowering of the maximum residue level and employee and consumer safety. For this reason, alternate measures of control are slowly being adopted by growers such as mating disruption, cultural methods and the use of baculovirus biopesticides as part of integrated pest management programmes. The reluctance of growers to accept baculovirus or other biological control products in the past has been due to questionable product quality and inconsistencies in their field performance. Moreover, the development and application of biological control products is more costly than the use of chemical alternatives. Baculoviruses are arthropod specific viruses that are highly virulent to a number of lepidopteran species. Due to the virulence and host specificity of baculoviruses, Cydia pomonella granulovirus has been extensively and successfully used as part of integrated pest management systems for the control of C. pomonella in Europe and around the world, including South Africa. Commercial formulations have been typically based on the Mexican strain of CpGV. However due to long-term multiple applications of CpGV and the reliance on CpGV in organic farming practices in Europe, resistance to the CpGV-M strain has developed in a number of field populations of C. pomonella. This study aimed to identify and characterize novel isolates of CpGV in South Africa and compare their virulence with the commercial standard CpGV-M. Secondly, since C. pomonella is difficult to culture on a large scale, an alternate method of CpGV production was investigated in order to determine if CpGV could be produced more efficiently and at a reduced cost without negatively impacting the quality of the product. Several isolates of CpGV were recovered either from field collected larvae or from a laboratory-reared C. pomonella colony. Characterisation of DNA profiles using a variety of restriction enzymes revealed that only a single isolate, CpGV-SA, was genetically different from the Mexican strain of the virus used in the commercially available CpGV based products in South Africa. In dose-response bioassays using CpGV-SA, LC₅₀ and LC₉₀ values for neonate C. pomonella larvae were 3.18 x 10³ OBs/ml and 7.33 x 10⁴ respectively. A comparison of these values with those of CpGV-M indicated no significant difference in the virulence of the two isolates under laboratory conditions. This is a first report of a genetically distinct CpGV isolate in South Africa. The biological activity and novelty of CpGV-SA makes this isolate a potentially important tool for CpGV resistance management in South Africa. In order to justify production of CpGV in an alternative host, studies on the comparative biological performance of C. pomonella and T. leucotreta based on oviposition, time to hatch, larval developmental times and rearing efficiency as well as production costs were performed. Thaumatotibia leucotreta was found to be more fecund and to have significantly shorter egg and larval developmental times. In addition, larval production per unit of artificial diet was significantly higher than for C. pomonella. This resulted in T. leucotreta being more cost effective to produce with implications for reduced insectary space, sanitation practices as well as the labour component of production. Virus yield data generated by inoculation both C. pomonella and T. leucotreta with nine concentrations of CpGV resulted in comparable virus yields, justifying the continuation of the research into production of CpGV in T. leucotreta. It was important to determine the LC and LT values required for mass production of CpGV in late instar T. leucotreta larvae. Dose- and time-response bioassays with CpGV-M were conducted on artificial diet to determine these values. Fourth instar LC₅₀ and LC₉₀ values were 5.96 x 10³ OBs/ml and 1.64 x 10⁵ OBs/ml respectively. LT50 and LT90 values were 81.10 hours and 88.58 hours respectively. Fifth instar LC₅₀ and LC₉₀ values were 6.88 x 10⁴ OBs/ml and 9.78 x 10⁶ OBs/ml respectively. LT₅₀ and LT₉₀ values were 111.56 hours and 137.57 hours respectively. Virus produced in fourth instar T. leucotreta larvae was bioassayed against C. pomonella neonate larvae and compared to CpGV-M to establish if production in the heterologous host negatively affected the virulence of the isolate. No significant difference in virulence was observed between virus produced in T. leucotreta and that produced in C. pomonella. The data generated in the bioassays was used in CpGV mass production trials to evaluate production. All production methods tested produced acceptable virus yields. To examine the quality of the virus product, genomic DNA was extracted from larval cadavers and subjected to REN analysis with HindIII. The resulting DNA profiles indicated that the virus product was contaminated with the homologous virus, CrleGV. Based on the above results, the use of T. leucotreta as an alternate host for the in vivo production of CpGV on a commercial basis is not at this stage viable and requires further investigation before this production methodology can be reliable used to produce CpGV. However, this study has shown that CpGV can be produced in a homologous host, T. leucotreta and significant strides have been made towards developing a set of quality control standards that are essential for further development of successful production methodology. Finally a novel isolate of CpGV has been identified with comparable virulence to the CpGV-M. This is an important finding as it has broad reaching implications for resistance management of CpGV products in South Africa.
- Full Text:
Re-imagining the nation
- Mngomezulu, Nosipho Sthabiso Thandiwe
- Authors: Mngomezulu, Nosipho Sthabiso Thandiwe
- Date: 2015
- Subjects: Mauritius -- Truth and Justice Commission , Nationalism -- Mauritius , National characteristics, Mauritian , Social justice -- Mauritius , Youth -- Mauritius -- Social conditions , Youth -- Mauritius -- Attitudes , Mauritius -- Politics and government -- 1992- , Ethnicity -- Mauritius
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2124 , http://hdl.handle.net/10962/d1019999
- Description: This thesis examines young people’s constructions of nationhood in Mauritius. In 2008, the Mauritian government instituted a Truth and Justice Commission (TJC), set up to investigate the consequences of slavery and indentured labour. Through the Truth and Justice Commission, the Mauritian government indicated its desire to achieve social justice and national unity. Drawing on developments in studies of national identification practices in the 21st Century, this thesis addresses the question of young Mauritian’s locally and globally informed identification practices and asks how their unofficial narratives of nationhood challenge, or divert, or relate to official state narratives of nationhood. The basis of the study emerges from data collected from 132 participants during fieldwork in multiple fieldsites from May to September 2010 as well as research on Mauritian youth on-line from 2011-2014. The advent of the TJC offers an ideal moment to evaluate the dynamics of post-colonial nation-building and nationhood in a selfstyled multi-cultural state. Nationhood, does not exist apriori to the constructions of narratives of the nation, thus the stories told about the nation, imagine the nation into being. By situating the Truth and Justice Commission and other official state narratives alongside young people’s narratives, I argue that contemporary narratives of nationhood in Mauritius represent an intergenerational struggle to define the meaning of the past in the present and consequently outline the future. Reflecting on the ideas and socio-economic and political processes that induce national consciousness, I argue that young people’s narratives of everyday lived experiences are vital for an interpretation of how nationhood is produced in everyday life. The cultural projects of young people – often rendered as liminal or marginal – offer a critical vantage point from where to read constructions of nationhood. Far from being growing pains or childish games, young people’s identity making practices are what Sherry B. Ortner has called “serious games.” This research suggests that official state government narratives of multicultural nationhood in Mauritius narrowly define national identification along communal loyalties, overlooking the dynamism of interculturality and transnationalism in daily practice on the island. Although communalism and rigid colonial interpretations of ethnicity attempt to police and limit the possibilities of alternative modes of being in Mauritius, young people’s identification practices question, challenge, and threaten to disrupt official discourses of ethnic identification in Mauritius Scholarly investigations of young peoples’ lived experiences of nationhood extend theoretical and methodological frames for the study of nationalized subjects and deepen the understanding of the construction of national consciousness. The construction of nationhood always involves narratives of some sort – scholarship on this area has usually focused on official state narratives from social theorists, state governments, and state elites. I argue for the importance of considering subjectivity and lived experience in conceptions of nationhood. In contemporary post-colonial societies, young people are the numerical majority, however, their voices are seldom represented in theories and narratives of nationhood. Whilst young people may appear in state policies (especially education) and official narratives about the future of the nation, their creative imagining and reimagining of narratives of selfhood is often ignored. I examine how young people increasingly are aware of their transnational connections, through participation in transnational youth cultures, and they are consequently increasingly multi-lingual and multicultural. Fixed notions of ethnic identification and discourses of trauma are not at the forefront of young people’s identification of selfhood, rather their ability to take advantage of their multiply situated identification processes allows them new means to evade and transform these narratives. Their identification of selfhood is characterised by a greater degree of dynamism than previous generations had access to, and thus they do not only identify themselves through officially sanctioned national forms of identification. Loyalty to nationhood is thus less predictable, and young people represent a potential threat to the continuation of older forms of nationhood. While official narratives of nationhood may manipulate ethnic and racial cleavages to secure old loyalties, not all young people are persuaded by these notions
- Full Text:
- Authors: Mngomezulu, Nosipho Sthabiso Thandiwe
- Date: 2015
- Subjects: Mauritius -- Truth and Justice Commission , Nationalism -- Mauritius , National characteristics, Mauritian , Social justice -- Mauritius , Youth -- Mauritius -- Social conditions , Youth -- Mauritius -- Attitudes , Mauritius -- Politics and government -- 1992- , Ethnicity -- Mauritius
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2124 , http://hdl.handle.net/10962/d1019999
- Description: This thesis examines young people’s constructions of nationhood in Mauritius. In 2008, the Mauritian government instituted a Truth and Justice Commission (TJC), set up to investigate the consequences of slavery and indentured labour. Through the Truth and Justice Commission, the Mauritian government indicated its desire to achieve social justice and national unity. Drawing on developments in studies of national identification practices in the 21st Century, this thesis addresses the question of young Mauritian’s locally and globally informed identification practices and asks how their unofficial narratives of nationhood challenge, or divert, or relate to official state narratives of nationhood. The basis of the study emerges from data collected from 132 participants during fieldwork in multiple fieldsites from May to September 2010 as well as research on Mauritian youth on-line from 2011-2014. The advent of the TJC offers an ideal moment to evaluate the dynamics of post-colonial nation-building and nationhood in a selfstyled multi-cultural state. Nationhood, does not exist apriori to the constructions of narratives of the nation, thus the stories told about the nation, imagine the nation into being. By situating the Truth and Justice Commission and other official state narratives alongside young people’s narratives, I argue that contemporary narratives of nationhood in Mauritius represent an intergenerational struggle to define the meaning of the past in the present and consequently outline the future. Reflecting on the ideas and socio-economic and political processes that induce national consciousness, I argue that young people’s narratives of everyday lived experiences are vital for an interpretation of how nationhood is produced in everyday life. The cultural projects of young people – often rendered as liminal or marginal – offer a critical vantage point from where to read constructions of nationhood. Far from being growing pains or childish games, young people’s identity making practices are what Sherry B. Ortner has called “serious games.” This research suggests that official state government narratives of multicultural nationhood in Mauritius narrowly define national identification along communal loyalties, overlooking the dynamism of interculturality and transnationalism in daily practice on the island. Although communalism and rigid colonial interpretations of ethnicity attempt to police and limit the possibilities of alternative modes of being in Mauritius, young people’s identification practices question, challenge, and threaten to disrupt official discourses of ethnic identification in Mauritius Scholarly investigations of young peoples’ lived experiences of nationhood extend theoretical and methodological frames for the study of nationalized subjects and deepen the understanding of the construction of national consciousness. The construction of nationhood always involves narratives of some sort – scholarship on this area has usually focused on official state narratives from social theorists, state governments, and state elites. I argue for the importance of considering subjectivity and lived experience in conceptions of nationhood. In contemporary post-colonial societies, young people are the numerical majority, however, their voices are seldom represented in theories and narratives of nationhood. Whilst young people may appear in state policies (especially education) and official narratives about the future of the nation, their creative imagining and reimagining of narratives of selfhood is often ignored. I examine how young people increasingly are aware of their transnational connections, through participation in transnational youth cultures, and they are consequently increasingly multi-lingual and multicultural. Fixed notions of ethnic identification and discourses of trauma are not at the forefront of young people’s identification of selfhood, rather their ability to take advantage of their multiply situated identification processes allows them new means to evade and transform these narratives. Their identification of selfhood is characterised by a greater degree of dynamism than previous generations had access to, and thus they do not only identify themselves through officially sanctioned national forms of identification. Loyalty to nationhood is thus less predictable, and young people represent a potential threat to the continuation of older forms of nationhood. While official narratives of nationhood may manipulate ethnic and racial cleavages to secure old loyalties, not all young people are persuaded by these notions
- Full Text:
Reading identities: a case study of grade 8 learners' interactions in a reading club
- Scheckle, Eileen Margaret Agnes
- Authors: Scheckle, Eileen Margaret Agnes
- Date: 2015
- Subjects: Group reading -- South Africa , Reading (Middle school) -- South Africa , Literacy programs -- South Africa , Identity (Psychology) in adolescence , Identity (Psychology) in adolescence -- South Africa , Discourse analysis -- Social aspects , Critical realism
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1329 , http://hdl.handle.net/10962/d1017766
- Description: This study offers an account of reading clubs as a literacy intervention in a grade 8 English class at a former ‘Coloured’ high school in South Africa. Using Margaret Archer’s social realist methodology, it examines different practices of ‘reading’ used by learners in talking and writing about text. Archer’s analytical dualism and morphogenetic model provided an explanatory framework for this study. Analytical dualism allows for the separation of the parts (structural and cultural elements) from the people (the grade 8 learners) so as to analyse the interplay between structure and culture. The morphogenetic model recognises that antecedent structures predate this, and any study but that through the exercise of agency, morphogenesis, in the form of structural elaboration or morphostasis in the form of continuity, may occur. This study used a New Literacies perspective based on an ideological model of literacy which recognises many different literacies, in addition to dominant school literacies. Learners’ talk about books as well as personal journal writing provided an insight into what cultural mechanisms and powers children bring to the reading of novels. Understandings of discourses as well as of Gee’s (1990; 2008) construct of Discourse provided a framework for examining learners’ identities and shifts as readers. The data in this study, which is presented through a series of vignettes, found that grade 8 learners use many different experiences and draw on different discourses when making sense of texts. Through the separation of the structural and cultural components, this research could explore how reading clubs as structures enabled learners to access different discourses from the domain of culture. Through the process and engagement in the reading clubs, following Gee (2000b), learners were attributed affinity, discoursal and institutional identities as readers. It was found, in the course of the study, that providing a safe space, scaffolding, multiple opportunities to practice and a variety of reading material, helped learners to access and appropriate dominant literacies. In addition, learners need a repertoire of literacy practices to draw from as successful reading needs flexibility and adaptability. Reading and writing inform each other and through gradual induction into literary writing, learners began to appropriate and approximate dominant literacy practices. Following others who have contributed to the field of New Literacy Studies (Heath, 1983; Street, 1984; Gee 1990; Prinsloo & Breier, 1996), this study would suggest that literacies of traditionally underserved communities should not be considered in deficit terms. Instead these need to be understood as resources for negotiating meaning making and as tools or mechanisms to access dominant discourse practices. In addition the resilience and competition from Discourses of popular culture need to be recognised and developed as tools to access school literacies.
- Full Text:
- Authors: Scheckle, Eileen Margaret Agnes
- Date: 2015
- Subjects: Group reading -- South Africa , Reading (Middle school) -- South Africa , Literacy programs -- South Africa , Identity (Psychology) in adolescence , Identity (Psychology) in adolescence -- South Africa , Discourse analysis -- Social aspects , Critical realism
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1329 , http://hdl.handle.net/10962/d1017766
- Description: This study offers an account of reading clubs as a literacy intervention in a grade 8 English class at a former ‘Coloured’ high school in South Africa. Using Margaret Archer’s social realist methodology, it examines different practices of ‘reading’ used by learners in talking and writing about text. Archer’s analytical dualism and morphogenetic model provided an explanatory framework for this study. Analytical dualism allows for the separation of the parts (structural and cultural elements) from the people (the grade 8 learners) so as to analyse the interplay between structure and culture. The morphogenetic model recognises that antecedent structures predate this, and any study but that through the exercise of agency, morphogenesis, in the form of structural elaboration or morphostasis in the form of continuity, may occur. This study used a New Literacies perspective based on an ideological model of literacy which recognises many different literacies, in addition to dominant school literacies. Learners’ talk about books as well as personal journal writing provided an insight into what cultural mechanisms and powers children bring to the reading of novels. Understandings of discourses as well as of Gee’s (1990; 2008) construct of Discourse provided a framework for examining learners’ identities and shifts as readers. The data in this study, which is presented through a series of vignettes, found that grade 8 learners use many different experiences and draw on different discourses when making sense of texts. Through the separation of the structural and cultural components, this research could explore how reading clubs as structures enabled learners to access different discourses from the domain of culture. Through the process and engagement in the reading clubs, following Gee (2000b), learners were attributed affinity, discoursal and institutional identities as readers. It was found, in the course of the study, that providing a safe space, scaffolding, multiple opportunities to practice and a variety of reading material, helped learners to access and appropriate dominant literacies. In addition, learners need a repertoire of literacy practices to draw from as successful reading needs flexibility and adaptability. Reading and writing inform each other and through gradual induction into literary writing, learners began to appropriate and approximate dominant literacy practices. Following others who have contributed to the field of New Literacy Studies (Heath, 1983; Street, 1984; Gee 1990; Prinsloo & Breier, 1996), this study would suggest that literacies of traditionally underserved communities should not be considered in deficit terms. Instead these need to be understood as resources for negotiating meaning making and as tools or mechanisms to access dominant discourse practices. In addition the resilience and competition from Discourses of popular culture need to be recognised and developed as tools to access school literacies.
- Full Text:
Saving the Sowetan : the public interest and commercial imperatives in journalism practice
- Authors: Cowling, Lesley
- Date: 2015
- Subjects: Sowetan (Johannesburg, South Africa) , Journalism -- Economic aspects -- South Africa -- Soweto , Journalism -- Political aspects -- South Africa -- Soweto , Black newspapers -- South Africa -- Soweto , Public interest -- South Africa -- Soweto , Corporate culture -- South Africa -- Soweto , Journalistic ethics -- South Africa -- Soweto , Journalism -- Objectivity -- South Africa -- Soweto
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3540 , http://hdl.handle.net/10962/d1017781
- Description: This thesis examines the complex ways in which notions of the public interest and commercial imperatives intertwine in journalism practice. It does this through a study of the 2004 takeover and relaunch of the Sowetan newspaper, the highest circulation daily in South Africa throughout the 1990s and an institution of black public life. The ‘public interest’ and ‘the commercial’ are recurring ideas in journalism scholarship and practice, and the relaunch appeared to be a challenge to reconcile the Sowetan’s commercial challenges with its historical responsibility to a ‘nation-building’ public. However, the research shows that the public/commercial aspects of journalism were inextricably entangled with Sowetan’s organisational culture, which was the matrix through which its journalism practice was expressed. Conflict in the organisation over the changes was not simply a contest between commercial realities and the public interest, with journalists defending a responsibility to the public and managers pushing commercial solutions, but a conflict between the culture of Sowetan “insiders”, steeped in the legacy of the newspaper, and “outsiders”, employed by the new owners to effect change. Another conclusion of the research is that commercial “realities” – often conceptualised as counter to the public interest – are highly mutable. Basic conditions, such as a dependence on advertising, exist. However, media managers must choose from a range of strategies to be commercially viable, which requires risk-taking, innovation and, often, guesswork. In such situations, the ‘wall’ between media managers and senior editors is porous, as all executives must manage the relationship between business and editorial imperatives. Executives tend to overlook culture as a factor in changing organisations, but I argue that journalism could benefit from engaging with management theory and organisational psychology, which offer ways to understand the specific dynamics of the organisation. Finally, I argue that the case of the Sowetan throws into question the idea that there may be a broadly universal journalism culture. The attachment of Sowetan journalists to their particular values and practice suggests that forms of journalism evolve in certain contexts to diverge from the ‘professional’ Anglo-American modes. These ‘journalisms’ use similar terms – such as the ‘public interest’ – but operationalise them quite differently. The responsibility to the public is imagined in very different ways, but remains a significant attachment for journalists.
- Full Text:
- Authors: Cowling, Lesley
- Date: 2015
- Subjects: Sowetan (Johannesburg, South Africa) , Journalism -- Economic aspects -- South Africa -- Soweto , Journalism -- Political aspects -- South Africa -- Soweto , Black newspapers -- South Africa -- Soweto , Public interest -- South Africa -- Soweto , Corporate culture -- South Africa -- Soweto , Journalistic ethics -- South Africa -- Soweto , Journalism -- Objectivity -- South Africa -- Soweto
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3540 , http://hdl.handle.net/10962/d1017781
- Description: This thesis examines the complex ways in which notions of the public interest and commercial imperatives intertwine in journalism practice. It does this through a study of the 2004 takeover and relaunch of the Sowetan newspaper, the highest circulation daily in South Africa throughout the 1990s and an institution of black public life. The ‘public interest’ and ‘the commercial’ are recurring ideas in journalism scholarship and practice, and the relaunch appeared to be a challenge to reconcile the Sowetan’s commercial challenges with its historical responsibility to a ‘nation-building’ public. However, the research shows that the public/commercial aspects of journalism were inextricably entangled with Sowetan’s organisational culture, which was the matrix through which its journalism practice was expressed. Conflict in the organisation over the changes was not simply a contest between commercial realities and the public interest, with journalists defending a responsibility to the public and managers pushing commercial solutions, but a conflict between the culture of Sowetan “insiders”, steeped in the legacy of the newspaper, and “outsiders”, employed by the new owners to effect change. Another conclusion of the research is that commercial “realities” – often conceptualised as counter to the public interest – are highly mutable. Basic conditions, such as a dependence on advertising, exist. However, media managers must choose from a range of strategies to be commercially viable, which requires risk-taking, innovation and, often, guesswork. In such situations, the ‘wall’ between media managers and senior editors is porous, as all executives must manage the relationship between business and editorial imperatives. Executives tend to overlook culture as a factor in changing organisations, but I argue that journalism could benefit from engaging with management theory and organisational psychology, which offer ways to understand the specific dynamics of the organisation. Finally, I argue that the case of the Sowetan throws into question the idea that there may be a broadly universal journalism culture. The attachment of Sowetan journalists to their particular values and practice suggests that forms of journalism evolve in certain contexts to diverge from the ‘professional’ Anglo-American modes. These ‘journalisms’ use similar terms – such as the ‘public interest’ – but operationalise them quite differently. The responsibility to the public is imagined in very different ways, but remains a significant attachment for journalists.
- Full Text:
Sediment connectivity in the upper Thina Catchment, Eastern Cape, South Africa
- Van der Waal, Benjamin Cornelis Wentsel
- Authors: Van der Waal, Benjamin Cornelis Wentsel
- Date: 2015
- Subjects: Soil erosion -- South Africa -- Eastern Cape , Sedimentation and deposition -- South Africa -- Eastern Cape , Watersheds -- South Africa -- Eastern Cape , Arroyos -- South Africa -- Eastern Cape , Sediment transport -- South Africa -- Eastern Cape , Soil conservation -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4892 , http://hdl.handle.net/10962/d1019754
- Description: [Portion of abstract]: Sediment dynamics are influenced by transformed landscape connectivity in catchments worldwide. The upper Thina catchment, an important high rainfall resource in the northern Eastern Cape, South Africa, is an example of where ongoing subsistence farming on communal land has led to overgrazing and trampling that has initiated large erosive features (e.g. gullies) and river incision. The formation of gullies led to increased hillslope-channel connectivity and the resultant river incision decreased the channel-valley fill connectivity. These two changes in connectivity led to increased sediment export from the catchment that has various down-stream ecological and socio-economic impacts. This study investigates how the change in hillslope-channel and channel-valley fill connectivity has altered the sediment dynamics in the Vuvu catchment, a headwater tributary of the Thina River. A combination of methods were used to assess the changes in hillslope-channel and channel-valley fill connectivity. High resolution aerial images were used to map source features, such as fields, gullies, sheet erosion, landslides, roads and livestock tracks. Topographic and geological characteristics of the source features were extracted using a Geographic Information System. Furthermore, hillslope-channel pathways, such as the natural drainage network, continuous gullies, discontinuous gullies, roads and livestock tracks were mapped and analysed in terms of topographic and geological characteristics. Historic aerial images were assessed to calculate the date the larger gullies began forming. Recent aerial photos and cross sectional surveys of the valley fill were combined to map the various sediment sinks. Particle size and organic content were analysed for flood bench cores and terrace samples. The chronology of the flood benches was determined using unsupported Pb-210 and Cs-137 dating, and determined for the terraces using Optically Stimulated Luminescence dating. Quantitative and qualitative sediment tracing approaches, using mineral magnetic properties, were used to trace the origin of suspended sediment (collected during flood events), sediment stored in the flood benches and sediment stored in the terraces. Hydrological monitoring was used to assess the potential to store sediment on flood benches along the valley fill through flood bench inundation frequency. Hydrological and hydraulic modelling extended the measured inundation frequencies to a 73 year period and other cross sections along the valley fill. Furthermore, a future scenario of an increased vegetation cover and reduced hillslope-channel connectivity was assessed in terms of channel-valley fill inundation frequency.
- Full Text:
- Authors: Van der Waal, Benjamin Cornelis Wentsel
- Date: 2015
- Subjects: Soil erosion -- South Africa -- Eastern Cape , Sedimentation and deposition -- South Africa -- Eastern Cape , Watersheds -- South Africa -- Eastern Cape , Arroyos -- South Africa -- Eastern Cape , Sediment transport -- South Africa -- Eastern Cape , Soil conservation -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4892 , http://hdl.handle.net/10962/d1019754
- Description: [Portion of abstract]: Sediment dynamics are influenced by transformed landscape connectivity in catchments worldwide. The upper Thina catchment, an important high rainfall resource in the northern Eastern Cape, South Africa, is an example of where ongoing subsistence farming on communal land has led to overgrazing and trampling that has initiated large erosive features (e.g. gullies) and river incision. The formation of gullies led to increased hillslope-channel connectivity and the resultant river incision decreased the channel-valley fill connectivity. These two changes in connectivity led to increased sediment export from the catchment that has various down-stream ecological and socio-economic impacts. This study investigates how the change in hillslope-channel and channel-valley fill connectivity has altered the sediment dynamics in the Vuvu catchment, a headwater tributary of the Thina River. A combination of methods were used to assess the changes in hillslope-channel and channel-valley fill connectivity. High resolution aerial images were used to map source features, such as fields, gullies, sheet erosion, landslides, roads and livestock tracks. Topographic and geological characteristics of the source features were extracted using a Geographic Information System. Furthermore, hillslope-channel pathways, such as the natural drainage network, continuous gullies, discontinuous gullies, roads and livestock tracks were mapped and analysed in terms of topographic and geological characteristics. Historic aerial images were assessed to calculate the date the larger gullies began forming. Recent aerial photos and cross sectional surveys of the valley fill were combined to map the various sediment sinks. Particle size and organic content were analysed for flood bench cores and terrace samples. The chronology of the flood benches was determined using unsupported Pb-210 and Cs-137 dating, and determined for the terraces using Optically Stimulated Luminescence dating. Quantitative and qualitative sediment tracing approaches, using mineral magnetic properties, were used to trace the origin of suspended sediment (collected during flood events), sediment stored in the flood benches and sediment stored in the terraces. Hydrological monitoring was used to assess the potential to store sediment on flood benches along the valley fill through flood bench inundation frequency. Hydrological and hydraulic modelling extended the measured inundation frequencies to a 73 year period and other cross sections along the valley fill. Furthermore, a future scenario of an increased vegetation cover and reduced hillslope-channel connectivity was assessed in terms of channel-valley fill inundation frequency.
- Full Text:
Social-ecological resilience for well-being : a critical realist case study of Boksburg Lake, South Africa
- Authors: Fox, Helen Elizabeth
- Date: 2015
- Subjects: Boksburg Lake and Wetland project , Reservoirs -- South Africa -- Boksburg , Water -- Pollution -- South Africa -- Boksburg , Human ecology -- South Africa -- Boksburg , Social learning -- South Africa -- Boksburg , Critical realism
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:6048 , http://hdl.handle.net/10962/d1017872
- Description: This thesis is based on a case study of the degraded Boksburg Lake social-ecological system and an environmental education initiative that aimed to support its transformation. This initiative aimed to involve local people in reclaiming the lake’s social and ecological value, through a process of collectively reimagining possibilities, shaping identities, gaining knowledge and developing local human agency. The focus was on social learning processes in schools and churches to explore opportunities for co-engaged reflexivity that might produce transformation. Schools and Christian churches, two institutions that reflect modern, western socialecological worldviews also have the potential to bring about change. Critical Realism was chosen as my philosophical framework as it provided the tools to explore deeper mechanisms beyond empirical reality, both influencing the degrading trajectory as well as providing possibilities for transformation. It also legitimised case study research as a means to understand more generalised processes characterising modern social-ecological systems. The choice of Critical Realism informed the scope of my primary research question: What generative mechanisms constrain and enable the development of social-ecological resilience for well-being, in the modern social-ecological system of Boksburg Lake? The following three goals were formulated to address this primary question. Goal 1: Based on a multitheoretical perspective of social-ecological literature, develop conceptual tools that have explanatory power to probe generative mechanisms operating in the Boksburg Lake social-ecological system. Goal 2: Identify generative mechanisms driving the current degradation of the Boksburg Lake social-ecological system. Goal 3: Identify learning mechanisms that support transformation for greater social-ecological resilience of the Boksburg Lake social-ecological system. By addressing the primary question and research goals I aimed to gain insights into modern global socialecological systems, the mechanisms that drive high social-ecological risk and the requirements for and possibilities of global systemic change. Drawing on a broad reading of social-ecological literature from different vantage points, tools with explanatory power were developed to probe for generative mechanisms in the Boksburg Lake social-ecological system (goal 1). The human capacity for symbolic representation is identified as an emergent property of coevolving human-ecological systems. These symbolic representations become expressed in culture and worldviews, and influence patterns of identifying, types of knowledge and forms of agency. The nature of these will determine the degree that cultural systems are embedded within ecological reality and the extent of cultural-ecological coupling. A cultural system closely coupled with ecological realities is likely to value ecological systems and manage them for their health, while less coupled cultural-ecological systems are likely to lead to the opposite. Because of their integrated nature, the extent of ecological health and value will affect the decline or sustainability of cultural-ecological systems. There are numerous examples of the learning that can take place when cultural-ecological systems are facing decline. This learning can enhance or reduce biophyllic instincts that become encoded in patterns of identifying, types of knowledge and forms of agency. This in turn affects the strength of cultural-ecological coupling and the extent that human societies co-evolve with ecological systems. , Normalising ideologies is a concept coined in the thesis to refer to symbolic representations of reality that have become integral to a social fabric and determine meaning, while maintaining the domination of the powerful. These ideologies determine patterns of identifying, knowledge and agency and are recognised as having a fundamental influence on the resilience of social-ecological systems. Four normalising ideologies are identified that promote apparent human progress at the expense of ecological integrity and social equality and thus alienation with each other and the ecological world. These are human-ecological dualism, anthropocentrism, nature is mechanised and nature is to be controlled. There are also a number of ideologies promoting connectedness with the ecological world that, if they became normalised, would support greater social-ecological resilience for well-being. Generative mechanisms driving the current degradation of the Boksburg Lake socialecological system were identified (goal 2). Drawing on critical methodology, the main method adopted was document analysis of the Boksburg Advertiser archives, Boksburg’s local newspaper. Four generative mechanisms are recognised as most influential. Two of these have been named hegemonic symbolic systems. The primary symbolic system consists of the four normalising ideologies, mentioned above, that promote human progress at the expense of ecological health. The secondary, more explicit symbolic system, built on this, consists of the following normative ideologies: economic growth is imperative, unrestrained development is promoted, competition is the necessary means and consumerism is the good life. These two symbolic systems have had causal influence on the systematic erosion of ecological processes and biological diversity that has occurred in Boksburg, with the consequent undermining of social-ecological resilience for well-being. The third mechanism that constrains resilience is the power dynamics that have shaped Boksburg’s economic history and social-ecological system. This has resulted in a society built on inequality and injustice with all its associated social and environmental ills, expressed as externalities. The fourth mechanism resides in Boksburg’s political and municipal dynamics. These structures are not designed to tackle complex social-ecological problems and they hold considerable agential power, yet seem dysfunctional at present. Learning mechanisms that support transformation for greater social-ecological resilience of the Boksburg Lake social-ecological system were identified (goal 3). By adopting the role of a reflexive practitioner, supported by action research, case study and interpretivist methodologies, data on the empirical manifestations of the environmental educational initiative were collected. Methods included semistructured interviews, focus groups, document analysis and participant observation. Findings indicate that schools and churches are important institutions that can positively influence patterns of identifying, knowledge about and agency for Boksburg Lake and can thus play a role in transforming hegemonic normalising ideologies. Important learning mechanisms identified included: Learning reflexively together within communities of practice that provide opportunities for active rather than passive learning; involving the youth as they are a group of people with notable enthusiasm, vision, energy and motivation; learning through information acquisition, investigation, action and deliberation; learning about abstract concepts and theoretical knowledge but embedding this in local realities; and learning that provides reference markers for how things can be different.
- Full Text:
- Authors: Fox, Helen Elizabeth
- Date: 2015
- Subjects: Boksburg Lake and Wetland project , Reservoirs -- South Africa -- Boksburg , Water -- Pollution -- South Africa -- Boksburg , Human ecology -- South Africa -- Boksburg , Social learning -- South Africa -- Boksburg , Critical realism
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:6048 , http://hdl.handle.net/10962/d1017872
- Description: This thesis is based on a case study of the degraded Boksburg Lake social-ecological system and an environmental education initiative that aimed to support its transformation. This initiative aimed to involve local people in reclaiming the lake’s social and ecological value, through a process of collectively reimagining possibilities, shaping identities, gaining knowledge and developing local human agency. The focus was on social learning processes in schools and churches to explore opportunities for co-engaged reflexivity that might produce transformation. Schools and Christian churches, two institutions that reflect modern, western socialecological worldviews also have the potential to bring about change. Critical Realism was chosen as my philosophical framework as it provided the tools to explore deeper mechanisms beyond empirical reality, both influencing the degrading trajectory as well as providing possibilities for transformation. It also legitimised case study research as a means to understand more generalised processes characterising modern social-ecological systems. The choice of Critical Realism informed the scope of my primary research question: What generative mechanisms constrain and enable the development of social-ecological resilience for well-being, in the modern social-ecological system of Boksburg Lake? The following three goals were formulated to address this primary question. Goal 1: Based on a multitheoretical perspective of social-ecological literature, develop conceptual tools that have explanatory power to probe generative mechanisms operating in the Boksburg Lake social-ecological system. Goal 2: Identify generative mechanisms driving the current degradation of the Boksburg Lake social-ecological system. Goal 3: Identify learning mechanisms that support transformation for greater social-ecological resilience of the Boksburg Lake social-ecological system. By addressing the primary question and research goals I aimed to gain insights into modern global socialecological systems, the mechanisms that drive high social-ecological risk and the requirements for and possibilities of global systemic change. Drawing on a broad reading of social-ecological literature from different vantage points, tools with explanatory power were developed to probe for generative mechanisms in the Boksburg Lake social-ecological system (goal 1). The human capacity for symbolic representation is identified as an emergent property of coevolving human-ecological systems. These symbolic representations become expressed in culture and worldviews, and influence patterns of identifying, types of knowledge and forms of agency. The nature of these will determine the degree that cultural systems are embedded within ecological reality and the extent of cultural-ecological coupling. A cultural system closely coupled with ecological realities is likely to value ecological systems and manage them for their health, while less coupled cultural-ecological systems are likely to lead to the opposite. Because of their integrated nature, the extent of ecological health and value will affect the decline or sustainability of cultural-ecological systems. There are numerous examples of the learning that can take place when cultural-ecological systems are facing decline. This learning can enhance or reduce biophyllic instincts that become encoded in patterns of identifying, types of knowledge and forms of agency. This in turn affects the strength of cultural-ecological coupling and the extent that human societies co-evolve with ecological systems. , Normalising ideologies is a concept coined in the thesis to refer to symbolic representations of reality that have become integral to a social fabric and determine meaning, while maintaining the domination of the powerful. These ideologies determine patterns of identifying, knowledge and agency and are recognised as having a fundamental influence on the resilience of social-ecological systems. Four normalising ideologies are identified that promote apparent human progress at the expense of ecological integrity and social equality and thus alienation with each other and the ecological world. These are human-ecological dualism, anthropocentrism, nature is mechanised and nature is to be controlled. There are also a number of ideologies promoting connectedness with the ecological world that, if they became normalised, would support greater social-ecological resilience for well-being. Generative mechanisms driving the current degradation of the Boksburg Lake socialecological system were identified (goal 2). Drawing on critical methodology, the main method adopted was document analysis of the Boksburg Advertiser archives, Boksburg’s local newspaper. Four generative mechanisms are recognised as most influential. Two of these have been named hegemonic symbolic systems. The primary symbolic system consists of the four normalising ideologies, mentioned above, that promote human progress at the expense of ecological health. The secondary, more explicit symbolic system, built on this, consists of the following normative ideologies: economic growth is imperative, unrestrained development is promoted, competition is the necessary means and consumerism is the good life. These two symbolic systems have had causal influence on the systematic erosion of ecological processes and biological diversity that has occurred in Boksburg, with the consequent undermining of social-ecological resilience for well-being. The third mechanism that constrains resilience is the power dynamics that have shaped Boksburg’s economic history and social-ecological system. This has resulted in a society built on inequality and injustice with all its associated social and environmental ills, expressed as externalities. The fourth mechanism resides in Boksburg’s political and municipal dynamics. These structures are not designed to tackle complex social-ecological problems and they hold considerable agential power, yet seem dysfunctional at present. Learning mechanisms that support transformation for greater social-ecological resilience of the Boksburg Lake social-ecological system were identified (goal 3). By adopting the role of a reflexive practitioner, supported by action research, case study and interpretivist methodologies, data on the empirical manifestations of the environmental educational initiative were collected. Methods included semistructured interviews, focus groups, document analysis and participant observation. Findings indicate that schools and churches are important institutions that can positively influence patterns of identifying, knowledge about and agency for Boksburg Lake and can thus play a role in transforming hegemonic normalising ideologies. Important learning mechanisms identified included: Learning reflexively together within communities of practice that provide opportunities for active rather than passive learning; involving the youth as they are a group of people with notable enthusiasm, vision, energy and motivation; learning through information acquisition, investigation, action and deliberation; learning about abstract concepts and theoretical knowledge but embedding this in local realities; and learning that provides reference markers for how things can be different.
- Full Text:
Spatial and temporal variations in trophic connectivity within an estuarine environment : benthic-pelagic and terrestrial-aquatic linkages via invertebrates and fishes
- Authors: Bergamino Roman, Leandro
- Date: 2015
- Subjects: Estuarine ecology -- South Africa , Marine invertebrates -- South Africa -- Ecology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5921 , http://hdl.handle.net/10962/d1017799
- Description: Estuarine ecosystems are among the most biologically productive areas and they provide important ecosystem services such as erosion control, habitat and refugia for several species. These environments are characterized by the presence of a variety of organic matter sources due to their transitional position between rivers and the sea. The biotic compositions can undergo spatial and seasonal changes along the estuary due to the spatial and temporal fluctuations of environmental factors such as salinity, temperature and seston loads. Therefore, the different combinations of biotic and abiotic factors make each estuary a unique ecosystem. Because of this spatial and temporal complexity, the understanding of estuarine food web structure and which factors affect the trophic relationships within the ecosystem through space and time represent challenging tasks. Furthermore, estuaries are under an increasing number of anthropogenic perturbations because of the growing concentration of human populations in coastal areas. Knowledge of ecosystem structure and functioning is essential for effective conservation and management planning of coastal areas.In this dissertation, I combine the utilization of biological tracers to examine spatial and temporal variability in the food web structure within a small temperate and microtidal estuary located in South Africa. To this end, fatty acid profiles and stable isotope signatures were measured in several primary organic matter sources and consumers (including zooplankton, fishes and benthic invertebrates) during four consecutive seasons and in three different estuarine regions: upper, middle, and lower reaches. The three reaches had distinct habitat features of vegetation type and morphology, and in particular the lower reaches were colonized by the marsh grass Spartina maritima. Isotopic mixing models were used to estimate the relative contribution of each food source to the diets of invertebrates and fishes within the estuarine food web. The isotopic and fatty acid data showed similar results. In general, the lower reaches of the estuary were characterized by a higher deposition and assimilation by brachyuran crabs of carbon derived from marsh grass detritus, whiletowards the upper reaches a mixture of microphytobenthos and particulate organic matter (phytoplankton and detritus) was deposited and sustained the pelagic and benthic fauna. The highest deposition and assimilation of marsh grass detritus in the lower reaches of the estuary occurred during periods of low freshwater discharge (autumn and winter). In the upper reaches, microphytobenthos and suspended particulate organic matter were dominant basal food resources for the food web during all seasons. These results indicated that benthic consumers incorporated mainly local carbon sources from their local habitat.To clarify isotopic and fatty acid patterns I examined the trophic behaviour of the sesarmid crab Sesarma catenata through laboratory feeding experiments. Results from these experiments validated that decomposed leaves of riparian trees and the salt marsh plant S. maritima were the preferred food of the sesarmid crabs, potentially due to high bacterial loads. The remaining leaf material not assimilated by crabs, together with faecal material, are likely important subsidies for adjacent environments, hence representing an important energy pathway involving the microbial food chain. Furthermore, this dissertation showed the importance of mobile top predators as vectors energetically connecting distinct food chains within the estuary (i.e. littoral, benthic and pelagic). I concluded that a combination of physical (i.e. patterns of freshwater discharge and estuary morphology) and biological factors (i.e. organism feeding behaviour, mobility, primary productivity, the local vegetation type) influence the pattern of dominant primary organic matter sources, and therefore the food web structure along the estuarine environment. In particular, marsh grass detritus contributed substantially to the diets of estuarine fauna during periods of low freshwater discharge. Given the importance of the salt marsh habitat in providing trophic resources, it is important to preserve this environment to sustain the natural biota and ecosystem functioning.
- Full Text:
- Authors: Bergamino Roman, Leandro
- Date: 2015
- Subjects: Estuarine ecology -- South Africa , Marine invertebrates -- South Africa -- Ecology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5921 , http://hdl.handle.net/10962/d1017799
- Description: Estuarine ecosystems are among the most biologically productive areas and they provide important ecosystem services such as erosion control, habitat and refugia for several species. These environments are characterized by the presence of a variety of organic matter sources due to their transitional position between rivers and the sea. The biotic compositions can undergo spatial and seasonal changes along the estuary due to the spatial and temporal fluctuations of environmental factors such as salinity, temperature and seston loads. Therefore, the different combinations of biotic and abiotic factors make each estuary a unique ecosystem. Because of this spatial and temporal complexity, the understanding of estuarine food web structure and which factors affect the trophic relationships within the ecosystem through space and time represent challenging tasks. Furthermore, estuaries are under an increasing number of anthropogenic perturbations because of the growing concentration of human populations in coastal areas. Knowledge of ecosystem structure and functioning is essential for effective conservation and management planning of coastal areas.In this dissertation, I combine the utilization of biological tracers to examine spatial and temporal variability in the food web structure within a small temperate and microtidal estuary located in South Africa. To this end, fatty acid profiles and stable isotope signatures were measured in several primary organic matter sources and consumers (including zooplankton, fishes and benthic invertebrates) during four consecutive seasons and in three different estuarine regions: upper, middle, and lower reaches. The three reaches had distinct habitat features of vegetation type and morphology, and in particular the lower reaches were colonized by the marsh grass Spartina maritima. Isotopic mixing models were used to estimate the relative contribution of each food source to the diets of invertebrates and fishes within the estuarine food web. The isotopic and fatty acid data showed similar results. In general, the lower reaches of the estuary were characterized by a higher deposition and assimilation by brachyuran crabs of carbon derived from marsh grass detritus, whiletowards the upper reaches a mixture of microphytobenthos and particulate organic matter (phytoplankton and detritus) was deposited and sustained the pelagic and benthic fauna. The highest deposition and assimilation of marsh grass detritus in the lower reaches of the estuary occurred during periods of low freshwater discharge (autumn and winter). In the upper reaches, microphytobenthos and suspended particulate organic matter were dominant basal food resources for the food web during all seasons. These results indicated that benthic consumers incorporated mainly local carbon sources from their local habitat.To clarify isotopic and fatty acid patterns I examined the trophic behaviour of the sesarmid crab Sesarma catenata through laboratory feeding experiments. Results from these experiments validated that decomposed leaves of riparian trees and the salt marsh plant S. maritima were the preferred food of the sesarmid crabs, potentially due to high bacterial loads. The remaining leaf material not assimilated by crabs, together with faecal material, are likely important subsidies for adjacent environments, hence representing an important energy pathway involving the microbial food chain. Furthermore, this dissertation showed the importance of mobile top predators as vectors energetically connecting distinct food chains within the estuary (i.e. littoral, benthic and pelagic). I concluded that a combination of physical (i.e. patterns of freshwater discharge and estuary morphology) and biological factors (i.e. organism feeding behaviour, mobility, primary productivity, the local vegetation type) influence the pattern of dominant primary organic matter sources, and therefore the food web structure along the estuarine environment. In particular, marsh grass detritus contributed substantially to the diets of estuarine fauna during periods of low freshwater discharge. Given the importance of the salt marsh habitat in providing trophic resources, it is important to preserve this environment to sustain the natural biota and ecosystem functioning.
- Full Text:
Spatio-temporal variation in the phytobenthos and phytoplankton community structure and composition of particulate matter along a river-estuary continuum assessed using microscopic and stable isotope analyses
- Authors: Dalu, Tatenda
- Date: 2015
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/54416 , vital:26563
- Description: Phytoplankton and phytobenthos communities play an important role in lotic systems as primary producers providing essential biomolecules to higher trophic oganisms and are important indicators for environmental or ecological change. In this thesis, field studies (observational and experimental) along a river–estuary continuum were conducted to assess the spatio-temporal variation and development of phytobenthos and phytoplankton communities using a combination of stable isotope and community analyses in a temperate southern African system across four study periods: September (early spring) and November/December (late spring) 2012, and February (summer) and May/June (winter) 2013. Additionally, the sources and composition of the particulate organic matter were also analysed using stable isotope (δ15N and δ13C) analysis. The effects of substrate type and flood occurrence were assessed through experimental studies at an up- and downstream site of the river after a major flood event that occurred between October and November 2012. Common household tiles were used as artificial substrates to study the development/succession of phytobenthos communities after the flood disturbance. Distinct diatom communities were observed between upstream and downstream sites and at each site, community structure changed with time indicating succession. In addition to recording diatom characteristics on three natural substrates, namely; macrophytes, rocks and sediment, artificial substrates observations were also made on three different types of artificial substrates, namely; brick, brown clay and grey clay tiles. The natural (species richness 78) and artificial substrates (sp. richness 93) had different communities with the latter having greater species richness. Common phytobenthos taxa were not restricted to a single substrate but preference was generally high for the artificial substrates, especially brown tiles (mean sp. richness 47). Results of the redundancy analysis (RDA) analysis indicated that ammonium, conductivity, total dissolved solids, salinity, pH, oxygen reduction potential, phosphate and water depth were the major determinants of the phytobenthos composition at the two sites. The spatio–temporal variation of phytoplankton and phytobenthos communities and allochthonous organic matter along the river–estuary continuum was assessed at 8 sites using a combination of community and stable isotope analyses. A total of 178 species belonging to 78 genera were recorded with diatoms being predominant, accounting for 81.9 % of the total abundance. The total chl-a concentration along the river-estuary continuum increased from spring to a high in summer before decreasing to a low in winter. Periphyton communities were observed to be significantly different across sites (p < 0.05) in terms of species richness, abundances and isotopically The high periphytic δ15N values (range 7.9–15.2 ‰) recorded at the downstream sites compared to the pristine upstream sites (δ15N values range 4–7 ‰) suggest nutrient enrichment most likely derived from anthropogenic sources. Overall, our results reveal general patterns of periphyton communities and stable isotopes and provide improved information in the use of periphyton δ15N as an excellent indicator of anthropogenic nitrogen pollution. Ecologists are interested in the factors that control, and the variability in, the contributions of different sources to mixed organic materials traveling through lotic systems. We hypothesized that the source matter fuelling mixed organic pools in a river-estuary continuum varies over space and time, with the upper reaches of a system characterized by allochthonous-dominated material and autochthonous contributions becoming more important in the lower reaches. Samples of the mixed organic pools and allochthonous and autochthonous source materials were collected during the four study periods. The C:N ratios of suspended particulate matter (SPM) collected during summer and winter indicated that the lower reaches of the system had similar organic matter contributions from the freshwater and terrestrial sources. Stable isotope analysis in R revealed that the contributions of autochthonous organic matter were high in SPM along the entire continuum, and aquatic macrophytes were significant contributors to SPM specifically in the upper reaches. The terrestrial leaves made major contributions to the SPM in the middle regions of the system (i.e. downstream sites of the river, particularly in early and late spring). Bulk detritus had large allochthonous matter components in the lower reaches (estuary), and the contributions of aquatic macrophytes and benthic algae to bulk detritus were high (> 50 %) in the upper to middle reaches (river), but low (< 20 %) in the lower reaches (estuary). The current investigation represents the first attempt to assess the validity of the River Continuum Concept (RCC) in a southern African temperate river. The phytoplankton and phytobenthos communities, and chl-a concentration followed a trend similar to that proposed for the river continuum concept (RCC). The middle reaches based on the phytobenthos or phytoplankton communities and chl-a concentrations which were employed as proxies for primary production, were the most productive, while the upper reaches were the least primary productive. The evaluation of organic matter contributions to the SPM and detritus along the river–estuary continuum provided a baseline assessment of the nature and sources of potential food for consumers inhabiting different locations during different times of the year. Incorporating such spatio-temporal variations in SPM and detritus into food web studies will improve our understanding of the flow of carbon through aquatic systems.
- Full Text:
- Authors: Dalu, Tatenda
- Date: 2015
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/54416 , vital:26563
- Description: Phytoplankton and phytobenthos communities play an important role in lotic systems as primary producers providing essential biomolecules to higher trophic oganisms and are important indicators for environmental or ecological change. In this thesis, field studies (observational and experimental) along a river–estuary continuum were conducted to assess the spatio-temporal variation and development of phytobenthos and phytoplankton communities using a combination of stable isotope and community analyses in a temperate southern African system across four study periods: September (early spring) and November/December (late spring) 2012, and February (summer) and May/June (winter) 2013. Additionally, the sources and composition of the particulate organic matter were also analysed using stable isotope (δ15N and δ13C) analysis. The effects of substrate type and flood occurrence were assessed through experimental studies at an up- and downstream site of the river after a major flood event that occurred between October and November 2012. Common household tiles were used as artificial substrates to study the development/succession of phytobenthos communities after the flood disturbance. Distinct diatom communities were observed between upstream and downstream sites and at each site, community structure changed with time indicating succession. In addition to recording diatom characteristics on three natural substrates, namely; macrophytes, rocks and sediment, artificial substrates observations were also made on three different types of artificial substrates, namely; brick, brown clay and grey clay tiles. The natural (species richness 78) and artificial substrates (sp. richness 93) had different communities with the latter having greater species richness. Common phytobenthos taxa were not restricted to a single substrate but preference was generally high for the artificial substrates, especially brown tiles (mean sp. richness 47). Results of the redundancy analysis (RDA) analysis indicated that ammonium, conductivity, total dissolved solids, salinity, pH, oxygen reduction potential, phosphate and water depth were the major determinants of the phytobenthos composition at the two sites. The spatio–temporal variation of phytoplankton and phytobenthos communities and allochthonous organic matter along the river–estuary continuum was assessed at 8 sites using a combination of community and stable isotope analyses. A total of 178 species belonging to 78 genera were recorded with diatoms being predominant, accounting for 81.9 % of the total abundance. The total chl-a concentration along the river-estuary continuum increased from spring to a high in summer before decreasing to a low in winter. Periphyton communities were observed to be significantly different across sites (p < 0.05) in terms of species richness, abundances and isotopically The high periphytic δ15N values (range 7.9–15.2 ‰) recorded at the downstream sites compared to the pristine upstream sites (δ15N values range 4–7 ‰) suggest nutrient enrichment most likely derived from anthropogenic sources. Overall, our results reveal general patterns of periphyton communities and stable isotopes and provide improved information in the use of periphyton δ15N as an excellent indicator of anthropogenic nitrogen pollution. Ecologists are interested in the factors that control, and the variability in, the contributions of different sources to mixed organic materials traveling through lotic systems. We hypothesized that the source matter fuelling mixed organic pools in a river-estuary continuum varies over space and time, with the upper reaches of a system characterized by allochthonous-dominated material and autochthonous contributions becoming more important in the lower reaches. Samples of the mixed organic pools and allochthonous and autochthonous source materials were collected during the four study periods. The C:N ratios of suspended particulate matter (SPM) collected during summer and winter indicated that the lower reaches of the system had similar organic matter contributions from the freshwater and terrestrial sources. Stable isotope analysis in R revealed that the contributions of autochthonous organic matter were high in SPM along the entire continuum, and aquatic macrophytes were significant contributors to SPM specifically in the upper reaches. The terrestrial leaves made major contributions to the SPM in the middle regions of the system (i.e. downstream sites of the river, particularly in early and late spring). Bulk detritus had large allochthonous matter components in the lower reaches (estuary), and the contributions of aquatic macrophytes and benthic algae to bulk detritus were high (> 50 %) in the upper to middle reaches (river), but low (< 20 %) in the lower reaches (estuary). The current investigation represents the first attempt to assess the validity of the River Continuum Concept (RCC) in a southern African temperate river. The phytoplankton and phytobenthos communities, and chl-a concentration followed a trend similar to that proposed for the river continuum concept (RCC). The middle reaches based on the phytobenthos or phytoplankton communities and chl-a concentrations which were employed as proxies for primary production, were the most productive, while the upper reaches were the least primary productive. The evaluation of organic matter contributions to the SPM and detritus along the river–estuary continuum provided a baseline assessment of the nature and sources of potential food for consumers inhabiting different locations during different times of the year. Incorporating such spatio-temporal variations in SPM and detritus into food web studies will improve our understanding of the flow of carbon through aquatic systems.
- Full Text:
Synthesis and biological evaluation of truncated sarganaphthoquinoic acid derivatives as Hsp90 inhibitors
- Authors: Chiwakata, Maynard T
- Date: 2015
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/64708 , vital:28594
- Description: Hsp90 inhibition has been at the centre of attention in current research due to the possibility of “cracking down” on the entire process leading to the development of malignant cancers. Small underlying principles common in all types of cancers have been determined that govern the transformation of normal human cells into cancerous cells, with all relying on the ATPase activity of Hsp90 protein. Hsp90 protein is therefore an attractive drug target that if successfully inhibited can result in the remission of cancer tumours by one form of treatment. To date, no Hsp90 inhibitor has been sanctioned for cancer treatment as most are still in clinical development. Our research was therefore inspired by reports that indicated the potential of quinones / naphthoquinones to act as Hsp90 inhibitors. Preliminary results of a few selected marine natural product quinone systems i.e. sargaquinoic acid (SQA) (2.47) and lapachol (3.6) showed moderate cytotoxicity and weak interactions with the Hsp90 molecular chaperone, and evidence suggested C-terminal binding of these molecules. No correlation has been determined yet between cytotoxicity and Hsp90 inhibition, hence we aimed to develop natural product inspired molecules that exhibit both cytotoxic and Hsp90 inhibition properties. Due to limited amounts of the natural product that can be acquired from natural sources, synthetic analogues were opted for. Isolation of a few selected quinones was conducted to have material that could be used in biological assays. For structural modifications, a series of truncated naphthoquinone systems were prepared adopting the sarganaphthoquinoic acid (3.5) scaffold. The naphthoquinones were prepared via Diels-Alder reactions of relevant benzoquinones with myrcene, followed by aromatization reactions using MnO2. Various alkyl and aryl amines were then coupled to the C-2/3 position of the naphthoquinone using Michael’s addition reactions. Tricyclic naphthoquinones were also synthesized from reactions with hypotaurine and citral. Design of the analogues incorporated functionalities from known Hsp90 inhibitors e.g. geldanamycin (2.28) and its analogues. Preliminary results obtained showed that coupling of naphthoquinones with aryl-amines resulted in the most cytotoxic compounds (4.14-4.19) with IC50 values as low as 0.3 μM against Hs578T breast cancer carcinoma (triple negative). Most of the alkyl amines (4.20-4.25) had IC50 values greater than 50 μM except for 4.20 and 4.21 that showed IC50 values of 7.6 μM and 2.6 μM respectively. Tricyclic naphthoquinones (4.28-4.29) showed moderate cytotoxic activity of approximately 10 μM. Hsp90 inhibition was assessed by client protein degradation assays, of which SQA (2.47), showed the best Hsp90 inhibition properties, followed by compound 4.20. The most cytotoxic arylamino-naphthoquinone (4.16) and tricyclic naphthoquinones (4.28-4.29) showed only moderate inhibition. None of the compounds led to Hsp70 induction, suggesting possible binding to the C-terminus of Hsp90. Interactions at the binding site were assessed by molecular docking studies and saturation transfer difference (STD) NMR. Docking studies were conducted on the N-terminus of Hsp90 and better binding was observed for arylamino naphthoquinones (4.14-4.19) than for other series of compounds. Unfortunately, the co-crystal structure for the C-terminus of Hsp90 is unavailable, hence docking study comparisons on both domains could not be conducted. However, STD NMR offered a platform to assess binding interactions between the naphthoquinones and the N- or C-terminal domains of Hsp90. However no interactions were observed at both the N- and C- termini of Hsp90 due to either weak binding of ligands to the protein or poor water solubility of the ligands. From these preliminary results, naphthoquinones bind to Hsp90 protein but conclusive remarks to which terminal domain they bind to could not be made. The best candidate from amongst the series of naphthoquinones prepared that showed moderate cytotoxicity and promising Hsp90 inhibition was compound 4.20. We therefore succeeded in developing a new series of naphthoquinones that possess moderate cytotoxicity and show Hsp90 inhibition.
- Full Text:
- Authors: Chiwakata, Maynard T
- Date: 2015
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/64708 , vital:28594
- Description: Hsp90 inhibition has been at the centre of attention in current research due to the possibility of “cracking down” on the entire process leading to the development of malignant cancers. Small underlying principles common in all types of cancers have been determined that govern the transformation of normal human cells into cancerous cells, with all relying on the ATPase activity of Hsp90 protein. Hsp90 protein is therefore an attractive drug target that if successfully inhibited can result in the remission of cancer tumours by one form of treatment. To date, no Hsp90 inhibitor has been sanctioned for cancer treatment as most are still in clinical development. Our research was therefore inspired by reports that indicated the potential of quinones / naphthoquinones to act as Hsp90 inhibitors. Preliminary results of a few selected marine natural product quinone systems i.e. sargaquinoic acid (SQA) (2.47) and lapachol (3.6) showed moderate cytotoxicity and weak interactions with the Hsp90 molecular chaperone, and evidence suggested C-terminal binding of these molecules. No correlation has been determined yet between cytotoxicity and Hsp90 inhibition, hence we aimed to develop natural product inspired molecules that exhibit both cytotoxic and Hsp90 inhibition properties. Due to limited amounts of the natural product that can be acquired from natural sources, synthetic analogues were opted for. Isolation of a few selected quinones was conducted to have material that could be used in biological assays. For structural modifications, a series of truncated naphthoquinone systems were prepared adopting the sarganaphthoquinoic acid (3.5) scaffold. The naphthoquinones were prepared via Diels-Alder reactions of relevant benzoquinones with myrcene, followed by aromatization reactions using MnO2. Various alkyl and aryl amines were then coupled to the C-2/3 position of the naphthoquinone using Michael’s addition reactions. Tricyclic naphthoquinones were also synthesized from reactions with hypotaurine and citral. Design of the analogues incorporated functionalities from known Hsp90 inhibitors e.g. geldanamycin (2.28) and its analogues. Preliminary results obtained showed that coupling of naphthoquinones with aryl-amines resulted in the most cytotoxic compounds (4.14-4.19) with IC50 values as low as 0.3 μM against Hs578T breast cancer carcinoma (triple negative). Most of the alkyl amines (4.20-4.25) had IC50 values greater than 50 μM except for 4.20 and 4.21 that showed IC50 values of 7.6 μM and 2.6 μM respectively. Tricyclic naphthoquinones (4.28-4.29) showed moderate cytotoxic activity of approximately 10 μM. Hsp90 inhibition was assessed by client protein degradation assays, of which SQA (2.47), showed the best Hsp90 inhibition properties, followed by compound 4.20. The most cytotoxic arylamino-naphthoquinone (4.16) and tricyclic naphthoquinones (4.28-4.29) showed only moderate inhibition. None of the compounds led to Hsp70 induction, suggesting possible binding to the C-terminus of Hsp90. Interactions at the binding site were assessed by molecular docking studies and saturation transfer difference (STD) NMR. Docking studies were conducted on the N-terminus of Hsp90 and better binding was observed for arylamino naphthoquinones (4.14-4.19) than for other series of compounds. Unfortunately, the co-crystal structure for the C-terminus of Hsp90 is unavailable, hence docking study comparisons on both domains could not be conducted. However, STD NMR offered a platform to assess binding interactions between the naphthoquinones and the N- or C-terminal domains of Hsp90. However no interactions were observed at both the N- and C- termini of Hsp90 due to either weak binding of ligands to the protein or poor water solubility of the ligands. From these preliminary results, naphthoquinones bind to Hsp90 protein but conclusive remarks to which terminal domain they bind to could not be made. The best candidate from amongst the series of naphthoquinones prepared that showed moderate cytotoxicity and promising Hsp90 inhibition was compound 4.20. We therefore succeeded in developing a new series of naphthoquinones that possess moderate cytotoxicity and show Hsp90 inhibition.
- Full Text:
The associative behaviour of silky sharks, Carcharhinus falciformis, with floating objects in the open ocean
- Authors: Filmalter, John David
- Date: 2015
- Subjects: Silky shark , Silky shark -- Behavior , Silky shark -- Marking , Silky shark -- Food , Tuna fisheries -- Bycatches , Fish aggregation devices , Underwater acoustic telemetry , Fish tagging
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5381 , http://hdl.handle.net/10962/d1018177
- Description: The silky shark Carcharhinus falciformis forms the primary elasmobranch bycatch in tuna purse seine fisheries using fish aggregating devices (FADs) in all of the world’s tropical oceans. Its life-history traits of slow growth, late maturation and low fecundity make it vulnerable to over exploitation, as is apparent from historical bycatch trends. Very little is known about the associative behaviour of this species with floating objects, information which is essential in formulating effective mitigation and management measures. This study aims to address this knowledge gap through the use of various electronic tagging techniques in conjunction with dietary analysis. Dietary data were collected from 323 silky sharks incidentally caught at FADs. Approximately 40 percent of the diet consisted of prey associated with FADs while the remaining 60 percent were non-associated species of crustaceans, cephalopods and fishes. These results suggest that the associative behaviour is not primarily driven by trophic enhancement, but is likely a combination of predator avoidance, social interactions and feeding. Fine-scale behavioural data from silky sharks associated with drifting FADs were collected through the use of acoustic telemetry techniques. Acoustic tags were implanted into 38 silky sharks (69- 116 cm TL) at eight FADs. FADs were equipped with satellite linked acoustic receivers and abandoned to drift freely. Presence/absence and swimming depth data were telemetered via the Iridium satellite system. A total of 300 d of behavioural data were collected from 20 tagged individuals. Individuals remain associated with the same FAD for extended periods (min = 2.84 d, max = 30.60 d, mean = 15.69 d). Strong diel patterns were observed in both association and swimming depth. Typically individuals moved away from FADs after sunset and return later during the night, then remain closely associated until the following evening. Vertical behaviour also changed around sunset with sharks using fairly constant depths, within the upper 25 m, during the day and switching to rapid vertical movements during the night, with dives in excess of 250 m recoded. Broader scale movement behaviour was investigated using pop-up archival satellite tags (PSATs). Tags were deployed on 46 silky sharks (86-224.5 cm TL) for a total of 1495 d. Light data were used to calculate geolocation estimates and reconstruct the sharks’ trajectories. Movement patterns differed between animals and according to deployment duration. Several extensive horizontal movements were observed, with an average track length of 3240 km during an average tag deployment of 44.02 d. Horizontal movement patterns were found to correlate very closely with drift patterns of FADs. Consequently, it appears that the movement behaviour of juvenile silky sharks is strongly influenced by the movement of drifting FADs in this region. Ghost fishing of silky sharks through entanglement in FADs was also investigated using data derived from PSATs as well as underwater visual censuses. Thirteen per cent of the tagged sharks became entangled in FADs and entangled sharks were observed in 35 percent of the 51 FADs surveyed. Using this information in conjunction with estimated time that sharks remained entangled in the FAD (from depth data from PSATs), and scaling up according to estimates of FAD numbers, it was found that between 480 000 and 960 000 silky sharks are killed annually in this manner in the Indian Ocean. Subsequent management measures in this region prevent the deployment of FADs with netting that could lead to entanglement. Overall, floating objects appear to play a significant role in the juvenile life stages of silky sharks in this region. While their association with floating objects is clearly advantageous in an evolutionary sense, under current tuna fishery trends, this behaviour is certainly detrimental for the population.
- Full Text:
- Authors: Filmalter, John David
- Date: 2015
- Subjects: Silky shark , Silky shark -- Behavior , Silky shark -- Marking , Silky shark -- Food , Tuna fisheries -- Bycatches , Fish aggregation devices , Underwater acoustic telemetry , Fish tagging
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5381 , http://hdl.handle.net/10962/d1018177
- Description: The silky shark Carcharhinus falciformis forms the primary elasmobranch bycatch in tuna purse seine fisheries using fish aggregating devices (FADs) in all of the world’s tropical oceans. Its life-history traits of slow growth, late maturation and low fecundity make it vulnerable to over exploitation, as is apparent from historical bycatch trends. Very little is known about the associative behaviour of this species with floating objects, information which is essential in formulating effective mitigation and management measures. This study aims to address this knowledge gap through the use of various electronic tagging techniques in conjunction with dietary analysis. Dietary data were collected from 323 silky sharks incidentally caught at FADs. Approximately 40 percent of the diet consisted of prey associated with FADs while the remaining 60 percent were non-associated species of crustaceans, cephalopods and fishes. These results suggest that the associative behaviour is not primarily driven by trophic enhancement, but is likely a combination of predator avoidance, social interactions and feeding. Fine-scale behavioural data from silky sharks associated with drifting FADs were collected through the use of acoustic telemetry techniques. Acoustic tags were implanted into 38 silky sharks (69- 116 cm TL) at eight FADs. FADs were equipped with satellite linked acoustic receivers and abandoned to drift freely. Presence/absence and swimming depth data were telemetered via the Iridium satellite system. A total of 300 d of behavioural data were collected from 20 tagged individuals. Individuals remain associated with the same FAD for extended periods (min = 2.84 d, max = 30.60 d, mean = 15.69 d). Strong diel patterns were observed in both association and swimming depth. Typically individuals moved away from FADs after sunset and return later during the night, then remain closely associated until the following evening. Vertical behaviour also changed around sunset with sharks using fairly constant depths, within the upper 25 m, during the day and switching to rapid vertical movements during the night, with dives in excess of 250 m recoded. Broader scale movement behaviour was investigated using pop-up archival satellite tags (PSATs). Tags were deployed on 46 silky sharks (86-224.5 cm TL) for a total of 1495 d. Light data were used to calculate geolocation estimates and reconstruct the sharks’ trajectories. Movement patterns differed between animals and according to deployment duration. Several extensive horizontal movements were observed, with an average track length of 3240 km during an average tag deployment of 44.02 d. Horizontal movement patterns were found to correlate very closely with drift patterns of FADs. Consequently, it appears that the movement behaviour of juvenile silky sharks is strongly influenced by the movement of drifting FADs in this region. Ghost fishing of silky sharks through entanglement in FADs was also investigated using data derived from PSATs as well as underwater visual censuses. Thirteen per cent of the tagged sharks became entangled in FADs and entangled sharks were observed in 35 percent of the 51 FADs surveyed. Using this information in conjunction with estimated time that sharks remained entangled in the FAD (from depth data from PSATs), and scaling up according to estimates of FAD numbers, it was found that between 480 000 and 960 000 silky sharks are killed annually in this manner in the Indian Ocean. Subsequent management measures in this region prevent the deployment of FADs with netting that could lead to entanglement. Overall, floating objects appear to play a significant role in the juvenile life stages of silky sharks in this region. While their association with floating objects is clearly advantageous in an evolutionary sense, under current tuna fishery trends, this behaviour is certainly detrimental for the population.
- Full Text:
The call centre labour process : a study of work and workers’ experiences at Joburg Connect, South Africa
- Authors: Magoqwana, Babalwa Mirianda
- Date: 2015
- Subjects: Johannesburg (South Africa) -- Joburg Connect , Call center agents -- South Africa -- Johannesburg -- Case studies , Work environment -- South Africa -- Johannesburg -- Case studies , Customer services -- South Africa -- Johannesburg -- Case studies , Personnel management -- South Africa -- Johannesburg -- Case studies , Employee morale -- South Africa -- Johannesburg -- Case studies , Employees -- Attitudes -- Case studies , Municipal services -- South Africa -- Johannesburg -- Case studies , South Africa -- Economic conditions -- 1991- , South Africa -- Politics and government -- 1994- , South Africa -- Social conditions -- 1994-
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3400 , http://hdl.handle.net/10962/d1018569 , Johannesburg (South Africa) -- Joburg Connect , Call center agents -- South Africa -- Johannesburg -- Case studies , Work environment -- South Africa -- Johannesburg -- Case studies , Customer services -- South Africa -- Johannesburg -- Case studies , Personnel management -- South Africa -- Johannesburg -- Case studies , Employee morale -- South Africa -- Johannesburg -- Case studies , Employees -- Attitudes -- Case studies , Municipal services -- South Africa -- Johannesburg -- Case studies , South Africa -- Economic conditions -- 1991- , South Africa -- Politics and government -- 1994-
- Description: This thesis is an investigation of the call centre labour process focusing on both the way work is organised and experienced by the operators and the management of employee relations inside a local government workplace – The City of Johannesburg (COJ) Call Centre. The City of Johannesburg is used to understand labour process dynamics in local government. Johannesburg was recently named the ‘World’s Second Most Inspiring City’ (by Global City Index, 2014) possessing economic and political influence within and around South Africa. Johannesburg is the economic hub of the country, contributing nine per cent to the South African GDP. But it needs to be emphasised that the focus of this thesis is on the labour process rather than the City of Johannesburg. The nature of work in the COJ local government call centre involves answering calls about water, electricity, refuse removal, accounts and other general municipal services. The government’s objective was to have a more customer centred service delivery plan in compliance with the Batho Pele (People first) framework (RSA, 1997, White Paper on Local Government). This resulted in a shift in the government ‘mantra’ and philosophy from viewing Johannesburg residents as customers rather than citizens. This shift from public administration to New Public Management (NPM) has meant the introduction of private sector business principles into public services. This seeks to improve organisational and individual performance to enhance service delivery within South African municipalities. This is also meant to promote responsive and performance management culture. The study uses Labour Process Theory set out in Labour and Monopoly Capital (LMC-1974) by Harry Braverman to argue for the need to contextualise the labour process debate within the socio-political understanding of work in South Africa. In developing the argument about the narrow analysis of public sector call centres based on economic lines I have reviewed literature on call centres which is influenced by Michel Foucault and Harry Braverman to understand the public sector call centre labour process. Inspired by Adesina (2002) and Mafeje (1981) this study uses a ‘complementarity’ approach to knowledge. This means the local context tends to complement the global trends though not without contradictions within the local context. The case study approach was used for in-depth analysis of the local context through different methods (semi-structured interviews, focus group discussions, observations and survey questionnaires) to collect data from different stakeholders within the City of Johannesburg between 2010 and 2013. The concept of a ‘(dis)connecting city’ is fitting for the COJ as this city connects the rest of Sub-Saharan Africa and South Africa to the world through its commerce and political influence. Based on the challenges experienced in this local government call centre I attempt to show the the politicised nature of the public sector call centre labour process. I use the differential power relations in the frontline between customer and Joburg connect workers to illustrate this point. The lack of emphasis on the politicised nature of public sector call centres within literature is informed by the de-contextualised nature of these call centres. In the end, I argue that public sector call centre labour process is multilayered, contradictory and complicated because of these workers’ role as citizens, customers, community members and service providers from a politicised community environment.
- Full Text:
- Authors: Magoqwana, Babalwa Mirianda
- Date: 2015
- Subjects: Johannesburg (South Africa) -- Joburg Connect , Call center agents -- South Africa -- Johannesburg -- Case studies , Work environment -- South Africa -- Johannesburg -- Case studies , Customer services -- South Africa -- Johannesburg -- Case studies , Personnel management -- South Africa -- Johannesburg -- Case studies , Employee morale -- South Africa -- Johannesburg -- Case studies , Employees -- Attitudes -- Case studies , Municipal services -- South Africa -- Johannesburg -- Case studies , South Africa -- Economic conditions -- 1991- , South Africa -- Politics and government -- 1994- , South Africa -- Social conditions -- 1994-
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3400 , http://hdl.handle.net/10962/d1018569 , Johannesburg (South Africa) -- Joburg Connect , Call center agents -- South Africa -- Johannesburg -- Case studies , Work environment -- South Africa -- Johannesburg -- Case studies , Customer services -- South Africa -- Johannesburg -- Case studies , Personnel management -- South Africa -- Johannesburg -- Case studies , Employee morale -- South Africa -- Johannesburg -- Case studies , Employees -- Attitudes -- Case studies , Municipal services -- South Africa -- Johannesburg -- Case studies , South Africa -- Economic conditions -- 1991- , South Africa -- Politics and government -- 1994-
- Description: This thesis is an investigation of the call centre labour process focusing on both the way work is organised and experienced by the operators and the management of employee relations inside a local government workplace – The City of Johannesburg (COJ) Call Centre. The City of Johannesburg is used to understand labour process dynamics in local government. Johannesburg was recently named the ‘World’s Second Most Inspiring City’ (by Global City Index, 2014) possessing economic and political influence within and around South Africa. Johannesburg is the economic hub of the country, contributing nine per cent to the South African GDP. But it needs to be emphasised that the focus of this thesis is on the labour process rather than the City of Johannesburg. The nature of work in the COJ local government call centre involves answering calls about water, electricity, refuse removal, accounts and other general municipal services. The government’s objective was to have a more customer centred service delivery plan in compliance with the Batho Pele (People first) framework (RSA, 1997, White Paper on Local Government). This resulted in a shift in the government ‘mantra’ and philosophy from viewing Johannesburg residents as customers rather than citizens. This shift from public administration to New Public Management (NPM) has meant the introduction of private sector business principles into public services. This seeks to improve organisational and individual performance to enhance service delivery within South African municipalities. This is also meant to promote responsive and performance management culture. The study uses Labour Process Theory set out in Labour and Monopoly Capital (LMC-1974) by Harry Braverman to argue for the need to contextualise the labour process debate within the socio-political understanding of work in South Africa. In developing the argument about the narrow analysis of public sector call centres based on economic lines I have reviewed literature on call centres which is influenced by Michel Foucault and Harry Braverman to understand the public sector call centre labour process. Inspired by Adesina (2002) and Mafeje (1981) this study uses a ‘complementarity’ approach to knowledge. This means the local context tends to complement the global trends though not without contradictions within the local context. The case study approach was used for in-depth analysis of the local context through different methods (semi-structured interviews, focus group discussions, observations and survey questionnaires) to collect data from different stakeholders within the City of Johannesburg between 2010 and 2013. The concept of a ‘(dis)connecting city’ is fitting for the COJ as this city connects the rest of Sub-Saharan Africa and South Africa to the world through its commerce and political influence. Based on the challenges experienced in this local government call centre I attempt to show the the politicised nature of the public sector call centre labour process. I use the differential power relations in the frontline between customer and Joburg connect workers to illustrate this point. The lack of emphasis on the politicised nature of public sector call centres within literature is informed by the de-contextualised nature of these call centres. In the end, I argue that public sector call centre labour process is multilayered, contradictory and complicated because of these workers’ role as citizens, customers, community members and service providers from a politicised community environment.
- Full Text:
The detection of glyphosate and glyphosate-based herbicides in water, using nanotechnology
- De Almeida, Louise Kashiyavala Sophia
- Authors: De Almeida, Louise Kashiyavala Sophia
- Date: 2015
- Subjects: Water -- Glyphosate content , Aquatic herbicides -- South Africa , Aquatic herbicides -- Physiological effect , Nanotechnology , Invasive plants -- South Africa , Genetic toxicology , Thiazoles , Tetrazolium , Immunotoxicology , Colorimetry , Nanofibers
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4163 , http://hdl.handle.net/10962/d1019755
- Description: Glyphosate (N-phosphonomethylglycine) is an organophosphate compound which was developed by the Monsanto Company in 1971 and is the active ingredient found in several herbicide formulations. The use of glyphosate-based herbicides in South Africa for the control of alien invasive plants and weeds is well established, extensive and currently unregulated, which vastly increases the likelihood of glyphosate contamination in environmental water systems. Although the use of glyphosate-based herbicides is required for economic enhancement in industries such as agriculture, the presence of this compound in natural water systems presents a potential risk to human health. Glyphosate and glyphosate formulations were previously considered safe, however their toxicity has become a major focal point of research over recent years. The lack of monitoring protocols for pesticides in South Africa is primarily due to limited financial capacity and the lack of analytical techniques.
- Full Text:
- Authors: De Almeida, Louise Kashiyavala Sophia
- Date: 2015
- Subjects: Water -- Glyphosate content , Aquatic herbicides -- South Africa , Aquatic herbicides -- Physiological effect , Nanotechnology , Invasive plants -- South Africa , Genetic toxicology , Thiazoles , Tetrazolium , Immunotoxicology , Colorimetry , Nanofibers
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4163 , http://hdl.handle.net/10962/d1019755
- Description: Glyphosate (N-phosphonomethylglycine) is an organophosphate compound which was developed by the Monsanto Company in 1971 and is the active ingredient found in several herbicide formulations. The use of glyphosate-based herbicides in South Africa for the control of alien invasive plants and weeds is well established, extensive and currently unregulated, which vastly increases the likelihood of glyphosate contamination in environmental water systems. Although the use of glyphosate-based herbicides is required for economic enhancement in industries such as agriculture, the presence of this compound in natural water systems presents a potential risk to human health. Glyphosate and glyphosate formulations were previously considered safe, however their toxicity has become a major focal point of research over recent years. The lack of monitoring protocols for pesticides in South Africa is primarily due to limited financial capacity and the lack of analytical techniques.
- Full Text:
The development of amine-based extractants for separation of base metals in a sulfate medium
- Authors: Magwa, Nomampondo Penelope
- Date: 2015
- Subjects: Extraction (Chemistry) , Sulfates , Ligands , Benzimidazoles , Infrared spectroscopy , Nuclear magnetic resonance spectroscopy , Metal ions , Metals
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4559 , http://hdl.handle.net/10962/d1020010
- Description: Tridentate benzimidazole-based ligands, bis((1H-benzimidazol-2-yl)methyl)sulfide (BNSN) and bis((1H-benzimidazol-2-yl)methyl)amine (BNNN), along with dinonylnaphthalene sulfonic acid (DNNSA) as a synergist, were investigated as potential selective extractants for Ni2+ from base metals in a solvent extraction system using 2-octanol/Shellsol 2325 (8:2) as diluent and modifier. However, extraction studies show a lack of pH-metric separation of the later 3d metal ions with bis((1-octylbenzimidazol-2-yl)methyl)sulfide (BONSN) and bis((1- decylbenzimidazol-2-yl)methyl)amine (BDNNN) as extractants, but extractions occurred in the low pH range with an opportunity for back extraction. This investigation suggested that tridentate ligands (at least those of the nature investigated here) are not feasible extractants for separation of base metal ions due to their lack of stereochemical “tailor-making.”
- Full Text:
- Authors: Magwa, Nomampondo Penelope
- Date: 2015
- Subjects: Extraction (Chemistry) , Sulfates , Ligands , Benzimidazoles , Infrared spectroscopy , Nuclear magnetic resonance spectroscopy , Metal ions , Metals
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4559 , http://hdl.handle.net/10962/d1020010
- Description: Tridentate benzimidazole-based ligands, bis((1H-benzimidazol-2-yl)methyl)sulfide (BNSN) and bis((1H-benzimidazol-2-yl)methyl)amine (BNNN), along with dinonylnaphthalene sulfonic acid (DNNSA) as a synergist, were investigated as potential selective extractants for Ni2+ from base metals in a solvent extraction system using 2-octanol/Shellsol 2325 (8:2) as diluent and modifier. However, extraction studies show a lack of pH-metric separation of the later 3d metal ions with bis((1-octylbenzimidazol-2-yl)methyl)sulfide (BONSN) and bis((1- decylbenzimidazol-2-yl)methyl)amine (BDNNN) as extractants, but extractions occurred in the low pH range with an opportunity for back extraction. This investigation suggested that tridentate ligands (at least those of the nature investigated here) are not feasible extractants for separation of base metal ions due to their lack of stereochemical “tailor-making.”
- Full Text:
The diversity of root fungi associated with Erica species occurring in the Albany Centre of Endemism
- Authors: Bizabani, Christine
- Date: 2015
- Subjects: Ericaceae , Ericas , Roots (Botany) -- Diseases and pests , Mycorrhizal fungi , Polymerase chain reaction , Fungi -- Classification
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4160 , http://hdl.handle.net/10962/d1018575
- Description: South Africa has the highest species diversity of ericaceous plants belonging to the Erica genus. There are over 850 identified species in the Cape Floral Region. The Albany Centre of Endemism (ACOE) is located within this region and is a hotspot of diversity consisting of various plant genera. The success of Erica plants is ubiquitously attributed to mycorrhizal relationships they engage in with a diverse group of fungi. This symbiosis is known as the ericoid mycorrhizal (ERM) association. The overall aim of this study was to establish the diversity of root fungi associated with Erica plants using morphological, molecular and 454 pyrosequencing techniques. Six Erica species were identified using leaf and flower morphology according to taxonomic keys. The identified plants were Erica cerinthoides, Erica demissa, Erica chamissonis, Erica glumiflora, Erica caffra and Erica nemorosa. Roots from sampled plants were stained and examined microscopically to determine their mycorrhizal status. Ericoid mycorrhizal associations together with dark septate endophyte (DSE) structures and hyphae that did not form any specific structure were observed in all the roots. In addition arbuscular mycorrhizal (AM) structures in the form of vesicles were detected in E. glumiflora and E. cerinthoides. In order to identify the culturable fungi associated with the respective hosts, sterilised roots were placed on various culture media for cultivation. Thereafter isolated fungi were morphologically classified into 67 morphotypes. These were mostly sterile and darkly pigmented. Non-sporulating mycelia of variable colouration such as white, cream-yellowish, beige, green and brown were also observed. Further identification was carried out using molecular techniques. DNA was extracted separately from pure cultures and amplified using ITS1 and ITS4 primers in a polymerase chain reaction (PCR). Thereafter sequencing and Basic Local Alignment Search Tool (BLAST) were used to identify the isolates to generic level. The fungi were taxonomically classified into 54 operational taxonomic units and 94 percent were Ascomycetes and Helotiales was the dominant order. Unclassified Helotiales with affinities to fungi currently identified as Epacrid root fungus was common in all hosts. Other isolates that were identified included Oidiodendron, Meliniomyces, Phialocephala, Cadophora, Lachnum, Leohumicola Cryptosporiopsis, Chaetomium, Acremonium and Epicoccum species. Basidiomycetes were represented by two OTUs belonging to the genus Mycena. Four OTUs comprised fungi that had no significant alignments in the reference databases. Direct root DNA extraction together with 454 pyrosequencing was used to detect the diversity of culturable and unculturable fungi associated with the identified hosts. The ITS2 region was targeted for sequencing. Although Ascomycetes remained the dominant phyla, Basidiomycetes were also detected in all host plants. Glomeromycota was present in E. caffra and E. cerinthoides. Helotiales was dominant in all Erica plants with the exception of E. cerinthoides and E. chamissonis which were dominated by the order Chaetothyriales. The OTUs identified to genus level included Epacris pulchella root fungus, Oidiodendron cf. maius, Acremonium implicatum, Leohumicola, Lachnum, Capronia and Mycena species. Culture-based techniques and pyrosequencing detected similar fungal composition comprising Ascomycetes, while, pyrosequencing was able to detect Glomeromycetes and Basidiomycetes.
- Full Text:
The diversity of root fungi associated with Erica species occurring in the Albany Centre of Endemism
- Authors: Bizabani, Christine
- Date: 2015
- Subjects: Ericaceae , Ericas , Roots (Botany) -- Diseases and pests , Mycorrhizal fungi , Polymerase chain reaction , Fungi -- Classification
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4160 , http://hdl.handle.net/10962/d1018575
- Description: South Africa has the highest species diversity of ericaceous plants belonging to the Erica genus. There are over 850 identified species in the Cape Floral Region. The Albany Centre of Endemism (ACOE) is located within this region and is a hotspot of diversity consisting of various plant genera. The success of Erica plants is ubiquitously attributed to mycorrhizal relationships they engage in with a diverse group of fungi. This symbiosis is known as the ericoid mycorrhizal (ERM) association. The overall aim of this study was to establish the diversity of root fungi associated with Erica plants using morphological, molecular and 454 pyrosequencing techniques. Six Erica species were identified using leaf and flower morphology according to taxonomic keys. The identified plants were Erica cerinthoides, Erica demissa, Erica chamissonis, Erica glumiflora, Erica caffra and Erica nemorosa. Roots from sampled plants were stained and examined microscopically to determine their mycorrhizal status. Ericoid mycorrhizal associations together with dark septate endophyte (DSE) structures and hyphae that did not form any specific structure were observed in all the roots. In addition arbuscular mycorrhizal (AM) structures in the form of vesicles were detected in E. glumiflora and E. cerinthoides. In order to identify the culturable fungi associated with the respective hosts, sterilised roots were placed on various culture media for cultivation. Thereafter isolated fungi were morphologically classified into 67 morphotypes. These were mostly sterile and darkly pigmented. Non-sporulating mycelia of variable colouration such as white, cream-yellowish, beige, green and brown were also observed. Further identification was carried out using molecular techniques. DNA was extracted separately from pure cultures and amplified using ITS1 and ITS4 primers in a polymerase chain reaction (PCR). Thereafter sequencing and Basic Local Alignment Search Tool (BLAST) were used to identify the isolates to generic level. The fungi were taxonomically classified into 54 operational taxonomic units and 94 percent were Ascomycetes and Helotiales was the dominant order. Unclassified Helotiales with affinities to fungi currently identified as Epacrid root fungus was common in all hosts. Other isolates that were identified included Oidiodendron, Meliniomyces, Phialocephala, Cadophora, Lachnum, Leohumicola Cryptosporiopsis, Chaetomium, Acremonium and Epicoccum species. Basidiomycetes were represented by two OTUs belonging to the genus Mycena. Four OTUs comprised fungi that had no significant alignments in the reference databases. Direct root DNA extraction together with 454 pyrosequencing was used to detect the diversity of culturable and unculturable fungi associated with the identified hosts. The ITS2 region was targeted for sequencing. Although Ascomycetes remained the dominant phyla, Basidiomycetes were also detected in all host plants. Glomeromycota was present in E. caffra and E. cerinthoides. Helotiales was dominant in all Erica plants with the exception of E. cerinthoides and E. chamissonis which were dominated by the order Chaetothyriales. The OTUs identified to genus level included Epacris pulchella root fungus, Oidiodendron cf. maius, Acremonium implicatum, Leohumicola, Lachnum, Capronia and Mycena species. Culture-based techniques and pyrosequencing detected similar fungal composition comprising Ascomycetes, while, pyrosequencing was able to detect Glomeromycetes and Basidiomycetes.
- Full Text:
The isolation, characterisation and chemotaxonomic significance of secondary metabolites from selected South African Laurencia spp. Rhodophyta
- Authors: Fakee, Jameel
- Date: 2015
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/64696 , vital:28593
- Description: Bioprospection of marine organisms as a potential source for lead drugs is becoming increasingly popular. The secondary metabolome of these organisms consists of structurally diverse molecules possessing unprecedented carbon skeletons, the biosynthesis of which occurs via complex metabolomic pathways driven by specialist enzymes. This structural novelty is highly influential on the favourable bioactivity these compounds display. A prominent example of such a compound is trabectedin marketed as Yondelis®. Registered for the treatment of soft tissue sarcomas, this marine drug was developed from extracts of the tunicate Ecteinascidia turbinata. South Africa is renowned for possessing a highly diverse marine biota including several endemic species of marine red algae belonging to the Laurencia sensu stricto genus, which falls within the Laurencia complex. Despite having a good reputation for fascinating secondary metabolites, the taxonomy of Laurencia natural products is proving challenging for reasons including the presence of cryptic species, as well as individual species displaying morphological variability. The aim of this study was thus to isolate secondary metabolites from various South African Laurencia spp. and subsequently assess their chemotaxonomic significance by analysis of a parallel plastid rbcL phylogeny study of Laurencia spp. This study reports the first phycochemical investigation into Laurencia natalensis Kylin, Laurencia cf. corymbosa J.Agardh, Laurencia complanata (Suhr) Kützing, Laurencia sodwaniensis Francis, Bolton, Mattio and Anderson submitted, Laurencia multiclavata Francis, Bolton, Mattio and Anderson submitted, and a South African specimen of Laurenciella marilzae Gil-Rodríguez, Sentíes, Díaz-Larrea, Cassano and M.T. Fujii (basionym: Laurencia marilzae) originally described from Spain. Additionally, the chemical profiles of previously explored species Laurencia flexuosa Kützing and Laurencia glomerata Kützing were re-investigated. The organic extracts of the above species afforded 31 compounds belonging to a wide array of structural classes including halo-chamigranes, linear C15 acetogenins, indole alkaloids, cuparanes and cyclic bromo-ethers. A new tri-cyclic keto-cuparane (4.4) was isolated from L.cf. corymbosa alongside the new cuparanes 4.1 and 4.7. Algoane (5.9), a unique marker compound isolated from L. natalensis, was previously only reported from a sea-hare. Such marker compounds which are exclusive to an individual algal species increase the ease of their subsequent identification. The feasibility of chemotaxonomy as an additional tool to classify Laurencia spp. Was established as broad predictions of a specimen’s phylogeny, based on representatives of its secondary metabolome, proved viable. The study specimens were shown to possess similar chemical profiles to their sister species e.g. L. complanata, L. sodwaniensis and L. multiclavata produced similar metabolites to their sister species as inferred by an rbcL phylogeny tree. Finally, a 1H NMR profiling study on the crude organic extracts of various Laurencia spp. generated distinctive, reproducible spectra, exposing the value of NMR spectroscopy as a rudimentary species discernment tool.
- Full Text:
- Authors: Fakee, Jameel
- Date: 2015
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/64696 , vital:28593
- Description: Bioprospection of marine organisms as a potential source for lead drugs is becoming increasingly popular. The secondary metabolome of these organisms consists of structurally diverse molecules possessing unprecedented carbon skeletons, the biosynthesis of which occurs via complex metabolomic pathways driven by specialist enzymes. This structural novelty is highly influential on the favourable bioactivity these compounds display. A prominent example of such a compound is trabectedin marketed as Yondelis®. Registered for the treatment of soft tissue sarcomas, this marine drug was developed from extracts of the tunicate Ecteinascidia turbinata. South Africa is renowned for possessing a highly diverse marine biota including several endemic species of marine red algae belonging to the Laurencia sensu stricto genus, which falls within the Laurencia complex. Despite having a good reputation for fascinating secondary metabolites, the taxonomy of Laurencia natural products is proving challenging for reasons including the presence of cryptic species, as well as individual species displaying morphological variability. The aim of this study was thus to isolate secondary metabolites from various South African Laurencia spp. and subsequently assess their chemotaxonomic significance by analysis of a parallel plastid rbcL phylogeny study of Laurencia spp. This study reports the first phycochemical investigation into Laurencia natalensis Kylin, Laurencia cf. corymbosa J.Agardh, Laurencia complanata (Suhr) Kützing, Laurencia sodwaniensis Francis, Bolton, Mattio and Anderson submitted, Laurencia multiclavata Francis, Bolton, Mattio and Anderson submitted, and a South African specimen of Laurenciella marilzae Gil-Rodríguez, Sentíes, Díaz-Larrea, Cassano and M.T. Fujii (basionym: Laurencia marilzae) originally described from Spain. Additionally, the chemical profiles of previously explored species Laurencia flexuosa Kützing and Laurencia glomerata Kützing were re-investigated. The organic extracts of the above species afforded 31 compounds belonging to a wide array of structural classes including halo-chamigranes, linear C15 acetogenins, indole alkaloids, cuparanes and cyclic bromo-ethers. A new tri-cyclic keto-cuparane (4.4) was isolated from L.cf. corymbosa alongside the new cuparanes 4.1 and 4.7. Algoane (5.9), a unique marker compound isolated from L. natalensis, was previously only reported from a sea-hare. Such marker compounds which are exclusive to an individual algal species increase the ease of their subsequent identification. The feasibility of chemotaxonomy as an additional tool to classify Laurencia spp. Was established as broad predictions of a specimen’s phylogeny, based on representatives of its secondary metabolome, proved viable. The study specimens were shown to possess similar chemical profiles to their sister species e.g. L. complanata, L. sodwaniensis and L. multiclavata produced similar metabolites to their sister species as inferred by an rbcL phylogeny tree. Finally, a 1H NMR profiling study on the crude organic extracts of various Laurencia spp. generated distinctive, reproducible spectra, exposing the value of NMR spectroscopy as a rudimentary species discernment tool.
- Full Text:
The relationship between leadership and organisational effectiveness among indigenous banks in Kenya
- Authors: Muriithi, Samuel Muiruri
- Date: 2015
- Subjects: Leadership -- Kenya , Organizational effectiveness -- Kenya , Transformational leadership -- Kenya , Strategic planning -- Kenya , Community banks -- Kenya , Structural equation modeling , Emotional intelligence
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1208 , http://hdl.handle.net/10962/d1020015
- Description: Defining leadership effectiveness (LE) remains a controversial subject with scholars and researchers disagreeing on a common definition. Most studies term leadership effectiveness as the leaders’ ability to successfully exercise personal influence and abilities in order to accomplish set standards. Such leadership effectiveness was measured using three elements, namely influence, follow commitment and versatility. To be effective, leaders must possess certain competencies and perform specific tasks (independent variables). In this study, three leadership competencies, namely strategic thinking, emotional effectiveness and transformational leadership were examined. Similarly, seven leadership tasks (set organisational direction, develop human capital, build core competencies, create organisational alignment, sustain appropriate organisational culture, manage change and establish balanced organisational control) were identified as essential for the attainment of leadership effectiveness (intervening variable) which, in turn, leads to organisational effectiveness (dependent variable). Given the importance of leadership effectiveness to organisational effectiveness, the purpose of this study was to identify, investigate and empirically test the possible relationship between leadership effectiveness and organisational effectiveness within the Kenyan indigenous banks. To achieve the aim of the study, a survey was undertaken using a structured self-administered questionnaire. The respondents were identified using both probability and non-probability techniques with the survey yielding 257 usable questionnaires that were statistically analysed. The proposed hypothetical relationship between leadership effectiveness and organisational effectiveness was assessed using Structural Equation Modelling (SEM), a multivariate statistical technique. The SEM included Cronbach’s alpha and confirmatory factor analyses to assess the dicriminant reliability and validity of the measuring instrument, and Goodness-of-fit indices. The study findings demonstrated the existence of a strong relationship between leadership competencies, tasks performed and leadership effectiveness which in turn impacts on organisational effectiveness, in this case the overall effectiveness of the Kenyan indigenous banks.
- Full Text:
The relationship between leadership and organisational effectiveness among indigenous banks in Kenya
- Authors: Muriithi, Samuel Muiruri
- Date: 2015
- Subjects: Leadership -- Kenya , Organizational effectiveness -- Kenya , Transformational leadership -- Kenya , Strategic planning -- Kenya , Community banks -- Kenya , Structural equation modeling , Emotional intelligence
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1208 , http://hdl.handle.net/10962/d1020015
- Description: Defining leadership effectiveness (LE) remains a controversial subject with scholars and researchers disagreeing on a common definition. Most studies term leadership effectiveness as the leaders’ ability to successfully exercise personal influence and abilities in order to accomplish set standards. Such leadership effectiveness was measured using three elements, namely influence, follow commitment and versatility. To be effective, leaders must possess certain competencies and perform specific tasks (independent variables). In this study, three leadership competencies, namely strategic thinking, emotional effectiveness and transformational leadership were examined. Similarly, seven leadership tasks (set organisational direction, develop human capital, build core competencies, create organisational alignment, sustain appropriate organisational culture, manage change and establish balanced organisational control) were identified as essential for the attainment of leadership effectiveness (intervening variable) which, in turn, leads to organisational effectiveness (dependent variable). Given the importance of leadership effectiveness to organisational effectiveness, the purpose of this study was to identify, investigate and empirically test the possible relationship between leadership effectiveness and organisational effectiveness within the Kenyan indigenous banks. To achieve the aim of the study, a survey was undertaken using a structured self-administered questionnaire. The respondents were identified using both probability and non-probability techniques with the survey yielding 257 usable questionnaires that were statistically analysed. The proposed hypothetical relationship between leadership effectiveness and organisational effectiveness was assessed using Structural Equation Modelling (SEM), a multivariate statistical technique. The SEM included Cronbach’s alpha and confirmatory factor analyses to assess the dicriminant reliability and validity of the measuring instrument, and Goodness-of-fit indices. The study findings demonstrated the existence of a strong relationship between leadership competencies, tasks performed and leadership effectiveness which in turn impacts on organisational effectiveness, in this case the overall effectiveness of the Kenyan indigenous banks.
- Full Text:
The supervisor’s tale: postgraduate supervisors’ experiences in a changing Higher Education environment
- Authors: Searle, Ruth Lesley
- Date: 2015
- Subjects: Graduate students -- Supervision of -- South Africa , Education, Higher -- South Africa , Educational change -- South Africa , Archer, Margaret Scotford -- Political and social views , Critical realism , Knowledge, Sociology of , Dissertations, Academic , Faculty advisors -- South Africa , Education -- Study and teaching (Graduate) -- South Africa , Universities and colleges -- Graduate work
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1331 , http://hdl.handle.net/10962/d1019952
- Description: The environment in which higher education institutions operate is changing, and these changes are impacting on all aspects of higher education, including postgraduate levels. Changes wrought by globalisation, heralded by rapid advances in technology have inaugurated a new era in which there are long term consequences for higher education. The shift towards more quantitative and measurable "outputs" signifies a fundamental change in the educational ethos in institutions. Effectiveness is now judged primarily on numbers of graduates and publications rather than on other aspects. The drive is to produce a highly educated population, especially through increasing postgraduates who can drive national innovation and improve national economies. This affects academics in a range of ways, not least in the ways in which they engage in teaching, what they are willing to do and how they do it. Such changes influence the kinds of research done, the structures and funding which support research, and thus naturally shapes the kinds of postgraduate programmes and teaching that occurs. This study, situated in the field of Higher Education Studies, adopting a critical realist stance and drawing on the social theory of Margaret Archer and the concepts of expert and novice, explores the experiences of postgraduate supervisors from one South African institution across a range of disciplines. Individual experiences at the level of the Empirical and embodied in practice at the level of the Actual allow for the identification of possible mechanisms at the level of the Real which structure the sector. The research design then allows for an exploration across mezzo, macro and micro levels. Individuals outline their own particular situations, identifying a number of elements which enabled or constrained them and how, in exercising their agency, they develop their strategies for supervision drawing on a range of different resources that they identify and that may be available to them. Student characteristics, discipline status and placement, funding, and the emergent policy environment are all identified as influencing their practice. In some instances supervisors recognise the broader influences on the system that involve them in their undertaking, noting the international trends. Through their narratives and the discourses they engage a number of contradictions that have developed in the system with growing neo-liberal trends and vocationalism highlighting tensions between academic freedom and autonomy, and demands for productivity, efficiency and compliance, and between an educational focus and a training bias in particular along with others. Especially notable is how this contributes to the current ideologies surrounding knowledge and knowledge production. Their individual interests and concerns, and emergent academic identities as they take shape over time, also modifies the process and how individual supervisors influence their own environments in agentic moves becomes apparent. Whilst often individuals highlight the lack of support especially in the early phases of supervision, the emergent policy-constrained environment is also seen as curtailing possibilities and especially in limiting the possibilities for the exercise of agency. Whilst the study has some limitations in the range and number of respondents nevertheless the data provided rich evidence of how individual supervisors are affected, and how they respond in varied conditions. What is highlighted through these experiences are ways pressures are increasing for both supervisors and students and changing how they engage. Concerns in particular are raised about the growing functional and instrumental nature of the process with an emphasis on the effects on the kinds of researchers being developed and the knowledge that is therefore being produced. As costs increase for academics through the environments developed and with the varied roles they take on so they become more selective and reluctant to expand the role. This research has provided insights into ideas, beliefs and values relating to the postgraduate sector and to the process of postgraduate supervision and how it occurs. This includes the structures and cultural conditions that enable or constrain practitioners as they develop in the role in this particular institution. It has explored some of the ways that mechanisms at international, national and institutional levels shape the role and practices of supervisors. The effects of mechanisms are in no way a given or simply understood. In this way the research may contribute to more emancipatory knowledge which could be used in planning and deciding on emergent policies and practices which might create a more supportive and creative postgraduate environment.
- Full Text:
- Authors: Searle, Ruth Lesley
- Date: 2015
- Subjects: Graduate students -- Supervision of -- South Africa , Education, Higher -- South Africa , Educational change -- South Africa , Archer, Margaret Scotford -- Political and social views , Critical realism , Knowledge, Sociology of , Dissertations, Academic , Faculty advisors -- South Africa , Education -- Study and teaching (Graduate) -- South Africa , Universities and colleges -- Graduate work
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1331 , http://hdl.handle.net/10962/d1019952
- Description: The environment in which higher education institutions operate is changing, and these changes are impacting on all aspects of higher education, including postgraduate levels. Changes wrought by globalisation, heralded by rapid advances in technology have inaugurated a new era in which there are long term consequences for higher education. The shift towards more quantitative and measurable "outputs" signifies a fundamental change in the educational ethos in institutions. Effectiveness is now judged primarily on numbers of graduates and publications rather than on other aspects. The drive is to produce a highly educated population, especially through increasing postgraduates who can drive national innovation and improve national economies. This affects academics in a range of ways, not least in the ways in which they engage in teaching, what they are willing to do and how they do it. Such changes influence the kinds of research done, the structures and funding which support research, and thus naturally shapes the kinds of postgraduate programmes and teaching that occurs. This study, situated in the field of Higher Education Studies, adopting a critical realist stance and drawing on the social theory of Margaret Archer and the concepts of expert and novice, explores the experiences of postgraduate supervisors from one South African institution across a range of disciplines. Individual experiences at the level of the Empirical and embodied in practice at the level of the Actual allow for the identification of possible mechanisms at the level of the Real which structure the sector. The research design then allows for an exploration across mezzo, macro and micro levels. Individuals outline their own particular situations, identifying a number of elements which enabled or constrained them and how, in exercising their agency, they develop their strategies for supervision drawing on a range of different resources that they identify and that may be available to them. Student characteristics, discipline status and placement, funding, and the emergent policy environment are all identified as influencing their practice. In some instances supervisors recognise the broader influences on the system that involve them in their undertaking, noting the international trends. Through their narratives and the discourses they engage a number of contradictions that have developed in the system with growing neo-liberal trends and vocationalism highlighting tensions between academic freedom and autonomy, and demands for productivity, efficiency and compliance, and between an educational focus and a training bias in particular along with others. Especially notable is how this contributes to the current ideologies surrounding knowledge and knowledge production. Their individual interests and concerns, and emergent academic identities as they take shape over time, also modifies the process and how individual supervisors influence their own environments in agentic moves becomes apparent. Whilst often individuals highlight the lack of support especially in the early phases of supervision, the emergent policy-constrained environment is also seen as curtailing possibilities and especially in limiting the possibilities for the exercise of agency. Whilst the study has some limitations in the range and number of respondents nevertheless the data provided rich evidence of how individual supervisors are affected, and how they respond in varied conditions. What is highlighted through these experiences are ways pressures are increasing for both supervisors and students and changing how they engage. Concerns in particular are raised about the growing functional and instrumental nature of the process with an emphasis on the effects on the kinds of researchers being developed and the knowledge that is therefore being produced. As costs increase for academics through the environments developed and with the varied roles they take on so they become more selective and reluctant to expand the role. This research has provided insights into ideas, beliefs and values relating to the postgraduate sector and to the process of postgraduate supervision and how it occurs. This includes the structures and cultural conditions that enable or constrain practitioners as they develop in the role in this particular institution. It has explored some of the ways that mechanisms at international, national and institutional levels shape the role and practices of supervisors. The effects of mechanisms are in no way a given or simply understood. In this way the research may contribute to more emancipatory knowledge which could be used in planning and deciding on emergent policies and practices which might create a more supportive and creative postgraduate environment.
- Full Text:
The use of hydrological information to improve flood management-integrated hydrological modelling of the Zambezi River basin
- Vilanculos, Agostinho Chuquelane Fadulo
- Authors: Vilanculos, Agostinho Chuquelane Fadulo
- Date: 2015
- Subjects: Hydrologic models -- Zambezi River Watershed , Watershed management -- Zambezi River Watershed , Water resources development -- Zambezi River Watershed , Flood control -- Zambezi River Watershed , Flood forecasting -- Zambezi River Watershed , Rain gauges -- Zambezi River Watershed
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:6054 , http://hdl.handle.net/10962/d1018915
- Description: The recent high profile flooding events – that have occurred in many parts of the world – have drawn attention to the need for new and improved methods for water resources assessment, water management and the modelling of large-scale flooding events. In the case of the Zambezi Basin, a review of the 2000 and 2001 floods identified the need for tools to enable hydrologists to assess and predict daily stream flow and identify the areas that are likely to be affected by flooding. As a way to address the problem, a methodology was set up to derive catchment soil moisture statistics from Earth Observation (EO) data and to study the improvements brought about by an assimilation of this information into hydrological models for improving reservoir management in a data scarce environment. Rainfall data were obtained from the FEWSNet Web site and computed by the National Oceanic and Atmospheric Administration Climatic Prediction Center (NOAA/CPC). These datasets were processed and used to monitor rainfall variability and subsequently fed into a hydrological model to predict the daily flows for the Zambezi River Basin. The hydrological model used was the Geospatial Stream Flow Model (GeoSFM), developed by the United States Geological Survey (USGS). GeoSFM is a spatially semi-distributed physically-based hydrological model, parameterised using spatially distributed topographic data, soil characteristics and land cover data sets available globally from both Remote Sensing and in situ sources. The Satellite rainfall data were validated against data from twenty (20) rainfall gauges located on the Lower Zambezi. However, at several rain gauge stations (especially those with complex topography, which tended to experience high rainfall spatial variability), there was no direct correlation between the satellite estimates and the ground data as recorded in daily time steps. The model was calibrated for seven gauging stations. The calibrated model performed quite well at seven selected locations (R2=0.66 to 0.90, CE=0.51 to 0.88, RSR=0.35 to 0.69, PBIAS=−4.5 to 7.5). The observed data were obtained from the National Water Agencies of the riparian countries. After GeoSFM calibration, the model generated an integration of the flows into a reservoir and hydropower model to optimise the operation of Kariba and Cahora Bassa dams. The Kariba and Cahora Bassa dams were selected because this study considers these two dams as the major infrastructures for controlling and alleviating floods in the Zambezi River Basin. Other dams (such as the Kafue and Itezhi-Thezi) were recognised in terms of their importance but including them was beyond the scope of this study because of financial and time constraints. The licence of the reservoir model was limited to one year for the same reason. The reservoir model used was the MIKE BASIN, a professional engineering software package and quasi-steady-state mass balance modelling tool for integrated river basin and management, developed by the Denmark Hydraulic Institute (DHI) in 2003. The model was parameterised by the geometry of the reservoir basin (level, area, volume relationships) and by the discharge-level (Q-h) relationship of the dam spillways. The integrated modelling system simulated the daily flow variation for all Zambezi River sub-basins between 1998 and 2008 and validated between 2009 and 2011. The resulting streamflows have been expressed in terms of hydrograph comparisons between simulated and observed flow values at the four gauging stations located downstream of Cahora Bassa dam. The integrated model performed well, between observed and forecast streamflows, at four selected gauging stations (R2=0.53 to 0.90, CE=0.50 to 0.80, RSR=0.49 to 0.69, PBIAS=−2.10 to 4.8). From the results of integrated modelling, it was observed that both Kariba and Cahora Bassa are currently being operated based on the maximum rule curve and both remain focused on maximising hydropower production and ensuring dam safety rather than other potential influences by the Zambezi River (such as flood control downstream – where the communities are located – and environmental issues). In addition, the flood mapping analysis demonstrated that the Cahora Bassa dam plays an important part in flood mitigation downstream of the dams. In the absence of optimisation of flow releases from both the Kariba and Cahora Bassa dams, in additional to the contribution of any other tributaries located downstream of the dams, the impact of flooding can be severe. As such, this study has developed new approaches for flood monitoring downstream of the Zambezi Basin, through the application of an integrated modelling system. The modelling system consists of: predicting daily streamflow (using the calibrated GeoSFM), then feeding the predicted streamflow into MIKE BASIN (for checking the operating rules) and to optimise the releases. Therefore, before releases are made, the flood maps can be used as a decision-making tool to both assess the impact of each level of release downstream and to identify the communities likely to be affected by the flood – this ensures that the necessary warnings can be issued before flooding occurs. Finally an integrated flood management tool was proposed – to host the results produced by the integrated system – which would then be accessible for assessment by the different users. These results were expressed in terms of water level (m). Four discharge-level (Q-h) relationships were developed for converting the simulated flow into water level at four selected sites downstream of Cahora Bassa dam – namely: Cahora Bassa dam site, Tete (E-320), Caia (E-291) and Marromeu (E-285). However, the uncertainties in these predictions suggested that improved monitoring systems may be achieved if data access at appropriate scale and quality was improved.
- Full Text:
- Authors: Vilanculos, Agostinho Chuquelane Fadulo
- Date: 2015
- Subjects: Hydrologic models -- Zambezi River Watershed , Watershed management -- Zambezi River Watershed , Water resources development -- Zambezi River Watershed , Flood control -- Zambezi River Watershed , Flood forecasting -- Zambezi River Watershed , Rain gauges -- Zambezi River Watershed
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:6054 , http://hdl.handle.net/10962/d1018915
- Description: The recent high profile flooding events – that have occurred in many parts of the world – have drawn attention to the need for new and improved methods for water resources assessment, water management and the modelling of large-scale flooding events. In the case of the Zambezi Basin, a review of the 2000 and 2001 floods identified the need for tools to enable hydrologists to assess and predict daily stream flow and identify the areas that are likely to be affected by flooding. As a way to address the problem, a methodology was set up to derive catchment soil moisture statistics from Earth Observation (EO) data and to study the improvements brought about by an assimilation of this information into hydrological models for improving reservoir management in a data scarce environment. Rainfall data were obtained from the FEWSNet Web site and computed by the National Oceanic and Atmospheric Administration Climatic Prediction Center (NOAA/CPC). These datasets were processed and used to monitor rainfall variability and subsequently fed into a hydrological model to predict the daily flows for the Zambezi River Basin. The hydrological model used was the Geospatial Stream Flow Model (GeoSFM), developed by the United States Geological Survey (USGS). GeoSFM is a spatially semi-distributed physically-based hydrological model, parameterised using spatially distributed topographic data, soil characteristics and land cover data sets available globally from both Remote Sensing and in situ sources. The Satellite rainfall data were validated against data from twenty (20) rainfall gauges located on the Lower Zambezi. However, at several rain gauge stations (especially those with complex topography, which tended to experience high rainfall spatial variability), there was no direct correlation between the satellite estimates and the ground data as recorded in daily time steps. The model was calibrated for seven gauging stations. The calibrated model performed quite well at seven selected locations (R2=0.66 to 0.90, CE=0.51 to 0.88, RSR=0.35 to 0.69, PBIAS=−4.5 to 7.5). The observed data were obtained from the National Water Agencies of the riparian countries. After GeoSFM calibration, the model generated an integration of the flows into a reservoir and hydropower model to optimise the operation of Kariba and Cahora Bassa dams. The Kariba and Cahora Bassa dams were selected because this study considers these two dams as the major infrastructures for controlling and alleviating floods in the Zambezi River Basin. Other dams (such as the Kafue and Itezhi-Thezi) were recognised in terms of their importance but including them was beyond the scope of this study because of financial and time constraints. The licence of the reservoir model was limited to one year for the same reason. The reservoir model used was the MIKE BASIN, a professional engineering software package and quasi-steady-state mass balance modelling tool for integrated river basin and management, developed by the Denmark Hydraulic Institute (DHI) in 2003. The model was parameterised by the geometry of the reservoir basin (level, area, volume relationships) and by the discharge-level (Q-h) relationship of the dam spillways. The integrated modelling system simulated the daily flow variation for all Zambezi River sub-basins between 1998 and 2008 and validated between 2009 and 2011. The resulting streamflows have been expressed in terms of hydrograph comparisons between simulated and observed flow values at the four gauging stations located downstream of Cahora Bassa dam. The integrated model performed well, between observed and forecast streamflows, at four selected gauging stations (R2=0.53 to 0.90, CE=0.50 to 0.80, RSR=0.49 to 0.69, PBIAS=−2.10 to 4.8). From the results of integrated modelling, it was observed that both Kariba and Cahora Bassa are currently being operated based on the maximum rule curve and both remain focused on maximising hydropower production and ensuring dam safety rather than other potential influences by the Zambezi River (such as flood control downstream – where the communities are located – and environmental issues). In addition, the flood mapping analysis demonstrated that the Cahora Bassa dam plays an important part in flood mitigation downstream of the dams. In the absence of optimisation of flow releases from both the Kariba and Cahora Bassa dams, in additional to the contribution of any other tributaries located downstream of the dams, the impact of flooding can be severe. As such, this study has developed new approaches for flood monitoring downstream of the Zambezi Basin, through the application of an integrated modelling system. The modelling system consists of: predicting daily streamflow (using the calibrated GeoSFM), then feeding the predicted streamflow into MIKE BASIN (for checking the operating rules) and to optimise the releases. Therefore, before releases are made, the flood maps can be used as a decision-making tool to both assess the impact of each level of release downstream and to identify the communities likely to be affected by the flood – this ensures that the necessary warnings can be issued before flooding occurs. Finally an integrated flood management tool was proposed – to host the results produced by the integrated system – which would then be accessible for assessment by the different users. These results were expressed in terms of water level (m). Four discharge-level (Q-h) relationships were developed for converting the simulated flow into water level at four selected sites downstream of Cahora Bassa dam – namely: Cahora Bassa dam site, Tete (E-320), Caia (E-291) and Marromeu (E-285). However, the uncertainties in these predictions suggested that improved monitoring systems may be achieved if data access at appropriate scale and quality was improved.
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The value of locally isolated freshwater micro-algae in toxicity testing for water resource management in South Africa
- Authors: Gola, Nontutuzelo Pearl
- Date: 2015
- Subjects: Microalgae -- South Africa , Toxicity testing , Water resources development -- South Africa , Aquatic habitats -- South Africa , Water -- Pollution -- Toxicology , Water quality management -- South Africa , Sewage disposal in rivers, lakes, etc. -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:6049 , http://hdl.handle.net/10962/d1017873
- Description: The ecological position of micro-algae at the base of the aquatic food web makes them critical components of aquatic ecosystems. Their short generation time also makes them useful biological indicators because they respond quickly to changes in environmental condition, enabling timely identification and assessment of water quality changes. The inclusion of micro-algae as indicators in water resource regulation and management in South Africa has started recently, their more extensive use in biomonitoring and ecotoxicology programmes for water resource management would contribute to the South African policy if water resource protection. The standard algal growth inhibition assay with the species Pseudokirchneriella subcapitata is currently used for monitoring toxicity of in-stream and industrial wastewater discharges to freshwater micro-algae. The relevance of the data generated by standard toxicity bioassays has been questioned, since micro-algae in particular are extremely variable in their sensitivity to a range of contaminants and these standard species used may not occur in the local aquatic environment. As a result, international regulatory agencies, have recommended algal growth inhibition tests be changed from a single standard species to tests with a number of species. One recommendation, in addition to the use of standard toxicity tests, is the use of species isolated from the local environment which may be more relevant for assessing site specific impacts. This study investigated the value and application of locally isolated South African freshwater micro-algae in toxicity tests for water resource management and was carried out in three phases. The first phase involved isolating micro-algae from South African aquatic resources. Micro-algae suitable for toxicity testing were identified and selected using as set of criteria. Three (Scenedesmus bicaudatus, Chlorella sorokiniana and Chlorella vulgaris) out of eight successfully isolated species satisfied the prescribed selection criteria and these were selected as potential toxicity test species. The second phase focused on refining and adapting the existing algal toxicity test protocol (the algal growth inhibition assay) for use on the locally isolated algal species. The refinement of the test protocol was achieved by exposing the locally isolated species to reference toxicants in order to assess and compare their growth and sensitivity to the toxicants under the prescribed toxicity test conditions with that of the standard toxicity test species (Pseudokirchneriella subcapitata) and a commercial laboratory species (Chlorella protothecoides). During this phase, one of the three local species (Scenedesmus bicaudatus) was eliminated as a potential toxicity test species due to inconsistent growth. The third phase of the study involved assessing the sensitivity of the two remaining species (C. vulgaris and C. sorokiniana) to a range of toxicants (reference toxicants, salts, effluents and a herbicide) and comparing it to that of the standard toxicity test species P. subcapitata and C. protothecoides. The toxicants were selected based on their relative importance in the South African context, as well as the practicality of using these local micro-algae to routinely determine the impact of these toxicants on local aquatic resources. The growth of the four micro-algae was stimulated by the selected effluents. The standard toxicity test species P. subcapitata was ranked the most sensitive and of the four species to two reference toxicants and two inorganic salts. Chlorella sorokiniana was ranked the most sensitive of the three Chlorella species to two reference toxicants and two inorganic salts. The herbicide stimulated the growth of C. vulgaris while inhibiting the growth of the other species. Pseudokirchneriela subcapitata and C. sorokiniana showed high intra-specific variability in growth, which made it difficult to determine the effective concentrations of the herbicide and therefore compare the sensitivity of the species. This varied response of micro-algal species to toxicants may result in the biodiversity shifts in aquatic ecosystems, and also supports the recommendation of using a battery of different species to support more informed decisions in water resource management.
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- Authors: Gola, Nontutuzelo Pearl
- Date: 2015
- Subjects: Microalgae -- South Africa , Toxicity testing , Water resources development -- South Africa , Aquatic habitats -- South Africa , Water -- Pollution -- Toxicology , Water quality management -- South Africa , Sewage disposal in rivers, lakes, etc. -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:6049 , http://hdl.handle.net/10962/d1017873
- Description: The ecological position of micro-algae at the base of the aquatic food web makes them critical components of aquatic ecosystems. Their short generation time also makes them useful biological indicators because they respond quickly to changes in environmental condition, enabling timely identification and assessment of water quality changes. The inclusion of micro-algae as indicators in water resource regulation and management in South Africa has started recently, their more extensive use in biomonitoring and ecotoxicology programmes for water resource management would contribute to the South African policy if water resource protection. The standard algal growth inhibition assay with the species Pseudokirchneriella subcapitata is currently used for monitoring toxicity of in-stream and industrial wastewater discharges to freshwater micro-algae. The relevance of the data generated by standard toxicity bioassays has been questioned, since micro-algae in particular are extremely variable in their sensitivity to a range of contaminants and these standard species used may not occur in the local aquatic environment. As a result, international regulatory agencies, have recommended algal growth inhibition tests be changed from a single standard species to tests with a number of species. One recommendation, in addition to the use of standard toxicity tests, is the use of species isolated from the local environment which may be more relevant for assessing site specific impacts. This study investigated the value and application of locally isolated South African freshwater micro-algae in toxicity tests for water resource management and was carried out in three phases. The first phase involved isolating micro-algae from South African aquatic resources. Micro-algae suitable for toxicity testing were identified and selected using as set of criteria. Three (Scenedesmus bicaudatus, Chlorella sorokiniana and Chlorella vulgaris) out of eight successfully isolated species satisfied the prescribed selection criteria and these were selected as potential toxicity test species. The second phase focused on refining and adapting the existing algal toxicity test protocol (the algal growth inhibition assay) for use on the locally isolated algal species. The refinement of the test protocol was achieved by exposing the locally isolated species to reference toxicants in order to assess and compare their growth and sensitivity to the toxicants under the prescribed toxicity test conditions with that of the standard toxicity test species (Pseudokirchneriella subcapitata) and a commercial laboratory species (Chlorella protothecoides). During this phase, one of the three local species (Scenedesmus bicaudatus) was eliminated as a potential toxicity test species due to inconsistent growth. The third phase of the study involved assessing the sensitivity of the two remaining species (C. vulgaris and C. sorokiniana) to a range of toxicants (reference toxicants, salts, effluents and a herbicide) and comparing it to that of the standard toxicity test species P. subcapitata and C. protothecoides. The toxicants were selected based on their relative importance in the South African context, as well as the practicality of using these local micro-algae to routinely determine the impact of these toxicants on local aquatic resources. The growth of the four micro-algae was stimulated by the selected effluents. The standard toxicity test species P. subcapitata was ranked the most sensitive and of the four species to two reference toxicants and two inorganic salts. Chlorella sorokiniana was ranked the most sensitive of the three Chlorella species to two reference toxicants and two inorganic salts. The herbicide stimulated the growth of C. vulgaris while inhibiting the growth of the other species. Pseudokirchneriela subcapitata and C. sorokiniana showed high intra-specific variability in growth, which made it difficult to determine the effective concentrations of the herbicide and therefore compare the sensitivity of the species. This varied response of micro-algal species to toxicants may result in the biodiversity shifts in aquatic ecosystems, and also supports the recommendation of using a battery of different species to support more informed decisions in water resource management.
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