Potential effects of different salinities on the survival of the mangrove crab, Uca urvillei and its associated chemoautotrophic bacterial symbionts
- Mbobo, Tumeka https://orcid.org/0000-0002-0159-6569
- Authors: Mbobo, Tumeka https://orcid.org/0000-0002-0159-6569
- Date: 2015-06
- Subjects: Mangrove ecology http://id.loc.gov/authorities/subjects/sh85080528 , Crabs--South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/19225 , vital:43033
- Description: The ability of natural populations to maintain fitness is important to their long-term persistence and has further relevance in the light of climate change scenarios. Fitness is however also influenced strongly by interactions with other species of the community. It is, therefore, important to focus on how environmental change can alter key biological interactions. The present study aimed to investigate the effects of different salinity levels on one species of mangrove crab, Uca urvillei and the associated chemoautotrophic bacterial symbionts, from the Mngazana estuary, South Africa. To examine the influence of different salinities over time on the symbiotic bacterial community, salinity experiments were set up, choosing three salinity exposures (5, 20 and 35percent) and four time exposures (3, 7, 14 and 21 days). The results showed that microbial community associated with U. urvillei was generally stable throughout the three salinity treatments, while the survival of the host (crab), was influenced by high salinities, particularly after day 14. Overall, the results of this study suggest that over time, environmental salinity (35percent) has the potential to affect significantly the physiology of U. urvillei, but this might not necessarily be the case for the associated microbial communities. The modes at which the significant symbionts are transferred from mother to offspring were also investigated by analysing the bacterial profiles from eggs, ovigerous and non-ovigerous females, along with mud. The results were fairly complex, but with significant differences in the bacterial communities of eggs from mud and females. These differences were driven mostly by two dominant phyla: Actinobacteria and Proteobacteria. The presence of both these phyla throughout the categories (even though in different percentages) suggest that U. urvillei might employ a mixed mode strategy of acquiring and maintaining the bacterial symbionts. Overall, this study contributes to further understand the dynamic and complex effects of environmental Abstract ii change on symbiotic communities, with overall potential cascading repercussions to the persistence of mangrove systems. , Thesis (MSc) (Zoology) -- Faculty of Science and Agriculture, 2015
- Full Text:
- Date Issued: 2015-06
- Authors: Mbobo, Tumeka https://orcid.org/0000-0002-0159-6569
- Date: 2015-06
- Subjects: Mangrove ecology http://id.loc.gov/authorities/subjects/sh85080528 , Crabs--South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/19225 , vital:43033
- Description: The ability of natural populations to maintain fitness is important to their long-term persistence and has further relevance in the light of climate change scenarios. Fitness is however also influenced strongly by interactions with other species of the community. It is, therefore, important to focus on how environmental change can alter key biological interactions. The present study aimed to investigate the effects of different salinity levels on one species of mangrove crab, Uca urvillei and the associated chemoautotrophic bacterial symbionts, from the Mngazana estuary, South Africa. To examine the influence of different salinities over time on the symbiotic bacterial community, salinity experiments were set up, choosing three salinity exposures (5, 20 and 35percent) and four time exposures (3, 7, 14 and 21 days). The results showed that microbial community associated with U. urvillei was generally stable throughout the three salinity treatments, while the survival of the host (crab), was influenced by high salinities, particularly after day 14. Overall, the results of this study suggest that over time, environmental salinity (35percent) has the potential to affect significantly the physiology of U. urvillei, but this might not necessarily be the case for the associated microbial communities. The modes at which the significant symbionts are transferred from mother to offspring were also investigated by analysing the bacterial profiles from eggs, ovigerous and non-ovigerous females, along with mud. The results were fairly complex, but with significant differences in the bacterial communities of eggs from mud and females. These differences were driven mostly by two dominant phyla: Actinobacteria and Proteobacteria. The presence of both these phyla throughout the categories (even though in different percentages) suggest that U. urvillei might employ a mixed mode strategy of acquiring and maintaining the bacterial symbionts. Overall, this study contributes to further understand the dynamic and complex effects of environmental Abstract ii change on symbiotic communities, with overall potential cascading repercussions to the persistence of mangrove systems. , Thesis (MSc) (Zoology) -- Faculty of Science and Agriculture, 2015
- Full Text:
- Date Issued: 2015-06
Application of the Lewis Labour Surplus Model in the smallholder agricultural sector of the Eastern Cape Province
- Mgwangqa, Noluchulumanco Petronella
- Authors: Mgwangqa, Noluchulumanco Petronella
- Date: 2015-06
- Subjects: Economic development -- Mathematical models , Labor economics , Surplus (Economics)
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/23969 , vital:62148
- Description: Rural-urban migration is historically connected to industrialization, urbanization and economic growth. The Lewis model is one of the development theories which provide a good framework of explaining the ways in which the fruits of economic development are spread. Previous studies done in Lewis model in South Africa are still minimal and are only related to the mining sector. Understanding the Lewis labour surplus model in the smallholder agricultural sector is very crucial as agriculture is one of the industries that contribute to the GDP of the country. The application of the Lewis model in the agricultural sector will contribute modestly to available knowledge on labour transition, clarify the ongoing argument on the broad application of the Lewis labour surplus model and more importantly is the need to tease out factors that confirm its validity to the given environment. Thus, the research examines the applicability of the Lewis labour surplus model in the smallholder agricultural sector of the Eastern Cape. It first describes the rate of rural urban migration, causes of rural-urban migration and determines the impact of rural-urban migration on agricultural production.The study was carried in Nkonkobe and Mnquma local Municipalities. Both local municipality were purposively selected because of the high numbers of youth known to have migrated to the urban centres.This study employed a cross-sectional research design. Data was collected at one point in time. Multistage random sampling technique was employed to arrive at the sample size of the study. Data was analysed using descriptive and econometric models. Linear regression model was used to examine the causes of rural urban migration and T-test was also used to test the wage rate difference between rural and urban areas. Lastly Cobb Douglas model was used to test the impact of rural-urban migration on agricultural production. The findings of this research showed that rural urban migration is caused by higher wages, employment opportunities, lack of infrastructure and access to productive land. The results also indicated that urban areas have higher wages than rural areas. Lastly this study provides evidence that the loss of labour through increases in the existing rural-urban migration following rapid urbanizations has an impact on agricultural production. The government should formulate effective policy making in tackling the problems that force people to leave their rural origin and narrowing the development gap between urban and rural areas through the introduction of rural development strategies and effective urban management. , Thesis (MSc) -- Faculty of Science and Agriculture, 2015
- Full Text:
- Date Issued: 2015-06
- Authors: Mgwangqa, Noluchulumanco Petronella
- Date: 2015-06
- Subjects: Economic development -- Mathematical models , Labor economics , Surplus (Economics)
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/23969 , vital:62148
- Description: Rural-urban migration is historically connected to industrialization, urbanization and economic growth. The Lewis model is one of the development theories which provide a good framework of explaining the ways in which the fruits of economic development are spread. Previous studies done in Lewis model in South Africa are still minimal and are only related to the mining sector. Understanding the Lewis labour surplus model in the smallholder agricultural sector is very crucial as agriculture is one of the industries that contribute to the GDP of the country. The application of the Lewis model in the agricultural sector will contribute modestly to available knowledge on labour transition, clarify the ongoing argument on the broad application of the Lewis labour surplus model and more importantly is the need to tease out factors that confirm its validity to the given environment. Thus, the research examines the applicability of the Lewis labour surplus model in the smallholder agricultural sector of the Eastern Cape. It first describes the rate of rural urban migration, causes of rural-urban migration and determines the impact of rural-urban migration on agricultural production.The study was carried in Nkonkobe and Mnquma local Municipalities. Both local municipality were purposively selected because of the high numbers of youth known to have migrated to the urban centres.This study employed a cross-sectional research design. Data was collected at one point in time. Multistage random sampling technique was employed to arrive at the sample size of the study. Data was analysed using descriptive and econometric models. Linear regression model was used to examine the causes of rural urban migration and T-test was also used to test the wage rate difference between rural and urban areas. Lastly Cobb Douglas model was used to test the impact of rural-urban migration on agricultural production. The findings of this research showed that rural urban migration is caused by higher wages, employment opportunities, lack of infrastructure and access to productive land. The results also indicated that urban areas have higher wages than rural areas. Lastly this study provides evidence that the loss of labour through increases in the existing rural-urban migration following rapid urbanizations has an impact on agricultural production. The government should formulate effective policy making in tackling the problems that force people to leave their rural origin and narrowing the development gap between urban and rural areas through the introduction of rural development strategies and effective urban management. , Thesis (MSc) -- Faculty of Science and Agriculture, 2015
- Full Text:
- Date Issued: 2015-06
Assessment of the willingness-to-pay for indigenous animal products in Ngxakaxa households in Mbashe local municipality in Eastern Cape province of South Africa
- Authors: Lusawana, Nangamso
- Date: 2015-06
- Subjects: Willingness to pay , Animal products
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/24879 , vital:63667
- Description: The demand for animal products is projected to increase progressively due to extensive urbanization, rapid growth of the human population and income dynamics. The demand for indigenous animal products will increase due to increasing income levels and this will be happening at the time when the supply of indigenous product is reducing as a result urbanization. The purpose of the current study was to assess consumption and willingness to pay for indigenous animal products looking at chicken and pork. The study intended to determine the socio- economic determinants influencing consumer willingness and consumption. Multistage sampling was used to derive a sample of 120 consumers at households. Primary data were collected using a structured interview schedule. Data collected was on household consumer characteristics, responses to different bid levels for indigenous meat and socio-economic determinants. The study used a Contingent Valuation Method to assess consumers‟ mean WTP for indigenous meat and logit model to determine socio-economic determinants influencing consumers‟ WTP. Results indicated that consumers were willing to pay an average premium of 33percent above the current prevailing price of convectional meat. They also showed that about 87percent of consumers who were willing to pay for indigenous meat and about 12.8percent who are willing to pay if the price increases. Of those who were willing a greater proportions were females. About 64percent of those who are willing and aware of indigenous meat most of them obtained information from neighbours and friends, Age, level of education, consumer awareness and monthly household income had a positive and significant effect on WTP. Most of the consumers indicated that indigenous meats are affordable, healthier when compared conventionally-produced meat. The main significant barrier to the purchase of indigenous meat was identified as its limited availability at convenient locations. The study recommends policy intervention aimed at facilitating development of marketing infrastructure, creation of awareness of important nutritional and health benefits of indigenous meat, and boosting the development of animal production systems that can add value to indigenous meat, so as to capture existing market opportunities. This would enhance food security and income generation of the small-scale resource-constrained farmers. , Thesis (MSc) -- Faculty of Science and Agriculture, 2015
- Full Text:
- Date Issued: 2015-06
- Authors: Lusawana, Nangamso
- Date: 2015-06
- Subjects: Willingness to pay , Animal products
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/24879 , vital:63667
- Description: The demand for animal products is projected to increase progressively due to extensive urbanization, rapid growth of the human population and income dynamics. The demand for indigenous animal products will increase due to increasing income levels and this will be happening at the time when the supply of indigenous product is reducing as a result urbanization. The purpose of the current study was to assess consumption and willingness to pay for indigenous animal products looking at chicken and pork. The study intended to determine the socio- economic determinants influencing consumer willingness and consumption. Multistage sampling was used to derive a sample of 120 consumers at households. Primary data were collected using a structured interview schedule. Data collected was on household consumer characteristics, responses to different bid levels for indigenous meat and socio-economic determinants. The study used a Contingent Valuation Method to assess consumers‟ mean WTP for indigenous meat and logit model to determine socio-economic determinants influencing consumers‟ WTP. Results indicated that consumers were willing to pay an average premium of 33percent above the current prevailing price of convectional meat. They also showed that about 87percent of consumers who were willing to pay for indigenous meat and about 12.8percent who are willing to pay if the price increases. Of those who were willing a greater proportions were females. About 64percent of those who are willing and aware of indigenous meat most of them obtained information from neighbours and friends, Age, level of education, consumer awareness and monthly household income had a positive and significant effect on WTP. Most of the consumers indicated that indigenous meats are affordable, healthier when compared conventionally-produced meat. The main significant barrier to the purchase of indigenous meat was identified as its limited availability at convenient locations. The study recommends policy intervention aimed at facilitating development of marketing infrastructure, creation of awareness of important nutritional and health benefits of indigenous meat, and boosting the development of animal production systems that can add value to indigenous meat, so as to capture existing market opportunities. This would enhance food security and income generation of the small-scale resource-constrained farmers. , Thesis (MSc) -- Faculty of Science and Agriculture, 2015
- Full Text:
- Date Issued: 2015-06
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