Molecular characterization of microbial communities in the Sundays and Swartkops estuaries impacted by anthropogenic activities
- Kgomokhumo, Tlhoafalang Evah
- Authors: Kgomokhumo, Tlhoafalang Evah
- Date: 2022-04-06
- Subjects: Microbial ecology South Africa Sundays Estuary (Eastern Cape) , Microbial ecology South Africa Swartkops River Estuary , Estuarine health Effect of human beings on South Africa Sundays Estuary (Eastern Cape) , Estuarine health Effect of human beings on South Africa Swartkops River Estuary , Microorganisms South Africa Sundays Estuary (Eastern Cape) Molecular aspects , Microorganisms South Africa Swartkops River Estuary Molecular aspects , Eutrophication South Africa Sundays Estuary (Eastern Cape) , Eutrophication South Africa Swartkops River Estuary , Algal blooms South Africa Sundays Estuary (Eastern Cape) , Algal blooms South Africa Swartkops River Estuary
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/290994 , vital:56806
- Description: Anthropogenic activities are of concern in estuarine systems as they are the main source of water degradation. Water pollution in estuaries is indicated by eutrophication and the presence of pathogens and bacterial indicators which affect biodiversity and energy flow. This study focused on two geographically linked estuaries, namely the Sundays and Swartkops Estuaries. The Sundays Estuary is primarily impacted by agricultural activities in the river catchment with increased nutrients levels, particularly of total oxidised nitrogen (TOxN), likely derived from these farming activities. In contrast, the Swartkops Estuary, which is heavily influenced by urban/industrial activities, reflected increased levels of phosphates likely from wastewater and sewage water contamination from residential areas, leaking pipes, and poorly managed sewage treatment plants. The central objective of this study was to assess microbial population profiles and diversity impacted by agricultural activities in Sundays Estuary and industrial/urban-influenced Swartkops Estuary using 16S and 18S rRNA gene metabarcoding. A distinct difference in eukaryotic composition and diversity was evident between the two sampling exercises in 2018 and 2019 in Sundays Estuary. The eutrophication of both the Sundays and Swartkops estuaries was evident in the repeated occurrences of bloom events. In the Sundays Estuary, a bloom of Heterosigma akashiwo was observed in 2018 whilst Cyclotella dominated the estuary in 2019. The Swartkops Estuary exhibited seasonal variation in phytoplankton composition with Bacillariophyceae blooms in the upper reaches of the estuary in summer and increased prevalence of Dinophyceae in spring. Bacterial taxonomic variation was also noted between the two contrasting estuaries. Although members of the Proteobacteria dominated both estuaries, Gammaproteobacteria were in increased abundance in Sundays Estuary while members of Alphaproteobacteria were in high relative abundance in the marine dominated Swartkops Estuary. Members of the Bacteroidetes were the second most abundant bacterial phylum in both estuaries. Bacterial indicators of agricultural anthropogenic impacts identified in Sundays Estuary included members of Sporichthyaceae, Erysipelotrichaceae, Nostocaceae, and NS11-12_marine_group while some taxa such as the Flavobacteriaceae, Cryomorphaceae, and Halieaceae reflected their capability in degrading the phytoplankton bloom biomass present in the estuary. The urban impacts on the Swartkops Estuary was reflected by the contamination of the estuary with potential pathogens including Aeromonas caviae, Vibrio fluvialis, Mycobacterium intracellulare, Vibrio cholerae, and Bacillus cereus. Bacterial community profiles of the major water inflow points into the Swartkops Estuary included members of the Burkholderiaceae, Rhodocyclaceae, Aeromonadaceae, and Arcobacteriaceae which are typically indicative of raw sewage contamination. The Motherwell canal, which runs through informal settlements, was the most polluted input source with high levels of anthropogenic nutrients and pathogenic bacteria. The Chatty river, which also runs through townships, recorded increased nutrient concentrations and low bacterial richness and diversity which was likely due to an Arthrospira bloom at the time of sampling. The overall results of this study identified sources of pollution in Sundays and Swartkops Estuaries and highlighted the impacts of anthropogenic inputs on microbial population profiles and diversity. , Thesis (MSc) -- Faculty of Science, Biochemistry and Microbiology, 2022
- Full Text:
- Date Issued: 2022-04-06
- Authors: Kgomokhumo, Tlhoafalang Evah
- Date: 2022-04-06
- Subjects: Microbial ecology South Africa Sundays Estuary (Eastern Cape) , Microbial ecology South Africa Swartkops River Estuary , Estuarine health Effect of human beings on South Africa Sundays Estuary (Eastern Cape) , Estuarine health Effect of human beings on South Africa Swartkops River Estuary , Microorganisms South Africa Sundays Estuary (Eastern Cape) Molecular aspects , Microorganisms South Africa Swartkops River Estuary Molecular aspects , Eutrophication South Africa Sundays Estuary (Eastern Cape) , Eutrophication South Africa Swartkops River Estuary , Algal blooms South Africa Sundays Estuary (Eastern Cape) , Algal blooms South Africa Swartkops River Estuary
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/290994 , vital:56806
- Description: Anthropogenic activities are of concern in estuarine systems as they are the main source of water degradation. Water pollution in estuaries is indicated by eutrophication and the presence of pathogens and bacterial indicators which affect biodiversity and energy flow. This study focused on two geographically linked estuaries, namely the Sundays and Swartkops Estuaries. The Sundays Estuary is primarily impacted by agricultural activities in the river catchment with increased nutrients levels, particularly of total oxidised nitrogen (TOxN), likely derived from these farming activities. In contrast, the Swartkops Estuary, which is heavily influenced by urban/industrial activities, reflected increased levels of phosphates likely from wastewater and sewage water contamination from residential areas, leaking pipes, and poorly managed sewage treatment plants. The central objective of this study was to assess microbial population profiles and diversity impacted by agricultural activities in Sundays Estuary and industrial/urban-influenced Swartkops Estuary using 16S and 18S rRNA gene metabarcoding. A distinct difference in eukaryotic composition and diversity was evident between the two sampling exercises in 2018 and 2019 in Sundays Estuary. The eutrophication of both the Sundays and Swartkops estuaries was evident in the repeated occurrences of bloom events. In the Sundays Estuary, a bloom of Heterosigma akashiwo was observed in 2018 whilst Cyclotella dominated the estuary in 2019. The Swartkops Estuary exhibited seasonal variation in phytoplankton composition with Bacillariophyceae blooms in the upper reaches of the estuary in summer and increased prevalence of Dinophyceae in spring. Bacterial taxonomic variation was also noted between the two contrasting estuaries. Although members of the Proteobacteria dominated both estuaries, Gammaproteobacteria were in increased abundance in Sundays Estuary while members of Alphaproteobacteria were in high relative abundance in the marine dominated Swartkops Estuary. Members of the Bacteroidetes were the second most abundant bacterial phylum in both estuaries. Bacterial indicators of agricultural anthropogenic impacts identified in Sundays Estuary included members of Sporichthyaceae, Erysipelotrichaceae, Nostocaceae, and NS11-12_marine_group while some taxa such as the Flavobacteriaceae, Cryomorphaceae, and Halieaceae reflected their capability in degrading the phytoplankton bloom biomass present in the estuary. The urban impacts on the Swartkops Estuary was reflected by the contamination of the estuary with potential pathogens including Aeromonas caviae, Vibrio fluvialis, Mycobacterium intracellulare, Vibrio cholerae, and Bacillus cereus. Bacterial community profiles of the major water inflow points into the Swartkops Estuary included members of the Burkholderiaceae, Rhodocyclaceae, Aeromonadaceae, and Arcobacteriaceae which are typically indicative of raw sewage contamination. The Motherwell canal, which runs through informal settlements, was the most polluted input source with high levels of anthropogenic nutrients and pathogenic bacteria. The Chatty river, which also runs through townships, recorded increased nutrient concentrations and low bacterial richness and diversity which was likely due to an Arthrospira bloom at the time of sampling. The overall results of this study identified sources of pollution in Sundays and Swartkops Estuaries and highlighted the impacts of anthropogenic inputs on microbial population profiles and diversity. , Thesis (MSc) -- Faculty of Science, Biochemistry and Microbiology, 2022
- Full Text:
- Date Issued: 2022-04-06
Culture, gender and forests: social differentiation in coping and adapting to climate change and other stressors in the south west and east regions of Cameroon
- Authors: Enokwena Baa, Ojongetakah
- Date: 2021-10-29
- Subjects: Climatic changes Cameroon , Differentiation (Sociology) Cameroon , Climatic changes Social aspects Cameroon , Cultural awareness Cameroon , Environmental justice Cameroon , Social justice Cameroon , Environmental risk assessment Cameroon , Political ecology Cameroon , Ecofeminism Cameroon , Social capital (Sociology) Cameroon , Community forests Cameroon , Deforestation Cameroon
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/295040 , vital:57284 , DOI 10.21504/10962/295040
- Description: Climate change adaptation scholars and practitioners are beginning to acknowledge that the impact of climate change and other related shocks and stressors will be felt, and reacted to, differently across genders and other types of intersecting social categories, such as age, wealth, and culture, in rural communities. However, to date, most research unpacking these differential impacts and responses has been limited to 'men' versus 'women'. Few studies go beyond this male-female dichotomy to include the different gender structures of households and the intersection with other social factors that contribute to marginalisation, such as ethnicity. This research aimed to explore how different gendered household types in two ethnically diverse communities, the Ejagham and the Baka communities in the SSouth West and East regions of Cameroon, experienced and responded to climate change and other stressors. The central argument of the study is that social differentiation present dynamics and complexities across intersecting identities which determines varied levels of vulnerabilities, adaptive capacity, and livelihood outcomes. The study thus sets out to examine cultural and gendered differentiation in household assets and livelihood activities, how multiple shocks and stressors are experienced, and the differentiated responses to these, focussing specifically on forest and social safety nets. The findings were used to develop an integrated understanding of the complex socially differentiated dimensions of vulnerability and adaptation within the two communities and the implications for more climate secure and equitable livelihoods. The study drew on social-ecological systems, social justice, and feminist political ecology as guiding theoretical lenses. The study further integrated the Moser gender planning and Harvard analytical frameworks as tools for unpacking gender inequality. It followed a mixed methods research design that included household surveys, key informant interviews, and focus group discussions that applied participatory exercises. Financial, human, and physical capital were arguably limited within all household types in both the Ejagham and the Baka communities. Social and natural capital were the most common form of assets that households relied on, with ‘savings groups’ in the Ejagham communities being particularly prevalent. Most households were involved in crop cultivation and forest product collection although there were gendered and cultural differences. Collection of wild fruits, medicinal plants, and condiments, for example, was a more common livelihood activity within the Baka communities and amongst female-headed households. Cultivation of pumpkins and vegetables was dominant amongst households in Ejagham, with these being grown mainly by women, while the cultivation of yams was done by men. Across both communities, female-headed households had less ownership of land compared to male-headed households. The current pressure on agricultural land in the Ejagham communities has decreased crop productivity, with female-headed households disproportionately affected by less ownership of land and thus, options to diversify agricultural activities. Similarly, the rise in individual and private land ownership, in response to resource scarcity and large-scale deforestation in East Cameroon, has further dispossessed female-headed households in the Baka communities, already marginalised by their ethnicity, of land. Inequitable access to assets and the disparity in ownership of these assets across the study communities was both a cause and effect of households' differential livelihood activities and responses to shocks and stressors. Several of the shocks and stressors households were exposed to differed across the two sites. The Ejagham communities, being predominantly agricultural, frequently identified warming temperatures as a climatic stressor and increased sensitivity to the impacts of these. The Baka faced similar climate stressors, although more frequent storms were mentioned as a shock by a significant number of households. The impacts of these storms include damage and destruction of houses due to the traditional construction methods used. Since women are often tasked with the building of houses this adds another layer of stress for them. In terms of idiosyncratic shocks, the death of the main breadwinner was most frequently reported in both communities as a non-climatic shock, although this was higher within the Ejagham communities than in the Baka communities, and particularly so for female-headed households. The varied experiences from multiple shocks and stressors resulted in households' differential coping and adaptation responses. Among the different response options, social and forest safety nets, especially the use and sale of forest products (NTFPs) remained the main response options used by households in both communities. Forest products further supported households during periods of food shortage, especially female-headed households in the Ejagham communities. Households further supported one another through social groups such as savings, farming, hunting (particularly for men) and NTFP collection (for women) groups. By exploring social-ecological interactions, the study highlights the complexities around gender inequalities, vulnerabilities, and responses across socially differentiated groups of people which should be considered in policy, practice, and research. Several of my findings challenge mainstream discourses that generally group women, for instance, as a homogenous category when looking at vulnerability. For example, findings revealed that it is possible for different types of households, both women and men, to be both advantaged and vulnerable at the same time, depending on the shock or stressor faced and the livelihood activities they engage in. The same also applies to ethnicity. , Thesis (PhD) -- Faculty of Science, Environmental Science, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Enokwena Baa, Ojongetakah
- Date: 2021-10-29
- Subjects: Climatic changes Cameroon , Differentiation (Sociology) Cameroon , Climatic changes Social aspects Cameroon , Cultural awareness Cameroon , Environmental justice Cameroon , Social justice Cameroon , Environmental risk assessment Cameroon , Political ecology Cameroon , Ecofeminism Cameroon , Social capital (Sociology) Cameroon , Community forests Cameroon , Deforestation Cameroon
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/295040 , vital:57284 , DOI 10.21504/10962/295040
- Description: Climate change adaptation scholars and practitioners are beginning to acknowledge that the impact of climate change and other related shocks and stressors will be felt, and reacted to, differently across genders and other types of intersecting social categories, such as age, wealth, and culture, in rural communities. However, to date, most research unpacking these differential impacts and responses has been limited to 'men' versus 'women'. Few studies go beyond this male-female dichotomy to include the different gender structures of households and the intersection with other social factors that contribute to marginalisation, such as ethnicity. This research aimed to explore how different gendered household types in two ethnically diverse communities, the Ejagham and the Baka communities in the SSouth West and East regions of Cameroon, experienced and responded to climate change and other stressors. The central argument of the study is that social differentiation present dynamics and complexities across intersecting identities which determines varied levels of vulnerabilities, adaptive capacity, and livelihood outcomes. The study thus sets out to examine cultural and gendered differentiation in household assets and livelihood activities, how multiple shocks and stressors are experienced, and the differentiated responses to these, focussing specifically on forest and social safety nets. The findings were used to develop an integrated understanding of the complex socially differentiated dimensions of vulnerability and adaptation within the two communities and the implications for more climate secure and equitable livelihoods. The study drew on social-ecological systems, social justice, and feminist political ecology as guiding theoretical lenses. The study further integrated the Moser gender planning and Harvard analytical frameworks as tools for unpacking gender inequality. It followed a mixed methods research design that included household surveys, key informant interviews, and focus group discussions that applied participatory exercises. Financial, human, and physical capital were arguably limited within all household types in both the Ejagham and the Baka communities. Social and natural capital were the most common form of assets that households relied on, with ‘savings groups’ in the Ejagham communities being particularly prevalent. Most households were involved in crop cultivation and forest product collection although there were gendered and cultural differences. Collection of wild fruits, medicinal plants, and condiments, for example, was a more common livelihood activity within the Baka communities and amongst female-headed households. Cultivation of pumpkins and vegetables was dominant amongst households in Ejagham, with these being grown mainly by women, while the cultivation of yams was done by men. Across both communities, female-headed households had less ownership of land compared to male-headed households. The current pressure on agricultural land in the Ejagham communities has decreased crop productivity, with female-headed households disproportionately affected by less ownership of land and thus, options to diversify agricultural activities. Similarly, the rise in individual and private land ownership, in response to resource scarcity and large-scale deforestation in East Cameroon, has further dispossessed female-headed households in the Baka communities, already marginalised by their ethnicity, of land. Inequitable access to assets and the disparity in ownership of these assets across the study communities was both a cause and effect of households' differential livelihood activities and responses to shocks and stressors. Several of the shocks and stressors households were exposed to differed across the two sites. The Ejagham communities, being predominantly agricultural, frequently identified warming temperatures as a climatic stressor and increased sensitivity to the impacts of these. The Baka faced similar climate stressors, although more frequent storms were mentioned as a shock by a significant number of households. The impacts of these storms include damage and destruction of houses due to the traditional construction methods used. Since women are often tasked with the building of houses this adds another layer of stress for them. In terms of idiosyncratic shocks, the death of the main breadwinner was most frequently reported in both communities as a non-climatic shock, although this was higher within the Ejagham communities than in the Baka communities, and particularly so for female-headed households. The varied experiences from multiple shocks and stressors resulted in households' differential coping and adaptation responses. Among the different response options, social and forest safety nets, especially the use and sale of forest products (NTFPs) remained the main response options used by households in both communities. Forest products further supported households during periods of food shortage, especially female-headed households in the Ejagham communities. Households further supported one another through social groups such as savings, farming, hunting (particularly for men) and NTFP collection (for women) groups. By exploring social-ecological interactions, the study highlights the complexities around gender inequalities, vulnerabilities, and responses across socially differentiated groups of people which should be considered in policy, practice, and research. Several of my findings challenge mainstream discourses that generally group women, for instance, as a homogenous category when looking at vulnerability. For example, findings revealed that it is possible for different types of households, both women and men, to be both advantaged and vulnerable at the same time, depending on the shock or stressor faced and the livelihood activities they engage in. The same also applies to ethnicity. , Thesis (PhD) -- Faculty of Science, Environmental Science, 2021
- Full Text:
- Date Issued: 2021-10-29
Inhibition of aluminium corrosion using phthalocyanines: Experimental and computational studies
- Authors: Nnaji, Nnaemeka Joshua
- Date: 2022-04-08
- Subjects: Aluminum Corrosion , Electrochemistry , Phthalocyanines , Corrosion and anti-corrosives , Protective coatings , Density functionals
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/294643 , vital:57240 , DOI 10.21504/10962/294643
- Description: Metal deterioration over time is a process known as corrosion, an electrochemical process, which can occur by surface chemical actions on metals by its environment. Metal corrosion have great economic, security, and environmental consequences, and its control is a major research area in corrosion science. Amongst the different corrosion protecting approaches, the use of corrosion inhibitors and protective coatings have attracted enormous research interest in this area of scholasticism. This has necessitated the computational and electrochemical investigations of aluminium corrosion inhibitive potentials of some compounds in 1M HCl. Metal free (5_H2), ClGa(III) (5_Ga) and Co(II) (5_Co) tetrakis(4-acetamidophenoxy)phthalocyanines as well as Co(II) 2,9,16-tris(4-(tert-butyl)phenoxy)-23-(pyridin-4-yloxy)phthalocyanine (6) and Co(II) 2,9,16,24-tetrakis(4-(tert-butyl)phenoxy)phthalocyanine (7) were synthesized for the first time and studied for corrosion inhibition. The reported ClGa(III) tetrakis(benzo[d]thiazol-2-yl-thio)phthalocyaninine (1), ClGa(III) tetrakis(benzo[d]thiazol-2ylphenoxy)phthalocyanine (2), ClGa(III) tetrakis-4-(hexadecane-1,2-dioxyl)-bis(phthalocyanine) (3) and ClGa(III) tetrakis-4,4′-((4-(benzo[d]thiazol-2-yl)-1,2-bis(phenoxy)-bis(phthalocyanine) (4) were also employed for corrosion inhibition of Al in HCl. Corrosion inhibition measurements using electrochemical techniques showed that increased π conjugation caused (1) to (2) to outperform (1a) and (2a) respectively as aluminium corrosion inhibitors in 1.0 M hydrochloric acid. For similar reason, (4) outperformed 2. (1) and (2) were successfully electrodeposited onto aluminium for corrosion retardation in 1.0 M hydrochloric acid solution. Measurements obtained from electrochemical impedance spectroscopy gave corrosion inhibition efficiency values of 82% for 1 and 86% for 2 in 1.0 M hydrochloric acid solution and showed that electrodeposited phthalocyanines have enhanced aluminium corrosion retardation than when in solution. The use of reduced graphene oxide nanosheets (rGONS) alone as aluminium corrosion inhibitor is discouraged because of poor aluminium corrosion inhibition in 1M HCl. However, synergistic effects were observed when rGONS was mixed each with (4) and (3). (5_H2), (5_Ga) and (5_Co) decreased aluminium corrosion in 1M HCl and observation was that the heavier the atom the more decreased the protection and the free base performed best of the three. Studied tertbutylphenoxy-derived CoPcs (6 and 7) exhibited good aluminium corrosion inhibition properties in studied acidic solution and the unsymmetric CoPc (6) which has more heteroatoms, gave better performance. Quantum chemical calculations involved the use of density functional theoretical (DFT) approaches and gave results which corroborated with experimental findings. , Thesis (PhD) -- Faculty of Science, Chemistry, 2022
- Full Text:
- Date Issued: 2022-04-08
- Authors: Nnaji, Nnaemeka Joshua
- Date: 2022-04-08
- Subjects: Aluminum Corrosion , Electrochemistry , Phthalocyanines , Corrosion and anti-corrosives , Protective coatings , Density functionals
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/294643 , vital:57240 , DOI 10.21504/10962/294643
- Description: Metal deterioration over time is a process known as corrosion, an electrochemical process, which can occur by surface chemical actions on metals by its environment. Metal corrosion have great economic, security, and environmental consequences, and its control is a major research area in corrosion science. Amongst the different corrosion protecting approaches, the use of corrosion inhibitors and protective coatings have attracted enormous research interest in this area of scholasticism. This has necessitated the computational and electrochemical investigations of aluminium corrosion inhibitive potentials of some compounds in 1M HCl. Metal free (5_H2), ClGa(III) (5_Ga) and Co(II) (5_Co) tetrakis(4-acetamidophenoxy)phthalocyanines as well as Co(II) 2,9,16-tris(4-(tert-butyl)phenoxy)-23-(pyridin-4-yloxy)phthalocyanine (6) and Co(II) 2,9,16,24-tetrakis(4-(tert-butyl)phenoxy)phthalocyanine (7) were synthesized for the first time and studied for corrosion inhibition. The reported ClGa(III) tetrakis(benzo[d]thiazol-2-yl-thio)phthalocyaninine (1), ClGa(III) tetrakis(benzo[d]thiazol-2ylphenoxy)phthalocyanine (2), ClGa(III) tetrakis-4-(hexadecane-1,2-dioxyl)-bis(phthalocyanine) (3) and ClGa(III) tetrakis-4,4′-((4-(benzo[d]thiazol-2-yl)-1,2-bis(phenoxy)-bis(phthalocyanine) (4) were also employed for corrosion inhibition of Al in HCl. Corrosion inhibition measurements using electrochemical techniques showed that increased π conjugation caused (1) to (2) to outperform (1a) and (2a) respectively as aluminium corrosion inhibitors in 1.0 M hydrochloric acid. For similar reason, (4) outperformed 2. (1) and (2) were successfully electrodeposited onto aluminium for corrosion retardation in 1.0 M hydrochloric acid solution. Measurements obtained from electrochemical impedance spectroscopy gave corrosion inhibition efficiency values of 82% for 1 and 86% for 2 in 1.0 M hydrochloric acid solution and showed that electrodeposited phthalocyanines have enhanced aluminium corrosion retardation than when in solution. The use of reduced graphene oxide nanosheets (rGONS) alone as aluminium corrosion inhibitor is discouraged because of poor aluminium corrosion inhibition in 1M HCl. However, synergistic effects were observed when rGONS was mixed each with (4) and (3). (5_H2), (5_Ga) and (5_Co) decreased aluminium corrosion in 1M HCl and observation was that the heavier the atom the more decreased the protection and the free base performed best of the three. Studied tertbutylphenoxy-derived CoPcs (6 and 7) exhibited good aluminium corrosion inhibition properties in studied acidic solution and the unsymmetric CoPc (6) which has more heteroatoms, gave better performance. Quantum chemical calculations involved the use of density functional theoretical (DFT) approaches and gave results which corroborated with experimental findings. , Thesis (PhD) -- Faculty of Science, Chemistry, 2022
- Full Text:
- Date Issued: 2022-04-08
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