The presence and role of arbuscular mycorrhizal fungi in coastal sand dune systems
- Authors: Haller, Anjanette H. A
- Date: 2000
- Subjects: Mycorrhizas , Sand dune ecology -- South Africa , Mycorrhizal fungi
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4196 , http://hdl.handle.net/10962/d1003765 , Mycorrhizas , Sand dune ecology -- South Africa , Mycorrhizal fungi
- Description: Arbuscular mycorrhizas (AM) are mutually beneficial symbiotic associations between the roots of plants and certain Zygomycetous fungi. The role of AM fungi in coastal sand dunes has been explored in many parts of the world, though little work has been conducted in South African dune systems. This study aimed to investigate the presence and extent of mycorrhizal colonisation of a coastal sand dune in South Africa. The roots of five plant species (Scaevola plumieri, Arctotheca populifolia, Ipomoea pes-caprae, Ehrharta villosa and Chrysanthemoides monilifera) were sampled along a foredune profile at Old Woman's River in the Eastern Cape. These roots were assessed for the percentage mycorrhizal colonisation they supported. Spores extracted from the rhizosphere sand of each plant species were counted and identified to genus level. Results were related to seasonality and the position of the plants along the profile. All plant species were found to be mycorrhizal. Percentage colonisation ranged from 0-92%, depending on plant species and season. Mycorrhizal colonisation was generally highest in the winter months, and especially so in I pes-caprae and E. villosa. The extent of various mycorrhizal structures in root tissue varied between plant species. Spore numbers ranged from 0-48 spores 100g-1 sand with highest numbers occurring in winter. S. plumieri and A. populifolia were associated with greatest spore abundance. Four fungal genera (Glomus, Acaulospora, Scutellospora and Gigaspora) were identified. Distribution of these genera showed seasonal variations between plant species. A bioassay, using Sorghum, was conducted to test the inoculum potentials of sand from the Scaevola hummock and the IpomoealEhrharta dune. Highest percentage colonisation occurred in plants grown in the Scaevola sand, which also had the lowest root and shoot measurements. The bioassay confirmed that AM propagules are present and viable, even in the mobile sand of the foredune. This study showed that mycorrhizal colonisation and spore numbers varied seasonally, but that the extent of this was dependent on plant species. The position of plants along the foredune profile tended to be less important than plant species. It is thought that the growth cycle and rooting system of each plant species determines seasonal cycles and abundance of AM fungi. Variation within fungal populations probably also impacts on this. Knowledge of the presence and distribution of AM fungi in this system paves the way for more detailed studies which need to examine the role of these endophytes in South African sand dunes.
- Full Text:
- Date Issued: 2000
- Authors: Haller, Anjanette H. A
- Date: 2000
- Subjects: Mycorrhizas , Sand dune ecology -- South Africa , Mycorrhizal fungi
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4196 , http://hdl.handle.net/10962/d1003765 , Mycorrhizas , Sand dune ecology -- South Africa , Mycorrhizal fungi
- Description: Arbuscular mycorrhizas (AM) are mutually beneficial symbiotic associations between the roots of plants and certain Zygomycetous fungi. The role of AM fungi in coastal sand dunes has been explored in many parts of the world, though little work has been conducted in South African dune systems. This study aimed to investigate the presence and extent of mycorrhizal colonisation of a coastal sand dune in South Africa. The roots of five plant species (Scaevola plumieri, Arctotheca populifolia, Ipomoea pes-caprae, Ehrharta villosa and Chrysanthemoides monilifera) were sampled along a foredune profile at Old Woman's River in the Eastern Cape. These roots were assessed for the percentage mycorrhizal colonisation they supported. Spores extracted from the rhizosphere sand of each plant species were counted and identified to genus level. Results were related to seasonality and the position of the plants along the profile. All plant species were found to be mycorrhizal. Percentage colonisation ranged from 0-92%, depending on plant species and season. Mycorrhizal colonisation was generally highest in the winter months, and especially so in I pes-caprae and E. villosa. The extent of various mycorrhizal structures in root tissue varied between plant species. Spore numbers ranged from 0-48 spores 100g-1 sand with highest numbers occurring in winter. S. plumieri and A. populifolia were associated with greatest spore abundance. Four fungal genera (Glomus, Acaulospora, Scutellospora and Gigaspora) were identified. Distribution of these genera showed seasonal variations between plant species. A bioassay, using Sorghum, was conducted to test the inoculum potentials of sand from the Scaevola hummock and the IpomoealEhrharta dune. Highest percentage colonisation occurred in plants grown in the Scaevola sand, which also had the lowest root and shoot measurements. The bioassay confirmed that AM propagules are present and viable, even in the mobile sand of the foredune. This study showed that mycorrhizal colonisation and spore numbers varied seasonally, but that the extent of this was dependent on plant species. The position of plants along the foredune profile tended to be less important than plant species. It is thought that the growth cycle and rooting system of each plant species determines seasonal cycles and abundance of AM fungi. Variation within fungal populations probably also impacts on this. Knowledge of the presence and distribution of AM fungi in this system paves the way for more detailed studies which need to examine the role of these endophytes in South African sand dunes.
- Full Text:
- Date Issued: 2000
The response of the two interrelated river components, geomorphology and riparian vegetation, to interbasin water transfers in the Orange-Fish-Sundays River Interbasin Transfer Scheme
- Authors: du Plessis, A J E
- Date: 2000
- Subjects: Skoenmakers River (South Africa) , Riparian ecology -- South Africa -- Eastern Cape , Geomorphology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4850 , http://hdl.handle.net/10962/d1005526
- Description: The Skoenmakers River (located in the semi-arid Karoo region of the Eastern Cape) is being used as a transfer route for water transferred by the Orange-Fish-Sundays River Interbasin Transfer Scheme. The change in the hydrological regime of this once ephemeral stream to a much bigger perennial river led to dramatic changes to both the physical structure and riparian vegetation structure of the river system. These changes differ for each of the three river sections, the upper,middle and lower reaches. Qualitative, descriptive geomorphological data was gathered by means of field observations and this was then compared to the quantitative data collected by means of surveyed cross-sectional profiles at selected sites along the length of both the regulated Skoenmakers River and a nonregulated tributary of equivalent size, the Volkers River. Riparian vegetation data was gathered by means of plot sampling along belt transects at each site. A qualitative assessment of the vegetation conditions was also made at each site and then added to the quantitative data from the plot sampling. At each site the different morphological units were identified along the cross-section and changes in the vegetation and sediment composition were recorded. Aerial photographs were used as additional sources of data and observations made from these were compared to data gathered in the field. The pre-IBT channel in this river section was formed by low frequency flood flows but the hydrological regime has now been converted to base flows much higher than normal flood flows. Severe incision, erosion and degradation of both the channel bed and banks occurred. In the lower reaches, post-IBT base flows are lower than pre-IBT flood flows and, due to the increased catchment area, the impact of the IBT was better ‘absorbed’ by the river system. Aggradation and deposition increased for the regulated river in comparison to the non-regulated river due to more sediment introduced The IBT had the greatest impact in the upper reaches of the regulated river due to more sediment introduced at the top of the system.
- Full Text:
- Date Issued: 2000
- Authors: du Plessis, A J E
- Date: 2000
- Subjects: Skoenmakers River (South Africa) , Riparian ecology -- South Africa -- Eastern Cape , Geomorphology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4850 , http://hdl.handle.net/10962/d1005526
- Description: The Skoenmakers River (located in the semi-arid Karoo region of the Eastern Cape) is being used as a transfer route for water transferred by the Orange-Fish-Sundays River Interbasin Transfer Scheme. The change in the hydrological regime of this once ephemeral stream to a much bigger perennial river led to dramatic changes to both the physical structure and riparian vegetation structure of the river system. These changes differ for each of the three river sections, the upper,middle and lower reaches. Qualitative, descriptive geomorphological data was gathered by means of field observations and this was then compared to the quantitative data collected by means of surveyed cross-sectional profiles at selected sites along the length of both the regulated Skoenmakers River and a nonregulated tributary of equivalent size, the Volkers River. Riparian vegetation data was gathered by means of plot sampling along belt transects at each site. A qualitative assessment of the vegetation conditions was also made at each site and then added to the quantitative data from the plot sampling. At each site the different morphological units were identified along the cross-section and changes in the vegetation and sediment composition were recorded. Aerial photographs were used as additional sources of data and observations made from these were compared to data gathered in the field. The pre-IBT channel in this river section was formed by low frequency flood flows but the hydrological regime has now been converted to base flows much higher than normal flood flows. Severe incision, erosion and degradation of both the channel bed and banks occurred. In the lower reaches, post-IBT base flows are lower than pre-IBT flood flows and, due to the increased catchment area, the impact of the IBT was better ‘absorbed’ by the river system. Aggradation and deposition increased for the regulated river in comparison to the non-regulated river due to more sediment introduced The IBT had the greatest impact in the upper reaches of the regulated river due to more sediment introduced at the top of the system.
- Full Text:
- Date Issued: 2000
The scrum-down on brain damage effects of cumulative mild head injury in rugby: a comparison of group mean scores between national rugby players and non-contact sport controls
- Authors: Finkelstein, Melissa
- Date: 2000
- Subjects: Sports injuries , Head -- Wounds and injuries , Sports injuries -- Psychological aspects , Neuropsychological tests , Rugby football injuries
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:2976 , http://hdl.handle.net/10962/d1002485 , Sports injuries , Head -- Wounds and injuries , Sports injuries -- Psychological aspects , Neuropsychological tests , Rugby football injuries
- Description: The present study comprises the second phase of a larger and ongoing research study investigating the brain damage effects of cumulative mild head injury in rugby. The purpose of this study was to determine whether cumulative mild head injury sustained in the game of rugby would cause brain injury as evidenced by impaired performance on sensitive neuropsychological tests. Participants were Springbok professional rugby players (n = 26), Under 21 rugby players (n = 19), and a non-contact sport control of national hockey players (n = 21). Comparisons of performance were carried out across a spectrum of neuropsychological tests for the three rugby groups (Total Rugby, Springbok Rugby, and Under 21 Rugby) versus the performance of the non-contact sport control group (Hockey Control), as well as comparisons of performance f9r the subgroups of Rugby Forwards versus Rugby Backs. Comparisons revealed a consistent pattern of poorer performance across all rugby groups relative to the performance of the controls on tests highly sensitive to the effects of diffuse brain damage. Within rugby group comparisons (Forwards versus Backs) showed significantly poorer performance for Total Rugby Forwards and Springbok Rugby Forwards relative to the performance of the respective Total Rugby Backs and Springbok Rugby Backs on sensitive, as well as on somewhat less sensitive, neuropsychological tests. The performance of Under 21 Rugby Forwards relative to Under 21 Rugby Backs demonstrated similar trends. Brain reserve capacity theory was used as a conceptual basis for discussing the implications of these findings.
- Full Text:
- Date Issued: 2000
- Authors: Finkelstein, Melissa
- Date: 2000
- Subjects: Sports injuries , Head -- Wounds and injuries , Sports injuries -- Psychological aspects , Neuropsychological tests , Rugby football injuries
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:2976 , http://hdl.handle.net/10962/d1002485 , Sports injuries , Head -- Wounds and injuries , Sports injuries -- Psychological aspects , Neuropsychological tests , Rugby football injuries
- Description: The present study comprises the second phase of a larger and ongoing research study investigating the brain damage effects of cumulative mild head injury in rugby. The purpose of this study was to determine whether cumulative mild head injury sustained in the game of rugby would cause brain injury as evidenced by impaired performance on sensitive neuropsychological tests. Participants were Springbok professional rugby players (n = 26), Under 21 rugby players (n = 19), and a non-contact sport control of national hockey players (n = 21). Comparisons of performance were carried out across a spectrum of neuropsychological tests for the three rugby groups (Total Rugby, Springbok Rugby, and Under 21 Rugby) versus the performance of the non-contact sport control group (Hockey Control), as well as comparisons of performance f9r the subgroups of Rugby Forwards versus Rugby Backs. Comparisons revealed a consistent pattern of poorer performance across all rugby groups relative to the performance of the controls on tests highly sensitive to the effects of diffuse brain damage. Within rugby group comparisons (Forwards versus Backs) showed significantly poorer performance for Total Rugby Forwards and Springbok Rugby Forwards relative to the performance of the respective Total Rugby Backs and Springbok Rugby Backs on sensitive, as well as on somewhat less sensitive, neuropsychological tests. The performance of Under 21 Rugby Forwards relative to Under 21 Rugby Backs demonstrated similar trends. Brain reserve capacity theory was used as a conceptual basis for discussing the implications of these findings.
- Full Text:
- Date Issued: 2000
The solubility enhancement and the stability assessment of rifampicin, isoniazid and pyrazinamide in aqueous media
- Authors: Chen, Yu-Jen
- Date: 2000
- Subjects: Gel permeation chromatography , Rifampin , Isoniazid , Pyridazines
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4346 , http://hdl.handle.net/10962/d1005009 , Gel permeation chromatography , Rifampin , Isoniazid , Pyridazines
- Description: Tuberculosis (TB) is a highly contagious disease caused by the bacterium known as Mycobacterium tuberculosis which is widely spread in South Africa, especially in the rural areas of the Western Province. Rifampicin, isoniazid and pyrazinamide are the three most effective drugs against this organism. However, most of the current commercial anti-TB formulations are inconvenient to administrate. This results in patient non-compliance which has increased with incomplete tuberculosis treatment and further has intensified the mortality rate. The matter is especially severe amongst the paediatric and geriatric patients. Therefore, creating a "user-friendly" but non-alcoholic liquid formulation should improve the whole situation. The key to a successful formulation relies on sufficient concentrations of the drugs within the formulation together with acceptable stability of these drugs. Therefore, during the pre-formulation stage, the solubility and stability studies of rifampicin, isoniazid and pyrazinamide are to be conducted. Rifampicin, isoniazid and pyrazinamide were fully characterized and identified by means of spectroscopic and thermal techniques. A HPLC method for simultaneous analysis of the three drugs was developed and validated. This HPLC method was employed for all the solubility and stability assessments. Unbuffered HPLC water of pH value 7.01 was chosen as the aqueous solvent. This was decided after the stability of rifampicin, isoniazid and pyrazinamide was studied at a pH range of 2 to 10. The solubility and the stability studies of rifampicin, isoniazid, pyrazinamide, rifampicin with isoniazid, rifampicin with pyrazinamide, isoniazid with pyrazinamide and rifampicin combined with both isoniazid and pyrazinamide were performed in the presence of various agents. These agents can be categorized into three groups: the surfactants (poloxamer 188, poloxamer 407 and sorbitol) which could increase the intrinsic solubility or the drugs by altering the surface tensions of the aqueous solution medium, the suspending agents (carbopol 934 and carbopol 974P) which could enable the amount of dosage required to be homogeneously suspended in the formulation without considering the low intrinsic solubility factor of the drugs, and the complexing agents (ß-cyclodextrin, hydroxypropyl-ß-cyclodextrin and -cyclodextrin) which could initiated the inclusion complex between the host cyclodextrin and the drugs, thus further enhance the solubility of the drugs . The stability assessments were performed after 7-days stability trail with the HPLC method developed. Each drug/combination of drugs were stored in closed ampoules and subjected to 25, 40 and 60° C with or without nitrogen flushing while in the presence of the above mentioned agents. While assessing the solubility/stability of the drugs in the presence of the above mentioned surfactants, the phase-solubility curves indicate that both rifampicin and pyrazinamide fail to achieve the desired concentration. Moreover, the stability-time plots clearly indicate that these surfactants fail to enhance the general stabilities of the drugs. When the stabilizing effects of the above mentioned suspending agents were investigated, it was found that although the desired concentration could be easily accomplished by suspending the drug in the aqueous carbopol solutions, the stabilities of the different drug combinations were still below the regulatory level. Cyclodextrins are well known to form inclusion complexes with less polar drug molecules. The inclusion complexation could enhance both the solubility and the stability of the included drug molecules. The computer force field generated models of the cyclodextrin-drug were used to predict the complexation sites. The results indicated the all the inclusion complexation between the drugs and the cyclodextrins were favourable, but do not necessary protect the potential degradation sites of the drugs. The stability results confirmed the above findings as the cyclodextrins did not enhance the stability of the drugs. Various drug-drug interaction pathways were also predicted from the experimental observations which clearly indicated the stability reductions of these drugs in combination. This leads to the conclusion that a liquid formulation combining rifampicin, isoniazid and pyrazinamide should not initiate the use of aqueous solutions as the protic ions of the solution are able to initiate the degradation of these drugs.
- Full Text:
- Date Issued: 2000
- Authors: Chen, Yu-Jen
- Date: 2000
- Subjects: Gel permeation chromatography , Rifampin , Isoniazid , Pyridazines
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4346 , http://hdl.handle.net/10962/d1005009 , Gel permeation chromatography , Rifampin , Isoniazid , Pyridazines
- Description: Tuberculosis (TB) is a highly contagious disease caused by the bacterium known as Mycobacterium tuberculosis which is widely spread in South Africa, especially in the rural areas of the Western Province. Rifampicin, isoniazid and pyrazinamide are the three most effective drugs against this organism. However, most of the current commercial anti-TB formulations are inconvenient to administrate. This results in patient non-compliance which has increased with incomplete tuberculosis treatment and further has intensified the mortality rate. The matter is especially severe amongst the paediatric and geriatric patients. Therefore, creating a "user-friendly" but non-alcoholic liquid formulation should improve the whole situation. The key to a successful formulation relies on sufficient concentrations of the drugs within the formulation together with acceptable stability of these drugs. Therefore, during the pre-formulation stage, the solubility and stability studies of rifampicin, isoniazid and pyrazinamide are to be conducted. Rifampicin, isoniazid and pyrazinamide were fully characterized and identified by means of spectroscopic and thermal techniques. A HPLC method for simultaneous analysis of the three drugs was developed and validated. This HPLC method was employed for all the solubility and stability assessments. Unbuffered HPLC water of pH value 7.01 was chosen as the aqueous solvent. This was decided after the stability of rifampicin, isoniazid and pyrazinamide was studied at a pH range of 2 to 10. The solubility and the stability studies of rifampicin, isoniazid, pyrazinamide, rifampicin with isoniazid, rifampicin with pyrazinamide, isoniazid with pyrazinamide and rifampicin combined with both isoniazid and pyrazinamide were performed in the presence of various agents. These agents can be categorized into three groups: the surfactants (poloxamer 188, poloxamer 407 and sorbitol) which could increase the intrinsic solubility or the drugs by altering the surface tensions of the aqueous solution medium, the suspending agents (carbopol 934 and carbopol 974P) which could enable the amount of dosage required to be homogeneously suspended in the formulation without considering the low intrinsic solubility factor of the drugs, and the complexing agents (ß-cyclodextrin, hydroxypropyl-ß-cyclodextrin and -cyclodextrin) which could initiated the inclusion complex between the host cyclodextrin and the drugs, thus further enhance the solubility of the drugs . The stability assessments were performed after 7-days stability trail with the HPLC method developed. Each drug/combination of drugs were stored in closed ampoules and subjected to 25, 40 and 60° C with or without nitrogen flushing while in the presence of the above mentioned agents. While assessing the solubility/stability of the drugs in the presence of the above mentioned surfactants, the phase-solubility curves indicate that both rifampicin and pyrazinamide fail to achieve the desired concentration. Moreover, the stability-time plots clearly indicate that these surfactants fail to enhance the general stabilities of the drugs. When the stabilizing effects of the above mentioned suspending agents were investigated, it was found that although the desired concentration could be easily accomplished by suspending the drug in the aqueous carbopol solutions, the stabilities of the different drug combinations were still below the regulatory level. Cyclodextrins are well known to form inclusion complexes with less polar drug molecules. The inclusion complexation could enhance both the solubility and the stability of the included drug molecules. The computer force field generated models of the cyclodextrin-drug were used to predict the complexation sites. The results indicated the all the inclusion complexation between the drugs and the cyclodextrins were favourable, but do not necessary protect the potential degradation sites of the drugs. The stability results confirmed the above findings as the cyclodextrins did not enhance the stability of the drugs. Various drug-drug interaction pathways were also predicted from the experimental observations which clearly indicated the stability reductions of these drugs in combination. This leads to the conclusion that a liquid formulation combining rifampicin, isoniazid and pyrazinamide should not initiate the use of aqueous solutions as the protic ions of the solution are able to initiate the degradation of these drugs.
- Full Text:
- Date Issued: 2000
The structure and function of the gametes of the striped field mouse (Rhabdomys pumilio)
- Authors: Tinney, Gregory Michael
- Date: 2000
- Subjects: Gametes , Microtus , Mice
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5774 , http://hdl.handle.net/10962/d1005462 , Gametes , Microtus , Mice
- Description: This study was initiated in an attempt toadd the four-striped field mouse (Rhabdomys pumilio) to the small group of mammals that are used to study and develop assisted reproductive technologies. To accomplish this, a complete knowledge of both the male and female gametes was necessary, as well as a repeatable and successful IVF protocol. The gametes of the field mouse, both the falciformspermand the mature oocytes, were shown to be similar in several respects to those of many other rodent species. The induction of both the capacitated state and the acrosome reaction in the sperm were readily achieved. The success of retrieving mature oocytes was very low, with the rare occurrence of polar bodies within ovulated oocytes. The difficulties with oocytes was either related to the lack of a regular oestrous cycle, or to the hormonal regime used to induce superovulation. Although several protocols were used to accomplish superovulation in this species, it was seldom achieved. In in vitro fertilization trials, sperm were found to attach to both the cumulus oophorus and the zona pellucida of the oocytes. However, fertilization was never accomplished. This failure to achieve fertilization was probably related to the immaturity of the oocytes. Without further studies on Rhabdomys pumilio and further attempts at accomplishing in vitro fertilization, it would seem that this species would not easily be introduced as an animalmodelfor assisted reproduction.
- Full Text:
- Date Issued: 2000
- Authors: Tinney, Gregory Michael
- Date: 2000
- Subjects: Gametes , Microtus , Mice
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5774 , http://hdl.handle.net/10962/d1005462 , Gametes , Microtus , Mice
- Description: This study was initiated in an attempt toadd the four-striped field mouse (Rhabdomys pumilio) to the small group of mammals that are used to study and develop assisted reproductive technologies. To accomplish this, a complete knowledge of both the male and female gametes was necessary, as well as a repeatable and successful IVF protocol. The gametes of the field mouse, both the falciformspermand the mature oocytes, were shown to be similar in several respects to those of many other rodent species. The induction of both the capacitated state and the acrosome reaction in the sperm were readily achieved. The success of retrieving mature oocytes was very low, with the rare occurrence of polar bodies within ovulated oocytes. The difficulties with oocytes was either related to the lack of a regular oestrous cycle, or to the hormonal regime used to induce superovulation. Although several protocols were used to accomplish superovulation in this species, it was seldom achieved. In in vitro fertilization trials, sperm were found to attach to both the cumulus oophorus and the zona pellucida of the oocytes. However, fertilization was never accomplished. This failure to achieve fertilization was probably related to the immaturity of the oocytes. Without further studies on Rhabdomys pumilio and further attempts at accomplishing in vitro fertilization, it would seem that this species would not easily be introduced as an animalmodelfor assisted reproduction.
- Full Text:
- Date Issued: 2000
The structure and microbiology of floating sulphide oxidising biofilms
- Authors: Gilfillan, Joanne Criseyde
- Date: 2000
- Subjects: Biofilms , Sulfides
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3903 , http://hdl.handle.net/10962/d1003962 , Biofilms , Sulfides
- Description: Floating sulphur biofilms are observed as surface layers in numerous aquatic sulphide-rich environments, and apparently play an important role in the cycling of sulphur in its various oxidation states. In addition to the conversion of sulphide to sulphur and/or sulphate species, it has been suspected that subsequent reduction back to sulphide may occur within the floating sulphur biofi1m in organic-rich environments. The use of sulphur biofilms for the harvesting of elemental sulphur from wastewater treatment systems has also been suggested. There is, however, little documented information in the literature on the structure of floating sulphur biofilms, or the microbial species responsible for their occurrence. In this study, floating sulphur biofilms were generated in a continuous flow baflle reactor and their structure was examined using scanning electron microscopy. It was found that they occur as layered structures with morphologically distinct bacterial forms present in different layers of the biofilm. The biofilpl structure was also found to be dynamic, with structural changes observed as feed conditions were altered. An enriched culture derived from the biofi1m demonstrated rates of sulphide oxidation comparable to values reported in the literature for liquid culture systems. The microbiology of the biofi1m was studied using traditional plate culture techniques and analysis ofrRNA genes. Identification of plate culture isolates as representatives of the biofi1m community proved to be limited, leading to a PeR-based cloning approach. The majority of the organisms present in the sulphur biofi1m were classified as species in the genus ~eudomonas, and a number of other bacterial species whose sulphide oxidising capacity has been noted previously. Surprisingly, only 2% of the clone library consisted of Thiobacillus spp., and no sulphate reducing bacteria were identified in the biofilm at all. These results indicate that in organic sulphide-rich environments facultative chemolithoheterotrophic bacterial forms predominate in floating sulphur biofilms, and that the complete biological cycling of sulphur may not occur in these systems.
- Full Text:
- Date Issued: 2000
- Authors: Gilfillan, Joanne Criseyde
- Date: 2000
- Subjects: Biofilms , Sulfides
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3903 , http://hdl.handle.net/10962/d1003962 , Biofilms , Sulfides
- Description: Floating sulphur biofilms are observed as surface layers in numerous aquatic sulphide-rich environments, and apparently play an important role in the cycling of sulphur in its various oxidation states. In addition to the conversion of sulphide to sulphur and/or sulphate species, it has been suspected that subsequent reduction back to sulphide may occur within the floating sulphur biofi1m in organic-rich environments. The use of sulphur biofilms for the harvesting of elemental sulphur from wastewater treatment systems has also been suggested. There is, however, little documented information in the literature on the structure of floating sulphur biofilms, or the microbial species responsible for their occurrence. In this study, floating sulphur biofilms were generated in a continuous flow baflle reactor and their structure was examined using scanning electron microscopy. It was found that they occur as layered structures with morphologically distinct bacterial forms present in different layers of the biofilm. The biofilpl structure was also found to be dynamic, with structural changes observed as feed conditions were altered. An enriched culture derived from the biofi1m demonstrated rates of sulphide oxidation comparable to values reported in the literature for liquid culture systems. The microbiology of the biofi1m was studied using traditional plate culture techniques and analysis ofrRNA genes. Identification of plate culture isolates as representatives of the biofi1m community proved to be limited, leading to a PeR-based cloning approach. The majority of the organisms present in the sulphur biofi1m were classified as species in the genus ~eudomonas, and a number of other bacterial species whose sulphide oxidising capacity has been noted previously. Surprisingly, only 2% of the clone library consisted of Thiobacillus spp., and no sulphate reducing bacteria were identified in the biofilm at all. These results indicate that in organic sulphide-rich environments facultative chemolithoheterotrophic bacterial forms predominate in floating sulphur biofilms, and that the complete biological cycling of sulphur may not occur in these systems.
- Full Text:
- Date Issued: 2000
The use of indigenous macroinvertebrates and Daphnia pulex in acute toxicity testing
- Authors: Everitt, Victoria Jane
- Date: 2000
- Subjects: Water -- Pollution -- Toxicology , Toxicity testing , Daphnia pulex
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5795 , http://hdl.handle.net/10962/d1005483
- Description: Aquatic toxicology has been identified as a valuable tool in the identification and management of chemical pollution in aquatic ecosystems. Standardised methodologies for acute aquatic bioassays have been adopted from international agencies. As a result of these standard methods, the use of laboratory cultured organisms for toxicity testing has been more popular than that of indigenous field-caught organisms. Included in these adopted methods are those for the cultured crustacean Daphnia pUlex. D.pulex is adapted to living in standing water and the suitability of this species to determine toxic effects for South African riverine environments, which are largely flowing, has been questioned. Thus this thesis is a case-study ofthe use of D.pulex and indigenous site-specific macroinvertebrates as toxicity test organisms for setting acute water quality guidelines to protect aquatic ecosystems. The study highlights site-specific problems such as reference sites and organism identification. The acute tolerance of selected indigenous invertebrates was compared to that of D. pulex, using both a single-substance reference toxicant (zinc) and selected whole efiluents. The significance of source population and culture age as a potential source of biological variability between D.pulex cultures was also investigated. D.pulex cultures have been initiated in South Africa from females collected from a number of different local populations; also it is assumed that no genetic change (due to mutation) occurs within a D.pulex culture over time. In order to establish if source population and culture age are a source of biological variability between D.pulex experiments, the acute tolerJuce to zinc of two different D.pulex populations and three different generations within a population were compared. Due to experimental variability results were inconclusive, and differences in tolerance as a result of population difference or culture age could not be determined with confidence. The acute tolerance of D.pulex to a single reference chemical (zinc) and selected whole efiluents was compared to that of selected indigenous invertebrates. Acute 48 h D.pulex zinc tolerance (LC50 range: 0.22 - 0.60 mg/l Zn) was found to be more sensitive than acute 96 h tolerances shown by mayfly species A.fconurus peringueyi (Heptageniidae) (LC50: 17.42 mg/l Zn), Euthrauluselegans (Leptophlebiidae) (LC50: 0.98 mg/IZn), Ba~tidae (LC50: 0.94mg/IZn) and shrimp, Caradina nilotica (Atyidae) (LC50: 3.17 mg/l Zn). This result suggests that guidelines for zinc set using D.pulex will protect the selected indigenous invertebrates. Selected whole eftluents were not acutely toxic to either D.pulex or selected indigenous invertebrates. These experiments were used as a case study for method development regarding the comparative use of D.pulex and indigenous invertebrates in acute whole eftluent toxicity testing. Finally, it is recommended that a suite of indigenous organisms (e.g. macroinvertebrates, fish and algae), as well as laboratory cultured D.pulex, be used in the initial setting of guidelines and that D.pulex be used for routine compliance monitoring. It is futher recommended that a suite of available monitoring methods, such as chemical and biomonitoring methodologies, be used in conjuction with toxicity testing in water quality management.
- Full Text:
- Date Issued: 2000
- Authors: Everitt, Victoria Jane
- Date: 2000
- Subjects: Water -- Pollution -- Toxicology , Toxicity testing , Daphnia pulex
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5795 , http://hdl.handle.net/10962/d1005483
- Description: Aquatic toxicology has been identified as a valuable tool in the identification and management of chemical pollution in aquatic ecosystems. Standardised methodologies for acute aquatic bioassays have been adopted from international agencies. As a result of these standard methods, the use of laboratory cultured organisms for toxicity testing has been more popular than that of indigenous field-caught organisms. Included in these adopted methods are those for the cultured crustacean Daphnia pUlex. D.pulex is adapted to living in standing water and the suitability of this species to determine toxic effects for South African riverine environments, which are largely flowing, has been questioned. Thus this thesis is a case-study ofthe use of D.pulex and indigenous site-specific macroinvertebrates as toxicity test organisms for setting acute water quality guidelines to protect aquatic ecosystems. The study highlights site-specific problems such as reference sites and organism identification. The acute tolerance of selected indigenous invertebrates was compared to that of D. pulex, using both a single-substance reference toxicant (zinc) and selected whole efiluents. The significance of source population and culture age as a potential source of biological variability between D.pulex cultures was also investigated. D.pulex cultures have been initiated in South Africa from females collected from a number of different local populations; also it is assumed that no genetic change (due to mutation) occurs within a D.pulex culture over time. In order to establish if source population and culture age are a source of biological variability between D.pulex experiments, the acute tolerJuce to zinc of two different D.pulex populations and three different generations within a population were compared. Due to experimental variability results were inconclusive, and differences in tolerance as a result of population difference or culture age could not be determined with confidence. The acute tolerance of D.pulex to a single reference chemical (zinc) and selected whole efiluents was compared to that of selected indigenous invertebrates. Acute 48 h D.pulex zinc tolerance (LC50 range: 0.22 - 0.60 mg/l Zn) was found to be more sensitive than acute 96 h tolerances shown by mayfly species A.fconurus peringueyi (Heptageniidae) (LC50: 17.42 mg/l Zn), Euthrauluselegans (Leptophlebiidae) (LC50: 0.98 mg/IZn), Ba~tidae (LC50: 0.94mg/IZn) and shrimp, Caradina nilotica (Atyidae) (LC50: 3.17 mg/l Zn). This result suggests that guidelines for zinc set using D.pulex will protect the selected indigenous invertebrates. Selected whole eftluents were not acutely toxic to either D.pulex or selected indigenous invertebrates. These experiments were used as a case study for method development regarding the comparative use of D.pulex and indigenous invertebrates in acute whole eftluent toxicity testing. Finally, it is recommended that a suite of indigenous organisms (e.g. macroinvertebrates, fish and algae), as well as laboratory cultured D.pulex, be used in the initial setting of guidelines and that D.pulex be used for routine compliance monitoring. It is futher recommended that a suite of available monitoring methods, such as chemical and biomonitoring methodologies, be used in conjuction with toxicity testing in water quality management.
- Full Text:
- Date Issued: 2000
The utilisation of Asolla filiculoides Lam. as a biofertiliser under dryland conditions
- Authors: Kiguli, Lillian Nakibuuka
- Date: 2000
- Subjects: Asolla as fertilizer
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4206 , http://hdl.handle.net/10962/d1003775 , Asolla as fertilizer
- Description: The response of wheat to soil fertilised with varying quantities of the water fern Azolla filiculoides was investigated. Experiments were conducted to differentiate between the effects of increased soil mineral status and water status. In the preliminary investigation, experiments were carried out in the greenhouse using potted wheat grown in sand with varying proportions of A. filiculoides that had been subjected tovarious pre-treatments. The pre-treatments were fresh, dry and heated A. filiculoides applied at 20%, 50% and 80% volume per 3000 ml. There were significant differences in the measured growth parameters between the plants grown in the various treatments. In addition, the grain yield of wheat plants varied with the different treatments. Results of the preliminary study showed that the addition of heated and dried A. filiculoides resulted in significantly better growth than the addition of fresh A. filiculoides in sand. For fresh biomass, grain weights, Leaf area ratio (LAR) and relative growth rate (RGR), the performance of dried A. filiculoides was as good as that of the heated A. filiculoides. Productivity of wheat in the heated treatments increased significantly with increasing proportion of A. filiculoides added to sand, while in dry treatments there were no significant increases in productivity in the preliminary study. This supported the hypothesis that A. filiculoides, a notorious water weed can be put to agricultural use under dryland conditions in poor nutrient soils. Further investigations using dried A. filiculoides in sand and topsoil showed that the use of the same amounts of the dried fern made no significant short term impact on topsoil grown winter wheat but significantly improved the productivity of wheat in sand. Results showed that the addition of dried 20% Azolla to sand improved the soil fertility to levels equalling the quality of the control topsoil, but the addition of 80% Azolla to sand led to significantly greater wheat productivity than all other treatments. The addition of dried 20% Azolla (8.14 × 10^3 kg ha^(-1)) in sand produced as much wheat biomass as the addition of the recommended NPK fertiliser (30 kg N ha^(-1)) to sand. A comparison between the topsoil and sand-grown plants showed differences in flowering time but these had no effect on the final grain and above ground biomass.
- Full Text:
- Date Issued: 2000
- Authors: Kiguli, Lillian Nakibuuka
- Date: 2000
- Subjects: Asolla as fertilizer
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4206 , http://hdl.handle.net/10962/d1003775 , Asolla as fertilizer
- Description: The response of wheat to soil fertilised with varying quantities of the water fern Azolla filiculoides was investigated. Experiments were conducted to differentiate between the effects of increased soil mineral status and water status. In the preliminary investigation, experiments were carried out in the greenhouse using potted wheat grown in sand with varying proportions of A. filiculoides that had been subjected tovarious pre-treatments. The pre-treatments were fresh, dry and heated A. filiculoides applied at 20%, 50% and 80% volume per 3000 ml. There were significant differences in the measured growth parameters between the plants grown in the various treatments. In addition, the grain yield of wheat plants varied with the different treatments. Results of the preliminary study showed that the addition of heated and dried A. filiculoides resulted in significantly better growth than the addition of fresh A. filiculoides in sand. For fresh biomass, grain weights, Leaf area ratio (LAR) and relative growth rate (RGR), the performance of dried A. filiculoides was as good as that of the heated A. filiculoides. Productivity of wheat in the heated treatments increased significantly with increasing proportion of A. filiculoides added to sand, while in dry treatments there were no significant increases in productivity in the preliminary study. This supported the hypothesis that A. filiculoides, a notorious water weed can be put to agricultural use under dryland conditions in poor nutrient soils. Further investigations using dried A. filiculoides in sand and topsoil showed that the use of the same amounts of the dried fern made no significant short term impact on topsoil grown winter wheat but significantly improved the productivity of wheat in sand. Results showed that the addition of dried 20% Azolla to sand improved the soil fertility to levels equalling the quality of the control topsoil, but the addition of 80% Azolla to sand led to significantly greater wheat productivity than all other treatments. The addition of dried 20% Azolla (8.14 × 10^3 kg ha^(-1)) in sand produced as much wheat biomass as the addition of the recommended NPK fertiliser (30 kg N ha^(-1)) to sand. A comparison between the topsoil and sand-grown plants showed differences in flowering time but these had no effect on the final grain and above ground biomass.
- Full Text:
- Date Issued: 2000
Water requirements and distribution of Ammophila arenaria and Scaevola plumieri on South African coastal dunes
- Authors: Peter, Craig Ingram
- Date: 2000
- Subjects: Scaevola plumieri , Sand dune plants , Sand dune planting , Plants -- Transpiration , Sandworts , Plant-water relationships , Evapotranspiration , Plants, Effect of heat on
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4219 , http://hdl.handle.net/10962/d1003788 , Scaevola plumieri , Sand dune plants , Sand dune planting , Plants -- Transpiration , Sandworts , Plant-water relationships , Evapotranspiration , Plants, Effect of heat on
- Description: Phenomenological models are presented which predicts transpiration rates (E) of individual leaves of Scaevola plumieri, an indigenous dune pioneer, and Ammophila arenaria, an exotic grass species introduced to stabilise mobile sand. In both cases E is predictably related to atmospheric vapour pressure deficit (VPD). VPD is calculated from measurements of ambient temperature and humidity, hence, where these two environmental variables are known, E can be calculated. Possible physiological reasons for the relationships of E to VPD in both species are discussed. Scaling from measurements of E at the leaf level to the canopy level is achieved by summing the leaf area of the canopy in question. E is predicted for the entire canopy leaf area by extrapolation to this larger leaf area. Predicted transpiration rates of individual shoot within the canopy were tested gravimetrically and shown to be accurate in the case of S. plumieri, but less so in the case of A. arenaria. Using this model, the amount of water used by a known area of sand dune is shown to be less than the rainfall input in the case of S. plumieri in wet and dry years. The water use of A. arenaria exceeds rainfall in the low-rainfall year of 1995, while in 1998 rainfall input is slightly higher than water extraction by the plants. Using a geographic information system (GIS), regional maps (surfaces) of transpiration were calculated from surfaces of mean monthly temperature and mean monthly relative humidity. Monthly surfaces of transpiration were subtracted from the monthly median rainfall to produce a surface of mean monthly water deficit. Areas of water surpluses along the coast correspond with the recorded distribution of both species in the seasons that the plants are most actively growing and reproducing. This suggests that unfavourable water availability during these two species growth periods limit their distributions along the coast. In addition to unfavourable water deficits, additional climatic variables that may be important in limiting the distribution of these two species were investigated using a discriminant function analysis.
- Full Text:
- Date Issued: 2000
- Authors: Peter, Craig Ingram
- Date: 2000
- Subjects: Scaevola plumieri , Sand dune plants , Sand dune planting , Plants -- Transpiration , Sandworts , Plant-water relationships , Evapotranspiration , Plants, Effect of heat on
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4219 , http://hdl.handle.net/10962/d1003788 , Scaevola plumieri , Sand dune plants , Sand dune planting , Plants -- Transpiration , Sandworts , Plant-water relationships , Evapotranspiration , Plants, Effect of heat on
- Description: Phenomenological models are presented which predicts transpiration rates (E) of individual leaves of Scaevola plumieri, an indigenous dune pioneer, and Ammophila arenaria, an exotic grass species introduced to stabilise mobile sand. In both cases E is predictably related to atmospheric vapour pressure deficit (VPD). VPD is calculated from measurements of ambient temperature and humidity, hence, where these two environmental variables are known, E can be calculated. Possible physiological reasons for the relationships of E to VPD in both species are discussed. Scaling from measurements of E at the leaf level to the canopy level is achieved by summing the leaf area of the canopy in question. E is predicted for the entire canopy leaf area by extrapolation to this larger leaf area. Predicted transpiration rates of individual shoot within the canopy were tested gravimetrically and shown to be accurate in the case of S. plumieri, but less so in the case of A. arenaria. Using this model, the amount of water used by a known area of sand dune is shown to be less than the rainfall input in the case of S. plumieri in wet and dry years. The water use of A. arenaria exceeds rainfall in the low-rainfall year of 1995, while in 1998 rainfall input is slightly higher than water extraction by the plants. Using a geographic information system (GIS), regional maps (surfaces) of transpiration were calculated from surfaces of mean monthly temperature and mean monthly relative humidity. Monthly surfaces of transpiration were subtracted from the monthly median rainfall to produce a surface of mean monthly water deficit. Areas of water surpluses along the coast correspond with the recorded distribution of both species in the seasons that the plants are most actively growing and reproducing. This suggests that unfavourable water availability during these two species growth periods limit their distributions along the coast. In addition to unfavourable water deficits, additional climatic variables that may be important in limiting the distribution of these two species were investigated using a discriminant function analysis.
- Full Text:
- Date Issued: 2000