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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Evaluation of the applicability of diatom based indices as bioindicators of water quality in South African rivers / Pieter Arno de la Rey.

De la Rey, Pieter Arno January 2008 (has links)
Diatoms have been proven to be reliable indicators of water quality in many countries of the world particularly Europe. The potential use of diatoms as indicators of water quality in South Africa was tested in the studies in this document. This study evaluates the potential use of diatom based indices by testing it against a macroinvertebrate index (SASS 5) and evaluating the variation in the index scores of the two indices due to changes in chemical water quality and habitat. It was concluded that the diatom monitoring system performs well as bioindicator of water quality. It was also concluded that it should be used as a complementary system to the much used SASS 5 invertebrate index. This conclusion was made due to the fact that diatoms react more directly to changes in water quality than macroinvertebrates (SASS 5), and macroinvertebrates react more readily to changes in habitat than diatoms. A further part of the study was to assess whether aut-ecological or diversity based diatom indices performed best in South African conditions. This study found that the ecological indices were more sensitive to changes in water quality than the diversity indices. The diatom based indices that performed best as water quality indicators were the specific pollution sensitivity index (SPI) and the biological diatom index (BDI). A standard method for the sampling, preparation and enumeration for diatoms to be used for index score generation is also suggested to ensure the comparability of diatom based index data to facilitate use of such bio monitoring data for management purposes. The main focus of the study was to eliminate some of the obstacles for the use of diatoms as bio indicators of water quality in South Africa. It is believe that this aim has been accomplished in the study. / Thesis (Ph.D. (Environmental Science))--North-West University, Potchefstroom Campus, 2008.
2

Microbial diversity and metal pollution from a platinum mine tailings dam in the North-West Province (RSA) / by Molemi Evelyn Rauwane.

Rauwane, Molemi Evelyn January 2008 (has links)
The aim of this study was to determine the effects of the heavy metal pollution on microbial diversity along the gradient from a platinum mine tailings dam using culture-dependent (plating methods) and molecular methods. Tailings and soil samples were collected from seven sites (6 samples per site) at increasing distances from the tailings dam. Samples were collected over a two year period and included two rainy and two dry periods. Concentrations of various heavy metals were determined using an inductively coupled plasma mass spectrometer (ICP-MS). The results demonstrated that seasonal variations in metal concentrations occurred and also that concentrations were significantly different'(P < 0.05) between the experimental sites for each metal. The relative relationship between metals was in the following order: Al > Ni > Cu > Cr. Since soil metal concentration benchmarks for South Africa are lacking, the concentrations were compared to the Canadian microbial benchmarks (MB) and Netherlands maximum permissible concentrations (MPC). Concentrations of most of the heavy metals exceeded the MB and MPC. Levels and diversity of culturable fungi and bacteria at each site were determined using plate count methods. Results indicated that levels of bacteria and fungi were not suppressed by high concentrations of heavy metals. Significantly higher levels (P < 0.05) of fungi were found at the sites on the tailings dam (higher concentrations of heavy metals), compared to sites more than 300 m away. A commonly used soil health index (Shannon-Weaver diversity index) was used to compare microbial community diversity at each site and to evaluate whether or not the heavy metal contamination impacted negatively on these soil bacterial and fungal communities. Shannon-Weaver diversity indices were higher at sites on and close to the tailings dam than sites more than 300 m away. However, ratio of fungal to bacterial levels as determined by plate counts was inconsistent. Representatives of bacterial species that were grouped using colony morphology and whole cell protein profiles were identified by 16S rDNA sequences as Bacillus barbaricus (B. barbaricus) and -Paenibacillus lautus {P. Lautus). Restriction enzyme digest, SDS-PAGE and random amplified polymorphic DNA (RAPD) analyses provided supporting evidence that representatives were correctly grouped. Cluster analysis results demonstrated that the RAPD profiles of the metal tolerant P. lautus representatives were sufficiently dissimilar to discriminate between individuals from the spatially separated sites. The spatially separated sites also represented sites with high and low heavy metal concentrations. Observed genetic variability was thus also associated with varying levels of heavy metals. In conclusion, this study demonstrated the potential of using RAPD analysis as biomarkers for genotoxic effects of heavy metals on bacterial genomes. / Masters / Thesis (M.Sc. (Microbiology))--North-West University, Potchefstroom Campus, 2009.
3

Evaluation of the applicability of diatom based indices as bioindicators of water quality in South African rivers / Pieter Arno de la Rey.

De la Rey, Pieter Arno January 2008 (has links)
Diatoms have been proven to be reliable indicators of water quality in many countries of the world particularly Europe. The potential use of diatoms as indicators of water quality in South Africa was tested in the studies in this document. This study evaluates the potential use of diatom based indices by testing it against a macroinvertebrate index (SASS 5) and evaluating the variation in the index scores of the two indices due to changes in chemical water quality and habitat. It was concluded that the diatom monitoring system performs well as bioindicator of water quality. It was also concluded that it should be used as a complementary system to the much used SASS 5 invertebrate index. This conclusion was made due to the fact that diatoms react more directly to changes in water quality than macroinvertebrates (SASS 5), and macroinvertebrates react more readily to changes in habitat than diatoms. A further part of the study was to assess whether aut-ecological or diversity based diatom indices performed best in South African conditions. This study found that the ecological indices were more sensitive to changes in water quality than the diversity indices. The diatom based indices that performed best as water quality indicators were the specific pollution sensitivity index (SPI) and the biological diatom index (BDI). A standard method for the sampling, preparation and enumeration for diatoms to be used for index score generation is also suggested to ensure the comparability of diatom based index data to facilitate use of such bio monitoring data for management purposes. The main focus of the study was to eliminate some of the obstacles for the use of diatoms as bio indicators of water quality in South Africa. It is believe that this aim has been accomplished in the study. / Thesis (Ph.D. (Environmental Science))--North-West University, Potchefstroom Campus, 2008.
4

Microbial diversity and metal pollution from a platinum mine tailings dam in the North-West Province (RSA) / by Molemi Evelyn Rauwane.

Rauwane, Molemi Evelyn January 2008 (has links)
The aim of this study was to determine the effects of the heavy metal pollution on microbial diversity along the gradient from a platinum mine tailings dam using culture-dependent (plating methods) and molecular methods. Tailings and soil samples were collected from seven sites (6 samples per site) at increasing distances from the tailings dam. Samples were collected over a two year period and included two rainy and two dry periods. Concentrations of various heavy metals were determined using an inductively coupled plasma mass spectrometer (ICP-MS). The results demonstrated that seasonal variations in metal concentrations occurred and also that concentrations were significantly different'(P < 0.05) between the experimental sites for each metal. The relative relationship between metals was in the following order: Al > Ni > Cu > Cr. Since soil metal concentration benchmarks for South Africa are lacking, the concentrations were compared to the Canadian microbial benchmarks (MB) and Netherlands maximum permissible concentrations (MPC). Concentrations of most of the heavy metals exceeded the MB and MPC. Levels and diversity of culturable fungi and bacteria at each site were determined using plate count methods. Results indicated that levels of bacteria and fungi were not suppressed by high concentrations of heavy metals. Significantly higher levels (P < 0.05) of fungi were found at the sites on the tailings dam (higher concentrations of heavy metals), compared to sites more than 300 m away. A commonly used soil health index (Shannon-Weaver diversity index) was used to compare microbial community diversity at each site and to evaluate whether or not the heavy metal contamination impacted negatively on these soil bacterial and fungal communities. Shannon-Weaver diversity indices were higher at sites on and close to the tailings dam than sites more than 300 m away. However, ratio of fungal to bacterial levels as determined by plate counts was inconsistent. Representatives of bacterial species that were grouped using colony morphology and whole cell protein profiles were identified by 16S rDNA sequences as Bacillus barbaricus (B. barbaricus) and -Paenibacillus lautus {P. Lautus). Restriction enzyme digest, SDS-PAGE and random amplified polymorphic DNA (RAPD) analyses provided supporting evidence that representatives were correctly grouped. Cluster analysis results demonstrated that the RAPD profiles of the metal tolerant P. lautus representatives were sufficiently dissimilar to discriminate between individuals from the spatially separated sites. The spatially separated sites also represented sites with high and low heavy metal concentrations. Observed genetic variability was thus also associated with varying levels of heavy metals. In conclusion, this study demonstrated the potential of using RAPD analysis as biomarkers for genotoxic effects of heavy metals on bacterial genomes. / Masters / Thesis (M.Sc. (Microbiology))--North-West University, Potchefstroom Campus, 2009.
5

An investigation of environmental impacts on sediments by marine cage fish farms using long term metadata analysis

Mavraganis, Theodoros January 2012 (has links)
Many studies have investigated the impacts of marine cage fish farming on seabed sediments. Most of these studies have focused on organic loading or toxic chemicals used for the treatment of disease, normally for a single or a small number of sites over short time periods. Only very rarely has there been the opportunity to use large data sets consisting of a large number of fish farm sites over a long time scale. In Scotland, localised nutrient impacts have been well documented for marine cage salmon farms, but mixed effects of nutrient and chemicals such as SLICE (the active ingredient of which is emamectin benzoate) have not been investigated in the long term. The aim of this project was to investigate the ecological impacts on sediments from farming activities using very large spatial and temporal data to investigate the long term effects of nutrient and chemical waste. This was achieved using a metadata set collected from 403 sampling stations at 31 fish farms on the west coast of Scotland over a 9 year period. Data consisted of sediment macrofauna, carbon and nitrogen levels, redox potential, particle size for sediment characterisation and sediment concentrations of SLICE. The data was analysed for trends using statistical and multivariate analysis to look for changes in sediment community and related conditions, and the relationships between these parameters were investigated. At sampling stations that were less than 50 metres from the sea cages, 72% of the macrofauna communities were correlated with regard to their species composition and abundance. A significant relationship between the concentration of SLICE and sediment characteristics was represented as: SLICE= 0.000644*(median size particle size) + 0.0311*(C %) – 0.00213*(redox potential) + 1.453. Annelids were the most sensitive to the presence of emamectin benzoate, with the sipunculid Phascolion strombi, the echinoderm Ophiura affinis, and the custaceans Iphinoe, Diastylis and Iphimedia also showing sensitivity. During the data period, there was a clear change in species composition associated with improved seabed conditions. This correlated with biomass changes at the relevant sites, where there was a consequent decrease in nutrient input and SLICE usage. The statistical comparison of the AMBI and ITI indices indicated a 68.9% correlation, but they differed in their ability to indicate levels of organic disturbance. AMBI was shown to correlate more closely with conditions and thus a more reliable index when working with large databases. Univariate and multivariate analysis indicated that a combination of abundance (N), Shannon Wiener (H’) and AMBI, as biological indices for describing the status of the ecological level associated with the carbon percentage and redox potential of sediments gave the most reliable representation of environmental change over a series of sampling stations. In conclusion, the overall results suggest that, in the long-term, sampling stations which contained significant levels of SLICE had a higher impact status than those affected only by nutrient inputs. The accuracy of multiple regression models were increased by adding biotic and abiotic parameters, though fish biomass at the sites were not considered be as important factor for the prediction of impacts. However, this model could be sensitive to natural environmental conditions and variations. In light of these results and conclusions, recommendations can be made both for updating the existed environmental regulation of marine fish farms and in the development of meaningful models to relate sediment conditions to accurate estimations of overall environmental impacts.
6

A comparative study of arthropod diversity on conventional and Bt–maize at two irrigation schemes in South Africa / Truter J.M.

Truter, Jean-Maré January 2011 (has links)
The purpose of the research was to explore the experiences of educators regarding the training for the implementation of inclusive education in a Full Service school. A qualitative research design was chosen, using a case study. Three methods of gathering data were used, namely individual interviews, focus group interviews and observations. The study was conducted in a primary schools in the North West province that was converted into a fullservice school in 2008. The findings indicated that educators demonstrated misunderstanding of the Screening, Identification, Assessment and Support strategy. The misunderstanding can be ascribed to the kind of training educators received. The training lacked in–depth content and practical demonstration. Recommendations on the content and the dynamics of the training process are made. The overarching recommendation on the dynamics of the training indicated that the training should be revisited for improved methods of training. / Thesis (M.Sc. (Environmental Science))--North-West University, Potchefstroom Campus, 2011.
7

Plant and arthropod diversity of maize agro–ecosystems in the Highveld and Lowveld regions of South Africa / Bheki George Maliba

Maliba, Bheki George January 2011 (has links)
Surveys of plant and selected insect species was conducted in Highveld and Lowveld agro–ecosystems of four provinces of South Africa, namely North–West, Mpumalanga, KwaZulu–Natal and Limpopo. The objectives of the study were to compare insect and plant diversity between localities (grassland and savanna) and treatments (maize field, semi–transformed and untransformed) to test for a general relationship between plant and insect diversity along a maize field–field margin gradient. Plant and insect diversity patterns were studied along the gradient and quantified in terms of richness and diversity indices. Plant and insect species compositional turnover was also measured along the maize field–field margin gradient. Plant diversity increased with increasing distance from maize fields into the margin. The flora in maize fields and of margins differed, but in contrast, insect species assemblages were similar in maize fields and margins. There was no statistical difference in insect diversity between treatments (maize field, semi–transformed and transformed). A relationship was revealed between plant and insect diversity, as plant diversity enhanced insect diversity. / Thesis (M.Sc. (Environmental Sciences))--North-West University, Potchefstroom Campus, 2011.
8

A comparative study of arthropod diversity on conventional and Bt–maize at two irrigation schemes in South Africa / Truter J.M.

Truter, Jean-Maré January 2011 (has links)
The purpose of the research was to explore the experiences of educators regarding the training for the implementation of inclusive education in a Full Service school. A qualitative research design was chosen, using a case study. Three methods of gathering data were used, namely individual interviews, focus group interviews and observations. The study was conducted in a primary schools in the North West province that was converted into a fullservice school in 2008. The findings indicated that educators demonstrated misunderstanding of the Screening, Identification, Assessment and Support strategy. The misunderstanding can be ascribed to the kind of training educators received. The training lacked in–depth content and practical demonstration. Recommendations on the content and the dynamics of the training process are made. The overarching recommendation on the dynamics of the training indicated that the training should be revisited for improved methods of training. / Thesis (M.Sc. (Environmental Science))--North-West University, Potchefstroom Campus, 2011.
9

Plant and arthropod diversity of maize agro–ecosystems in the Highveld and Lowveld regions of South Africa / Bheki George Maliba

Maliba, Bheki George January 2011 (has links)
Surveys of plant and selected insect species was conducted in Highveld and Lowveld agro–ecosystems of four provinces of South Africa, namely North–West, Mpumalanga, KwaZulu–Natal and Limpopo. The objectives of the study were to compare insect and plant diversity between localities (grassland and savanna) and treatments (maize field, semi–transformed and untransformed) to test for a general relationship between plant and insect diversity along a maize field–field margin gradient. Plant and insect diversity patterns were studied along the gradient and quantified in terms of richness and diversity indices. Plant and insect species compositional turnover was also measured along the maize field–field margin gradient. Plant diversity increased with increasing distance from maize fields into the margin. The flora in maize fields and of margins differed, but in contrast, insect species assemblages were similar in maize fields and margins. There was no statistical difference in insect diversity between treatments (maize field, semi–transformed and transformed). A relationship was revealed between plant and insect diversity, as plant diversity enhanced insect diversity. / Thesis (M.Sc. (Environmental Sciences))--North-West University, Potchefstroom Campus, 2011.
10

Exploração de Euterpe edulis Mart. (Arecaceae): efeitos sobre a estrutura de comunidades vegetais

Silva, Talita Ariela Sampaio e 27 February 2015 (has links)
Made available in DSpace on 2016-06-02T19:30:13Z (GMT). No. of bitstreams: 1 6775.pdf: 3213380 bytes, checksum: 36de81e56297427d70c405207779962f (MD5) Previous issue date: 2015-02-27 / Universidade Federal de Sao Carlos / The harvesting of non-timber forest products (NTFPs) has been considered as a low-impact activity. However, the increasing demand of these products made greater the exploitation, which may cause depletion of resources in Nature. Euterpe edulis Mart. (Arecaceae) is one of the most studied plant species in Brazil, because it is economically important, listed among the most relevant products provided by Atlantic Rainforest. Moreover, this species is considered ecologically important, because it is a valuable food resource for fauna. In natural conditions, E. edulis is the most abundant species in Atlantic Rainforest. Nevertheless, illegal and massive harvesting lead the species to local extinction in some remnants, which resulted in the inclusion of the palm tree amongst the endangered plant species in Brazil. In this context, this study aimed to evaluate the impact of palm tree harvest on diversity at seed rain, regeneration layer and their relationship with the adult plant community. Thus, this study was carried out in two areas at Ilha do Cardoso State Park, both of them with the same land use history, despite the occurrence of massive palm heart harvest within one of them until 20 years ago. At these areas, we sampled seed rain with and without pulp, the regeneration layer and the adult plant community. The major motivations for this study were to apply diversity analysis on the assessment of harvesting impact, and to provide scientific information to the establishment of viable guidelines to the sustainable harvest of palm tree products. Our results showed that the abundance of E. edulis is related to the change of diversity patterns and species composition in seed rain and regeneration layer, and may have an influence on species composition in the future. This confirms the general hypothesis of this study, i.e. the disturbance caused by palm heart harvesting causes changes on species abundance enough to modify plant community structure. These changes could be detected even it has been 20 years after the end of illegal harvesting within the harvested area. The results also indicate that it is viable to make the sustainable harvest of E. edulis products, considering a selective removal of adult individuals and avoiding total suppression of clumps of palm tree. These actions promote heterogeneity on species composition of seed rain and regeneration layer. / Pelas caracteristicas de seu uso e exploracao, a extracao de produtos florestais nao madeireiros (PFNMs) e tida como sendo de baixo impacto ecologico. Entretanto, a crescente utilizacao destas materias primas nos mercados consumidores levou a um aumento da demanda de exploracao, o que pode levar a deplecao dos produtos explorados. Euterpe edulis (Arecaceae) e uma das especies vegetais mais estudadas do pais, pois tem uma alta importancia economica, sendo um dos principais PFNMs obtidos da Mata Atlantica. Alem disso, a especie tem grande importancia ecologica, por ser um recurso alimentar valioso para a fauna. Em condicoes naturais, E. edulis e a especie dominante na comunidade adulta nas areas cobertas por Floresta Atlantica. Entretanto, a exploracao ilegal e massiva levou a especie a extincao local em certos remanescentes de Mata Atlantica, culminando em sua inclusao entre as especies ameacadas no pais. Diante deste contexto, o presente estudo teve como objetivo geral avaliar o impacto da exploracao do palmito de E. edulis sobre a diversidade na chuva de sementes, no estrato regenerante e a sua relacao com a comunidade adulta. Deste modo, o estudo foi realizado em duas areas no Parque Estadual Ilha do Cardoso, ambas com historico de uso similar, porem, uma delas sofreu exploracao massiva de palmito de E. edulis ate ha cerca de 20 anos, enquanto que a outra nao foi alvo deste tipo de uso. Nestas areas, amostramos a chuva de sementes com e sem polpa, o estrato regenerante e a comunidade adulta. As principais motivacoes deste estudo foram aplicar analises de diversidade na avaliacao e fornecer subsidio cientifico para o estabelecimento de diretrizes mais especificas e viaveis para o uso sustentavel deste produto, que e economicamente importante, mas que tambem e considerada uma especie chave na Floresta Atlantica. Os resultados mostraram que a abundancia de E. edulis altera padroes de diversidade e composicao em especies na chuva de sementes e no estrato regenerante, podendo influenciar na composicao das comunidades vegetais no futuro, confirmando a hipotese geral desta tese, de que o disturbio causado pela exploracao de E. edulis produz alteracoes na densidade de individuos da palmeira suficiente para modificar a estrutura das comunidades vegetais. Tais mudancas puderam ser detectadas mesmo apos 20 anos sem a atividade de exploradores ilegais na area estudada. Os resultados indicam, tambem, que o uso sustentavel do palmito de E. edulis pode ser viavel, considerando a remocao seletiva de individuos adultos, evitando a total supressao de adensamentos desta palmeira, promovendo a heterogeneidade da composicao da chuva de sementes e do estrato regenerante.

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