Diarrhoea caused by strains of Escherichia coli is recognised as a significant cause of morbidity and mortality world-wide. Efficient isolation of these bacteria from water is necessary for effective management of available water sources and for the control and prevention of waterborne disease. Methods that are currently available do not allow for the efficient isolation of the diarrhoeagenic E. coli. Therefore, the aims of the current study were: to determine the efficacy of Chromocult® Coliformen Agar for identification of diarrhoeagenic E. coli; correlate virulence gene carriage with biochemical profiles of diarrhoeagenic E. coli; and develop an enrichment method for the selective isolation of diarrhoeagenic E. coli. Chromocult® Coliformen Agar proved unreliable for identifying diarrhoeagenic E. coli – 30% of strains would have been incorrectly identified using this medium. The carriage of pathotype-specific virulence genes by enteroaggregative E. coli strains was associated with the production of ornithine decarboxylase and the fermentation of sucrose. The enrichment procedure detailed in this study was an improvement upon an existing method. In addition, the improved method proved effective for the isolation of five diarrhoeagenic E. coli pathotypes. In contrast, the original procedure was only shown to be effective when isolating enterohaemorrhagic E. coli. The improved method was applied on environmental water and two samples yielded colonies positive for genes carried by enteropathogenic E. coli and enterotoxigenic E. coli, respectively. As confirmation of these results PCR products were sequenced and corresponded to published sequences of the virulence genes. / Ms. P.S. Kay Dr. T. G. Barnard Prof. P. Jagals

No description available.

Magister Philosophiae - MPhil / The Lesotho Highlands Development Authority routinely uses the South African Scoring System version 4 (SASS4) in conjunction with water chemistry to monitor water quality of rivers in the Lesotho Highlands Water Project areas. The objective of this study was to test the efficiency of SASS4 in these areas. / South Africa

With numerous bioassessment methodologies available, a regional protocol needs to be developed to ensure that results are comparable. A regional assessment protocol was developed that includes collecting five benthic macroinvertebrate samples, identifying organisms to genus, and calculating the following metrics: Number of Taxa, Total Number of Individuals, Simpson's Diversity Index, Shannon's Diversity Index, Percent Contribution of Dominant Taxa, Hilsenhoffs Biotic Index, and Percent Contribution of Dipterans. Once the protocol was developed, it was used to assess the Bayou Chico tributaries and watershed. All three tributaries had been significantly impacted by human activity as had the watershed as a whole. This study indicates that a regional protocol could be developed and is appropriate for biomonitoring at the watershed scale.

Pigment-based chemotaxonomy uses relative amounts of photosynthetic pigments (biomarkers) within algae samples to determine the algal class composition of each sample. Chemotaxonomy has been applied successfully to phytoplankton communities, but its efficacy for periphyton has not yet been established. This study examined the ability of simultaneous linear equations (SLE), CHEMTAX, and the Bayesian Compositional Estimator (BCE) to determine algal class composition in Florida Everglades periphyton. The methods were applied to artificial datasets, mixed lab cultures of known composition, and Everglades periphyton samples for which microscopic biovolume data was available. All methods were able to return accurate sample compositions for artificial data and mixed lab cultures. Correlation between pigment methods and microscopic results for natural periphyton samples was poor. SLE and CHEMTAX returned similar results for all samples while BCE performed less well. / by Jamie L. Browne. / Thesis (M.S.)--Florida Atlantic University, 2010. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2010. Mode of access: World Wide Web.

Three streams with watersheds of different land uses (urban, agricultural, and forested) were chosen for this study. A composite sample of diatoms was obtained from small rocks in a riffle of each stream and identified to genera. Water chemistry measurements included chloride, sulfate, nitrate, conductivity, pH, alkalinity and temperature.Conductivity, chloride, and sulfate were significantly higher in the urban watershed and lowest in the forested watershed. However, the forested watershed had the highest levels of nitrate, which may have come from groundwater or organic matter decomposition. Alkalinity, pH andtemperature did not vary among watersheds.Diatom diversity was significantly higher in the forested watershed. Several diatom genera, Amphora, Cymbella and Gyrosigma, were positively correlated with nitrate and negatively correlated with conductivity, chloride and sulfate, which indicate their potential use as indicators of water quality. / Department of Natural Resources and Environmental Management

published_or_final_version / Ecology and Biodiversity / Doctoral / Doctor of Philosophy

The Lesotho Highlands Development Authority routinely uses the South African Scoring System version 4 (SASS4) in conjunction with water chemistry to monitor water quality of rivers in the Lesotho Highlands Water Project areas. The objective of this study was to test the efficiency of SASS4 in these areas.

A biological monitoring tool to assess water quality using bivalve gape behavior was developed and demonstrated. The purpose of this work was to develop methodologies for screening water quality appropriate to the goals of the watershed paradigm. A model of bivalve gape behavior based on prediction of behavior using autoregressive techniques was the foundation of the bivalve biomonitoring system. Current technology was used in developing the system to provide bivalve gape state data in a continuous real-time manner. A laboratory version of the system, including data collection and analysis hardware and software, was developed for use as a toxicological assay for determination of effective concentrations of toxicant(s) or other types of stress on bivalve gape behavior. Corbicula fluminea was monitored and challenged with copper, zinc, and chlorpyrifos using the system. Effective concentrations of 176±23µg/L copper, 768±412µg/L zinc, and 68µg/L chlorpyrifos were observed using a natural water with high dissolved organic carbon concentrations. A rugged field version of the bivalve biomonitoring system was developed and deployed in two locations. The field systems were fitted with a photovoltaic array, a single board computer, and a CDPD telemetry modem for robust remote operation. Data were telemetered at a time relevant rate of once every ten minutes. One unit was deployed in Lake Lewisville, Denton County, TX in February 2000. Data were telemetered and archived at a 92% success rate. Bivalve gape data demonstrated significant behavioral deviations on average 5 times per month. A second unit was deployed in Pecan Creek, Denton, TX in June 2001. Data from this site were telemetered and archived at a 96% success rate. Over the months of June-August 2001, 16 significant behavioral deviations were observed, 63% of which were correlated with changes in physical/chemical parameters. This work demonstrated the relative sensitivity of bivalve gape as a toxicological endpoint and the feasibility of its use in a continuous, real-time, bivalve biomonitoring system. Technical aspects of collecting, telemetering, and analyzing this type of data in a time-relevant manner were developed resulting in a system appropriate for use as a means of data collection within the watershed paradigm.

Ph.D. / South Africa is the highest produce-producing and therefore the highest pesticide consumer on the African continent. Although greatly beneficial to the industry, indiscriminate and over usage of these agrochemicals pose a risk to the aquatic ecosystems through non-point source pollution. Data on these risks are limited in the developing countries such as Africa since limited environmental monitoring of pesticides is undertaken. This is due to technical, logistical and economical constraints in determining the links between exposure and effect on non-target organisms. Methods that are able to screen for and monitor pesticides that could pose a risk according to site-specific scenarios are therefore necessary. Economical and easy-to-use predictive models incorporated into Preliminary Risk Assessments (PRA’s) are useful in this regard and have been developed and applied globally to assist in estimating the probability of risks of pesticides associated with aquatic ecosystems. Currently no such risk assessment model is applied in South Africa for this purpose. The main aim of the present study was to present and assess the suitability of selected PRA models as preliminary screening tools for estimating potential pesticide exposure and associated effects within aquatic ecosystems. To achieve this, the primary objectives were to apply and validate these models for assessing predicted risks and to relate these to actual ecological hazards by monitoring the exposure and effects of selected pesticides that were identified as potentially posing a risk. It was hypothesised that the data determined by these models would elucidate the association between potential risks of pesticides and actual environmental impacts and could therefore be applied and validated for South African conditions. A framework was thus developed using multidisciplinary approaches to predict the risks of agricultural pesticides to non-target aquatic organisms and to validate these risks in an area known to have a high pesticide usage, namely the Crocodile (west) Marico catchment. This area is representative of a typical farming community in the subtropical central area of South Africa. It is a catchment area that exhibits high urban and agricultural usage, which has compromised the overall ecological integrity of the aquatic systems. The focus of the study was on the Crocodile (west) and Magalies Rivers and the associated irrigation canal network systems. The present study was based on integrating multidisciplinary techniques following the implementation of a tiered approach for assessing the ecological risks of selected pesticides known to be used within the Crocodile (west) Marico catchment. Tier 1 starts with the PRA assuming a relatively worst-case scenario by identifying pesticides most commonly used (through surveys) and estimating exposures posing a potential risk to the aquatic environment using the PRIMET (Pesticide Risks In the tropics to Man, Environment and Trade) model. The second tier can establish a more realistic characterisation of risk for the pesticide application scenarios of interest by using models such as PERPEST (Predicting the Ecological Risks of PESTicides), PEARL (Pesticide Emission Assessment of Regional and Local Scales), TOXSWA (TOXic substances in Surface Waters), or SSDs (Species Sensitivity Distributions). Higher tiers then include comparing the results from the PRA model predictions to the actual hazards of pesticides and can determine if these risk models are valid under South Africa conditions. This can be achieved using a combination of laboratory- and field-based monitoring assessments in the form of a triad approach (using chemical, toxicological and ecological assessments) to construct several lines-of-evidence (LoEs). The risk assessment process ends with a summary and integration of the data based on the multiple LoEs gathered during monitoring using a weight-of-evidence (WoE) approach.