This study assessed the pathogenicity of source waters in the Nwanedi River catchment surface waters including rivers as well as its related non perennial tributaries (storm run-off) by determining the presence of diarrhoeagenic Escherichia coli pathotypes namely Enteropathogenic Escherichia coli, Enterotoxigenic Escherichia coli, Enterohaemorrhagic Escherichia coli, Enteroaggregative Escherichia coli and Enteroinvasive Escherichia coli. The faecal pollution levels in the surface waters was assessed by measuring indicator Escherichia coli numbers in water samples at various sampling sites carried from its land-based faecal sources into the receiving surface water bodies. Sampling sites were selected to represent the human, livestock as well as wildlife sources of faecal generation and the possible infection risk posed to domestic, full body contact, agriculture uses as well as for abstraction intended for drinking were determined by comparing the Escherichia coli numbers with the guidelines summarised in Table 2.6: Chapter 2. A total of 199 proposed water samples were collected and analysed by the Miniaturised Most Probable Numbers method using 96-well micro-titre plates to enumerate Escherichia coli from the water samples. Twenty eight of 199 water samples were also analysed with a multiplex polymerase chain reaction using specific primers for the identification of diarrhoeagenic Escherichia coli related virulent genes namely – Mdh for commensal E. coli, Eagg and pCVD for Enteroaggregative E. coli, ST1 and LT1 for Enterotoxigenic E. coli, Stx1 and Stx2 for Enterohaemorrhaegic E. coli, EaeA for Enteropathogenic E. coli and Enterohaemorrhagic E. coli, Ial for Enteroinvasive E. coli. River water samples were directly filtered and 100-mℓ of filtered water samples were extracted while 1-mℓ pre-cultured Escherichia coli from storm run-off samples were extracted for use in the multiplex polymerase chain reaction. Because of the villages along the Nwanedi River catchment, Enteropathogenic E. coli followed by Enterotoxigenic E. coli was suspected to be the dominant diarrhoeagenic Escherichia coli. Contrary to this Enteroaggregative E. coli (54%) was dominant followed by Enterohaemorrhaegic E. coli (29%), Enteroinvasive E. coli (7%), Enteropathogenic E. coli (4%) and Enterotoxigenic E. coli (4%) respectively, in the surface water samples. The Escherichia coli numbers were significantly higher in storm run-off compared to the river water samples. Literature report Enteroaggregative E. coli to be associated with diarrhoea in HIV/AIDS patients, to whom its dominance in the surface water samples could pose serious infection risk to the Nwanedi River catchment communities, more especially the young, elderly and the immuno-compromised at the period of sampling if the waters are used untreated. The high Escherichia coli numbers could possibly be the results of continuous faecal contamination into the water sources and the rain storm events carrying faecal materials from land surface. Results show that Nwanedi River catchment waters harbour pathogens indicated by diarrhoeagenic Escherichia coli occurrence as well as commensal Escherichia coli numbers , which suggest the possible infection risk posed to the consumers if the waters are used untreated. / Prof. P. Jagals Dr. T.G. Barnard

β-N-methylamino-L-alanine (BMAA) is a non-proteinogenic amino acid associated with human neurodegenerative diseases. The content of BMAA in cyanobacteria is modulated by nitrogen in laboratory cultures. In order to evaluate the potential for human exposure, the nitrogen modulation of BMAA content needed verification in a natural environment. In accordance with laboratory culture studies, data presented in this study show that combined nitrogen was the most significant modulator of both cellular microcystin (MC) and BMAA content in phytoplankton in an environmental cyanobacterial bloom. While BMAA is produced upon nitrogen deprivation, MC is only produced at a specific nitrogen threshold where the rate of increase of nitrogen in the cell exceeds the carbon fixation rate. As BMAA and MC were detected in phytoplankton sourced from the Hartbeespoort Dam reservoir, the transfer of these cyanotoxins to organisms of higher trophic levels was investigated. Both BMAA and MC were detected at high concentrations in the liver and muscle tissue of fish sourced from the Hartbeespoort Dam reservoir indicating that consumption of fish from this reservoir constitutes a serious risk of exposure to cyanotoxins. In addition to the dietary exposure route to BMAA, two recent studies reported a correlation between Amyotrophic Lateral Sclerosis (ALS) incidence and the potential for aerosol exposure to cyanobacteria. With the absence of any evidence of the systemic distribution of BMAA following inhalation, an evaluation of the potential exposure risk associated with living in close proximity to this reservoir was deemed premature. A laboratory experiment investigating the effect and systemic fate of inhaled aerosolised BMAA was therefore conducted in order to determine the feasibility of inhalation as a potential BMAA exposure route. Data from the rat inhalation exposure study, however, showed that in rats BMAA inhalation may not constitute a significant mechanism of toxicity at environmental BMAA levels.

M.Sc. / The health of aquatic ecosystems can be severely compromised by a variety of pollutants, such as heavy metals, which are related to anthropogenic activities. Increased recognition is given to the use of organisms, especially molluscs, in the biomonitoring of aquatic ecosystems. This promising approach complements the interpretation of the physico-chemical measurements of water quality. The bioaccumulation of pollutants as well as the resultant biological responses (biomarkers) in organisms can be used in assessing the spatial and temporal trends of chronically polluted environments. The aim of this study was to determine if selected freshwater gastropods (Melanoides tuberculata, Physa acuta, Helisoma duryi and Lymnaea columella) can be used as suitable biomonitors or indicators of water quality. Interspecies differences in metal bioaccumulation and biomarker responses were determined in order to select the most suitable biomonitor/indicator organism to be used. The bioaccumulation of metals was related to the biomarker responses of the organisms. This study was divided into an active biomonitoring (ABM) study and a laboratory exposure study. In the first study, the organisms, M. tuberculata and L. columella were chronically (two, four and six week period) exposed to field conditions. Metal bioaccumulation as well as the biomarker techniques, DNA damage, catalase (CAT) activity, reduced glutathione (GSH) content and cellular energy allocation (CEA) were measured in the organisms. These general biomarkers of exposure and effect, on the biochemical and cellular levels of biological organisation can give a rapid and sensitive assessment of organism health. The second study consisted of exposing the gastropods, M. tuberculata, P. acuta, H. duryi and L. columella to sub-lethal zinc and cadmium concentrations. The uptake and depuration kinetics of these metals were determined in M. tuberculata and H. duryi for a six hour and 48 hour period, respectively. The bioaccumulation of Zn and Cd as well as the biomarkers, DNA damage, CAT activity, GSH content and CEA were measured in all the species, after a two week exposure period. / Prof. J.H.J. van Vuren

An Investigation Into the ecology of benthic macro-invertebrates in earthen ponds subjected to intensive trout (Salmo trutta L.) culture practices at Howletoun, Central Scotland, was conducted between May 1984 and January 1986. Soil and water quality, seasonal changes in benthos, its role in the trout diet and the Interaction between fish and benthos were studied. Pond benthos mainly comprised 6 major groups including Oligochaeta. (10 species), Chironomldae (18 species), Molluscs and Hirudinea (2 species each) and an asellid and a sialid species. Oligochaeta formed 78 to 90% of benthic fauna, dominated by Tubifex tubifex. Limnodrilus hoffmeisteri, L. udekemianus and Psammoryctides barbatus, with an average population density of 68,400 - 191,200 worms mˉ², and exhibited peaks in summer and late autumn corresponding to two major breeding periods. The principal species of Chironomidae were Chironomus spp., Procladius spp. and Prodiamesa olivacea, with a population density of 5,400 to 14,900 ind. mˉ² and forming 7 to 13% of the total benthos with peaks in spring and autumn. Dry biomass of total benthos varied from 24-59 g mˉ² in the cultured ponds with oligochaetes accounting for 14-49 g mˉ² and chironomids 4-7 g mˉ². The mean annual dry weight production of total benthos varied from 130-215 g mˉ² in the cultured ponds, with oligochaete production of 94-160 g mˉ² and chironomid production of 20.6-33.5 g mˉ². An investigation into the ecology of benthic macro-invertebrates in earthen ponds subjected to intensive trout (Salmo trutta L.) culture practices at Howietoun, Central Scotland, was conducted between May 1984 and January 1986. Soil and water quality, seasonal changes in benthos, its role in the trout diet and the interaction between fish and benthos were studied. Pond benthos mainly comprised 6 major groups including Oligochaeta (10 species), Chironomidae (I8 species), Mollusca and Hirudinea (2 species each) and an asellid and a sialid species. Oligochaeta formed 78 to 90% of benthic fauna, dominated by Tubifex tubifex. Limnodrilus hoffmeisteri, L. udekemianus and Psammoryctides barbatus, with an average population density of 68,400 - 191,200 worms mˉ², and exhibited peaks in summer and late autumn corresponding to two major breeding periods. The principal species of Chironomidae were Chironomus spp., Procladius spp. and Prodiamesa olivacea, with a population density of 5,400 to 14,900 ind. mˉ² and forming 7 to 13% of the total benthos with peaks in spring and autumn. Dry biomass of total benthos varied from 24-59 g mˉ² in the cultured ponds with oligochaetes accounting for 14-49 g mˉ² and chironomids 4-7 g mˉ². The mean annual dry weight production of total benthos varied from 130-215 g mˉ² in the cultured ponds, with oligochaete production of 94-160 g mˉ² and chironomid production of 20.6-33.5 g mˉ². In an unstocked control pond the total production was 55 g mˉ², 35 g mˉ² of which was accounted for by oligochaetes and 8.06 g mˉ² by chironomids. Analyses of gut contents of the farmed trout showed that 12% of the diet by volume consisted of natural food, mainly benthos. Fish selectively fed on chironomid larvae, Mollusca, Asellus aquaticus and Sialis lutaria. Fish took maximum natural food in the morning and evening. Experimental enclosures to exclude fish from selected areas of the ponds demonstrated that number of species increased outside the enclosures but, except for chironomids, population density, biomass and production generally increased inside the enclosure. The possibility of explaining this result in terms of differential predation is discussed.

Graduation date: 2003

Thesis (Ph. D.)--University of Washington, 2002. / Vita. Includes bibliographical references (leaves 105-115).

Effective use of bioassessments requires an understanding of their performance. This study evaluated the performance of Skeena Reference Condition Approach (RCA) bioassessments by calculating Type I and Type II error rates and power using a data set of artificially-impacted test sites. Results from this study demonstrated that there are trade-offs between the two error types. Type I error rates – the chance of concluding that a site is impacted when it isn’t – were higher than expected based on decision points set in the assessments. Type II error rates – the chance of concluding that a site is not impacted when it is – were often even greater. To achieve sustainable development, resource managers who use Skeena bioassessments must carefully consider the risks associated with making errors, and may wish to set decision points that result in more Type I errors in order to reduce the likelihood of making costly Type II errors.

Thesis (M.S.)--University of Wisconsin--Stevens Point, 2007. / Includes bibliographical references (leaves 62-66).

Thesis (Ph. D.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains xi, 170 p. : ill. (some col.), maps. Vita. Includes abstract. Includes bibliographical references.

Thesis (B. Sc.(Hons.))--University of Adelaide, Department of Environmental Science and Rangeland Management, 1992. / Includes bibliographical references (leaves 28-29).