There are many types of chemicals/contaminants present in the environment, ranging from synthetic chemicals to trace metals that are required for life. When an organism is exposed to a toxicant, adverse effects are generally first at the sub-organismal level. There is thus a need for physiological and biochemical indicators of organismal health and sub-lethal toxicant effects. A bio-indicator, or biomarker, is a response of a living organism to environmental changes or because of exposure to contaminants. The main objectives of this study were to evaluate and investigate the possible use of biomarkers as indicators of sub-lethal (chronic) effects induced by certain chemicals/pollutants on the Mozambique tilapia, Oreochromis mossambicus. The biomarkers were evaluated as a possible sensitive and reliable measure of effects due to exposure to pollutants. This study was divided into laboratory experiments and field evaluations. The laboratory experiments consisted of the evaluation of biomarkers in exposure studies on 18-24 day old O. mossambicus juvenile fish, to determine the sub-lethal effects induced by chemicals. Acetylcholinestrase (AChE), Ethoxyresorufin-O-deethylase (EROD) and glucose levels acted as the battery of biomarkers evaluated. Thirty (30) juvenile fish were exposed for 24 and 96-hours to sub-lethal concentrations of cadmium, zinc, pentachlorophenol (PCP) and cyanide. For the field evaluation, mature Oreochromis mossambicus of both sexes, were caught during the summer and winter at the Rust de Winter Dam, Loskop Dam and Hartebeespoort Dam. Rust de Winter Dam acted as the reference site. The biomarkers evaluated during the field studies include: erythrocyte AChE, ƒx-Aminolevulinic acid dehydratase (ALAD) and plasma glucose levels, EROD and liver glycogen. The laboratory (exposure) test used during this study was not sensitive enough to obtain reliable, repeatable results. But standardised procedures were established for possible use in future studies. During the field studies, ALAD, EROD and plasma glucose showed significant results and differences between the reference and polluted sites. More accurate results could be obtained at impoundments with higher levels of pollution. Although, erythrocyte AChE and liver glycogen did not show significant results during this study, they might also show more accurate and reliable results at higher levels of pollution. In future, chemical water analysis should be carried out during field evaluation to determine what chemicals/toxicants are present in the aquatic environment. Biomarkers will show the level of effects of the toxicant on the organism, while chemical analysis will determine the specific pollutant present in the water. / Prof. J.H.J. Van Vuren

M.Sc. / The increasing demand for water in South Africa arises from a rapid population growth and supporting industrial development. This demand has to be met from limited water resources that are shared by competing user groups and neighbouring states. Deteriorating water quality further limits the sustainable use of water through point and diffuse source pollution of macro constituents, metals and biocides. Metals in the environment can originate as point sources, including industrial and mining effluent, or diffuse sources from geological origin, agricultural activities, acid mine draining and leachate from dumps. Biocides increase crop yields, protect forests and control vectors of serious human disease, but are in the process also carried to water courses. Bioaccumulation studies have been identified as a method to monitor pollutants in the environment. The analyses of data from bioaccumulation studies share a common problem in having to deal with many independent variables, for example variations in time and space, environmental conditions and biological parameters. The objectives of this study were to; investigate the metal levels in water and metal and biocide bioaccumulation in fish tissues from the Berg, Luvuvhu, Olifants and Sabie Rivers; develop a procedure to predict areas and biocides at risk of causing diffuse source pollution and; evaluate the available data and procedures to propose more efficient and cost effective bioaccumulation programmes. The investigation evaluated current and potential contamination of the selected catchments and identified research needs. Fish tissues and water grab samples were collected in the Berg, Luvuvhu, Olifants and Sabie Rivers. The samples were tested for physical variables and analysed for macro constituents and metal levels according to standard analytical procedures. Fish were caught (gill and seine nets) and larger specimens were selected for tissue analyses. Species were identified and standard length, mass, gender, gonadotrophic development index and age indicators were collected. Standard procedures were used to analyse fish tissues for metal levels with the atomic absorption spectrophotometer (AAS) and biocide levels with gas chromatographic methods. A flow diagram of a statistical methodology was developed to incorporate the effects of all biological parameters in the analyses of bioaccumulation data. The procedures used to calculate human health risks are that of the Risk Assistant package reviewed by the United States Environmental Protection Agency (EPA). A Geographical Information System (GIS) model was developed, incorporating the factors affecting runoff of surface water and biocides, to predict areas and variables that could cause diffuse source pollution. The pH values of the rivers studied ranged from of 7.2 to 8.7 except for the Klipspruit River before its confluence with the Olifants River that had a pH of 4.8. Nutrient levels in the Berg River are within the South African guidelines. Nutrients in the Luvuvhu River mostly exceed the guideline values for ortho-phosphate, ammonia nitrogen, nitrate nitrogen and total phosphorus. In the Olifants River the values for ortho-phosphate, total phosphorus, ammonia nitrogen and nitrate and nitrite nitrogen often exceed the South African guideline values. Nutrients in the Sabie River have low concentrations with only ammonia nitrogen exceeding the guideline values. TDS values in the Olifants River is the highest, which is an indication of the high salt loads in the river. The concentrations of various metals in water from the Berg, Luvuvhu, Sabie and Olifants Rivers exceeded the proposed South African and international guidelines.

The biological integrity of aquatic ecosystems has become threatened by the effects of eutrophication, acidification as well as increased organic and inorganic chemical loads. It is necessary to identify the effects of xenobiotics before the onset of death in an exposed organism or deteriorating changes at population level. Biochemical and physiological indicators such as enzymes and stress proteins could be used as a valuable tool for detecting chemical exposure and evaluating their effects on aquatic organisms. The use of selected enzymes in different organs/tissue was evaluated as possible indicators of stress in fish, in their natural environment as well as under controlled laboratory conditions. During the field assessment of enzymes it was found that selected enzymes could be used as indicators of pollution between high flow and low flow seasons when pollution conditions are more concentrated. However, the various enzymes are non-specific indicators of stress and could therefore, be influenced by environmental changes, handling and struggling in the nets. Exposure to sub-lethal and lethal iron concentrations caused significant differences between the levels of enzymes in exposed and control Oreochromis mossambicus, indicating that the use of enzymes under controlled laboratory conditions, toxicity testing is more effective. The demand for sensitive and specific biological assays needed to be satisfied. Heat shock induction after sub-lethal iron exposure was investigated in the reproductive organs/gonads of O. mossambicus. After the refinement of the standard protocol for the assessment of Heat shock protein 70 (HSP 70) it was found that HSP 70 induction are more intense in male individuals than in female individuals. Higher protein concentrations were also found in female reproduction organs possibly due to the presence of vitellogenin. The use of HSP 70 as a diagnostic tool to monitor cell damage after sub-lethal iron exposure was less effective due to several factors including (1) the selection of the target organ, (2) the different stages of sexual development between individuals, (3) the selection of the exposure toxicant and (4) the presence of another stress protein in female gonads. Most researchers use the Atomic Absorption Spectrophotometry (AAS) method to determine the metal content in fish organs/tissues. During this research it was attempted to find a more time effective, rapid, less hazardous and more economic method to determine metal content in fish organs/tissues. After comparison between the AAS method and Scanning Electron Microscope Energy Dispersive X-ray (SEM-EDX) microanalyses the AAS method was found to be the most effective method to determine metal content in fish organs/tissues. SEM-EDX microanalyses techniques need more refined sample preparation, calibration and operation skills. / Prof. J.H.J Van Vuren

M.Sc. / Please refer to full text to view abstract

M.Sc. (Aquatic Health) / The lower Olifants River within the Kruger National Park is regarded as an environmentally sensitive area which has been found to exhibit high levels of aquatic diversity. The biodiversity in this lower section of the Olifants River is under threat as a result of the cumulative impacts upstream within the catchment. These impacts are apparent in water pollution, siltation and reduced stream flows as a result of agriculture, mining, industry and power generation. Although the impacts within the upper catchment have been well documented, it was the numerous fish kills within the river which brought the issue of river health into the public eye. Due to the intensive industrial activities on the Ga-Selati River, a tributary of the Olifants River, and its close proximity to the Kruger National Park, much focus has been placed on the river’s water quality, especially industrial effluent containing high concentrations of pollutants. Currently bi-annual monitoring of the aquatic ecosystems associated with the industries along the Ga-Selati River is being conducted, providing information of the ichthyofaunal communities within the system. In addition to this, the separate industries collect water quality data as frequently as weekly. The aim of this project is to lay the foundation for understanding the state of the Ga-Selati River, and to determine what water quality variables may be influencing the ichthyofaunal structure within the river. Analysis of water quality data showed that elevated levels of salts are evident, with a downstream increase in concentrations being observed along the length of the Ga-Selati River at a given point in time. Over the eight years of data considered, the overall trend indicates a general water quality improvement (decreased concentrations). A reoccurring trend showed an increase in salts between two of the sites, suggesting a source of contamination within this area. A statistical analysis of the fish community data and environmental data showed there to be a clear distinction between historical (2003, 2004 and 2005) and recent surveys (2009 and 2010). During the first time period, Site 1 showed the lowest diversity and showed to be significantly different from the remainder of the sites. During the second time period, diversity at Site 1 increased, and it was noted that overall, there was greater variability within the data. In general it was observed that upstream species richness was lower compared with downstream sites. This trend is likely linked to the proximity of the Olifants River, which allows migration into the lower reaches of the Ga-Selati River. The historical monitoring data revealed that water quality and in particular salts are influential in the structuring of ichthyofaunal communities. This change can be substantiated by identifying that an improvement in water quality has resulted in a positive shift in ichthyofaunal community structure. The analysis of this information will contribute towards the improved management and conservation of the Ga-Selati River system. Although mining houses/industries are collecting and sharing water quality data, it would be valuable if a strategic approach to sample collection and management was perused. A centralised database will increase the understanding of the driving variables behind ichthyofaunal community structure within the river and would lay the foundation for future closure plans. It is imperative that an excellent set of water quality data is available during the design of appropriate rehabilitation and treatment facilities.

The cichlid fish Pseudocrenilabrus philander is widely distributed in southern Africa. Many of the populations occur in small, insular, geographically isolated water bodies, some of which are in arid areas. These small allopatric populations have been isolated for thousands of years and gene flow between them is non-existent or severely restricted. Populations were found to be different in terms of coloration, size of individuals, sexual dimorphism and behaviour. This thesis involved the determination of the taxonomic status of these isolated populations, from a morphological point of view. This has been part of a larger project, involving genetic and behavioural studies, to determine whether the different populations are geographic races of a single species, or whether they are species. Heritability of the observed differences was tested by breeding through three generations under uniform laboratory conditions. The populations from which wild-caught individuals were drawn could be identified on the basis of colour. There were some differences in anatomy between populations, but none of these were entirely distinctive for a particular population. When bred under laboratory conditions, populations did not show a tendency towards uniformity, as would be expected if morphological differences were environmentally induced. However, there were slight changes in the oral and pharyngeal bone form which may be diet related. Although there are morphological differences between populations and between wild-caught and laboratory-bred populations, it is suggested that the populations of P. philander are not fully differentiated and thus in the stages of incipient speciation. other studies on P. philander have introduced an element of uncertainty in that they show different results. Behavioural work suggests that different populations would behave as different species if they were to become sympatric. Karyological and mitochondrial studies showed that there were no differences between populations. Protein electrophoresis showed that populations were genetically unique. Since the various species and subspecies of Pseudocrenilabrus have been based on morphological criteria, the approach and conclusions in this study are based entirely on morphological criteria. These studies have practical implications for conservation, as some of the small populations are threatened with extinction. If the differences between the populations were ecophenotypic (i.e. related to their environment), then threats to some populations would not affect the conservation status of the species as a whole. If, however, such differences were genetic (i.e. the populations have evolved separately), then the extinction of small, isolated populations could mean the loss of actual species. This study strongly suggests that populations are incipient species and thus should be conserved.

A total of 670 critical thermal maxima (CTMax) and minima (CTMin) were determined for three freshwater fishes acclimated to three constant temperatures and a diel regimen cycling between the lowest and highest acclimation temperatures. In all species temperature tolerance was directly related to acclimation temperature and slopes relating these variables indicate that acclimation temperature has a greater influence on tolerance of low rather than high temperatures. CTMax and CTMin values generated following exposure to 32 days of oscillating temperatures indicate that in general, fishes had temperature tolerance acclimation states consistent with the average temperature and not either the highest or lowest temperature of the diel cycle.

No description available.

Thesis (Ph. D.)--University of Tennessee, Knoxville, 2001. / Title from title page screen. Document formatted into manuscript-like pagination: vii, 98 leaves : ill. Vita. Includes bibliographical references (leaves 85-86).

M.Sc. (Zoology) / Please refer to full text to view abstract