Doctoral Degrees (Botany and Zoology)

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Browsing Doctoral Degrees (Botany and Zoology) by browse.metadata.advisor "Botha-Oberholster, Anna-Maria"

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    A comparative exotoxicological study of two major South African river systems : a catchment scale approach for improved risk assessment and environmental management through the integration of abiotic, biotic, biochemical and molecular endpoints
    (Stellenbosch : Stellenbosch University, 2016-12) De Klerk, Arno Reed; Botha-Oberholster, Anna-Maria; Van Wyk, Johannes H.; Oberholster, Paul J.; Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology.
    ENGLISH ABSTRACT: Along with the prosperity of humankind, the inevitable increase in developments to support this often results in water resources becoming repositories for the waste generated by such progress. To ensure sustainable development, anthropogenic impacts need to be properly assessed and anticipated in order to respond accordingly to mitigate such events. With the Mokolo River being at the center of plans to exploit the largest remaining coalfield in South Africa, this study was initiated to improve our understanding of the range of expected water resource impacts that may occur, by taking lessons learned from the upper Olifants River system, which has been severely impacted by coal mining for more than a century. The aim of this study was to conduct a comparative ecotoxicological study at a catchment scale on both the Mokolo River and upper Olifants River systems. Study sites in the upper Olifants and Mokolo rivers, their major tributaries, as well as major impoundments were selected and assessed seasonally for a number of years. Water and sediment samples were analyzed for various constituents, whilst biological samples (invertebrates and fish) were also sampled to gain perspectives on the impact of pollution at molecular, cellular and community levels. Lastly, a case study to examine the potential use of rehabilitation measures on ecological infrastructure to mitigate the potential impact of acid mine drainage (associated with coal mining activities) was conducted. Important abiotic ecosystem drivers were identified, whilst the influence of the tributaries and impoundments on the main stream rivers were determined. The major exposure routes of bioaccumulation were found to be through the dietary uptake of contaminated sediment and algae. The use of the fresh water crab, Potamonautes warreni, provided an excellent model organism to study the fate, transport and impact of pollution and also to monitor various degrees of molecular and cellular impacts. In contrast to the general use of fish as bioindicators, the use of aquatic invertebrate community structures and freshwater crabs proved more useful to characterize the ecosystem integrity of these systems, detect turnover and determine the links with possible contaminants. From the various biochemical and molecular markers used, several endpoints proved useful in monitoring chronic impacts on biota, which may be used as early warning indicators, whilst others are linked to acute anthropogenic impacts. A significant improvement in water quality occurred after the wetland rehabilitation case study, including increased productivity, reduced toxicity (embryotoxicity and teratogenicity) and changes in the biotic community structures. Therefore, the benefit of the rehabilitation of ecological infrastructure to mitigate the impact of coal mining associated pollution was proven. Overall, the use of a comparative catchment approach, employing both an impacted and less impacted river system, proved extremely useful and valuable to support the future management of the Mokolo River in the face of ever increasing land use activities. This catchment scale comparative study is a rare and unique opportunity which few studies are able to utilize to assess the likely impacts of future land use change.