| Summary: | M.Sc. === The main objective of this study was to perform active biomonitoring in the Rietlvlei Wetland System. Active biomonitoring, which can be defined as “the translocation of organisms from one place to another and quantifying their biochemical, physiological and/or organismal responses for the purpose of water quality monitoring” (De Kock and Kramer, 1994), has several advantages over the chemical monitoring system. Effluents often are complex and poorly characterized mixtures of a large number of chemicals. A combination of many chemicals being present in very small amounts (even below detection limits) can have a substantial impact on organisms, and a chemical-based approach may not identify the source of pollution nor will effect of synergism or antagonism be taken into account (Smolders et al., 2003). A suite of biomarkers of oxidative stress and histopathology were investigated in the fish Oreochromis mossambicus and the mollusk Melanoides tuberculata. The organisms were bred under laboratory conditions. They were deployed during the high-flow and low-flow periods, in cages at three sites down the flow gradient of the Rietvlei wetland system, to determine spatial and temporal variations in biomarker responses and general water chemistry in the system. The oxidative stress biomarkers analyzed were catalase (CAT), superoxide dismutase (SOD), peroxidase (GPx), as well as levels of reduced glutathione (GSH) and lipid peroxidation as malondialdehyde (MDA). There was evidence of presence of chemicals inducing oxidative stress in the organisms as indicated by the high levels of MDA, GSH and GPx. Induction of CAT and SOD was not substantial due to possible inhibitory factors. This study established that organism transplantation is a feasible strategy for biomonitoring. Overall, no distinct variations were observed in the spatial and temporal comparisons in all the biomarker responses. The findings of this investigation also provide a basis for further investigation into the application of these biomarkers in ecological risk assessment. === Dr. V. Wepener
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