M.Sc. / The water quality in the Vaal River system has deteriorated due to increasing industrial, mining and agricultural activities in the Vaal Dam and Vaal River Barrage catchment areas. This study was undertaken to determine the water quality in the Vaal Dam, and three localities within the Vaal River Barrage reservoir (i.e. the Riviera Aquatic Club, Abrahamsrust Pleasure Resort and at the Barrage structure). The objectives of this study, was to determine the fish population species composition, evaluate the general health of the selected fish species and obtain site specific metal bioaccumulation data for each locality. Suggestions and proposals for future monitoring and management of these waterbodies were also made. Metereological information on the Vaal River Barrage area was supplied by Rand Water, as well as physical and chemical data of fixed localities, sampled fortnightly (January 1997 to September 1998). In addition, water samples were collected at the Vaal Dam and the three Vaal River Barrage localities mentioned above, during February, May, August and November 1997. These samples were analysed by the Chemistry Department of the Rand Afrikaans University in accordance with standard methods. The chemical and physical characteristics and metal concentrations (aluminium, cadmium, calcium, copper, iron, magnesium, manganese, nickel, strontium and zinc) of these separate sets of data were then compared with Rand Water's Raw Water Quality Criteria. The aluminium, ammonia, chromium, copper, dissolved organic carbon, fluoride, iron, lead, manganese, nitrate, sulphate, total hardness and turbidity variables did not comply with the recommended guideline values. No guideline levels for strontium are available, however. Sedimentation, turbidity, salination and eutrophication within the Vaal River system play an important role in the bioaccumulation of metals by benthic organisms. Metals that adsorb to sediment particles, through various processes, are generally more persistent and less mobile than those in the overlying water and pose a severe long-lasting threat to the aquatic environment. Generally, the highest metal concentrations (AI, Cd, Cu, Fe, Mn, Ni, Pb, Sr and Zn) in the sediment samples collected at the four localities and seasons, were found in the finer sediment classes (class D). The Riviera Aquatic Club locality had the highest overall concentrations of the metals analysed. The adult fish communities within the Vaal Dam and Vaal River Barrage were assessed, as it is believed that the fish community structure is indicative of environmental conditions. Adult Labeo capensis, Labeo umbratus, Cyprinus carpio, Clarias gariepinus, Barbus aeneus and Micropterus sa/moides, were collected (using gill nets) to determine the adult fish community composition and age. When compared with a study conducted by Mulder (1971), it is clear that Labeo capensis has remained the most abundant species within the system, but that Barbus aeneus has now been replaced by Labeo umbratus as the second most abundant species. Furthermore, age determination tables (Mulder, 1971) were used to classify the fish population between the ages of 2 and 7 years. This indicates a healthy, dynamic community structure where recruitment is taking place. The Health Assessment Index (HAl) was used to determine the general health of the two fish species selected for metal analysis (i.e. Labeo capensis and Labeo umbratus). Except for moderate to severe gill damage recorded, no damage to external variables, were of concern. However, both Labeo capensis and Labeo umbratus had high percentages (89% and 93%, respecii tively) of abnormal livers. Using the Plascon Colour Chart (Watson, personal communication), these livers were classified as ranging from tan to "coffee with cream" in colour. High haematocrit and plasma protein levels were observed and could be due to environmental stress, while the White Blood Cell Counts were within normal ranges. Generally speaking, only mild to moderate parasite infections were observed and probably do not pose a serious health threat to the fish host. Total HAl values for Labeo capensis indicate that this this fish population was in relatively good health, but too few Labeo umbratus individuals were collected to make accurate assumptions about this population. Metal analysis (AI, Cd, Cu, Fe, Mn, Ni, Pb, Sr and Zn) was carried out on the tissues and organs (skin, muscle, gill filaments, gill arches, liver, hindgut content, gonads and vertebrae) of Labeo capensis and Labeo umbratus, collected during the study period. Only aluminium, iron and strontium are discussed. Aluminium concentrations were relatively high at all of the localities, but as pH values were mostly alkaline, aluminium is rendered biologically unavailable and as for iron, was mostly accumulated in the non-edible portion and viscera of the fish. Strontium accumulates in bony tissues due to its similarity with calcium, but is not essential for bone formation. The human health risks of these metals in the edible portion of the fish still have to be refined and communicated to the general public of South Africa. In conclusion, this baseline study has determined the metal concentrations in the aquatic environment (due to anthropogenic activities) that may be accumulated by fish and may affect the adult fish community structures and their general health.

Thesis (PhD(Microbiology))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Pathogenic Flavobacterium spp. cause serious disease outbreaks in a variety of farmed fish, which lead to large economic losses in the aquaculture industry on an annual basis. The ability of Flavobacterium johnsoniae-like isolates to grow as surface-associated communities (biofilms) in aquaculture systems poses a threat to fish health over extended periods of time. The biofilmforming ability of 28 F. johnsoniae-like isolates obtained from diseased fish were correlated with their chitin-degrading abilities and extracellular carbohydrate complexes (ECC) and their pulsed-field gel electrophoresis (PFGE) genotypes. Physiological changes in the proteome of 5 day planktonic, biofilm and agar surface-associated cultures of F. johnsoniae-like isolates YO12 and YO64 were analyzed by two-dimensional (2-D) gel electrophoresis and 17 differentially expressed and 14 uniquely expressed proteins were identified using matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). Thirty-two differentially expressed genes in 5 day biofilm and agar surface-associated cultures of F. johnsoniae-like isolates YO12 and YO64 were identified using suppression subtractive hybridization (SSH). Significant negative correlations were observed between the chitin-degrading abilities and ECC and the biofilmforming capacity of 24 h biofilm cultures of F. johnsoniae-like isolates. Genetic heterogeneity was displayed by the F. johnsoniae-like isolates following PFGE. A significant positive correlation was observed between PFGE types and fish host species. Differentially and uniquely expressed proteins identified in planktonic, biofilm and agar surface-associated phases by 2-D/MS as well as differentially expressed genes identified in the biofilm and agar surface-associated phases by SSH were categorized as being involved in adaptation/protection, metabolic processes, membrane/transport/ motility and transcription/ translation. As far as we know, this is the first report on the characterization of differentially expressed genes and gene products of F. johnsoniae-like isolates obtained from diseased fish in South Africa. / AFRIKAANSE OPSOMMING: Patogene Flavobacterium spp. veroorsaak ernstige infeksie uitbrake in ’n verskeidenheid gekweekte vissoorte, wat jaarliks tot groot ekonomiese verliese in die akwakultuur bedryf lei. Die vermoë van Flavobacterium johnsoniae-tipe isolate om as oppervlak-gehegde gemeenskappe (biofilms) in akwakultuur sisteme te groei bedreig visgesondheid oor verlengde periodes. Die vermoë van 28 F. johnsoniae-tipe isolate om biofilms te vorm is vergelyk met hul vermoë om chitien te degradeer, die profiel van hul ekstrasellulêre koolhidraat komplekse (EKK) en bandpatrone verkry met puls-veld jel elektroforese (PVJE). Fisiologiese veranderinge in die proteoom van 5-dagoue planktoniese-, biofilm- en agar oppervlak-geassosieerde kulture van F. johnsoniae-tipe isolate YO12 en YO64 is met twee-dimensionele (2-D) jel elektroforese geanaliseer. Sewentien differensieël uitgedrukte en 14 uniek uitgedrukte proteïene is deur middel van matriks-geassisteerde laser desorpsie ioniserings-tyd van vlug-massa spektrometrie (MGLDI-TVV MS) geïdentifiseer. Twee-en-dertig differensieël uitgedrukte gene in 5-dag-oue biofilm- en agar oppervlak-geassosieerde kulture van F. johnsoniae-tipe isolate YO12 en YO64 was deur middel van suppressie afgetrokke hibridisasie (SAH) geïdentifiseer. Beduidende negatiewe korrelasies is tussen die chitin-degraderings vermoë en EKK en die biofilm-vormings kapasiteit van 24-uur-oue biofilm kulture van F. johnsoniae-tipe isolate waargeneem. Resultate verkry met PVJE het die heterogene samestelling van F. johnsoniae-tipe isolate uitgewys. ‘n Beduidende positiewe korrelasie is tussen PVJE groeperings en vis gasheer spesie waargeneem. Differensieël en uniek uitgedrukte gene geidentifiseer in die planktoniese-, biofilm- en agar oppervlak-geassosieerde fases is deur middel van 2-D/MS asook differensieël uitgedrukte gene geïdentifiseer in die biofilm en agar oppervlakgeassosieerde fases deur middel van SAH was as betrokke by aanpassing/beskerming, metaboliese prosesse, membraan/vervoer/ beweeglikheid en transkripsie/translasie gekategoriseer. Sover bekend is hierdie die eerste beskrywing van differensieël uitgedrukte gene en geenprodukte van F. johnsoniae-tipe isolate afkomstig van geinfekteerde vis in Suid Afrika.

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