M.Sc. / A comprehensive histology-based fish health assessment was implemented at the Roodeplaat Dam (RD), Pretoria, South Africa, to determine the health status of two fresh water fish species, Clarias gariepinus (n = 20) and Oreochromis mossambicus (n = 18), after exposure to pollutants. RD is known to be polluted, being impacted from two sewage treatment plants, industry, housing and agriculture all upstream of the reserve. Excessive nutrient loads, such as orthophosphate, resulted in the dam becoming eutrophic. The quality of water in the RD was a cause for concern, as the fish from the dam are being used as a source of food by the local people. The histology-based fish health assessment included fish necropsy, calculation of gross body indices and histological assessment. Water quality (chemical and physical) analysis was also carried. Furthermore, target chemical analysis of fish tissue (skeletal muscle) was performed to determine the levels of contaminants in the consumable parts of the fish. These results were compared with existing international guidelines to determine whether the harvested fish were safe for human consumption. All the information obtained was integrated in a qualitative and quantitative scenario-based health risk assessment.

Eutrophication is a nutrient enrichment of dams and lakes. Increased eutrophication in dams results in blooms of cyanobacteria. Cyanobacteria are troublesome as they form massive surface scums, impart taste and odour to the water. Some strains of cyanobacteria such as Microcystis aeruginosa are dangerous to humans and animals. They produce toxins that can kill animals drinking the contaminated water and have also been implicated in human illnesses. The study investigated the effectiveness of techniques deployed in controlling cyanobacterial growth in Rietvlei, Roodeplaat and Hartbeespoort Dams. This was done by interpreting data from April 2010 to March 2012. The conditions in the three dams show that Microcystis produced toxins in the summer season and all the variables analysed were favourable for the production of toxins. The methods deployed to rehabilitate the dams do not completely solve the problems of toxins experienced by the dams. / Environmental Sciences / M. Sc. (Environmental Management)

Eutrophication is a nutrient enrichment of dams and lakes. Increased eutrophication in dams results in blooms of cyanobacteria. Cyanobacteria are troublesome as they form massive surface scums, impart taste and odour to the water. Some strains of cyanobacteria such as Microcystis aeruginosa are dangerous to humans and animals. They produce toxins that can kill animals drinking the contaminated water and have also been implicated in human illnesses. The study investigated the effectiveness of techniques deployed in controlling cyanobacterial growth in Rietvlei, Roodeplaat and Hartbeespoort Dams. This was done by interpreting data from April 2010 to March 2012. The conditions in the three dams show that Microcystis produced toxins in the summer season and all the variables analysed were favourable for the production of toxins. The methods deployed to rehabilitate the dams do not completely solve the problems of toxins experienced by the dams. / Environmental Sciences / M. Sc. (Environmental Management)