M.Sc. / Please refer to full text to view abstract / Prof. A. Avenant-Oldewage

M.Sc. / Metal ions have become an increasing source of pollution in the natural waters of South Africa. This phenomenon is related to the rapid industrial, mining and agricultural activity growth along rivers, especially in the Upper catchment of the Olifants River, Mpumalanga. In general, metal ions have - negative effects on the physiology of fish and other aquatic biota in metal polluted waters. In this study. the sublethal effects of, manganese were determined by exposing the freshwater fish, Oreochromis mossambicus, to this metal in an experimental flow-through system. The exposure times were divided in acute (96 hours) and chronic (26 days) exposures, both at 23 ± 1°C. The results obtained showed changes in the general, haematological, metabolic, osmoregulatory variables, as well as the differential white blood cell counts. These changes indicated several effects in the physiology of a mossainblais after sublethal manganese exposure. Significant differences (P < 0.05) were found between the haematological variables of the control and exposed fish. During chronic exposure, an oxygen deficiency developed due to , the epithelial lifting of gill lamellae. As a result of hypoxia the red blood cell numbers, haemoglobin-, haematocrit and lactate concentrations increased to uplift the depleted oxygen situation. The significant differences (P < 0.05) found in the sodium, potassium,. calcium and chloride concentrations are mainly as a result of gill damage. Manganese showed a disruptive influence on the structural organization of the gill. The differential white blood cell counts performed , showed significant fluctuations. This leucocytosis and leucopenia are normal reactions of the fishes’ body against infections of foreign substances, such as metal ions. It was concluded that the general haematology, metabolism, osmoregulation and differential white blood cell counts can, be used as indicators in detecting the effects of sublethal manganese exposure on fish.

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

M.Sc. (Zoology) / The world’s ever increasing human population has lead to an almost unimaginable amount of waste being released in to the aquatic environment every day. Aquatic systems are faced with the greatest risk due to the fact that water is an indispensable resource required for industrial and agricultural processes. In recent years there has been a dire need for the monitoring and rehabilitation of aquatic systems. As a result many biological monitoring programmes were set into place in an attempt to manage this problem. The use of aquatic organisms as sentinels for biomonitoring studies has been wildly accepted with the majority of biomonitoring research focusing on the use of various fish and invertebrate species as aquatic sentinel organisms. However, the use of parasites as sentinel organisms is a relatively new field and as a result there has been little published work on the use of monogenean ectoparasites parasites as such sentinels. The bioaccumulation and subsequent biomagnification of metals by certain parasite species is well known, with bulk of the published work focusing on endoparasites (cestodes, acanthocephalans & nematodes), these published studies indicate that some species of endoparasites exhibit a remarkable ability to biomagnify metals in concentrations that far exceed that of their respective hosts as well as the ambient environment. Thus this project aims to assess the bioaccumulation and biomagnification of metals by the ectoparasitic diplozoon. The study site that was chosen for this project was the Vaal Dam; this site was deemed appropriate due to its near pristine condition and major economic importance. This meant that this particular site is ideal for the testing of a new biomonitoring system. All field sampling was performed around UJ Island (26°52.249’S; 20°10.249’E) from February 2011 to April 2011. A total of 29 Labeo umbratus (Smith, 1841) were collected with the aid of gill nets and three sediment samples were also taken using a grab sampler. Water quality data was obtained from the Rand Water Analytical Facility in Vereeniging as this organisation routinely monitors of the water quality parameters and the metal concentrations within the surface waters of the Vaal Dam, this information was obtained with the aid of data loggers situated in the dam...

M.Sc. (Zoology) / The Vaal River system is constantly subjected to pollution from various industrial, mining and agricultural activities. Consequently, pressure is continually exerted on the health of its fish communities and it was suspected that this may be a contributing factor to the repeated fish kills that have occurred in various sections of the river over the past few years. The aim of this study was to assess the health status of three fish species that were affected by the most recent mass fish mortality in the Vaal River. This was done using a combination of techniques including a histology-based health assessment (HHA) that involved a standard fish necropsy, the evaluation of blood parameters as well as a microscopic assessment of the liver, kidney, gills, and gonads. The histological results were semi-quantitatively assessed. Selected chemical substances were also tested for in water, sediment and the skeletal muscle tissue of the fish. Clarias gariepinus, Labeo capensis and Labeo umbratus specimens were collected from the Vaal River, approximately 2480m below the Vaal Dam (Latitude 26°51'17.47"S; Longitude 28° 7'16.58"E) following the latest occurrence of a fish kill in November 2011. Fish were collected using gill nets. Water was sampled in triplicate at three locations, and in situ measurements were done for selected physico-chemical parameters. Sediment samples were also collected and subjected to a sequential extraction technique and quantification of the heavy metals was done using Inductively Coupled Plasma-Mass Spectroscopy (ICP-MS). Metals in skeletal muscle tissue and water were quantified using the same technique. An analysis of variance (ANOVA), followed by the appropriate post-hoc test was performed to determine differences between means of variables i.e. morphometric, histological, substance concentration and blood parameters...