M.Sc. / South Africa is a developing country in which the rapid increase in population size is accompanied by expanding mining and industrial sectors. All these factors have resulted in an increase in the demand for good quality water, but various anthropogenic activities continually result in pollution of the freshwater reserves in the country, via either diffuse or point sources. Metals resulting from both mining and industry are common pollutants of South African aquatic systems. Although some are essential elements that are necessary for normal growth and metabolism in organisms, all metals can become toxic at elevated levels, thus resulting in either lethal and sublethal effects. Aquatic organisms can also bioaccumulate metals thereby transferring them to their predators, including man. Monitoring of freshwater systems is thus necessary in order to protect the environment from these toxic substances, and ultimately to protect mankind. Most monitoring programmes should use an integrated approach in which both physico-chemical and biological aspects are monitored. The present study employed an integrated approach in order to investigate the state of metal pollution in two water bodies that are subjected to differential levels of metal contamination. Selected physico-chemical characteristics of the water and sediment were analysed, as were the levels of metals bioaccumulated by the Freshwater River crab, Potamonautes warreni. The specific object of this study was to assess the potential of P. warreni as a suitable bioaccumulative indicator of metal pollution in the aquatic environment. Water and sediment samples were collected from Germiston Lake and Potchefstroom Dam every alternate month between February 1995 and February 1996. Water quality data revealed that although the quality of the water at both sites was relatively high, Germiston Lake appeared to be more anthropogenically impacted than Potchefstroom Dam. Analysis of metal levels in the water and sediment indicated that while levels of copper, manganese, nickel, lead and zinc were higher in Germiston Lake, calcium and iron were present in higher concentrations in Potchefstroom Dam. Cadmium levels differed little between the two sites. With the exception of iron in Potchefstroom Dam, nickel in Germiston Lake, and zinc at both sites, all of the physical and chemical characteristics of the water from the two sites were within the boundaries of the South African guideline values laid down for the protection of aquatic life. Potamonautes warreni individuals were also collected every alternate month, and metal concentrations in these organisms were determined using atomic absorption spectrophotometry. The results of this investigation showed that metal levels in these organisms did tend to reflect those in the environment, with lower levels of calcium and iron and significantly higher (p < 0.05) levels of copper, manganese, lead, nickel, and zinc in P. warreni from Germiston Lake. Cadmium concentrations detected in these crabs were essentially the same at the two sites. All metals, except for cadmium, were influenced by the size of the crabs at one or other site, but never at both, thus suggesting that the presence of size-related trends is influenced by ambient metal levels in the system. Iron and lead concentrations in P. warreni from Potchefstroom Dam were the only metals that were influenced by the sex of the organisms, with higher levels found in female crabs. The results of the present study clearly indicate that metal levels in P. warreni are indicative of the environmental levels of metals to which these crabs are exposed since higher metal levels were found in the organisms from the site that had higher environmental metal levels. These organisms have proven to be useful bioaccumulative indicators of metal pollution in the aquatic environments from which they were captured, and they should therefore be incorporated into biomonitoring protocols. It must, however, be stressed that further research is required to increase our database on metal levels in these crabs from different aquatic systems.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uj/uj:9234 |
| Date | 14 August 2012 |
| Creators | Sanders, Michele Jeanette |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
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