An assessment of the ecological integrity of Reed Pans on the Mpumalanga Highveld
- Authors: De Klerk, Arno Reed
- Date: 2011-05-16T07:53:33Z
- Subjects: Pans (Geomorphology) , Ecological integrity , Lake ecology , Aquatic invertebrates , Water quality biological assessment , Mpumalanga (South Africa)
- Type: Thesis
- Identifier: uj:7074 , http://hdl.handle.net/10210/3637
- Description: M.Sc. , Mpumalanga, “the place where the sun rises”, sets the scene for one of the rarest wetland types in South Africa. They are formed on one of the last remnants of the ancient African land surface, contain peat and together with a variety of other pan types make up the Mpumalanga Lakes District. Of these approximately 320 pans, only ±2.3% are reed pans. These endorheic wetlands are unique from other pan types and peatlands in South Africa and support an abundant biodiversity. They perform vital functions such as water storage, filtering out impurities and carbon fixation, which prevents an excess release of CO2 into the atmosphere. There is very little known about these endorheic wetlands and thus they are constantly being threatened by various activities such as agriculture, livestock and mining. The objectives of this study were to determine the spatial and temporal variation of macroinvertebrate community structures of reed pans and the environmental factors, such as water quality, responsible for the maintenance of these structures; to determine the best method for sampling aquatic invertebrates in reed pans; as well as to determine the relationship between aquatic invertebrates and the water, sediment and habitat quality of a reed pan. Together with this the amphibian diversity as well as the occurrence of other biotic components was determined. Four reed pans were assessed during four different seasons over a one year period to account for the different hydrological extremes. Sub-surface water samples were analyzed for their suspended solid content, nutrient levels, metals and chlorophyll-a concentrations as well as in situ water quality parameters. Sediment samples were analyzed for metal concentrations, organic carbon and water content, as well as sediment size distribution. Invertebrates were collected using the following sampling techniques: aquatic light trap, terrestrial light trap, emergent trap, sweep net, plankton net, as well as benthic sampling using an Eckman grab.
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The inorganic chemistry and geochemical evolution of pans in the Mpumalanga Lakes District, South Africa
- Authors: Russell, Jennifer Lee
- Date: 2009-11-06
- Subjects: Pans (Geomorphology) , Water chemistry , Chemistry, Inorganic , Mpumalanga (South Africa)
- Type: Thesis
- Identifier: uj:8636 , http://hdl.handle.net/10210/2994
- Description: Master of Science , Despite Chrissie Lake being South Africa’s largest freshwater lake, the chemistry of this lake and the surrounding lakes and pans in the Mpumalanga Lake District has never been studied in detail. These closed systems show varying chemistry while being in very close proximity to one another, adding to the uniqueness of this area where pans, usually typical of arid regions, are found in a humid area. The factors affecting the water chemistry of these lakes needed to be identified and explained. In order to evaluate the water chemistry in this unique environment, water samples were taken at the end of the wet and dry seasons, in April and September 2007 respectively. The major pans were sampled, as were adjacent fountains or springs, indicative of the perched groundwater aquifers found in this area, as well as borehole water from the surrounding farms. Alkalinity was determined by manual titration upon returning from the field while pH and conductivity measurements were performed on site. Major cations and anions were analysed for using ICP-OES and Ion Chromatography respectively. Sediment samples were collected from the floor of each pan in the summer sampling and the mineralogy determined by X-ray diffraction (XRD). During September 2007 sampling, precipitates found on the floors and banks of the pans were also collected and analysed using XRD, to identify mineral species precipitating from solution. Results from the above analyses show that each pan in the MLD has a unique chemistry, which cannot be inferred from neighbouring pans. The inorganic chemistry differs from pan to pan as a result of these separate, closed systems being at different stages of the evaporation process. Throughout the path from groundwater to the pan, waters are subject to mineral dissolution and precipitation, adsorption and biological mechanisms, which continually add or remove solutes from solution. Although seemingly simple, there are certainly other factors that play a role in the evolution of the water chemistry. Key to the current inorganic chemistry is the balance between import and export of solutes. The groundwater, predominantly the perched aquifer water, brings solutes into the pans and blowouts of precipitates on the pan floor at the end of the dry season, when the wind is strongest, results in the export of solutes. This process is significant in maintaining the overall freshness of the pans in the MLD, contrasting to their western counter parts that evolve to highly saline saltpans. Other factors such as the periodicity of pans drying completely, the surface area to catchment area ratio (CA/SA), the formation and dissolution of efflorescent crusts and the presence or absence of reeds all have varying effects on the water chemistry of the lakes and pans. Significantly, the amount of evaporative concentration that a pan evolves through has been shown to be dependant on the CA/SA ratio with pans having larger ratios being lower in salinity compared to those with low ratios being the most saline pans. The reservoir available to the pans with the large catchment areas sustains these pans through the dry months and slows the progression of evaporation. It is clear that the factors affecting the hydrochemistry of the pan waters can not be simplified to a single process affecting a single dilute inflow of water to produce our final solution of evaporated pan water. Instead, water in the pans reflects a long-term evolution of solute species, with some memory effect remaining after each season of evaporation. The result is an accumulation of solutes as they are added continuously via dilute inflow and then removed from the waters at various times, particularly during dry periods when evaporite minerals are formed and transported out of the system.
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The present utilisation of pans on the East Rand
- Authors: Welling, Diana
- Date: 2009-01-29T12:09:49Z
- Subjects: Pans (Geomorphology) , Gauteng (South Africa)
- Type: Thesis
- Identifier: http://ujcontent.uj.ac.za8080/10210/371331 , uj:14855 , http://hdl.handle.net/10210/1977
- Description: M.A. , Pan are naturally occurring depressions or closed basins and play a very important role in ecosystems. The East Rand is characterized by more than one hundred pans dotting its landscape. The impact of urbanisation on these pans is significant. To determine exactly how the characteristics of the pans on the East Rand has changed, a comparison was done between the characteristics and utilization of the pans in 1992, as then described by Le Grange (1992) and the current situation in 2003. Water samples were also collected over a period of three months and analysed in the laboratories of Rand Water. The current utilization of the pans leaves much to be desired. Informal settlements, industries, residential areas and mine dumps are all found on the pan floors. Large waste dumping sites are developing at five out of the 19 pans in the study area. This has severely negatively affected the water quality within the pans, and the quality of bird life at thee pans. Continuous research is needed from government and private organisations on the pans found on the East Rand to improve their current quality and condition. Responsibility and proper management strategies must be implemented to protect the pans from negative human impacts.
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