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University of Johannesburg (2018)

An assessment of the aquatic macroinvertebrate diversity within the Nyl River Floodplain system, Limpopo, South Africa

Baker, Nathan Jay

Titre : An assessment of the aquatic macroinvertebrate diversity within the Nyl River Floodplain system, Limpopo, South Africa

Auteur : Baker, Nathan Jay

Université de soutenance : University of Johannesburg

Grade : Magister Scientiae in Aquatic Health 2018

Résumé
South Africa is a water scarce country with uneven distributions of rainfall both spatially and temporally. With the proposed pressures of climate change, it has been foreseen that within the coming decades, water availability may become a limiting factor for further development in South Africa. Regardless of the usable conversion rate of catchment runoff to riverine surface water flow, most of South Africa’s surface water resources are provided by rivers. Due to over exploitation, anthropogenic influences and mismanagement, all river systems within South Africa are impacted to some extent. Due to a lack of knowledge regarding much of the biota supported by freshwater systems, specifically in semi-arid countries such as South Africa, it is of utmost importance to study freshwater ecosystems to determine the full extent of the biodiversity supported by such systems and how this biodiversity may become affected through anthropogenic impacts and its use as ecological indicators. Macroinvertebrate taxa form much of the global freshwater biodiversity and due to their wide taxonomic diversity, they show adaptations to extremely variable environments, ubiquitous distributions and varying sensitivities to stressors. Therefore, macroinvertebrate taxa are readily used as bioindicator test organisms for many biomonitoring and management studies. The Nyl and Mogalakwena Rivers are important water sources for the semi-arid Limpopo Province and despite this, they are continually being stressed through increased urbanisation, industrial and mining development as well as intensive agricultural activities. The Nyl River flows through and provides water for the towns of Modimolle (population of >68 513), Mookgophong (population of >35 640) and Mokopane (population of >30 151). The Nyl River provides water resources for the internationally acclaimed Nyl River Floodplain including the RAMSAR accredited Nylsvley Wetland, a recognised biodiversity hot spot. Notwithstanding its importance to aquatic fauna and flora, the Nylsvley Wetland provides suitable habitat and breeding grounds to over 400 avian species, the endangered Roan antelope Hippotragus equinus (É. Geoffroy Saint-Hilaire, 1803) and South Africa’s only wild rice Oryza longistaminata A. Chev. & Roehrich. The wetland also aids in flow attenuation, water retention and water purification during periods of flooding and drought. After the floodplain, the name of the river changes to the Mogalakwena River which becomes an important source of water for many large- and small-scale agricultural and industrial activities established within the Mogalakwena municipality. The Mogalakwena River then flows downstream into the transboundary Limpopo River...

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