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North-West University (2020)

Assessment of phytobenthos in the lower Phongolo River catchment in relation to changing environmental conditions

Kock, Anrich

Titre : Assessment of phytobenthos in the lower Phongolo River catchment in relation to changing environmental conditions

Auteur : Kock, Anrich

Université de soutenance : North-West University

Grade : Doctor of Philosophy in Science with Environmental Sciences 2020

Résumé partiel
Floodplain ecosystems are important since they provide numerous services and resources, including food, wood and water to humans. The lower Phongolo River floodplain is one such ecosystem and is the most unique and diverse floodplain in South Africa due to its biodiversity and economic value. The floodplain is located in northern KwaZulu-Natal and stretches from the Pongolapoort Dam to the confluence between the Phongolo and Usuthu rivers in the Ndumo Game Reserve (NGR). The Pongolapoort Dam was constructed with the aim to supply nearby towns with water as well as provide irrigation water for sugarcane and cotton plantations. Controlled flood releases were implemented from the dam to ensure that the ecosystem infrastructure is maintained, but there have been no flood releases since December 2014 due to an ongoing drought in the area. The NGR is the only protected section in the floodplain area and is a Ramsar wetland of international importance due to its high biodiversity and unique wetlands. The lower Phongolo River floodplain is at risk due to increasing human population pressure (extensive fishing, irrigation schemes, water abstraction and agriculture) and spraying of DDT in the floodplain area for mosquito vector control. Only a few studies have focussed on the phytobenthos of South Africa’s floodplain ecosystems, with no published work on the diatom community of the lower Phongolo River floodplain. There are various advantages for including diatoms in ecological and ecotoxicology studies as they have a relatively short life span, are sensitive to any changes within their environment, are species rich, can colonise almost all substrata, are found in nearly all aquatic habitats, are primary producers in all aquatic ecosystems and can be preserved for many centuries in sediment due to their siliceous cell wall. The main aim of this study was to increase our knowledge on the spatial and temporal diatom community structures of the lower Phongolo River floodplain. Ecological and ecotoxicological studies were carried out to assess the i

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