Show simple item record

dc.contributor.advisorVan As, J. G.
dc.contributor.advisorVan As, L. L.
dc.contributor.advisorTaylor, J. C.
dc.contributor.authorOtto, Mia
dc.date.accessioned2018-07-31T08:42:53Z
dc.date.available2018-07-31T08:42:53Z
dc.date.issued2018-04
dc.identifier.urihttp://hdl.handle.net/11660/9046
dc.description.abstractEnglish: This study sought to assess diatom community composition across ecological gradients on selected rivers in the Eastern and Western Cape Provinces, South Africa, as well as in the lowland section of the Okavango River. For South Africa data were collected over a one-year period with three-monthly or seasonal sampling conducted between spring 2014 and winter 2015. Five to ten cobbles were scrubbed and diatoms fixed with 70% ethanol to produce an end product of >20% alcohol content. In Botswana samples were collected during July and August 2014. A phytoplankton net with a mesh size of 25 m and introduced substrate were sampled in the panhandle, Nxamaseri Floodplain and the Thamalakane River. The Hot HCl method was used to clean samples of organic material. Permanent slides were made using Pleurax as mounting agent. All information was added to the National Diatom Collection since one of the main objectives of this study was to fill the current information gap on these regions. A minimum of 400 individuals was identified per slide to produce a community composition. Multivariate statistics showed that diatom communities responded geospatially more strongly than seasonally. In South Africa the diatom communities responded at an Ecoregion Level 1. At Ecoregion Level II, catchment signatures were not strictly followed as would have been expected. Instead more localised impacts and natural fluctuations in physico-chemical changes were found to drive group formation. The influence of flow modification, such as the inter-basin transfer schemes in the Drought Corridor ecoregion, was indicated in diatom community composition. While diatoms are extremely useful as small-scale impact specific indicators and assessment tools, the results produced in this study showed that the use of diatom information for larger scale climate change impact monitoring initiatives towards sustainable freshwater resource management in future, remains untapped. Further research on the relationship between diatom community composition and more detailed environmental drivers of landscape scale ecosystem changes would greatly improve our understanding of the role diatoms play in the resilience of natural freshwater ecosystems to large-scale changes and impacts. The diatom data proved to be very robust and reliable in this study, suggesting that there exists a great resilience at the base of the food web in the highly volatile and dynamic African freshwater ecosystems. Properly functioning diatom communities could be a more important component of ecosystem resilience than currently recognised. This study also found that the exclusion of certain low abundance diatom information does not contribute to a more accurate result but instead removes valuable biodiversity information in a time when it should be promoted, protected and well documented. It is clear that in a country expected to experience severe and direct climate change induced impacts, the exclusion of diatoms when managing freshwater sustainability and continued optimal ecosystem functioning for the delivery of associated good and services, is rather reckless. This study has provided the foundation of updated diatom information for a majority of the major rivers in the Eastern Cape in particular and some of the smaller coastal rivers in the Western Cape. This method should be applied in other regions of the country to produce diatom reference conditions, which speak directly to Ecological Reserve scale approaches in order to contribute to a more holistic approach to ecosystem management in future. In Botswana a significant difference between the community compositions of the Thamalakane River, Nxamaseri Floodplain and the Okavango Panhandle was found to be present. These differences are suspected to be caused by micro-environments with differences in nutrient load and associated water quality. These micro-habitats allowed for some species, that are more tolerant to higher nutrient loads, to be found but did not interfere with the larger scale diatom community composition in a specific geographic region. The difference between diatom communities in the panhandle and other areas in the system highlights the importance of upstream conservation in the Okavango River for continued optimal ecological functioning of the downstream Okavango Delta and its associated systems. Diatoms are able to make a considerable contribution to our current understanding of freshwater resource functioning and the consequent conservation, monitoring and management of sustainable water security for all.en_ZA
dc.description.abstractAfrikaans: Hierdie studie was daarop gemik om die samestelling van diatoom gemeenskappe oor ekologiese gradiënte van geselekteerde riviere in die Oos- en Wes-Kaap Provinsies, Suid-Afrika, asook die laagliggende gedeelte van die Okavango Rivier te assesseer. Die data is oor 'n tydperk van een jaar versamel met drie-maandelikse of seisoenale steekproefnemings wat tussen lente 2014 en winter 2015 uitgevoer is. Vyf tot tien klippe is geskrop en diatome is met 70% etanol gefiskeer om 'n eindproduk van minstens 20% te lewer. In Botswana is data versamel gedurende Julie en Augustus van 2014. ‘n Plankton net met n deurlatings ruimte van 25 m en kunsmatige substraat is gebruik om monsters mee te versamel in die Okavango Panhandle, Nxamaseri Vloedvlakte en die Thamalakane Rivier. Die Warm HCl-metode is gebruik om organiese materiaal in monsters te verwyder. Permanente mikroskoop-skyfies is gemaak deur van Pleurax gebruik te maak as monteermiddel. Alle inligting is by die Nasionale Diatoom Versameling gevoeg aangesien een van die hoof doelstellings van hierdie studie was om die huidige inligtingsgaping oor hierdie areas te vul. ‘n Minimum van 400 individue is per skyfie geïdentifiseer om die gemeenskapsamestelling te gee. Meerveranderlike statistiese analise het getoon dat diatoom gemeenskappe in Suid Afrika eerder op ‘n Ekostreek Vlak I reageer as wat hulle seisoenaal differensieer. In teenstelling met wat verwag is het gemeeskappe op Ekostreek Vlak II is geen opvangsgebied uniekheid geopenbaar nie. In plaas daarvan is gevind dat gelokaliseerde impakte en natuurlike fluktuasies in fisies-chemiese veranderinge groepvorming bestuur. Die invloed van interbekken-waterverplasings skemas op natuurlike vloeipatrone, soos gesien is met die monsters in the Droogte Gang ekostreek was sigbaar in die diatoom gemeenskaps samestelling. Hierdie studie het daarin geslaag om diatoom gemeenskappe met Ekostreek Vlak I verbind. Gevolglik kon die studie ‘n verwysingsvoorwaarde beskrywing vir beide Vlak I en II lewer. Terwyl diatome uiters nuttig is as kleinskaalse impakspesifieke aanwysers en assesseringsinstrumente, het die resultate in hierdie studie getoon dat die gebruik van diatoom inligting vir die monitering van grootskaalse klimaatsverandering en volhoubare bestuur van varswaterhulpbronne tans grootliks onbenut bly. Verdere navorsing oor die verhouding tussen die samestelling van diatoom gemeenskappe en meer spesifieke besonderhede rakende omgewingsfaktore sal ons begrip rondom die rol van diatome in veerkragtigheid van varswater-ekosisteme baie kan bevorder. Die data was baie robuust en betroubaar in hierdie studie, wat daarop dui dat daar 'n goeie veerkragtigheid aan die basis van die voedselweb tans bestaan. Selfs met natuurlike versteurings in Afrika se hoogs dinamiese varswater-ekosisteme. Behoorlik funksionerende diatoom gemeenskappe kan 'n belangriker komponent van varswater-ekosisteem veerkragtigheid wees as wat tans bekend is of erken word. Hierdie studie het ook bevind dat die uitsluiting van sekere laer digtheid diatoom inligting nie bydra tot 'n meer akkurate resultaat nie, maar eerder waardevolle inligting oor biodiversiteit verwyder. Suider Afrika gaan in die nabye toekoms al ernstiger en meer direkte klimaatsverandering-geïnduseerde impakte ervaar. Dit is daarom taamlik roekeloos om diatoom inligting uit varswater volhoubaarheids waarnemings te laat. Hierdie studie het die grondslag gegee vir volgehoue opdatering van diatoom inligting op verkeie riviere in die Oos- en Wes-Kaap Provinsies. Hierdie metode moet in ander streke van die land ook toegepas word sodat diatoom verwysingsvoorwaardes produseer kan word vir ander Ekostreek Vlak I en II gebiede. Sodoende kan verseker word dat diatoom inligting ingesluit word by Ekologiese Reserwe studies en in die toekoms kan bydra tot 'n meer holistiese benadering tot varswater ekostelselbestuur. In Botswana is daar gevind dat n noemenswaardige verskil in gemeenskaps samestelling bestaan tussen the Thamalakane Rivier, Nxamaseri Vloedvlakte en die Okavango Panhandle. Die verskil word toegeskryf aan die teenwoordigheid van mikro-habitats wat ‘n verskil in nutrient lading het en dus ‘n invloed om die lokale water kwaliteit het. Hierdie mikro-habits bevorder tollerante spesies wat bestand en aangepas is teen die hoër nutrient lading. Ondanks hierdie kleinskaalse veranderinge in gemeeskaps samestelling was daar nie ‘n invloed op die groterskaalse ekostreeks vlak groepering nie. ‘n Duidelike verskil tussen die verskillende streke van die Okavango Rivier en geassosieerde stelses kon nogtans waargeneem word. Hierdie geografiese stratifikasie beklemtoon die belangrike rol wat die stroom-op ekostelsel speel in die laer gedeeltes van die Okavango Rivier, veral die delta wat ‘n bewarings area van internationale belang is. Diatome kan 'n aansienlike bydrae lewer tot ons huidige begrip van varswaterhulpbron funksionering, handhawing van ekosisteem integriteit en die gevolglike bio-assessering, monitering en bestuur van volhoubare watersekuriteit vir almal.en_ZA
dc.description.sponsorshipNational Research Foundation (NRF)en_ZA
dc.language.isoenen_ZA
dc.publisherUniversity of the Free Stateen_ZA
dc.subjectEcological geneticsen_ZA
dc.subjectPopulation geneticsen_ZA
dc.subjectDiatomen_ZA
dc.subjectThamalakane Riveren_ZA
dc.subjectCommunity compositionsen_ZA
dc.subjectThesis (Ph.D. (Zoology and Entomology))--University of the Free State, 2018en_ZA
dc.titleDiatom community composition and ecological gradients on selected rivers in the Eastern and Western Cape, South Africaen_ZA
dc.typeThesisen_ZA
dc.rights.holderUniversity of the Free Stateen_ZA


Files in this item

Thumbnail

This item appears in the following Collection(s)

Show simple item record