Disturbance and temporal variability in invertebrate assemblages in two South African rivers

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dc.contributor.advisorKing, J Men_ZA
dc.contributor.advisorField, John Gen_ZA
dc.contributor.authorRactliffe, Sylvia Georgianaen_ZA
dc.date.accessioned2015-02-17T13:06:11Z
dc.date.available2015-02-17T13:06:11Z
dc.date.issued2009en_ZA
dc.descriptionIncludes abstract.en_ZA
dc.description.abstractThis thesis presents an examination of the relationship between floods as disturbances, the disturbance regime and the temporal dynamics of invertebrate assemblages, over the short term and at intra- and inter-annual time scales in the Molenaars and Berg Rivers in the Western Cape of South Africa. Invertebrate responses to individual floods were investigated by a field study that links the displacement of river-bed stones by a flood to change in invertebrate densities and community and population structure from before to after flood events. The magnitude of the hydraulic force acting on each marked stone during the peak of each flood was also calculated, providing a second measure of physical disturbance. Multivariate analyses of similarity, hierarchical clustering and multidimensional scaling were used for analysis of invertebrate patterns before and after floods. Size frequency data for 28 species or genera were analysed to explore changes in population structure over the flood season. Flood records were developed from the daily discharge hydrological record of both study rivers collected by the South African Department of Water Affairs and Forestry. Flood frequency analysis and descriptive statistics were combined with graphical methods to describe the flood regime and to test flood predictability in these rivers. Quantitative monthly samples of invertebrates from the Molenaars River collected over 17 months were used together with a further 2 ½ years of semi-quantitative monthly data, to identify intra- and inter-annual patterns in communities. Multivariate analysis of community patterns was combined with a range of indices that reflect community persistence and stability over periods longer than one generation. Population dynamics of the common species were also studied. Life history attributes, specifically seasonality of life cycle stages and generation time, were explored using size frequency data from the samples.en_ZA
dc.identifier.apacitationRactliffe, S. G. (2009). <i>Disturbance and temporal variability in invertebrate assemblages in two South African rivers</i>. (Thesis). University of Cape Town ,Faculty of Science ,Department of Biological Sciences. Retrieved from http://hdl.handle.net/11427/12522en_ZA
dc.identifier.chicagocitationRactliffe, Sylvia Georgiana. <i>"Disturbance and temporal variability in invertebrate assemblages in two South African rivers."</i> Thesis., University of Cape Town ,Faculty of Science ,Department of Biological Sciences, 2009. http://hdl.handle.net/11427/12522en_ZA
dc.identifier.citationRactliffe, S. 2009. Disturbance and temporal variability in invertebrate assemblages in two South African rivers. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Ractliffe, Sylvia Georgiana AB - This thesis presents an examination of the relationship between floods as disturbances, the disturbance regime and the temporal dynamics of invertebrate assemblages, over the short term and at intra- and inter-annual time scales in the Molenaars and Berg Rivers in the Western Cape of South Africa. Invertebrate responses to individual floods were investigated by a field study that links the displacement of river-bed stones by a flood to change in invertebrate densities and community and population structure from before to after flood events. The magnitude of the hydraulic force acting on each marked stone during the peak of each flood was also calculated, providing a second measure of physical disturbance. Multivariate analyses of similarity, hierarchical clustering and multidimensional scaling were used for analysis of invertebrate patterns before and after floods. Size frequency data for 28 species or genera were analysed to explore changes in population structure over the flood season. Flood records were developed from the daily discharge hydrological record of both study rivers collected by the South African Department of Water Affairs and Forestry. Flood frequency analysis and descriptive statistics were combined with graphical methods to describe the flood regime and to test flood predictability in these rivers. Quantitative monthly samples of invertebrates from the Molenaars River collected over 17 months were used together with a further 2 ½ years of semi-quantitative monthly data, to identify intra- and inter-annual patterns in communities. Multivariate analysis of community patterns was combined with a range of indices that reflect community persistence and stability over periods longer than one generation. Population dynamics of the common species were also studied. Life history attributes, specifically seasonality of life cycle stages and generation time, were explored using size frequency data from the samples. DA - 2009 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 2009 T1 - Disturbance and temporal variability in invertebrate assemblages in two South African rivers TI - Disturbance and temporal variability in invertebrate assemblages in two South African rivers UR - http://hdl.handle.net/11427/12522 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/12522
dc.identifier.vancouvercitationRactliffe SG. Disturbance and temporal variability in invertebrate assemblages in two South African rivers. [Thesis]. University of Cape Town ,Faculty of Science ,Department of Biological Sciences, 2009 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/12522en_ZA
dc.language.isoengen_ZA
dc.publisher.departmentDepartment of Biological Sciencesen_ZA
dc.publisher.facultyFaculty of Scienceen_ZA
dc.publisher.institutionUniversity of Cape Town
dc.subject.otherZoologyen_ZA
dc.titleDisturbance and temporal variability in invertebrate assemblages in two South African riversen_ZA
dc.typeDoctoral Thesis
dc.type.qualificationlevelDoctoral
dc.type.qualificationnamePhDen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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