Kelp forests in False Bay: urchins vs. macroalgae in South Africa's south-west coast biogeographical transition zone

dc.contributor.advisorBlamey, Laura Ken_ZA
dc.contributor.authorMorris, Kathrynen_ZA
dc.date.accessioned2017-09-06T07:08:50Z
dc.date.available2017-09-06T07:08:50Z
dc.date.issued2017en_ZA
dc.description.abstractThere is ongoing global concern over unwanted regime shifts in marine systems. Shifts from diverse and productive algal-dominated ecosystems to less productive urchin and coralline-dominated temperate reefs are becoming increasingly common. Kelp forests found along South Africa's south-west coast between Cape Point and Cape Agulhas occur in a region of biogeographical overlap. They are commonly referred to as transition zone kelp forests and are dynamic ecosystems that are particularly susceptible to grazing influence from species such as sea urchins. This study (1) explores the uniformity of these transition zone kelp forests along the western side of False Bay, with a focus on macroalgae and urchins, (2) identifies a threshold in urchin density above which algal abundance declines and (3) seeks to identify relationships between attached and drift algal abundance. Twenty replicate quadrats were sampled in six kelp forests along the western side of False Bay. Within each quadrat, urchins (Parechinus angulosus) and kelps (Ecklonia maxima) were counted, percentage covers of various understorey algal species were recorded and drift algae were collected. Although there was significant variability in algal and urchin cover across the six sites, kelps generally increased from north to south, while urchins did the opposite. Urchins were negatively correlated with algal communities, and a localised threshold of 1.43kg/m² (50 urchins/m²) was identified, above which attached kelp density failed to increase above 10/m² and percentage cover of understorey algae usually remained below 20%. Surprisingly, no relationship was discovered between abundance of drift kelp and attached kelp, understorey algae or urchin density. This result was likely distorted by the naturally turbulent conditions of South African waters. Results highlight the complexity of these cool-water environments. To better understand the role of urchins in this system, experimental research into the feeding behaviour and effect of P. angulosus on kelps and understorey seaweeds in the presence/absence of drift algae is advised.en_ZA
dc.identifier.apacitationMorris, K. (2017). <i>Kelp forests in False Bay: urchins vs. macroalgae in South Africa's south-west coast biogeographical transition zone</i>. (Thesis). University of Cape Town ,Faculty of Science ,Department of Biological Sciences. Retrieved from http://hdl.handle.net/11427/25072en_ZA
dc.identifier.chicagocitationMorris, Kathryn. <i>"Kelp forests in False Bay: urchins vs. macroalgae in South Africa's south-west coast biogeographical transition zone."</i> Thesis., University of Cape Town ,Faculty of Science ,Department of Biological Sciences, 2017. http://hdl.handle.net/11427/25072en_ZA
dc.identifier.citationMorris, K. 2017. Kelp forests in False Bay: urchins vs. macroalgae in South Africa's south-west coast biogeographical transition zone. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Morris, Kathryn AB - There is ongoing global concern over unwanted regime shifts in marine systems. Shifts from diverse and productive algal-dominated ecosystems to less productive urchin and coralline-dominated temperate reefs are becoming increasingly common. Kelp forests found along South Africa's south-west coast between Cape Point and Cape Agulhas occur in a region of biogeographical overlap. They are commonly referred to as transition zone kelp forests and are dynamic ecosystems that are particularly susceptible to grazing influence from species such as sea urchins. This study (1) explores the uniformity of these transition zone kelp forests along the western side of False Bay, with a focus on macroalgae and urchins, (2) identifies a threshold in urchin density above which algal abundance declines and (3) seeks to identify relationships between attached and drift algal abundance. Twenty replicate quadrats were sampled in six kelp forests along the western side of False Bay. Within each quadrat, urchins (Parechinus angulosus) and kelps (Ecklonia maxima) were counted, percentage covers of various understorey algal species were recorded and drift algae were collected. Although there was significant variability in algal and urchin cover across the six sites, kelps generally increased from north to south, while urchins did the opposite. Urchins were negatively correlated with algal communities, and a localised threshold of 1.43kg/m² (50 urchins/m²) was identified, above which attached kelp density failed to increase above 10/m² and percentage cover of understorey algae usually remained below 20%. Surprisingly, no relationship was discovered between abundance of drift kelp and attached kelp, understorey algae or urchin density. This result was likely distorted by the naturally turbulent conditions of South African waters. Results highlight the complexity of these cool-water environments. To better understand the role of urchins in this system, experimental research into the feeding behaviour and effect of P. angulosus on kelps and understorey seaweeds in the presence/absence of drift algae is advised. DA - 2017 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 2017 T1 - Kelp forests in False Bay: urchins vs. macroalgae in South Africa's south-west coast biogeographical transition zone TI - Kelp forests in False Bay: urchins vs. macroalgae in South Africa's south-west coast biogeographical transition zone UR - http://hdl.handle.net/11427/25072 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/25072
dc.identifier.vancouvercitationMorris K. Kelp forests in False Bay: urchins vs. macroalgae in South Africa's south-west coast biogeographical transition zone. [Thesis]. University of Cape Town ,Faculty of Science ,Department of Biological Sciences, 2017 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/25072en_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.otherBiological Sciencesen_ZA
dc.titleKelp forests in False Bay: urchins vs. macroalgae in South Africa's south-west coast biogeographical transition zoneen_ZA
dc.typeMaster Thesis
dc.type.qualificationlevelMasters
dc.type.qualificationnameMScen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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