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

 

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dc.contributor.advisor Blamey, Laura K en_ZA
dc.contributor.author Morris, Kathryn en_ZA
dc.date.accessioned 2017-09-06T07:08:50Z
dc.date.available 2017-09-06T07:08:50Z
dc.date.issued 2017 en_ZA
dc.identifier.citation Morris, 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.uri http://hdl.handle.net/11427/25072
dc.description.abstract 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. en_ZA
dc.language.iso eng en_ZA
dc.subject.other Biological Sciences en_ZA
dc.title Kelp forests in False Bay: urchins vs. macroalgae in South Africa's south-west coast biogeographical transition zone en_ZA
dc.type Thesis / Dissertation en_ZA
uct.type.publication Research en_ZA
uct.type.resource Thesis en_ZA
dc.publisher.institution University of Cape Town
dc.publisher.faculty Faculty of Science en_ZA
dc.publisher.department Department of Biological Sciences en_ZA
dc.type.qualificationlevel Masters en_ZA
dc.type.qualificationname MSc en_ZA
uct.type.filetype Text
uct.type.filetype Image


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