Scales of variability of phytoplankton composition and biomass in Algoa Bay, South Africa

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dc.contributor.advisorMoloney, Coleenen_ZA
dc.contributor.advisorPitcher, Grant Cen_ZA
dc.contributor.advisorJackson, Sueen_ZA
dc.contributor.authorMbambo, Sifiso Walteren_ZA
dc.date.accessioned2014-11-05T03:56:09Z
dc.date.available2014-11-05T03:56:09Z
dc.date.issued2014en_ZA
dc.descriptionIncludes bibliographical referencesen_ZA
dc.description.abstractThis study investigated the variability of environmental drivers of phytoplankton communities and biomass at different time scales in Algoa Bay. This research was motivated by Pacific oyster culturing at an Algoa Bay oyster farm. Time series of winds, sea surface temperatures (SSTs) and fluorescence were presented for the period from September/October 2010 to May/June 2012. The time series showed strong seasonal and interannual variability in the winds and SSTs. SSTs ranged from 12.5–25.5°C with a mean (±S.D.) of 18.4 ± 2.3°C. The dominance of south-easterly and south-westerly winds in summer of 2010/11 resulted in cooler temperatures and higher chlorophyll-a concentrations than were found in 2011/12. The summer of 2011/12 had non-persistent south-westerly winds that lead to warm temperatures and low chlorophyll-a concentrations. Two short field trips in early summer 2011 and early autumn 2012 sampled physical, chemical and biological variables. There was minor variability in the winds during these sampling periods and little spatial variability in SST. However, there were spatial differences in nutrient concentrations and chlorophyll-a distributions. The sampling trip in early summer 2011 found a strong thermocline at a depth of approximately 15 m, and SST ranged between 13.5 and 21°C. In early autumn 2012, deep water mixing was evident when the thermocline dropped to about 30 m, with a range of SSTs from 16.5–21°C. Temperature and nutrient values were significantly correlated (at p < 0.001) for NO3, PO4, and SiO4 in both field trips. Phytoplankton community structure in early summer 2011 showed a 30% level of similarity in grouping of species for stations closest to the shore, which had depleted NO3 concentrations. There was a dominance of dinoflagellates of Gonyaulax polygramma and other species, which are known for creating hypoxic conditions in the water column, leading to shellfish mortalities. In early autumn 2012 there was a strong grouping of samples at a 50% level of similarity alongshore, at stations with high NO3 concentrations. In this period pennate diatoms of Pseudo-nitzschia sp. were abundant; this genus has been reported to produce the neurotoxin, domoic acid. Variable environmental conditions with low chlorophyll-a concentrations at Algoa Bay’s marine culture site indicate unsuitable conditions for Pacific oyster production.en_ZA
dc.identifier.apacitationMbambo, S. W. (2014). <i>Scales of variability of phytoplankton composition and biomass in Algoa Bay, South Africa</i>. (Thesis). University of Cape Town ,Faculty of Science ,Department of Biological Sciences. Retrieved from http://hdl.handle.net/11427/9193en_ZA
dc.identifier.chicagocitationMbambo, Sifiso Walter. <i>"Scales of variability of phytoplankton composition and biomass in Algoa Bay, South Africa."</i> Thesis., University of Cape Town ,Faculty of Science ,Department of Biological Sciences, 2014. http://hdl.handle.net/11427/9193en_ZA
dc.identifier.citationMbambo, S. 2014. Scales of variability of phytoplankton composition and biomass in Algoa Bay, South Africa. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Mbambo, Sifiso Walter AB - This study investigated the variability of environmental drivers of phytoplankton communities and biomass at different time scales in Algoa Bay. This research was motivated by Pacific oyster culturing at an Algoa Bay oyster farm. Time series of winds, sea surface temperatures (SSTs) and fluorescence were presented for the period from September/October 2010 to May/June 2012. The time series showed strong seasonal and interannual variability in the winds and SSTs. SSTs ranged from 12.5–25.5°C with a mean (±S.D.) of 18.4 ± 2.3°C. The dominance of south-easterly and south-westerly winds in summer of 2010/11 resulted in cooler temperatures and higher chlorophyll-a concentrations than were found in 2011/12. The summer of 2011/12 had non-persistent south-westerly winds that lead to warm temperatures and low chlorophyll-a concentrations. Two short field trips in early summer 2011 and early autumn 2012 sampled physical, chemical and biological variables. There was minor variability in the winds during these sampling periods and little spatial variability in SST. However, there were spatial differences in nutrient concentrations and chlorophyll-a distributions. The sampling trip in early summer 2011 found a strong thermocline at a depth of approximately 15 m, and SST ranged between 13.5 and 21°C. In early autumn 2012, deep water mixing was evident when the thermocline dropped to about 30 m, with a range of SSTs from 16.5–21°C. Temperature and nutrient values were significantly correlated (at p < 0.001) for NO3, PO4, and SiO4 in both field trips. Phytoplankton community structure in early summer 2011 showed a 30% level of similarity in grouping of species for stations closest to the shore, which had depleted NO3 concentrations. There was a dominance of dinoflagellates of Gonyaulax polygramma and other species, which are known for creating hypoxic conditions in the water column, leading to shellfish mortalities. In early autumn 2012 there was a strong grouping of samples at a 50% level of similarity alongshore, at stations with high NO3 concentrations. In this period pennate diatoms of Pseudo-nitzschia sp. were abundant; this genus has been reported to produce the neurotoxin, domoic acid. Variable environmental conditions with low chlorophyll-a concentrations at Algoa Bay’s marine culture site indicate unsuitable conditions for Pacific oyster production. DA - 2014 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 2014 T1 - Scales of variability of phytoplankton composition and biomass in Algoa Bay, South Africa TI - Scales of variability of phytoplankton composition and biomass in Algoa Bay, South Africa UR - http://hdl.handle.net/11427/9193 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/9193
dc.identifier.vancouvercitationMbambo SW. Scales of variability of phytoplankton composition and biomass in Algoa Bay, South Africa. [Thesis]. University of Cape Town ,Faculty of Science ,Department of Biological Sciences, 2014 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/9193en_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.titleScales of variability of phytoplankton composition and biomass in Algoa Bay, South Africaen_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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