Browsing by Author "Barlow, RG"
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- ItemOpen AccessBio-optical investigation of phytoplankton production in the southern Benguela ecosystem(2011) Lamont, Tarron; Barlow, RG; Shillington, FrankThis study aims to evaluate various existing models for the estimation of PP in the southern Benguela ecosystem, and to investigate the photophysiological responses of phytoplankton to changes in environmental conditions.
- ItemOpen AccessComparative laboratory study of photoacclimation in selected dinoflagellate and diatom species of the Benguela ecosystem(2010) Balarin, Marianne G; Field, John G; Barlow, RG; Pitcher, Grant CIn their natural environment the diatoms (mixers) are exposed to fluctuations in incident irradiance due to vertical displacements in the water column induced by turbulence whereas the dinoflagellates (migrators and layer-formers) tend to control their vertical positions. In these two groups of phytoplankton physiological acclimation to these fluctuations results in the variation of a number of measurable photosynthetic parameters and variables which can be evaluated in controlled laboratory experiments. The processes can be expressed in time scales from seconds to hours e.g. carbon to chlorophyll ratio changes over several hours. Photoacclimative responses in five species of dinoflagellates (Alexandrium catenella, Protoceratium reticulatum, Prorocentrum micans, Prorocentrum triestinum, Gymnodinium zeta) and three diatom species (Chaetoceros sp., C. capense, C. cf. pendulus) were investigated with respect to parameters of P versus E curves (P*m, α* and Ek) and variability in chemical composition (C and N), photosynthetic capacity, pigment ratios, maximum quantum yield and chlorophyll to carbon ratio. These species were grown at irradiances of 33 (LL), 178 (ML) and 647 μmol quanta . m-2 . s-1 (HL) at a 12:12h day: night length at 17 ºC. The photosynthetic parameters, pigment concentration and Chl a-specific absorption were mostly affected by photoacclimational status. Species-specific differences were observed at the three different light levels in P versus E curves, pigment concentrations, absorption, carbon to chlorophyll a ratios and quantum yield. Photoprotective carotenoids (diadinoxanthin and diatoxanthin) were significantly different relative to Chl a in eight species of dinoflagellates and diatoms.
- ItemOpen AccessSpecific applications of satelite remote sensing to the Benguela ecosystem(2005) Weeks, Scarla Jeanne; Shillington, Frank; Barlow, RG; Roy, ClaudeThe objective of this thesis was to utilise high resolution satellite data, from the NOAA AVHRR and OrbView-2 SeaWiFS sensors, to investigate the upper layer dynamics of the Benguela ecosystem in more detailed space and time scales than previously undertaken. The standard for SeaWiFS bio-optical algorithms and processing parameters are not ideal for the highly productive Benguela waters. Hence, a detailed investigation was undertaken, and the processing parameters modified for more optical application to Benguela waters. Examination of the individual radiances used in the bio-optical algorithm revealed that constituents, other than chlorophyll, were at times contributing significantly to the in-water light field. The approach adopted in this thesis was that the application of satellite data to Benguela waters should be considered either as qualitative, for event scale phenomena, or quantitative, for the longterm study.