Phytoplankton production and physiological adaptation on the southeastern shelf of the Agulhas ecosystem |
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| Authors: | R Barlow T Lamont M Kyewalyanga H Sessions T Morris |
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| Institution: | 1. Marine and Coastal Management, Private Bag X2, Rogge Bay 8012, Cape Town, South Africa;2. Marine Research Institute, University of Cape Town, South Africa;3. Institute of Marine Sciences, University of Dar-es-Salaam, Zanzibar, Tanzania;4. Bayworld Centre for Research and Education, Cape Town, South Africa |
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| Abstract: | An investigation of phytoplankton production and physiology was undertaken during two research cruises on the southeastern shelf of southern Africa. The data set included photosynthesis-irradiance and active fluorescence parameters, phytoplankton absorption coefficients and HPLC pigment concentrations. Primary production was estimated to vary over a similar range for both cruises within 0.27–3.69 g C m−2 d−1. Pigment indices indicated that diatoms were dominant on the first cruise and the communities were subject to conditions where the mixed layer was deeper than the euphotic zone and they optimized their photosynthesis to very low light intensities at the bottom and below the euphotic zone. Mixed diatom-flagellate populations were observed during the second cruise where the euphotic zone was deeper than the mixed layer and the populations adapted to irradiances higher in the euphotic zone. In response to a mean lower water column PAR, it was found that these mixed communities increased the proportion of chlorophyll a in the pigment pool and had a higher quantum yield of photochemistry and higher light-limited photosynthetic efficiency. |
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| Keywords: | Phytoplankton Production Physiology Agulhas ecosystem Indian Ocean |
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