The influence of light on copper‐limited growth of an oceanic diatom,Thalassiosira oceanica (Coscinodiscophyceae) |
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Authors: | Jun‐Woo Kim Neil M. Price |
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Affiliation: | 1. Department of Chemical and Biochemical Engineering, Western University, London, Ontario, Canada;2. Department of Biology, McGill University, Montréal, Québec, Canada |
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Abstract: | Thalassiosira oceanica (CCMP 1005) was grown over a range of copper concentrations at saturating and subsaturating irradiance to test the hypothesis that Cu and light were interacting essential resources. Growth was a hyperbolic function of irradiance in Cu‐replete medium (263 fmol Cu′ · L?1) with maximum rates achieved at 200 μmol photons · m?2 · s?1. Lowering the Cu concentration at this irradiance to 30.8 fmol Cu′ · L?1 decreased cellular Cu quota by 7‐fold and reduced growth rate by 50%. Copper‐deficient cells had significantly slower (P < 0.0001) rates of maximum, relative photosynthetic electron transport (rETRmax) than Cu‐sufficient cells, consistent with the role of Cu in photosynthesis in this diatom. In low‐Cu medium (30.8 fmol Cu′ · L?1), growth rate was best described as a positive, linear function of irradiance and reached the maximum value measured in Cu‐replete cells when irradiance increased to 400 μmol photons · m?2 · s?1. Thus, at high light, low‐Cu concentration was no longer limiting to growth: Cu concentration and light interacted strongly to affect growth rate of T. oceanica (P < 0.0001). Relative ETRmax and Cu quota of cells grown at low Cu also increased at 400 μmol photons · m?2 · s?1 to levels measured in Cu‐replete cells. Steady‐state uptake rates of Cu‐deficient and sufficient cells were light‐dependent, suggesting that faster growth of T. oceanica under high light and low Cu was a result of light‐stimulated Cu uptake. |
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Keywords: | copper diatom growth interaction light limitation photosynthesis quota resource |
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