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UBC Theses and Dissertations

Utility of a carbon-14 bioassay for detecting selenium limitation in marine phytoplankton Clifford, Peter John


A ¹⁴C primary productivity bioassay was developed to detect selenium limitation in marine phytoplankton. Addition of Na₂Se0₃ to Se-deplete cultures of Thalassiosira pseudonana stimulated carbon uptake rates by up to 40%, when uptake was expressed on a per cell volume or relative basis. Recovery from Se-starvation was verified by changes in the growth rate and morphology of T. pseudonana. Carbon uptake rates of Katodinium rotundatum, grown in nutrient enriched artificial seawater supplemented with 10⁻¹⁰ M or 10⁻⁶ M Se, were unaffected by Na₂SeO₃ additions. Since Katodinium rotundatum did not exhibit growth responses to Se additions, it was concluded that 10⁻¹⁰ M Se was sufficient for the growth of this alga, which has not displayed an obligate Se requirement. Natural phytoplankton assemblages in the Strait of Georgia were examined for Se limitation with this ¹⁴C bioassay. Relative carbon uptake rates did not change following Na₂SeO₃ addition, indicating that these assemblages were not Se-limited at the time of the study.

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