The Influence of Cobalt and Cadmium Speciation on Marine Cyanobacteria in the Costa Rica Upwelling Dome and at Station Aloha

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ABSTRACTOCE-0327225While the influence of iron on phytoplankton growth has been the subject of extensive investigations, comparatively little work has been conducted on the influence of other trace metals such as cobalt, cadmium and zinc. Building on results from culture studies indicating differences in growth rates depending on trace metal concentrations, a scientist from Woods Hole Oceanographic Institution hypothesizes that shifts in relative abundances and speciation of trace elements could influence the composition of phytoplankton assemblages. To test the hypothesis, the investigator plans to examine the influence of cobalt and cadmium speciation on Synechococcus and Crocosphaera at two sites in the Pacific Ocean. In addition, he will determine the distribution of cobalt across transects in the Eastern Equatorial Pacific to improve our understanding of the global biogeochemical cycle of cobalt. To attain these goals, the scientist will develop and calibrate a cadmium speciation method, measure cobalt and cadmium speciation on vertical profiles, analyze cyanobacterial abundances relative to cadmium and cobalt speciation, conduct physiological experiments to determine the sensitivity of nitrogen fixing cyanobacteria to cobalt and zinc limitations and cadmium toxicity, analyze functional gene expression of metalloenzymes in Synechococcus and assess changes in cell number of Crocosphaera and nitrogen fixation gene expression.