| Co-Investigator(Kenkyū-buntansha) |
HASEGAWA Hiroshi Kanazawa University, Faculty of Engineering, Associate Professor, 工学部, 助教授 (90253335)
SUZUKI Koji Hokkaido University, Graduate School of Environmental Earth Science, Associate Professor, 大学院・地球環境科学研究科, 助教授 (40283452)
OKAMURA Kei Kyoto University, Institute for the Chemical Research, Instructor, 化学研究所, 助手 (70324697)
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| Research Abstract |
1. An analytical method for the determination of trace metals in seawater has been developed on the basis of chelating adsorbent column extraction-ICP mass spectrometry. The distributions of Fe, Co, Ni, Cu, Zn, Cd, and Pb in the North Pacific have been observed. The concentration of acid-dissolvable Fe is higher than that of dissolved Fe, showing the dominance, of labile particulate Fe in seawater. Although dissolved Fe and Zn in summer surface water are depleted in the subarctic North Pacific, they are abundant in the subtropical North Pacific.
2. We have found that there was an east-west gradient in the photosynthetic, competence of phytoplankton in the subarctic North Pacific in the summer of 1999 and that the difference was probably caused by Fe levels in seawater. A dramatic floristic shift was found by pigment signatures.
3. We have participated a mesoscale Fe enrichment in the western subarctic North Pacific (SEEDS2001). The photochemical quantum efficiency of algal photosystem suggested that the phytoplankton community was suffered from Fe stress and the Fe enrichment improved the physiological condition. There was some 5 nM of labile particulate Fe in the field. It had been supplied by aeolian dust, but it was not readily available for phytoplankton. The decrease in dissolved Co, Ni, Cu, Zn, and Cd occurred during the phytoplankton bloom.
4. A sensitive analytical method has been developed using chelating ligand exchange-adsorptive cathodic stripping voltammetry, and Fe ligands derived from eukaryotic phytoplankton have been detected.
5. We have developed a technique to separate and purify RNA from phytoplankton under Fe stress. The composition change in membrane proteins of Fe-stressed phytoplankton has been observed.
6. Incubation experiments of phytoplankton have shown that the growth of phytoplankton is controlled by the species and concentrations of co-existing organic ligands.
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