Importance of intracellular Fe pools on growth of marine diatoms by using unialgal cultures and on the Oyashio region phytoplankton community during spring |
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| Authors: | Koji Sugie Kenshi Kuma Satoshi Fujita Satomi Ushizaka Koji Suzuki Tsutomu Ikeda |
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| Institution: | (1) Graduate School of Environmental Science, Hokkaido University, North 10 West 5 Kita-ku, Sapporo Hokkaido, 060-0810, Japan;(2) Present address: Central Research Institute of Electric Power Industry, 1646 Abiko, Abiko Chiba, 270-1194, Japan;(3) Faculty of Fisheries Sciences, Hokkaido University, 3-1-1 Minato-cho, Hakodate Hokkaido, 041-8611, Japan;(4) Faculty of Environmental Earth Science, Hokkaido University, North 10 West 5 Kita-ku, Sapporo Hokkaido, 060-0810, Japan |
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| Abstract: | We report on the ability for luxury Fe uptake and the potential for growth utilizing intracellular Fe pools for 4 coastal
centric diatom isolates and in situ phytoplankton assemblages, mainly composed of diatoms. Iron uptake of the diatom isolates
and natural phytoplankton assemblages in the Oyashio region during spring blooms were prevented by adding hydroxamate siderophore
desferrioxamine B (DFB). After the addition of DFB, intracellular Fe in the diatom isolates supported 2.4–4.2 cell divisions
with 1.2–2.6 Chl a doublings. The intracellular Fe was primarily used for cell generation rather than Chl a production, leading to a reduction in the Chl a cell quota in the Fe-starved cells with time. The metabolic properties of the Fe-starved cells with their cell morphologies
were different among species or genera. An on-deck incubation experiment also exhibited 1.9 cell divisions and 0.81 Chl a doublings of phytoplankton after the addition of DFB, also indicating the preference of cell generation over Chl a production. A decrease in the level of cellular Chl a, a main light-harvesting pigment in Fe-starved diatoms, may become a superior survival strategy to protect the cells from
high irradiance that can cause photo-oxidative damages through photosynthesis. Such relatively low-Fe with high-light conditions
could often occur in surface waters of the Oyashio region from spring to summer. |
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