Nutrient and diatom dynamics during late winter and spring in the Oyashio region of the western subarctic Pacific Ocean
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概要
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We investigated the nutrient and diatom dynamics during late winter and spring (9-March to 1-May 2007) in the Oyashio region as part of the OECOS-WEST research cruises. Macronutrients, iron, chlorophyll a (Chl-a) and biogenic silica (BSi) concentrations in the upper mixed layer varied remarkably ranges were 1.88-18.8 μmol L^[-1] for NO3+NO2, 0.64-1.85 μmol L^[-1] for PO4, 3.14-35.7 μmol L^[-1] for Si(OH)4, 0.14-0.54 nmol L^[-1] for D-Fe, 0.64-24.6 nmol L^[-1] for T-Fe, 0.30-17.4 μg L^[-1] for Chl-a, and 0.34-14.1 μmol L^[-1] for BSi. Mixed layer depth (MLD) also varied from 8-190 m during the cruises. The growth rate of in situ phytoplankton communities, dominated by centric diatoms, varied in shipboard culture experiments from 0.55 d^[-1] for iron-replete to 0.14 d^[-1] for iron-limited conditions. A relationship between BSi and Chl-a concentrations indicates that the in situ diatom community in the warmer water system (>4℃) was heavily silicified, probably due to iron-limitation. The in situ macronutrient and dissolved iron concentrations below the MLD and estimated macronutrient concentrations during winter were negatively correlated to temperature (1-6℃), that is to the relative proportion of warm modified Kuroshio Water mixed into the colder Oyashio water system. The rate of decrease in Si(OH)4 per ℃ increase was greater than the rates for NO3+NO2 and PO4 for both in situ and estimated winter values. These results suggest that the spring bloom in the cold water system with high macronutrients and iron concentrations would progress rapidly and intensely, and then be terminated by nitrogenous nutrient depletion. However, the diatom bloom in warmer waters with lower macronutrients and iron concentrations would be terminated by Si- and/or iron-limitation of heavily-silicified diatoms. In the OECOS study, variation of macronutrients and iron due to the surface intrusions of several water masses and modification from different chemical conditions during winter were the most important factors regulating the progression, magnitude and probably fate of the spring phytoplankton bloom in the Oyashio region.
- Elsevierの論文
著者
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Kuma Kenshi
Faculty Of Fisheries Sciences Hokkaido University
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Ikeda Tsutomu
Hokkaido Univ. Hokkaido Jpn
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Ikeda Tsutomu
Faculty Of Fisheries Sciences Hokkaido University
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Fujita Satoshi
Graduate School Of Environmental Science Hokkaido University
関連論文
- Temporal variability and bioavailability of iron and other nutrients during the spring phytoplankton bloom in the Oyashio region
- Preface
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- Comparing the vertical distribution of iron in the eastern and western North Pacific Ocean
- Iron distributions in the water column of the Japan Basin and Yamato Basin (Japan Sea)
- Abundance, vertical distribution and life cycle patterns of the hydromedusa Aglantha digitale in the Oyashio region, western subarctic Pacific
- Importance of intracellular Fe pools on growth of marine diatoms by using unialgal cultures and on the Oyashio region phytoplankton community during spring
- Effects of Mn and Fe on growth of a coastal marine diatom Talassiosira weissflogii in the presence of precipitated Fe(III) hydroxide and EDTA-Fe(III) complex
- Iron and humic-type fluorescent dissolved organic matter in the Chukchi Sea and Canada Basin of the western Arctic Ocean
- Importance of intracellular Fe pools on growth of marine diatoms by using unialgal cultures and on the Oyashio region phytoplankton community during spring
- Nutrient and diatom dynamics during late winter and spring in the Oyashio region of the western subarctic Pacific Ocean
- Increase in Si:N drawdown ratio due to resting spore formation by spring bloom-forming diatoms under Fe- and N-limited conditions in the Oyashio region