Temporal variability and bioavailability of iron and other nutrients during the spring phytoplankton bloom in the Oyashio region

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概要

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• Iron [dissolved Fe (D-Fe) and total dissolvable Fe (T-Fe)] and nutrient concentrations in the surface water of the Oyashio region (northwestern North Pacific) were measured before and during spring phytoplankton bloom (March to May in 2007). During the pre-bloom period (middle of March), we observed vertically uniform concentrations of iron (0.3-0.5 nM [D-Fe] and 3-5 nM [T-Fe]), macronutrients (10-15 μM NO3+NO2, 1.0-1.5 μM PO4 and 20-30 μM Si(OH)4) and chlorophyll a (Chl-a, 0.3-0.4 μg ^[-1]) throughout the upper 125 to 150 m due to vertical mixing during winter. Water temperature and salinity before the bloom were also vertically uniform with > 5℃ and S > 33.5, the conditions of a modified Kuroshio warm-water (MKW) ring, higher than those of the Coastal Oyashio Water (COW). The cold COW ( < 2℃, S < 33.2) intruded a few times into the surface during the bloom period with high iron (0.4-0.6 nM [D-Fe] and 10-25 nM [T-Fe]) and Chl-a (10-23 μg l^[-1]) concentrations. The high Chl-a observed in the COW is due to the higher original concentrations of iron and macronutrients in the COW than in the MKW. An incubation experiment conducted during a COW intrusion in early April resulted in robust phytoplankton growth and complete exhaustion of nutrients, indicating an adequate supply of bioavailable iron. This result is also consistent with robust in situ phytoplankton growth and Chl-a production due to the presence of high iron levels in the COW. The most important mechanisms transporting iron to the surface water, which would regulate the primary production during spring bloom in the Oyashio region, are the surface intrusions of iron- and nutrient-rich COW derived from vertical and lateral mixing processes and vertical mixing in MKW during winter and spring.

著者

• Kuma Kenshi

  Faculty Of Fisheries Sciences Hokkaido University

• Fujio Shinzo

  Ocean Research Institute The University Of Tokyo

• Ikeda Tsutomu

  Hokkaido Univ. Hokkaido Jpn

• Ikeda Tsutomu

  Faculty Of Fisheries Sciences Hokkaido University

• 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
• Benthic Front and the Yamato Basin Bottom Water in the Japan Sea
• Processes Influencing Iron Distribution in the Coastal Waters of the Tsugaru Strait, Japan
• Effect of aging time on the availability of freshly precipitated ferric hydroxide to coastal marine diatoms
• 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

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