A biogeochemical study in surface waters of the subtropical ocean using a highly-sensitive method for measuring nanomolar nutrients

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  • Hashihama Fuminori
    Department of Ocean Sciences, Tokyo University of Marine Science and Technology

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Other Title
  • 高感度栄養塩類分析法を用いた亜熱帯海域表層の生物地球化学的研究
  • 2013年度日本海洋学会岡田賞受賞記念論文 高感度栄養塩類分析法を用いた亜熱帯海域表層の生物地球化学的研究
  • 2013ネンド ニホン カイヨウ ガッカイ オカダショウ ジュショウ キネン ロンブン コウカンド エイヨウ エンルイ ブンセキホウ オ モチイタ アネッタイ カイイキ ヒョウソウ ノ セイブツ チキュウ カガクテキ ケンキュウ

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<p>To understand nutrient biogeochemistry in vast oligotrophic subtropical ocean, surface distributions of nanomolar nutrients were investigated in extensive regions of the Pacific Ocean using a highly-sensitive method with a long-path liquid-waveguide spectrophotometry. Nitrate+nitrite concentrations were consistently depleted in most of the study area (<10 nM). In contrast, phosphate concentrations varied from the detection limit (3 nM) to 300 nM over the study area. Despite the prominence of excess phosphate in most of the regions, an almost complete depletion of phosphate (<10 nM) was observed at a horizontal scale of >2,000 km in the western North Pacific. Phosphate depletions were also observed at a horizontal scale of <100 km in the vicinity of the South Pacific islands. These depletions were ascribed to phytoplankton utilization of phosphate, and active dinitrogen fixation, as enhanced by iron supply, likely contributed to the utilization. Further more, characterization of dissolved organic phosphorus (DOP) and its distribution pattern were investigated in the western North Pacific and the East China Sea using the highly-sensitive method with an enzymatic procedure. In the phosphate-depleted waters where alkaline phosphatase (AP) activity was remarkably high, AP-labile fraction of total DOP was depleted (<10 nM) compared with that in the phosphate-replete waters. This implies that ambient labile DOP is actively hydrolyzed under phosphate-depleted conditions and utilized by micro organisms as an alternative of phosphate.</p>

Journal

  • Oceanography in Japan

    Oceanography in Japan 22 (5), 169-185, 2013-09-15

    The Oceanographic Society of Japan

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