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Study on the distributions of Th-234 and biological production in the open ocean

Research Project

Project/Area Number 10640475
Research Category

Grant-in-Aid for Scientific Research (C)

Allocation TypeSingle-year Grants
Section一般
Research Field 地球化学
Research InstitutionMie University

Principal Investigator

TAGUCHI Kazunori  Mie University, Faculty of Bioresources, Assistant Professor, 生物資源学部, 助手 (30226972)

Project Period (FY) 1998 – 2000
Project Status Completed (Fiscal Year 2000)
Budget Amount *help
¥3,300,000 (Direct Cost: ¥3,300,000)
Fiscal Year 2000: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 1999: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 1998: ¥2,700,000 (Direct Cost: ¥2,700,000)
Keywordsthorium-234 / primary production / scavenging / oligotorophic ocean / chlorophyll α / 地形湧昇
Research Abstract

Observation results repeatedly done at a station of the Shikoku Basin mid latitude showed that ^<234>Th in seawaters were nearly equilibrium with its parent nuclide ^<238>U during the ocean stratified. This means that this area is located in the subtropical regions and belongs to the oligotorophic regimes having few particulate fluxes. On the other hand, a profile of distinct disequilibrium of ^<234>Th against ^<238>U was found during the winter cruise in December 1999. Through these observations, the significant deficiency of ^<234>Th was always found in the subsurface layer of chlorophyll α maximum even in summer. Therefore, it shows that the particulate removal process does surely work there. Some continuous biological activities are considered to usually exist in the bottom of euphotic zone where nutrients are fueled up from deep waters.
However, chlorophyll α inventories were not always related to ^<234>Th deficiency. For instance, ^<234>Th deficiency was small in June 2000 when the high amount of integrated chlorophyll α was observed, and it was large in December 1999 when the approximately half amount of chlorophyll α of June. Though the issue of this decoupling is not irrelevant to the difference of retention time in seawaters between two parameters, it seems that the low productivity in this region dependent on the enhanced production by some pulsant events causes to amplify that. In case of winter, relative high chlorophyll α was widely distributed in the upper waters, and such a pattern looked like that of ^<234>Th deficiency. As this pattern is largely different from that in summer having the peaked subsurface maximum, it is suggested that ^<234>Th deficiency profiles are influenced by the productive structure ascribed to the physical mixing in winter waters. Therefore, these things mean that one shot observation is not always effective on the annual biological production of oligotorophic oceans.

Report

(4 results)
  • 2000 Annual Research Report   Final Research Report Summary
  • 1999 Annual Research Report
  • 1998 Annual Research Report
  • Research Products

    (4 results)

All Other

All Publications (4 results)

  • [Publications] 宇田紀之: "船舶ネットワークを利用した練習船「勢水丸」の海洋観測支援システム"大学情報システム環境研究. 2. 12-18 (1999)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2000 Final Research Report Summary
  • [Publications] Noriyuki Uda: "A Supporting System for Ocean Environment Research on "Seisui-Maru" Based on the Shipping Network"Academic Information Processing Environment Research. 2. 12-18 (1999)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2000 Final Research Report Summary
  • [Publications] 宇田紀之: "船舶ネットワークを利用した練習船「勢水丸」の海洋観測支援システム"大学情報システム環境研究. 2. 12-18 (1999)

    • Related Report
      2000 Annual Research Report
  • [Publications] 宇田 紀之: "船舶ネットワークを利用した練習船「勢水丸」の海洋観測支援システム"大学情報システム環境研究. 2. 12-18 (1999)

    • Related Report
      1999 Annual Research Report

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Published: 1998-04-01   Modified: 2016-04-21  

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