1999年ラニーニャ時の西部太平洋赤道海域における珪藻フラックス変動 Seasonal fluxes of diatoms in the western equatorial Pacific during the 1999 La Nina conditions

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著者

    • 高橋 孝三 Takahashi Kozo
    • 九州大学大学院理学研究院地球惑星科学部門 Department of Earth and Planetary Sciences, Faculty of Sciences, Kyushu University
    • 小林 扶美子 Kobayashi Fumiko
    • 九州大学大学院理学府地球惑星科学 Department of Earth and Planetary Sciences, Graduate School of Sciences, Kyushu University
    • 小野 逸郎 Ono Itsuro
    • 九州大学大学院理学研究院地球惑星科学部門 Department of Earth and Planetary Sciences, Graduate School of Sciences, Kyushu University

抄録

西部太平洋赤道海域において,1999年の1月から約1年間係留されたセディメントトラップより回収された試料から珪藻フラックス変動を明らかにした.本海域は西部のWPWPと東部のEURの2つの水塊に大きく分けられた.珪藻の種組成は2つの水塊間で明らかに異なり,WPWPでは羽状目の割合が高くNitzschia bicapitataが優占種であったが,EURでは円心目の割合が増加しRhizosolenia bergoniiが優占種であった.この東西の種組成の差は,水塊の違い,とくに栄養塩環境の違いを顕著に反映したものと考えられる.また,本海域において全珪藻フラックスに季節変動が認められたが,その種組成には大きな季節変動が認められなかった.このことは,季節的な栄養塩供給の増減に関わらず,その栄養塩の供給源が変化しなければ珪藻の種組成に大きな変化が現れないことを示唆するものと考えられる.

Time-series sediment traps were deployed at two water depths, about 1,000m and 3,000m, in the western equatorial Pacific during 1999, which revealed seasonal changes of diatom fluxes. Two types of oceanographic conditions were investigated : Sites MT1, MT2 and MT3 were located in the Western Pacific Warm Pool (WPWP) ; and Site MT5 was located in the Equatorial Up-welling Region (EUR). Annual mean fluxes of total diatoms were high at Sites MT1 and MT5, and the lowest at Site MT2. The taxonomic composition of the diatoms was different between the two regions (the WPWP and the EUR). Pennate diatoms dominated the assemblages at Sites MT1, MT2 and MT3 in the WPWP. However, at Site MT5 in the EUR, the average percent occurrence of pennate diatoms was lower than that in the WPWP and the contribution of centric diatoms was higher than the latter. Nitzschia bicapitata was the dominant species in the WPWP, while Rhizosolenia bergonii was the dominant species in the EUR. Such a different composition of the diatom taxa is attributed to difference in environmental conditions, especially nutritional conditions between the WPWP and the EUR. At all sites, the flux levels of diatom taxa showed distinct seasonal patterns, while the relative abundances of the diatom assemblages did not show such a seasonality. Thus, the taxonomic composition of the equatorial diatom assemblages are considered to be stable with changes of source of nutrient supply. In the western equatorial Pacific, the seasonal changes of diatom fluxes reflect the seasonal change of nutrient concentrations, while the relative abundances of the diatom assemblages reflect the hydrographic and nutritional conditions of the surface waters.

収録刊行物

  • 地質學雜誌

    地質學雜誌 108(11), 721-732, 2002-11-15

    日本地質学会

参考文献:  41件中 1-41件 を表示

被引用文献:  2件中 1-2件 を表示

各種コード

  • NII論文ID(NAID)
    110003009736
  • NII書誌ID(NCID)
    AN00141768
  • 本文言語コード
    JPN
  • 資料種別
    ART
  • ISSN
    00167630
  • NDL 記事登録ID
    6368519
  • NDL 雑誌分類
    ZM49(科学技術--地球科学--地質)
  • NDL 請求記号
    Z15-174
  • データ提供元
    CJP書誌  CJP引用  NDL  NII-ELS  J-STAGE 
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