亜熱帯表層植物プランクトン群集に対する海洋深層水の肥沃化効果 Fertilization Effects of Deep Ocean Water on Phytoplankton Community in Subtropical Surface Water

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Abstract

水産生物資源の増産, 地球温暖化減速のための大気中二酸化炭素の吸収, 海洋深層水の効率的な資源利用などで, 貧栄養な表層水へ富栄養な海洋深層水を添加して植物プランクトンの生産を加速することが真剣に考えられている. そのためには, 実際に海域を肥沃化する前に現場モデル実験や数値シミュレーションによる効果予測が必要である. 特に, 深層水によってもたらされる栄養塩類量とそれによる植物プランクトンの生産増加 (一次生産) 効果の定量把握が重要である. 亜熱帯外洋の試水を用いた屋外培養実験を整理した結果, クロロフィルα濃度の比増殖速度は0.3日<I>-1</I>/μM-硝酸態窒素で増加し, クロロフィルα濃度の収量は1.48μg/μM-硝酸態窒素となった. これらの変化は表層水中にごく僅かに存在していた珪藻類を主とする植物プランクトンが増加したためで, ナノ・ミクロ植物プランクトンの割合は20%以下から80%前後に増加し, クロロフィルα濃度の増加と共に消費されたSi/N比は0.87に達した. ここで得られた速度や係数は深層水による海域肥沃化効果のモデル推定に役立つと考えられる.

Acceleration of oceanic phytoplankton production by enriching oligotrophic surface seawater with eutrophic deep ocean water has becoming a recent desirable subject in order to achieve sustainable fisheries as well as contributing to possible absorption of carbon dioxide in the atmosphere to slow down global warming andefficient resource utilization of deep ocean water for multiple-purposes. Beforemaking actual operation of ocean fertilization, prior prediction of the probableeffects is required by means of field experiments and numerical simulation model. In this study, parameters and the applicable values for the model estimation of fertilization effects of deep ocean water on phytoplankton community in oligotrophic subtropical surface water were examined based on the data collected in out-door culture experiments using natural seawater samples. The addition of deep ocean water to surface seawater resulted 214-fold increase of chlorophyll <I>a</I>concentration after several days of lag period. The specific growth constant of chlorophyll <I>a</I>concentration increased at a rate of 0.3 days<SUP>-1</SUP> perμM-nitrate and the yield of chlorophyll <I>a</I>was 1.48μg/μM-nitrate. These changes were resulted from the increase of phytoplankton, mainly diatoms. Due to the preferential growth of diatoms, the relative abundance of nano- and microphytoplankton increased from 20% or less to around 80%, and the Si/N ratio ofthe nutrients, consumed with the increase in chlorophyll <I>a</I> concentration, amounted to 0.87.

Journal

  • DEEP OCEAN WATER RESEARCH

    DEEP OCEAN WATER RESEARCH 4(1), 29-37, 2003

    DEEP OCEAN WATER APPLICATION SOCIETY

Codes

  • NII Article ID (NAID)
    130005450591
  • NII NACSIS-CAT ID (NCID)
    AA11858274
  • Text Lang
    UNK
  • ISSN
    1345-8477
  • NDL Article ID
    6708718
  • NDL Source Classification
    ZR26(科学技術--農林水産--水産)
  • NDL Call No.
    Z74-C70
  • Data Source
    NDL  J-STAGE 
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