北西太平洋セジメント・トラップ実験による放散虫フラックスと科レベルの群集の季節変動  [in Japanese] Seasonal changes in fluxes and assemblages of radiolarians collected by sediment trap experiments in the northwestern Pacific: a family-level analysis  [in Japanese]

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Author(s)

    • 本山 功 Motoyama Isao
    • 筑波大学大学院生命環境科学研究科地球進化科学専攻 Institute of Geoscience, University of Tsukuba
    • 大田 美由紀 Ota Miyuki
    • 筑波大学大学院生命環境科学研究科地球進化科学専攻 Institute of Geoscience, University of Tsukuba
    • 田中 裕一郎 Tanaka Yuichiro
    • 産業技術総合研究所地質情報研究部門:筑波大学連携大学院生命環境科学研究科 Institute of Geology and Geoinformation, Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology:Institute of Geoscience, University of Tsukuba

Abstract

北西太平洋の亜熱帯域と漸移帯域に係留されたセジメント・トラップ装置に捕集された1年間分の放散虫フラックスと群集組成について解析を行った.Polycystina目フラックスは, 漸移帯域において春季に高く, 夏季に低くなる傾向がみられ, 一方, 亜熱帯域では明瞭な季節変動はみられなかった.Polycystina目フラックスとPhaeodaria目フラックスは, 共に亜熱帯域よりも漸移帯域で高いことが示された.Polycystina目の科レベルの群集組成は, 亜熱帯域においても漸移帯域においても統計的に有意な季節変動を示さなかった.両水域を比較すると, 亜熱帯域の方で優勢になる科にはCollosphaeridae科, Coccodiscidae科, Pterocorythidae科があり, 漸移帯域はPlagiacanthidae科の多産で特徴づけられることが明らかになった.

Time-series sediment traps were deployed in the subtropical (Station WCT-1) and transitional (Station WCT-2) areas in the northwestern Pacific for one year from 1997 to 1998. Radiolarians were counted and categorized into families to study seasonal and regional changes in radiolarian productivity and faunal composition. The polycystine annual mean flux was 10,406 shells m^<-2> day^<-2> at WCT-2, which was higher than that at WCT-1 (3,901 shells m^<-2> day^<-1>). The phaeodarian annual mean flux was low (1,583 shells m^<-2> day^<-1>) at WCT-2 and extremely low (7 shells m^<-2> day^<-1>) at WCT-1. These indicate that radiolarian productivity is generally higher in the transitional area than in the subtropical area. Temporal fluxes of polycystines at the transitional site showed variations associated with high flux during the spring and low flux during the summer, while polycystine fluxes at the subtropical site did not show apparent seasonal variations. Family-level percentage composition and statistical testing did not show significant seasonal changes at either site. This seasonal stability in faunal composition was a quite unexpected result, since there were seasonal changes in the sea surface temperature in the studied areas. This stability indicates lack of response of polycystine radiolarians to oceanic seasonality in the subtropical and transitional regions. There was a difference in the annual polycystine composition between the two sites, probably corresponding to differences in oceanic water masses. Comparing the polycystine annual composition and flux between the two sites, three families, Collosphaeridae, Coccodiscidae and Pterocorythidae, are more abundant elements in the subtropical region, whereas dominance of Plagiacanthidae characterizes the transitional region.

Journal

  • Journal of the Geological Society of Japan

    Journal of the Geological Society of Japan 111(7), 404-416, 2005-07-15

    The Geological Society of Japan

References:  26

Codes

  • NII Article ID (NAID)
    10016622618
  • NII NACSIS-CAT ID (NCID)
    AN00141768
  • Text Lang
    JPN
  • Article Type
    ART
  • ISSN
    00167630
  • NDL Article ID
    7431042
  • NDL Source Classification
    ZM49(科学技術--地球科学--地質)
  • NDL Call No.
    Z15-174
  • Data Source
    CJP  NDL  NII-ELS  J-STAGE 
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