溜池堆積物に記録された過去200年間の水域環境変遷史 : 大阪府高槻市小寺池の例  [in Japanese] Water Environmental Changes during the Past 200 Years Recorded in Recent Sediments of Kodera-ike in Takatsuki City, Osaka Prefecture, Japan  [in Japanese]

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Abstract

ここ数百年における人間活動の活発化が,溜池の水域生態系にどのような影響を与えてきたかを歴史的に明らかにすることを目的とし,池底堆積物を用いて珪藻およびリン・重金属(銅・亜鉛)と年代推定のためのセシウム分析を行った.<br>調査対象の小寺池は,大阪府の高槻市に位置する沖積低地上の皿池で,池底下の堆積物2.2mを用いて約200年間の水域環境変遷の解明を試みた.その結果,(1)溜池堆積物は数年単位の高時間分解能で解析が可能であること,(2)1955年頃より栄養塩類の指標となるリンの流入量が大幅に増え,珪藻の浮遊性優占種が短期間で段階的に<i>Aulacoseira subarctica</i> f. <i>subborealis</i>から<i>Stephanodiscus delicatus</i>, <i>S. hantzschii</i>,さらに<i>Cyclotella meneghiniana</i>へと変化した.この変化は人為的攪乱による水質変化に対応した珪藻群集の応答過程,すなわち富栄養化の段階を示唆する可能性が高い.また,(3)ここ数十年での珪藻の付着性優占種の<i>Nitzschia palea</i>から<i>Achnanthes minutissima</i> var. <i>minutissima</i>への変化は,現在から約150年ほど前の時代に優占していた種の復帰であり,下水道など社会的基盤の整備による汚濁負荷が減少したことに起因する可能性が高いことが明らかとなった.

To grasp the impacts of human activities on lakes and to develop realistic goals for water quality improvement, many paleolimnological assessments have been carried out. This paper examines diatoms, geochemical proxies (P, Cu, Zn), and historical research on past limnological change from a <sup>137</sup>Cs dated 2.2m core, which accumulated over a period of about 200 years from Kodera-ike (pond) located in an urban area in Takatsuki City, Osaka Prefecture. We have focused on reconstruction of the processes of eutrophication and the changes in ecosystems disturbed by human activities. As a result, several findings have been identified. 1) These data using the pond sediment have allowed us to detailed reconstruction of human impacts. 2) P concentrations were remarkably elevated in the upper sediments, and this abrupt increase reveals the extent of eutrophication which occurred since about 1955, which clearly caused replacement of planktonic diatom taxon (i. e., from <i>Aulacoseira subarctica</i> f. <i>subborealis</i> to <i>Stephanodiscus delicates</i>, <i>S. hantzschii</i>, and <i>Cyclotella meneghiniana</i>). 3) Replacement of benthic diatom taxon between <i>Achnanthes minutissima</i> var. <i>minutissima</i> and <i>Nitzschia palea</i> during the last a few tens years reflects the change in water quality associated with the improvement of the social infrastrucuture such as the sewerage system around the pond.<br>From the social point of view, these analyses will serve to define appropriate goals for natural state of ecosystems and to preserve a detailed record of subsequent environmental disturbances.

Journal

  • The Quaternary Research (Daiyonki-Kenkyu)

    The Quaternary Research (Daiyonki-Kenkyu) 41(3), 161-170, 2002-06-01

    Japan Association for Quaternary Research

References:  36

Codes

  • NII Article ID (NAID)
    10008631858
  • NII NACSIS-CAT ID (NCID)
    AN0034136X
  • Text Lang
    JPN
  • Article Type
    ART
  • ISSN
    04182642
  • NDL Article ID
    6178607
  • NDL Source Classification
    ZM49(科学技術--地球科学--地質)
  • NDL Call No.
    Z15-67
  • Data Source
    CJP  NDL  J-STAGE 
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