湖底堆積物中の有機炭素含有率と湖水中の生物生産性, および気象要素との関係 : 長野県, 木崎湖における21年間の湖沼観測からの検証 Relationships among weather factors, biological productivity and TOC content of sediments in Lake Kizaki, central Japan

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木崎湖において2003年12月に採取した35cm長の柱状堆積物について検討し, 1969年以降の3回の大洪水の層準を認定した.その年代をもとにして平均堆積速度を求め, 有機炭素含有率の経年的な変化を求めた.一方, 1981年以降に木崎湖で行われてきた毎月の湖沼観測記録をまとめ, 21年間のクロロフィルα量の経年的な変化を明らかにして, 湖水中の生物生産量の指標とした.また, アメダス気象観測資料を用いて, 気温や降水量などの気象要素の資料を得た.これら3者間の相関を検討して, 有機炭素含有率は, 年間クロロフィルα量および冬の平均気温と有意な相関をもつことを見出した.冬の暖かさ(厳しい冬の短さ)が冬季の生物生産性を高め, それが年間の生物生産量に影響を与えて, 堆積物として沈積する有機物量を増加させたと考えられる.湖沼堆積物中の有機炭素含有率は, 過去の気温(冬の平均気温)の指標として有効である.

Total organic carbon content (TOC) of lake sediments has been used recently as a useful paleoclimate proxy. But, no study has shown the genuine relationship between TOC content of lake sediments and climate parameters. Therefore, we try to examine modern relationships among TOC in lake sediments, biological productivity of lake water and weather factors using limnological observation data conducted monthly in Lake Kizaki since AD 1981. The sediment cored on 11 December 2003 was cut into 0.5cm interval, and apparent density and TOC content were measured. Apparent density peaks can be correlated with the known flood events. Sedimentation rates were determined precisely on the basis of flood ages, and were used for the age determination of the cored sediment. Then, annual TOC content can be determined from AD 1981 to 2002. Monthly measurements of chlorophyll a amount in water column were integrated to annual chlorophyll a amount which can be a representative of annual biological productivity. Meteorological data at Omachi City, 4km south to the lake were used as weather factors during the same period. As a result, we have found a correlation (n=21, r=0.47) between winter temperature and annual chlorophyll a amount. The TOC of sediment also shows some concordance with chlorophyll a (n=21, r=0.50) and winter temperature (n=23, r=0.44). When we compare TOC content in sediments with 3-year moving average of winter temperature and annual chlorophyll a, the correlations between them become much better. These results suggest that organic carbon of lake sediment reflects the lake biological productivity which is controlled by winter temperature, namely, shortness of the coldest season. It is concluded that the TOC content of lake sediments can be used as a useful paleoclimate proxy when sedimentation rate is almost constant.

収録刊行物

  • 地質學雜誌

    地質學雜誌 111(10), 599-609, 2005-10-15

    日本地質学会

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各種コード

  • NII論文ID(NAID)
    110003025011
  • 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
    7717197
  • 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  IR  J-STAGE 
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