Laguna : 汽水域研究

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Laguna : 汽水域研究 3
1996-03 発行

湖水環境の人為的改造と底生有孔虫の群集変化(その4) : 有孔虫の群集変化に対応した化学的酸素要求量(COD)と宍道湖水の変化

Benthic Foraminiferal Changes in Relation to Human Activities in Brackish Environment(Part 4) : Chemical Oxygen Demands (COD) Correlated with Foraminiferal Event and the Changes of Waters in Lake Shinji
野村 律夫
ファイル
内容記述(抄録等)

  A variation of chemical oxygen demands of bottom water in Lake Shinji was examined for 24 years of 1972-1995, based on the reports from Shimane Prefectural Government. A critical change of COD values in the time series occurred in 1980, which is exactly correlated with the benthic foraminiferal changes, as reported by Nomura and Yoshikawa (1995).
 An increase of Ammonia beccarii in sediment surface indicates an increase of organic matter in bottom water, which is reasonably interpreted from the view Point of COD.
  The increased values of COD during 1980-1982 indicate that the water characters of Lake
 Shinji change to nutrients rich water, with an input of organic matter. The cause of this change might have been due to a construction of several embankments or bottom sediments dredging to reclaim the northwestern part of Lake Nakaumi, which hindered the movement of bottom water. So far as COD values indicating constant variations after 1983, such water characters do not changed to the present. However, foraminiferal occurrence indicates a continuation of increased organic matter into bottom water.