諏訪湖の水中沈降物 : 諏訪湖陸水学資料 IV

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タイトル別名
  • PRECIPITATING SUBSTANCES OF LAKE SUWA : MATERIALS FOR THE LIMNOLOGY OF LAKE SUWA, IV
  • 諏訪湖の水中沈降物(諏訪湖陸水学資料-4-)
  • スワコ ノ スイチュウ チンコウブツ スワコ リクスイ ガクシリョウ 4

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1. Settling substances were collected from the lake water for 24 hours every 10 days from August to December, 1966,at three stations in the pelagic region and at three places in the shallow zones covered with larger aquatic plants by taking them into an apparatus of funnel type with the opening of 30cm in diameter each set 50cm above the bottom. 2. The precipitating substances greatly vary in amount from station to station. The amounts are generally larger at places in the bare pelagic zone than those where floating or submerged plants grow densely. The largest amount was obtained in the shore region of Kamisuwa City where the lake is most severely polluted. In average the amount collected is estimated to be 15.57 g/m^2/day in dry weight. 3. Depositing to the bottom is always more extensive on windy days. Significant correlation was found between the amount and the mean velocity of the wind of the day the samples were taken. The relation in the bare pelagic zone is expressed by P=10^<(1.19V-2.41)> where P is the amount of deposition per day, V the mean velocity of the wind of the day. No correspondence is found in the amount of deposition either to the wind velocity of the day before the collection or to the amount of rainfall of the previous day inclusive of that day. 4. Microscopic examination reveals that the predominating substances consist of diatom shells occupying about 50 per cent in volume of the total samples. The remainders are all finely divided inert detritus of either organic or inorganic nature. The diatom shells are of the species which were dominant during the previons spring, i.e. Melosira, Synedra and Asterionella. 5. Thus a conclusion may be drawn that the precipitation in this case do not entirely represent the addition of the new bottom-making materials settling through the water, but for the most part the re-precipitation of the so-called gyttja stirred and floated up by the forces of winds and waves. 6. Pure precipitating materials through the water was estimated to be less than 3g/m^2/day from the actual data obtained on calm days.

収録刊行物

  • 日本生態学会誌

    日本生態学会誌 18 (5), 212-217, 1968

    一般社団法人 日本生態学会

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