高山湖沼ミクリガ池における水温,pH,溶存酸素量,透明度の季節変化

Water temperature, pH, dissolved oxygen and transparency of a small Japanese high mountain lake, L. Mikuriga-ike, were measured from May to November 1974 -1978. The lake formed winter stratification until about the middle of July. Measurements in May and the middle of June showed that the water temperature from the surface to about 8 m deep was below 1°C, and that the water near the bottom was approximately anoxic with a slightly higher pH. Subsequently the lake water overturned at 2.5°C in the middle of July, and the circulation period continued to the end of July with the temperature rising to 4°C. Lake surface of the summer stratification had a temperature of over 15°C. In summer stratification, the water near the thermocline was supersaturated with oxygen. This study found that autumnal circulation began at the end of October (1974, 1976) or in the middle of November (1977) at about 5 or 6°C. The pH value of the lake water showed weak acidity between 5.2 and 6.6. Transparency changed from 1.0 m to 12.0 m in depth during the investigation.