Limnological Researches of Onne-to in the Akan Region

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Onne-to is a small dammed lake caused by the eruption of the volcano, Mt. Meakan, and is situated at the height of 610m amidt the natural forest of the western slope of the mountain. Its area is 0.21km2, and its greatest depth is 9.8m. Inflowing water is little and its outflow disapears under the ground. Numerous sunken trees stand on the sandy bottom, and gases and hot springs are emitted everywhere in the south-eastern part of the lake-bottom. The researches of the lake were made twice in the winter (March 16) and the summer (August 26) of 1936. At the time of the winter observation the lake was covered with ice and snow, the thickness of the ice-cover being 57-60cm. Water temperature ranged between 0.1-3.3°C and also pH value in 5.30-5.15 according to depth from the upper layer close to the ice-cover to the bottom layer of 9m. When the summer observation was made, water temperature was variable, 20.2-21.4°C, and pH value was 5.2. The emission of gases and mineral water from the lake-bottom inconspicuosly influences the water temperature, but apparently effects the pH of lake-water.-Dissolved oxygen content in ivaterwas. 5.81-6.22cc/l (60-70%) in the winter and 5.30-5.78cc/l (90-98%) in the summer. The distinct chemical stratification was not secured in both researches. The water of the lake is very clear on account of meagreness of dissolved organic matter and fairly acid band on a great content of dissolved sulphate (138-155 mgl as SO4). From the lake no fish has yet been found because there is no directt connection with other lakes and rivers. The Plankton production of the lake is very poor, 2 forms. of zooplaukton being examined in winter and summer. It is obvious from the present investigation that Onne-to is an acidotrophic lake with a very poor biological productivity.
日本陸水学会の論文

Limnological Researches of Onne-to in the Akan Region

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日本陸水学会 | 論文

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