1980 年 41 巻 1 号 p. 41-50
Many volcanic acid lakes having pH from 0.9 to 5.5 are distributed throughout Japan. Most of the lakes with pH less than 4.0 are found in craters of volcanos, and their acidity depends on an inflow of acidic water from the lake bottom. Many of the remaining lakes are located in caldelas or hare a volcanic dammed origin, and their acidity depends on an inflow of acidic river water.
Studies on inorganic acid lakes in Japan were initiated by Tanaka, who observed Lake Katanuma in 1915 and Lake Onumaike from 1920 to 1927. Next came the limnological works on the Goshikinuma lake group (pH 3.1-7.2) and Lake Katanuma by YOSHIMURA et al. The typology of acid lakes was discussed by UENO who observed the lakes located at North Shinano, South Kyushu and the Kuril islands. The biota in acid lakes were studied by NEGORO, KIKUCHI, KOKUBO, FUJIMATSU, TAMURA and MASIKO et al.
They researchers reported Pinnularia braunii var. amphicephala in Lake Katanuma (pH 1.4 at that time), Brachionus urceoralis in Lake Ichibishinaiko (pH 2.8), Leptodictyum sp. and fish in Lake Osoresanko (pH 3.4), as will as the other algae, zooplankton and insects in the acid lakes. Anzai investigated the change of pH with the cease of volcanic activity, and he found that the deposition of iron compounds was followed by the occurrence of Pinnularia braunii var. amphicephala.
Acidification of lake water under the inflow of the acid river Tamagawa (pH 4.3) was studied by YOSHIMURA and UENO on Lake Tazawako.
After world War II was over study was resumed by MINAMI et al., who reported the chemical compositions of Lake Yugama which contains about 0.2 N sulfuric acid. Observation of biota in acid lakes was commenced by Suzuki who reported the mold and bacteria in acid lakes. Phytoplankton and zooplankton were observed by MIZUNo on the lake Group located in Kirishima volcano (pH 3.7-7.5), and WATANABE and OYAGI observed benthic diatoms in Lake Fudoike. Macrophytes and fish were observed by YAMAMOTO et al., in Lake Osoresanko. In Lake Katanuma SATAKE and SAIJO measured total CO2 and CO2 uptake in oxic and anoxic water, and they also clarified the mechanism of sulfurdiatom lamination in the sediment.
Sato observed the change of biota caused by the acidification of Lake Tazawako. EGUCHI et al., observed the inflow of acid river and the change of biota in Lake Toyako.