抄録
In the work reported here the vitamin B12 content and its variation in lake and river water was measured.
In May 1958, the vitamin B12 content in the water of Lake Ikeda, mesured by Euglena method; it was very small (e. g. less than 1 mγ/l) and no distinct variation in the vertical and horizontal distribution was observed, however, in August, the vitamin increased in content more than twice as much as that of the spring value, the vertical distribution of it showed a close correlation with the quantity of dissolved oxygen and the maximum was shown at the depth of 20m. (Fig. 2) Fish school were also observed in this region. Similar seasonal change in vitamin B12 content was found in water from Kotsuki River, with a low spring level (about O.1 mγ/l) (Table 2, I) and a high autumn level (0.4-4.5 mγ/l) (Table 2, II). And in the river water, high level of vitamin B12 was observed in the morning, and in the daytime the vitamin content decreased with the lapse of time. It was found also that considerable amount of vitamin B12 poured into the river water from the banksoil with the rain-water. (Table 2, II)
