抄録
Concentration of dissolved thiamine, biotin, and vitamin B12 in the water of a eutrophic lake, Lake Kojima, have been determined by microbiological assay methods at intervals of 2 to 4 months from August, 1971 to April, 1972. Also the relations between the distribution of in the B group vitamins and other physical, chemical, and biological environmental factors were studied. Thiamine was assayed with Lactobacillus fermenti ATCC 9338, biotin with L. plantarum ATCC 8014, and vitamin B12 with L. leichmannii ATCC 7830. It was found that Lake Kojima is an extremely eutrophic lake and that concentrations of the B group vitamins were fairly high: thiamine 20-2300ng/l, biotin 2.3-101.6ng/l, and vitamin B12 2.1-36.0ng/l.Thiamine and vitamin B12 were most abundant in summer and markedly decreased from autumn and winter to spring, while the biotin concentration was highest in winter and lowest in spring. Concentrations of thiamine and vitamin B12, not biotin, correlated negatively with abundances of both phytoplankto and aerobic heterotrophic bacteria. It was suggested that the seasonal fluctuation of the B group vitamins concentrations may be connected with the growth of phytoplankton species.
