Abstract
Strong summer calcium stratification in the water of harmonic type Lake Takanamiike (Itoigawa, Niigata), with a moderately high calcium concentration averaging 18.7 mg⋅l-1 annually was observed first by the authors. The average concentration in the epilimnion was 16.6 mg⋅l-1 and 20.4 mg⋅l-1 in the metalimnion in August, 1990. Supersaturation concerning calcite apparently occured in the epilimnion from June to August when a high pH value above 8 and high water temperature were obtained. Calcium stratification, calcite supersaturation and changes in calcium concentration and alkalinity suggest the possibility of calcite formation in these water layers owing to primary production.
