INFLUENCE OF PHYTOPLANKTON BY TOTAL NITROGEN AND CALCIUM ION AT DAM AND WEIR IN THE KINOKAWA RIVER BASIN

Abstract

The phytoplankton and their species were analyzed in the Otaki dam, the Sarutani dam and the Kinokawa flood gate. The Otaki dam, the Sarutani dam and the Kinokawa flood gate are stagnant condition. Ca⁺ concentrations in the Otaki dam and the Kinokawa flood gate were over 11 mg/l. Ca⁺ concentration in the Sarutani dam was equal to or less than 10 mg/l. Total nitrogen concentration in the Kinokawa flood gate was over 0.8 mg/l. Total nitrogen concentration in the Otaki dam and the Sarutani dam was equal to or less than 0.7 mg/l. In summer season blue-green algae increased in the Kinokawa flood gate but dinoflagellate did not increase. On the other hand, dinoflagellate increased in the Otaki dam. Then, blue-green algae increased, when total nitrogen concentration is over 0.8 mg/l. Dinoflagellate increased, when Ca⁺ concentration is over 11 mg/l.