Daily changes of uptake of inorganic carbon and nitrogen, and their relation to phytoplankton blooms in late spring-early summer in Lake Nakanuma, Japan

Abstract

Daily changes of inorganic carbon and nitrogen uptake were measured in May in 1986 in Lake Nakanuma, Japan. Uptake of inorganic carbon and ammonium in the light-bottle experiments in the 1 m layers, showed daily changes similar to chlorophyll a changes, though the uptake activities peaked before chlorophyll a peaks (phytoplankton blooms) appeared. Potential growth rates of phytoplankton and observed growth rates were calculated from the uptake rates and chlorophyll a changes. The potential growth rates did not always correspond to the observed growth rates. The potential growth rates did not correlate with the loss rates. The correlation between the observed growth rates and the loss rates was better. These results suggest that though the increase of uptake activities may be necessary for occurrence of phytoplankton blooms, loss processes may affect the occurrence of blooms.