AN ANALYSIS OF EARLY SUMMER NUTRIENT MINERALIZATION IN WATARASE RESERVOIR THROUGH FIELD MEASUREMENT AND NUMERICAL SIMULATION

Abstract

The concentration of phosphate and ammonium nitrogen increases in early to middle June in Watarase reservoir. Although the concentration of these inorganic components increases, both total phosphorus and nitrogen do not increase. Since total concentration does not increase, the augmentation may not be a simple result of nutrient release from bottom sediments. We have conducted a series of intensive field measurement of water quality change in Watarase reservoir and numerical simulation to analyze the mass balance quantitatively. Simulation results hypothesizing that phytoplankton was grazed by zooplankton and organic nutrients were mineralized rapidly agreed very well with the observed results. This shows the importance of the comparison of intensive field data and comprehensive ecological model.