|Budget Amount *help
¥42,380,000 (Direct Cost: ¥32,600,000、Indirect Cost: ¥9,780,000)
Fiscal Year 2020: ¥4,420,000 (Direct Cost: ¥3,400,000、Indirect Cost: ¥1,020,000)
Fiscal Year 2019: ¥9,100,000 (Direct Cost: ¥7,000,000、Indirect Cost: ¥2,100,000)
Fiscal Year 2018: ¥9,230,000 (Direct Cost: ¥7,100,000、Indirect Cost: ¥2,130,000)
Fiscal Year 2017: ¥19,630,000 (Direct Cost: ¥15,100,000、Indirect Cost: ¥4,530,000)
|Outline of Final Research Achievements
Vertical distributions of both concentrations and the O-17-excesses of nitrate were determined four times during one year within the mesotrophic water column of Lake Biwa. By using both the deposition rate of atmospheric nitrate onto the entire surface of the lake and the influx/efflux of nitrate via streams, we quantified the annual dynamics of nitrate (gross production rate of nitrate through nitrification and gross metabolic rate of nitrate through assimilation) based on the O-17-excess method. The results revealed that 642 Mmol of the remineralized nitrate was supplied into the water column through nitrification in the lake on an annual basis, while 810 Mmol of nitrate was metabolized in the lake through assimilation. In addition, the total metabolic rates of nitrate varied seasonally, with the highest rates in summer and the lowest in winter. We concluded that the O-17-excess method reliably estimates the dynamics of nitrate in mesotrophic lakes.