| Project/Area Number |
16310019
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (B)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
Environmental dynamic analysis
|
|---|
| Research Institution | Fisheries Research Agency |
|---|
Principal Investigator |
ONO Tsuneo Fisheries Research Agency, Subarctic Fisheries Oceanography Division Hokkaido National Fisheries Research Institute, Chief Scientist (40371786)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
KASAI Hiromi Fisheries Research Agency, Subarctic Fisheries Oceanography Division, Hokkaido National Fisheries Research Institute, Scientist (60371788)
NISHIOKA Jun Hokkaido University, Pan-Okhotsk research Center, Institute of Low Temperature Science, Assistant Professor (90371533)
WATANABE Yutaka Hokkaido University, Graduate School of Environmental Earth Science, Assistant Professor (90333640)
YOSHIMURA Takeshi Fisheries Research Agency, Central Research Institute of Electric Power industry, Scientist (20371536)
|
|---|
| Project Period (FY) |
2004 – 2006
|
| Project Status |
Completed (Fiscal Year 2006)
|
| Budget Amount *help |
¥15,700,000 (Direct Cost: ¥15,700,000)
Fiscal Year 2006: ¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 2005: ¥6,100,000 (Direct Cost: ¥6,100,000)
Fiscal Year 2004: ¥7,600,000 (Direct Cost: ¥7,600,000)
|
|---|
| Keywords | iron / nutrient / Oyashio / primary production / 親潮域 / 水塊トレーサ |
|---|
| Research Abstract |
2-D iron distribution in the subarctic northwestern Pacific was investigated repeatedly from 2003 to 2006 with high spacio-temporal resolution equally to major nutrients. Seasonal and interannual variations of iron observed in the Oyashio domain brought us the following information :
1] Monthly-mean concentration of dissolved iron (DFe) in the Oyashio mixed layer varies in parallel with nitrate, with its maximum anteceding the Kosa season. Ratio of DFe to the nitrate is fairly constant throughout the year (ΔDFe/ΔN=27×10^<-6>[mol/mol]), and this ratio resembles those of North Pacific intermediate water (NPIW). Based on these observation results and a simple model calculation, it is concluded that the seasonal variation of Dfe in the Oyashio mixed layer is mainly governed by spring-summer biological consumption and winter recirculation from the NPIW. Iron input from the dust deposition is implied to have small effect to the mixed-layer iron cycle, although small-scale high iron patch might sometimes be generated by local iron deposition.
2] More than half of the DFe data observed in Oyashio mixed layer at the bloom-termination period shows roughly constant value of 0.25 nM, implying that the bloom-forming diatoms incur significant iron limitation below this iron level. In spring, iron reaches this lower-limit faster than nitrate, forming iron-limited ecosystem conditions at the end of spring bloom. In summer, however, the ultimate depletion of mixed layer nitrate occurs faster than that of DFe at July, forming nitrate-limited ecosystem in the summer Oyashio domain.
|
