2001 Fiscal Year Final Research Report Summary
Transformation of bio-polymers into dissolved and colloidal organic matters in the ocean
| Project/Area Number |
11304039
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
地球化学
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| Research Institution | The University of Tokyo |
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Principal Investigator |
KOIKE Isao The University of Tokyo, Ocean Research Institute, Professor, 海洋研究所, 教授 (30107453)
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| Co-Investigator(Kenkyū-buntansha) |
SUZUKI Satoru Center for Marine Environmental Studies, Ehime Univ., Professor, 沿岸環境科学研究センター, 教授 (90196816)
TANOUE Eiichirou Hydrospheric Atmospheric Research Center, Graduate School of Environmental Studies, Nagoya Univ., Professor, 地球水循環研究センター, 教授 (50133129)
KOGURE Kazuhiro The University of Tokyo, Ocean Research Institute, Prof., 海洋研究所, 教授 (10161895)
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| Project Period (FY) |
1999 – 2001
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| Keywords | Dissolved organic carbon / Colloidal organic matter / Suspended organic matter / Aggregation process / Refractory organic matter / Thermocline / Microbial activitiy |
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| Research Abstract |
In the ocean, biochemical characters of bio-polymers produced by various planktonic assemblages are modified through the interaction with microbes and abiotic processes such as UV-radiation, and are believed to obtain their refractory characters. At the same time, aggregation of modified bio-polymeis into suspended or settling particle size would occur. In this project, fate of bio-polymers in the upper layer of the ocean was chased through extensive field process studies together with simple model experiments in the laboratory. One of the focus of the project is to determine biological and physico-chemical factors controlling aggregation of colloidal and submicron organic particles into large aggregates having enough settling velocities. Following findings and interpretation were obtained from this project. 1) Determination of submicron sized TEP concentration in environmental gradient from coastal waters to oligotrophic open waters prevailed that, irrespective of the depth and areas,
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some 70-80% of total TEP concentrations were located in the submicron-sized fraction, suggesting importance of colloidal sized TEP to form TEP of suspended dimension. 2) Production of semi-refractory organic carbon and nitrogen through microbial uptake and subsequent metabolisms of simple organic matters such as amino acids and glucose was observed within 10-15 days. There is striking similarities of biochemical characters between those freshly formed semi-refractory organic matters and those obtained in open ocean samples, suggesting that microbial processes are a possible factor for the formation of semi-refractory organic matters in the ocean.. 3) Significant contribution of attached micro-flagellates on the aggregation of submicron particles into large aggregates in the upper ocean. The above possibility was tested by an experimental approach using artificial submicron particles, and we obtained significant stimulation of aggregation processes by feeding current of attached microflagellates at least in coastal marine environments. 4) Detection of 100-150 micron sized aggregates within thermocline of coastal waters, sensed by in situ particle size counter. Using a newly developed sensor, clear difference of size distribution of suspended particles between in the mixing layer and within theirmocline was observed, which is direct evidence of active aggregation processes in the upper water column. Less
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