1997 Fiscal Year Final Research Report Summary
Secondary biological pump driven by food web interactions : A case study in Lake Biwa for gloval environmental issues
| Project/Area Number |
08308031
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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 |
Environmental dynamic analysis
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
NAKANISHI Masami Center for Ecological Research, Kyoto Univ., Professor, 生態学研究センター, 教授 (60025434)
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| Co-Investigator(Kenkyū-buntansha) |
SUGIYAMA Masato Department of Natural Environment Sciences, Faculty of Integrated Hu Studies, Ky, 総合人間学部, 助教授 (10179179)
NAKAYAMA Eiitirou School of environmental science, Shiga prefectural Univ., Associate Prof., 環境科学部, 助教授 (50108982)
OOKUBO Keizi Faculty of environmental science and technology, Okayama Univ., Associate Profes, 環境理工学部, 助教授 (50135612)
URABE Zyoutarou Center for Ecological Research, Kyoto Univ., Associate Professor, 生態学研究センター, 助教授 (50250163)
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| Project Period (FY) |
1996 – 1997
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| Keywords | Lake Biwa / sedimentation flux / biological production-decomposition / zooplankton / phytoplankton / bacteria / climate change / food chain |
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| Research Abstract |
To understando responses of aquatic ecosystems to global environmental change, we studied biological and decomposition processes in relation to environmental variables such as nutrients, light and water temperature, and relations between sedimentation flux of biological products and food chains.
1) Primary production of phytoplankton was limited by phosphorus in the layr above 5 m deep but by light intensity below 5 m deep. 2) Decomposition rate by bacteria was limited by phosphorus in the epilimnion and by water temperature in the hypolimnion.
3) Sedimentation flux corresponded with 12% of daily production of phytoplankton and most of the phytoplankton production were consumed by zooplankton and bacteria in the epilimnion. 4) 20-30% of the sedimentation flux were assimilated by Amphipoda gammarid in the aphotic zone. 5) The sedimentation flux changed seasonally depending on precipitation and propagation of microplanktonic algae such as Fragilaria crotonensis.
Biological production-decomposition rates and the sedimentation flux in Lake Biwa were strongly influensed by physical variable like light and water temperature, and food web structure. Further, they related closely to nutrients inflowing from rivers. These results suggest that climate change controlling precipitation, light, water temperature and nutrients influences directly acquatic ecosystems through processes of biological production-decomposition and vertical transportation of particulate organic matter.
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