2010 Fiscal Year Final Research Report
Study on the formation and maintenance mechanisms governing micro-structure of low dissolved oxygen water areas in a lake
| Project/Area Number |
20244079
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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 |
Meteorology/Physical oceanography/Hydrology
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| Research Institution | Lake Biwa Environmental Research Institute |
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Principal Investigator |
KUMAGAI Michio Lake Biwa Environmental Research Institute, 環境情報統括員 (40234512)
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| Co-Investigator(Kenkyū-buntansha) |
KITAZAWA Daisuke 東京大学, 生産技術研究所, 准教授 (30345128)
PARK HoーDong 信州大学, 理学部, 准教授 (20262686)
YAMAZAKI Hidekatsu 東京海洋大学, 海洋科学部, 教授 (80260537)
HASEGAWA Hiroshi 金沢大学, 物質化学系, 准教授 (90253335)
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| Co-Investigator(Renkei-kenkyūsha) |
NAGATA Toshi 東京大学, 大気海洋研究所, 教授 (40183892)
MIYAJIMA Toshihiro 東京大学, 大気海洋研究所, 助教 (20311631)
BAN Syuhei 滋賀県立大学, 環境科学部, 教授 (50238234)
NAKAMURA Yoshiyuki 独立行政法人港湾空港技術研究所, 研究主監 (90172460)
SATOMURA Takehiko 京都大学, 理学研究科, 教授 (20273435)
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| Project Period (FY) |
2008 – 2010
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| Keywords | 湖底泥 / 水温 / 溶存酸素濃度 / 消散係数 / 湖底境界層 / 数値モデル / 内部波 / 琵琶湖 |
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| Research Abstract |
We had the following results from this study ;
(1) We deployed a lake bottom platform several times at about 90m depth in Lake Biwa to measure the dissolved oxygen concentration (DO) in the bottom sediments. We found thin layers of 2-3mm thickness between oxic water and anoxic sediment and conclude that these layers correspond to viscous sub-layers. The recovery of DO in sediments depends on the temperature difference between the water and sediment. It is not easy to oxidize bottom sediments completely once they become anoxic,
(2) We also deployed an ADCP-TP-1200F to measure mean and turbulent flows in benthic boundary layers (BBL). After calculation of Reynolds stress in the layers, we found the stress on the surface of bottom sediments was not great enough to re-suspend sediments. This suggests that turbidity in the BBL is not caused by shear instability, but originated from bottom sediment ebullition such as hydrothermal vents detected by the AUV "Tantan",
(3) We developed a three dimensional numerical simulation model based on a hydrodynamics and ecosystem coupling scheme to understand the formation and maintenance mechanisms of low dissolved oxygen water areas near the lake bottom. Using this model, we found the oscillation flow due to internal waves periodically moved the anoxic water over a rather wide area. This result can be important, because it is deeply related with the generation of low DO water areas and their influence on benthic animals endemic to Lake Biwa.
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[Journal Article] Phytoplankton community reorganization driven by eutrophication and warming in Lake Biwa.2010
Author(s)
Hsieh, C.H, K.Ishikawa, Y.Sakai, T.Ishikawa, S.Ichise, Y.Yamamoto, T.C.Kuo, H.D.Park, N.Yamamura, M.Kumagai
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Journal Title
Aquatic Sciences. 72
Pages: 467-483
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