1995 Fiscal Year Final Research Report Summary
A role of thermocline on biological activities in Lake Biwa.
| Project/Area Number |
06304048
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| Research Category |
Grant-in-Aid for Co-operative Research (A)
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| Allocation Type | Single-year Grants |
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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 (CER) , Kyoto Univ., Professor, 生態学研究センター, 教授 (60025434)
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| Co-Investigator(Kenkyū-buntansha) |
KIMOTO Takashi Research Institute of Oceano-Chemistry, Researcher, 研究員
KUMAGAI Michio Lake Biwa Research Institute, Senior Researcher, 主任研究員 (40234512)
SUGIYAMA Masahito Kyoto Univ., FAC.Integrated Human Studies, Assoc.Professor, 生態学研究センター, 助教授 (10179179)
HIGASHI Masahiko CER,Kyoto Univ., Professor, 生態学研究センター, 教授 (40183917)
WADA Eitaro CER,Kyoto Univ., Professor, 生態学研究センター, 教授 (40013578)
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| Project Period (FY) |
1994 – 1995
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| Keywords | thermocline / water shortage / precipitation / plankton / nutrients / matter transport / Lake Biwa / biological activities |
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| Research Abstract |
Vertical distribution of chlorophyll a differedl in the pattern between September 1994 when it was extraordinarily water shortage and September 1995 when it was a usual rain. In 1994, chlorophyll a was extremely low in the epilimnion and showed a peak in the thermocline. Phytoplankton growth was interrupted in the epilimnion because of nutrients deficiency due to shortage of river inflow. As a result, solar radiation available for photosynthesis could penetrate sufficiently into the thermocline. Nitrate-N was gradually supplied by the upward diffusion from the hypolimnion to the thermocline and phosphate-phosphorus was supplied continuously by release of phosphate from the phosphorus adsorbed with ferric iron and alminium in the turbid water transperted from share-bottom into the thermocline. In 1995, river water including rich nutrients inflowed just above the thermocline and supplied nutrients to the epilimnion. As a result, phytoplankton growth was enhanced in combination with photosynthesis in the epilimnion. Vertical distribution pattern of chlorophyll a seems to be determined by whether or not nutrients are supplied from river to the epilimnion.
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