| Project/Area Number |
10480144
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (B).
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
環境保全
|
|---|
| Research Institution | Shinshu University |
|---|
Principal Investigator |
HANAZATO Takayiki Suwa Hydrobiological Station, Shinshu University, Professor, 理学部・附属臨湖実験所, 教授 (60142105)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
PARK Ho-don Faculty of Science, Shinshu Univseity, Associate Professor, 理学部, 助教授 (20262686)
TODA Hideshige Faculty of Science, Shinshu University, Associate Professor, 理学部, 助教授 (60291382)
OKINO Okio Faculty of Science, Shinshu University, Professor, 理学部, 教授 (50020681)
KITANO Satoshi Nagano Nature Conservation Research Institute, Researcher, 研究員
SANEYOSHI Mineo Department of Biological Sciences, Teikyo University of Science & Technology, Professor, 理工学部, 教授 (20002339)
北野 総 長野県自然保護研究所(研究職), 研究員
|
|---|
| Project Period (FY) |
1998 – 2000
|
| Project Status |
Completed (Fiscal Year 2000)
|
| Budget Amount *help |
¥12,200,000 (Direct Cost: ¥12,200,000)
Fiscal Year 2000: ¥2,500,000 (Direct Cost: ¥2,500,000)
Fiscal Year 1999: ¥4,100,000 (Direct Cost: ¥4,100,000)
Fiscal Year 1998: ¥5,600,000 (Direct Cost: ¥5,600,000)
|
|---|
| Keywords | Water quality improvement / Lakes / Biomanipulation / Ecosystem manipulation |
|---|
| Research Abstract |
To improve water quality of the subalpine Lake Shirakaba, where cyanobacterial bloom often occurs in summer, we planned to control ecosystem structure to have less planktivorous fish and abundant the large cladoceran Daphnia, which is unfavorable for cyanobacteria to bloom. This is so called biomanipulation. In the project, we analyzed present ecosystem of the lake from 1997 to 2000, and performed experiments in the field and laboratories to understand the relationships between communities of fish and zooplankton and between zooplankton and cyanobacteria. Then, we obtained the following results. 1) the surface water temperature of the lake reaches to the maximum of 22℃, 2) lake water is stratified during May-August, when dissolved oxygen concentration declines below 1.5 mg O_2/L in the hypolimnion, 3) total nitrogen concentration and total phosphorus concentration are in the ranges of 500-600 ugN/L and 20-30 ugP/L, respectively, which may indicate that the lake is not highly eutrophic,
… More
4) the cvanobacterium Anabaena and Microcystis appear in the lake and attain the highest abundance in summer, 5) zooplankton community is dominated by the small cladoceran Bosmina and medium cladoceran Holopedium, while the lake is not inhabited by Daphnia, 6) fish community is composed of 16 species belonging to 14 genera, and is dominated by large mouth bass and pond smelt, 7) gut content analysis of fish shows that the pond smelt mostly preys on zooplankton and midge larvae while the large mouth bass favors pond smelt, 8) pond smelt selectively feeds on the larger cladoceran Holopedium and has an serious predation impact on the cladoceran population, 9) enclosure experiments show that Daphnia can effectively reduce the abundance of cyanobacteria in the lake.
We judged from the results that biomanipulation is an effective way to improve water quality of Lake Shirakaba. Then, we released rainbow trout into the lake to control planktivorous fish after making an agreement with the organization that has a right to control fish populations of the lake. Less
|
