1989 Fiscal Year Final Research Report Summary
Analysis of the growth mechanisms of a species causing freshwater red tide in a reservoir using in situ microcosms
| Project/Area Number |
63540521
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
生態学
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| Research Institution | Ehime University |
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Principal Investigator |
KAWABATA Zen'ichiro Ehime University, Department of Agriculture, Associate Professor, 農学部, 助教授 (80108456)
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| Project Period (FY) |
1988 – 1989
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| Keywords | reservoir / freshwater red tide / dinoflagellate / Ceratium / cyst / microcosm / depth / soluble organic phosphorus |
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| Research Abstract |
The dinoflagellate Ceratium hirundinella (O. F. Muller) Bergh often causes freshwater red tide in reservoirs. There has been, however, little investigation on the growth mechanisms of C. hirundinella in a reservoir due to the difficulty in obtaining its physiological characteristics from laboratory cultures.
The purpose of this study was to find the factors for the excystment and growth of C. hirundinella in a reservoir by culture experiments using microcosms in situ. In addition, field surveys and laboratory experiments were also carried out. The main results obtained were as follows:
1. Microcosms containing bottom mud with cysts of C. hirundinella were suspended at several depths when the water temperature was 20 ﾟC at all depths. More vegetative cells were found in the shallower depths and the excystment rate was 2 % at 0.5 m deep. No vegetative cells were found deeper than 30 m.
2. From the laboratory culture of the cysts, the optimum water temperature for excystment was 20 ﾟC and 25 ﾟC, here the excystment rate was 2 %. No excystment was observed lower than 10 ﾟC.
3. The period of excystment was predicted to be from May to September and the place for excystment to be the head of the reservoir, according to results 1 and 2 mentioned above.
4. It was suggested from a field survey that soluble organic phosphorus favors the growth of C. hirundinella.
5. Microcosms with PO_4-P and NO_3-N added contained higher concentrations of soluble organic phosphorus and C. hirundinella compared with microcosms without the addition of those nutrients. The microcosm experiment also suggested that soluble organic phosphorus was a factor favoring the growth of C. hirundinella.
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