| Project/Area Number |
06680525
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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 |
環境影響評価(含放射線生物学)
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| Research Institution | National Institute for Environmental Studies |
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Principal Investigator |
KASAI Fumie National Institute for Environmental Studies, Regional Environment Division, Senior Researcher, 地域環境研究グループ, 主任研究員 (70224376)
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| Project Period (FY) |
1994 – 1995
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| Project Status |
Completed (Fiscal Year 1995)
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| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1995: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1994: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Keywords | Environmental stress / Algal communities / Herbicides / Tolerance / Green algae / Growth rate / Scenedesmus / River |
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| Research Abstract |
I examined growth characteristics of two strains of the green alga Scenedesmus gutwinskii var. heterospina isolated from the herbicide-treated and untreated experimental ponds. Growth rate and maximum yield were lower in the herbicide tolerant strain than the susceptible strain, when the concentration of the herbicide was lower than 10-15 mug/L.This fact indicates that the susceptible strains are superior competitor to tolerant ones in the absence of herbicide contamination. The concentration 10-15 mug/L is equivalent to the value which suppresses population growth of the susceptible strain of the Scenedesmus by 50% (EC50). Using the EC50 values, I presumed that the most susceptible groups examined, e.g.Chlamydomonas.would be affected by the herbicide stress in a river, because the herbicide concentrations in the river water were as low as 10 mug/L.Susceptibility to the herbicide simetryn and pretilachlor were examined for individual strains isolated in the pre-, mid- and post-herbicide application period from a river running through an agricultural region. The EC50 values of simetryn and pretilachlor for strains of the genera chlamydomonas and Cyclotella increased when the herbicide concentrations in the water increased, although the maximum concentrations of simetryn and pretilachlor were as low as 2 and 4.5 mug/L,respectively. The increase in simetryn tolerance seemed to be correlated with the increase in pretilachlor tolerance. Thus, pretilachlor seems to exert a selective pressure on river periphyton communities. From these results, I conclude that the herbicide stress gives only a weak impact on river periphyton communities.
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