| Project/Area Number |
60560197
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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 |
General fisheries
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| Research Institution | HIROSHIMA UNIVERSITY |
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Principal Investigator |
ONBE Takashi Faculty of Applied Biological Science, Hiroshima University, 生物生産学部, 教授 (70034452)
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| Project Period (FY) |
1985 – 1986
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| Project Status |
Completed (Fiscal Year 1986)
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| Budget Amount *help |
¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 1986: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1985: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Keywords | Zooplankton / Resting eggs / Marine cladocerans / Sediment pollution / Distribution / 生残 |
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| Research Abstract |
It has become increasingly evident that some species of marine zooplankton in temperate and boreal waters spend a period unfavorable for their planktonic existence in the form of benthic resting eggs. This phenomenon gas been understood as an excellent adaptive strategy for respective species to insure the survival and maintenance of its population in such ever-changing coastal environment. The present research aimed at elucidating the effect of organic sediment pollution on the distribution and survival of resting eggs in order to assess the temporal fluctuations in abundance of planktonic populations in local zooplankton community.
The distribution and abundance of resting eggs of marine cladocerans, which comprise a major part of local zooplankton community in warmer months in the central Inland Sea of Japan, were investigated at 33 stations scatterd over Hiuchi-Nada in June 1985. Abundance of resting eggs of 5 species ranged 1-81x <10^3> eggs <m^(-2)> with a mean of 44.4x <10^3> eggs <m^(-2)> , of which eggs of Penilia avirostris were most abundant. High densities of eggs occurred in sediments with a high percentage of silt-clay sized particles. Hatchability was low in eggs recovered from sediments containing a high concentration of sulphide-S.
Since July 1986, a monthly collection of sediments has been made at 5 stations in eutrophicated Fukuyama Harbor area. Resting eggs of marine cladocerans recovered from sediments of the innermost, most polluted station did not hatch at all.
Resting eggs of zooplankton after release into the water column are considered to be transported to and accumulate in certain specific areas by current, where they are subject to endure various physico-chemical conditions until hatching occurs. Death of resting eggs in polluted sediments may cause a local decrease in recruitment of individuals into the planktonic populations.
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