| Project/Area Number |
08041089
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| Research Category |
Grant-in-Aid for international Scientific Research
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| Allocation Type | Single-year Grants |
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| Section | Field Research |
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| Research Institution | HOKKAIDO UNIVERSITY |
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Principal Investigator |
OKADA Hisatake Graduate School of Science, Hokkaido Univ., professor, 大学院・理学研究科, 教授 (80111334)
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| Co-Investigator(Kenkyū-buntansha) |
WINTER Amos Dept.of Marine Sciences, Univ.of Puerto Rico, 海洋科学科, 教授
JORDAN Richard Fac.of Science, Yamagata Univ., 理学部, 講師 (90260455)
MURAYAMA Masafumi Grad.School of Envi.Earth Sci., Hokkaido Univ., 大学院・地球環境科学研究科, 助手 (50261350)
HASEGAWA Shiro Grad.School of Envi.Earth Sci., Hokkaido Univ., 大学院・地球環境科学研究科, 助教授 (90142918)
MINAGAWA Masao Grad.School of Envi.Earth Sci., Hokkaido Univ., 大学院・地球環境科学研究科, 教授 (10250507)
OBA Tadamichi Grad.School of Envi.Earth Sci., Hokkaido Univ., 大学院・地球環境科学研究科, 教授 (60013588)
WINTER Amos プエルトリコ大学, 海洋科学科, 教授
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| Project Period (FY) |
1996
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| Project Status |
Completed (Fiscal Year 1996)
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| Budget Amount *help |
¥5,000,000 (Direct Cost: ¥5,000,000)
Fiscal Year 1996: ¥5,000,000 (Direct Cost: ¥5,000,000)
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| Keywords | Coral reef / Environmental Change / Oxygen istotopo / Calcareous nannoplankton / Carbon isotope |
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| Research Abstract |
Submonthly samples were prepared by a newly invented technique : shaving a frozen sliced coral with a microtome. A preliminary analysis of oxygen isotopes for the six year periods of typical Little Ice Age (A.D.1700-1705) and of the modern times (A.D.1984-1989) has revealed that while the annual variations in delta^<18>O were similar, the annual average was ca.0.4% heavier during the Little Ice Age. This result can be interpreted as, 1) the annual SST (sea-surface temperature) variation was ca.4ﾟC during the Little Ice Age which is the same as present, 2) the average SST of Little Ice Age period was approximately 2ﾟC lower than the present. Also, an influence of freshwater discharge from the Orinoco River is detected in the autumn (Sept.-Oct.) samples.
Annual average and annual variation of delta^<13>C were -86* and 1.2*, respectively for the Little Ice Age, whereas the values are -2.06* and 2.1*, respectively for the present. The lower annual average for the present reflects the influence of Suess Effect, and the smaller annual variation during the Little Ice Age is likely to indicate a lesser cloud cover variation between the dry and wet seasons than the modern times.
A preliminary light microscope observation of surface sediments recovered from the continental shelf off La Parguera revealed and abundant occurrence of Gephyrocapsa oceanica Since G.oceanicais a minor component of the modern nannoflora obtained from the outside of the continental shelf, the taxon's abundance is a uniquely local phenomenon restricted to the coastal environments. A similar preferential occurrence of the taxon has been reported from various marginal seas and bays of the Western Pacific and Indian Oceans, but the phenomenon has not been reported from the Atlantic Ocean or the Caribbean Sea. The new finding observed in this study opens the way to utilize the taxon's abundance as an environmental indicator for a semi-restricted lagoon and/or a shelf.
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