2004 Fiscal Year Final Research Report Summary
Palaeoenvironmental reconstruction of the Bering Sea during the Late Quatemary
| Project/Area Number |
13440152
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Stratigraphy/Paleontology
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| Research Institution | Yamagata University (2001-2002, 2004)
Kochi University (2003) |
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Principal Investigator |
WJ. Richard Yamagata University, Dept of Earth & Environmental Sciences, Associate Professor, 理学部, 助教授 (90260455)
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| Co-Investigator(Kenkyū-buntansha) |
TAKAHASHI Kozo Kyushu University, Dept of Earth & Planetary Sciences, Professor, 大学院・理学研究院, 教授 (30244875)
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| Project Period (FY) |
2001 – 2004
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| Keywords | diatoms / Bering Sea / radiolaria / palaeoenvironment / biogenic opal / organic carbon / calcium carbonate / foraminifera |
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| Research Abstract |
This project was conducted during the financial period, 2001-2004, with the aim of studying piston cores taken from the Bering Sea and subarctic Pacific in 1999. The lead researcher analyzed three of the cores for diatom and nannofossil taxonomy and palaeoenvironmental reconstruction, as well as studying the microplankton assemblages in water samples to provide modern ecological data. With regards to the water samples, two data sets were produces, 1)a transect across the Pacific via the Bering Sea, and 2)a time-series of vertical water samples from Station KNOT (Western Subarctic Gyre) using the CTD in January, May and August This study revealed that the most important diatom species in subarctic waters was Fragilariopsis pseudonana, and that the Parmales (tiny siliceous scaly algae) dominated the whole assemblage near the Aleutian Islands and at Station KNOT (especially in May). There was also a large number of Emiliania huxleyi (coccolithophorid) cells in the top 10m at Station KNOT
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and in the Alaskan Gyre in August With regards to the core samples, there were two main findings, 1)in the Emperor Seamount core it was shown that the coccolith size of Coccolithus pelagicus varied downcore and could be related to the changes in watermass movement ; and 2)the most northern core (GAT) showed evidence of meltwater outflow from the Yukon River, presumably, as the number of marine benthic and freshwater diatoms increased during that time.
The collaborative researcher from Kyushu University analyzed 7 cores from the Bering Sea and subarctic Pacific, reconstructing the palaeoenvironment using radiolaria, diatoms, foraminifera, organic carbon, organic nitrogen, opal and calcium carbonate. The data allowed palaeocirculation and past sea-ice distribution maps to be constructed for the first time over the last 100-300 kyrs, and showed that the drop in sea-level during the last glacial period prevented water entering the southern Bering Sea. At the southeastern Bering Sea site (Umnak) during the glacial period, production was low due to increased sea-ice as corroborated by the increased presence of sea-ice related diatoms. The LAD of the radiolarian species, Lychocanoma nipponica sakaii, was consistently found to occur around 50 ka and therefore is a useful biostratigraphic marker in these sediments. Less
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[Journal Article] Diatom paleoceanography during the last 340 kyr in the Bering Sea and the western subarctic Pacific.2004
Author(s)
Katsuki, K., Takahashi, K., Matsushita, K.
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Journal Title
Proceedings of the 17^<th> International Diatom Symposium 2002, Ottawa, Canada (Poulin, M., ed.)(Biopress, Bristol, England)
Pages: 147-159
Description
「研究成果報告書概要(欧文)」より
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