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jpn
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Title Transcription | ナカウミ シュンセツ クボチ ニ タイセキ スル ネンコウ タイセキブツ ガ シメス シュンセツ ゴ ノ ミズ カンキョウ ヘンカ
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Title Alternative (English) | Hydro-environmental change in southern Lake Nakaumi based on annually laminated sediments in a dredged channel
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Author | |
Description | Dredged channels, trenches, and pits are common in waterways throughout Japan. Lake Nakaumi, located in western Honshu, also has 8 million meter2 of channels that were dredged after the 1960s for coastal reclamation. Areas normally 3-4 m deep were dredged to depths of 6-15 m during construction. A sediment core, 17N1, was obtained from a dredged area in the southeast end of Lake Nakaumi in order to investigate environmental change after land reclamation and dredging. Core 17N1 is 57 cm in length, and the top 43 cm contains 35 laminated layers. Lithologies were clearly different between the laminated and lower sediments. The laminated layers have high water content (> 80 %) and are high in organic matter derived from plankton. The laminae in core 17N1 are inferred to be annual, meaning that the coring site was dredged in approximately 1982. After that time an anoxic water mass developed in the dredged channel and laminated sediments were preserved due to the absence of bioturbation and high seasonal variation in primary production. Although the total organic carbon and nitrogen contents have continuously increased in core 17N1, diatoms follow a different pattern. The total number of diatom valves increased until 1995, after which they gradually decreased. This pattern suggests that phytoplankton sourced in red-tide events shifted from diatoms to other taxa, perhaps dinoflagellates. In contrast, the C/S ratio has continuously increased in core 17N1, particularly in light laminae layers, suggesting that the anoxic water mass in this deep channel might be gradually dissipating.
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Subject | Lagoon
annual varve
dredged channel
diatom
CNS
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Journal Title |
Laguna
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Volume | 26
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Start Page | 73
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End Page | 83
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ISSN | 2185-2995
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Published Date | 2019
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Publisher | 汽水域研究会
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Publisher Transcription | キスイ イキ ケンキュウ カイ
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Publisher Aalternative | Japanese Association for Estuarine Science
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NII Type |
Journal Article
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Format |
PDF
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Text Version |
出版社版
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Gyoseki ID | e37566
e37584
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OAI-PMH Set |
Estuary Research Center
Faculty of Science and Engineering
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