1996 Fiscal Year Final Research Report Summary
A comparative study of materials flows between seagrss-and seaweed-based ecosystemes in tropical lagoon.
| Project/Area Number |
06041028
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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 | University of tokyo |
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Principal Investigator |
KOIKE Isao Ocean Research Institute, University of Tokyo, Professor, 海洋研究所, 教授 (30107453)
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| Co-Investigator(Kenkyū-buntansha) |
KOMATSU Teruhisa ORI.Univ.of Tokyo, Research Associate, 海洋研究所, 助手 (60215390)
POLLARD P.C Department of Chemical Engineering and Microbiology, The Univ.of Queensland, 研究員
YAMAMURO Masumi Department of Marime Geology, Geological Survey of Japan, 地質調査所, 研究官
SUZUKI Takao Faculty of Science, Tohoku Univ.Research Associate, 理学部, 助手 (10124588)
MINAGAWA Masao Hokkaido Univ.Associate Professor, 地球環境科学, 助教授 (10250507)
KUNII Hidenobu Fuculty of Science, Shimane Univ.Associate Professor, 汽水域研究センター, 助教授 (70161651)
AIOI Keiko ORI.Univ.of Tokyo, Research Associate, 海洋研究所, 助手 (90107459)
KOGURE Kazuhiro ORI.Univ.of Tokyo, Associate Professor, 海洋研究所, 助教授 (10161895)
IIZUMI Hitoshi Hokkaido National Fisheries Institute, Section Head, 北海道区水産研究所, 室長 (00159550)
NOJIMA Satoshi Faculty of Science, Kyushu Univ.Associate Professor, 理学部, 助教授 (30112288)
MUKAI Hiroshi Faculty of Science, Hokkaido Univ.Professor, 理学部, 教授 (00013590)
NISHIHIRA Moritaka Faculty of Science, Tohoku Univ.Professor, 理学部, 教授 (80004357)
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| Project Period (FY) |
1994 – 1996
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| Keywords | Halimeda / tropical lagoon / symbiotic system / seagrass / herbivores fish / nitrogen fixation / nutrients / nitrogen cycle / stable isotope |
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| Research Abstract |
The Purpose of this study is to evaluate the cycling of carbon and nitrogen and their coupling with the metabolisms of biological communities in seagrass beds and in seaweeds in tropical lagoon. We made an extensive field observation in the tropical lagoon located at south of Suva, Fiji from 1994-1996. In the lagoon, there is a dense Syringodium seagress bed and also Halimeda population around the seagrass bed. Following are the some outcomes from the field survey.
(1) Combing with the available data of aero-photographs and our field observation, the seagrass bed near the Dravuni Island expanded their size to about 6 times during the last 20 years. This increase in size was also confirmed for the latest 3 years field observation, indicating 22m expansion of seagrass bed to the shore side. The island has a population of some 100 peoples, which is rather stable during the last 20 years. But, the village equipped water supply system from the well about 5-6 years ago. Possible reason for th
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e seagrass increase is the change of nutrients load from the island due to the increase of water usage.
(2) Together with the change of seagrass bed, we found the change of epibenthic community distribution such as Ascidians and Lagenophyra. Some of those animals harbor symbiotic alage, which are significant primary producers in the tropical lagoon. The symbiotic character of those animals seems to be important factor controlling the small scale distribution with in seagrass bed and Halimeda communities.
(3) Stable isotope analyzes of 15-N and 13-C in various biological communities and suspended organic materials in the seagrass bed and its vicinity gave some interesting insight of food web structure in this ecosystem. Using the significant difference in both 13-C and 15-N rations in seagrass and their epiphytic algae, which are partially due to the nitrogen fixation by blue green algae, filamentous algae was suggested as a primary food source of epibenthic and other benthic animals. Active nitrogen fixation by filamentous blue green was also confirmed experimentally using C2H2 method. Less
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