| Co-Investigator(Kenkyū-buntansha) |
POLLARD P.C. Department of Chemical Engineering and Microbiology, The Univ. of Queensland, Departmen
YMAMURO Masumi Department of Msrine Geology, Geological Survey of Japan, 工業技術院地質調査所, 研究員
SUZUKI Tkao Faculty of Science, Tohoku Univ. Research Associate, 理学部, 助手 (10124588)
KUNII Hidenobu Faculty of Science, Shimane Univ. Associate Professor, 理学部, 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, 室長 (00159550)
NOJIMA Satoshi Faculty of Science, Kumamoto Univ. Associate Professor, 理学部, 助教授 (30112288)
MUKAI Hiroshi Faculty of Science. Hokkaido Univ. Professor, 理学部, 教授 (00013590)
NISHIMURA Moritaka Faculty of Science, Tohoku Univ. Professor, 理学部, 教授 (80004357)
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| Research Abstract |
During the spring season in 1991 and 1992, we sent scientific party to Dravuni Island, Fiji, to investigate the biological structure and clcling of bioelements in tropical seagrass bed ecosystem.
In 1991, the participants were mostly biologists doing the field observation of seagrass biomass, their growth, transfer of produced organic materials to secondary producers, benthic as well as epiphytes, and fine biological structures of those communities. In 1992, environmental and experimental studies on metabolic rates of dominated animals were carried out. Following are the main results of 1991-1992 field studies.
(1)Averaged turnover time of above the ground part of dominated seagrass, i.c., Syringodium, was estimated to be ca. 1 month, while that of underground part, rhizome, was more than 500 days. We also obtained similar result from Thalassia in Papua New Guinea, and large standing stock of underground part of seagrass and slow turnover time is rather common characters of tropical seagrass, reflecting nutrient poor outer environments.
(2)For the supply of nitrogen, nitrogen fixation by benthic communities as well as epiphytes seems to be significant contribution to the total nitrogen budget of the system. In Papuan seagrass bed, which is near the continent, contribution of nitrogen fixations ca. 10 % of nitrogen demand by seagrass population. But, in Fiji as an nutrient poor ocean island, nitrogen fixation accounted upto several 10% of community nitrogen demand.
(3)For the decomposition of seagrass, there was not so many direct grazers and major population of heterotrophic animals were filter feeders, including bivalves and compound ascidians., indicating the importance of suspended organic materials as the food. On the other hand, bacterial activities at the interface of sediment-water column were high, suggesting the importance of their processes on decomposition of the dead seagrass.
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