Grant-in-Aid for international Scientific Research
|Allocation Type||Single-year Grants|
|Research Institution||The University of Tokyo|
KOIKE Isao Ocean Research Institute, The University of Tokyo, 海洋研究所, 教授 (30107453)
POLLAND Pete CSIRO, オーストラリア, 研究員
IIZUMI Hitoshi Otsuchi Marine Laboratory, Ocean Research Inst., Univ. Tokyo, 海洋研究所大槌臨海センター, 助手 (00159550)
NOJIMA Satoshi Amakusa Marine Biological Laboratory, Kyushu University, 理学部臨海実験所, 助手 (30112288)
KOGURE Kazuhiro Ocean Research Institute, The University of Tokyo, 海洋研究所, 助手 (10161895)
AIOI Keiko Ocean Research Institute, The University of Tokyo, 海洋研究所, 教務職員 (90107459)
MUKAI Hiroshi Ocean Research Institute, The University of Tokyo, 海洋研究所, 助手 (00013590)
NISHIHIRA Moritaka Department of Biology, Ryukyu University, 理学部, 教授 (80004357)
POLLARD Peter C. CSIRO, Australia
|Project Period (FY)
1989 – 1990
Completed(Fiscal Year 1990)
|Budget Amount *help
¥9,000,000 (Direct Cost : ¥9,000,000)
Fiscal Year 1990 : ¥2,000,000 (Direct Cost : ¥2,000,000)
Fiscal Year 1989 : ¥7,000,000 (Direct Cost : ¥7,000,000)
|Keywords||Seagrass bed ecosystem / Primary production / Nitrogen metabolism / Filter feeders / Symbiosis / Epiphytes / Benthos / Herbivorous fish|
It has been clarified by previous studies that tropical seagrass ecosystem has several food-chains consisting by high diversity of seagrasses and benthic animals in Papua New Guinean seagrass bed, which locates in center of seagrass distribution. Otherwhile, in marginal Fijian seagrass beds, there was pure stands of Syringodium isoetifolium.
1. Concentration of nutrients in ambient seawater and within seagrass vegetation was very low, while it in interstitial water of seagrass bed sediment was 10-100 times of ambient seawater. It is originated from decomposition of detritus accumulated in sediments. Organic carbon and nitrogen in sediment of bare bottom did not change from bottom surface to 20 cm deep, and the C/N ratio was ca.10 (g/g). While, organic carbon in seagrass bed sediment reduced to 1/3 at 20 cm deep, but organic nitrogen did not change unlikely in carbon. This suggests that nitrogen has never been lost in bacterial metabolism and is effectively taken up again by seagrasses.
. Biomass and primary production of Syringodium pure stand were measured by (1) marking method, (2) oxygen evolution measurement, (3) lacuna gas volumetry. The production rates were 2.5-11.2 g/m2/day. This range of primary production was not low compared with high diversity seagrass beds in Papua New Guinea, because of very dense stand in Syringodium stand.
3. Characteristics of Fijian seagrass bed are in abundant filter feeding benthic animals, in spite of poverty in phytoplankton. Among the animals, bivalves can be sustained themselves by a mechanism in which detritus from seagrass and epiphytes is accumulated in high concentration within dense seagrass stands. Otherwhile, compound ascidians attached to seagrass leaf, having abundant biomass (ave. 14.8 g/m2), contribute also to primary production, because of symbiosis with algae. It was estimated by our experiments that the ascidians obtained half and half of nutrients from CO2 fixation by symbiotic algae and subordinate nutrition by filter feeding. In nitrogen metabolism, independent nutrition was effective. Less