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A full list of Corals at Okinotorishima



Graduate School of Science / Faculty of Science

Top: Location of Okinotorishima in relation to Japan and the Japanese Exclusive Economic Zone 
© Hajime Kayanne
bottom: Okinotorishima
© MLIT Keihin River Office

Professor Hajime Kayanne and his research group at the University of Tokyo’s Graduate School of Science, Department of Earth and Planetary Science, have identified ninety-three coral species at Okinotorishima (Okinotori Island), an isolated table reef located in the center of the Philippine Sea. The species composition of the island is similar to that of other islands in the northwestern Pacific, but the number of species is small in comparison with surrounding islands. The coral fauna at the island is characterized by a unique species composition that is independent of the Ryukyu Islands, mainland Japan, Palau, and the Mariana Islands. No endemic species were found, but the dominant Acropora species (A. aculeus, A. sp. aff. divaricata, and A. globiceps) were morphologically different from corresponding species at the Ryukyu Islands. The relatively low species diversity at the island despite the close proximity to an area of high diversity is explained by its small habitat diversity and isolation from other islands. The island is located in a subtropical gyre and is isolated from major currents. Thus, only coral larvae with a long competency period (as long as 70 days) can settle at the island from surrounding islands. This unique species composition seems to have been maintained for at least the last 7600 years, since the last stage of sea level rise in the post-glacial period (Holocene).

Press release (Japanese)


Hajime KAYANNE, Chuki HONGO, Ken OKAJI, Yoichi IDE, Takeshi HAYASHIBARA, Hidekazu YAMAMOTO, Nobuo MIKAMI, Kiyoshi ONODERA, Takaaki OOTSUBO, Hiroyuki TAKANO, Makoto TONEGAWA, Shogo MARUYAMA,
“Low species diversity of hermatypic corals on an isolated reef, Okinotorishima, in the northwest Pacific(孤立したサンゴ礁,北西太平洋沖ノ鳥島における造礁サンゴの低い多様性)”.
Galaxea, Journal of Coral Reef Studies Online Edition: 2013/2/4 (Japan time), doi: 10.3755/galaxea.14.73.
Article link


Graduate School of Science

Department of Earth and Planatary Science, Graduate School of Science

Kayanne Lab, Department of Earth and Planetary Science, Graduate School of Science(Japanese)

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