Home > Ryukyu Islands > Tonaki Island
Tonaki Island is located northwest of the Kerama Islands and east of Kume Island, lying approximately midway between the two island groups. It is a small island with an area of about 3.5 km² and a coastline of 12.5 km. Considerable differences have been observed between coral reef communities on the western side of Kerama Islands and those on the eastern side of Kume Island, including the Hatenohama sandbar. Using eDNA, the primary objective of this study was to understand the composition of coral communities on Tonaki Island, which is situated between these two regions. The survey was conducted on August 15, 2025. Five sampling sites were established. Sites 1 and 5 were located on the western side of the island, Site 2 on the northern side, Site 3 on the eastern side, and Site 4 on the southern side.
| Point Number | Point Name | Latitude/Longitude | Dominant Genus | Percentage |
|---|---|---|---|---|
| 1 | Tonaki_west | 26.375047, 127.132271 | Anacropora (トゲミドリイシ属) / Montipora (コモンサンゴ属) | 35.77 % |
| 2 | Sugaer_Bama_northwest | 26.38681, 127.136843 | Pocillopora (ハナヤサイサンゴ属) | 37.49 % |
| 3 | Agari_Bama_east | 26.372197, 127.155104 | Acropora (ミドリイシ属) | 23.71 % |
| 4 | Shimazirizaki | 26.353777, 127.152174 | Anacropora (トゲミドリイシ属) / Montipora (コモンサンゴ属) | 27.82 % |
| 5 | Yubuku_Hama_west | 26.357255, 127.136697 | Echinopora (リュウキュウキッカサンゴ属) | 24.8 % |
Although only five sites were surveyed because of the island's relatively small size, comparisons of the coral generic composition of Tonaki Island with those of the Kerama Islands to the east and Kume Island to the west suggests that Tonaki Island possesses a distinctive coral reef community structure. In both the Kerama Islands and Kume Island, Acropora is among the dominant coral genus. On Tonaki Island, however, clear dominance of Acropora was observed only at Site 3 on the eastern side of the island, whereas at the other four sites it was not. Dominance of Montipora is shared with both the Kerama Islands and Kume Island, but on Tonaki Island, Pocillopora and Goniastrea also appeared as dominant genera. Furthermore, Echinopora was notably abundant at Sites 3, 4, and 5. These results suggest that coral reefs of Tonaki Island support coral genera different from those of both the Kerama Islands and Kume Island.
ミドリイシ属
(
Acropora
)
トゲミドリイシ属
(
Anacropora
)
/
コモンサンゴ属
(
Montipora
)
リュウキュウキッカサンゴ属
(
Echinopora
)
ハナヤサイサンゴ属
(
Pocillopora
)