Home > Ryukyu Islands > Miyako and Irabu island
Irabu Island is located approximately 5 km west of Miyako Island. Although it is difficult to discern from aerial photographs, Shimoji Island lies immediately to the west of Irabu Island, separated only by a narrow channel. Coral reefs of the Miyako Island region suffered particularly severe damage during the mass coral bleaching event of 2016, compared with reefs around Okinawa Island and other relatively high-latitude regions of Japan. By 2023, recovery from the 2016 bleaching event had progressed considerably.
| Point Number | Point Name | Latitude/Longitude | Dominant Genus | Percentage |
|---|---|---|---|---|
| 1 |
Karimata west
|
24.87574, 125.27656 | Cyphastrea (トゲキクメイシ属) | 15.97 % |
| 2 |
Ohsaki north
|
24.84699, 125.28408 | Acropora (ミドリイシ属) | 23.82 % |
| 3 |
Hisamatu east
|
24.79783, 125.24909 | Acropora (ミドリイシ属) | 24.97 % |
| 4 |
Irabujima south
|
24.76155, 125.21001 | Acropora (ミドリイシ属) | 31.79 % |
| 5 |
Kurimajima west
|
24.71364, 125.22952 | Acropora (ミドリイシ属) | 51.64 % |
| 6 |
Makiyama east
|
24.82143, 125.22807 | Acropora (ミドリイシ属) | 36.89 % |
| 7 |
Bijashi
|
24.85852, 125.19313 | Acropora (ミドリイシ属) | 90.01 % |
| 8 |
Shiratorizaki west
|
24.8631, 125.13872 | Anacropora (トゲミドリイシ属) / Montipora (コモンサンゴ属) | 40.18 % |
| 9 |
Toguchi south
|
24.80119, 125.1813 | Anacropora (トゲミドリイシ属) / Montipora (コモンサンゴ属) | 57.44 % |
Coral reefs of Irabu Island and western Miyako Island can be broadly characterized as follows: reefs located between western Miyako Island and Irabu Island tend to be dominated by Acropora, whereas those on the northern and southern sides of Irabu Island (Shiratorizaki West and Toguchi South Reef) are characterized by a greater abundance of Montipora. However, eDNA data show that with the exception of Bijashi, even sites with relatively high proportions of Acropora DNA were not overwhelmingly dominated by this genus.
Divers who conducted visual surveys concurrently with the eDNA sampling reported that the reefs at Bijashi and Makiyama East Reef were indeed dominated by Acropora, whereas other reefs supported a wide variety of coral taxa. In other words, the coral reefs of western Miyako Island and Irabu Island appear to be characterized less by the dominance of a single coral genus and more by the coexistence of diverse coral assemblages.
