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Tarama Island is located approximately 67 km west of Miyako Island and about 35 km east of Ishigaki Island. The island has an elliptical shape, measuring approximately 6 km from east to west and 4.3 km from north to south. Minna Island is also located about 8 km to the north of Tarama Island. Tarama Island is a raised coral reef island, with a generally flat landscape and sandy beaches surrounding the island. The seawater is highly transparent, and rich coral communities cover rocky outcrops scattered across the sandy seabed. Miyako Island and Ishigaki Island are separated by a distance of approximately 100 km. We expected that Tarama Island could provide clues about the characteristics of coral reefs between these two islands. Therefore, on October 16 and 17, 2025, we collected surface seawater samples from 13 sites on Tarama Island and 5 sites on Minna Island, and analyzed the coral eDNA in these samples. (We did not obtain photographs during surveys on Tarama Island; therefore, only eDNA data are displayed.)
| Point Number | Point Name | Latitude/Longitude | Dominant Genus | Percentage |
|---|---|---|---|---|
| 1 | Minna_hanarezaki | 24.743337, 124.71301 | Acropora (ミドリイシ属) | 22.73 % |
| 2 | Minna_northeast | 24.762475, 124.70635 | Pocillopora (ハナヤサイサンゴ属) | 26.99 % |
| 3 | Minna_north | 24.780151, 124.67799 | Acropora (ミドリイシ属) | 42.01 % |
| 4 | Minna_northwest | 24.760658, 124.67429 | Acropora (ミドリイシ属) | 36.32 % |
| 5 | Minna_west | 24.747795, 124.68654 | Acropora (ミドリイシ属) | 35.02 % |
| 6 | Maedomari_west | 24.686412, 124.70214 | Acropora (ミドリイシ属) | 25.22 % |
| 7 | Nagasyagi_reef_edge | 24.678053, 124.68393 | Acropora (ミドリイシ属) | 51.03 % |
| 8 | Auru_reef_edge | 24.672542, 124.6753 | Anacropora (トゲミドリイシ属) / Montipora (コモンサンゴ属) | 24.59 % |
| 9 | Takashibama_reef_edge | 24.657906, 124.66771 | Anacropora (トゲミドリイシ属) / Montipora (コモンサンゴ属) | 43.42 % |
| 10 | Akadan_reef_edge | 24.646403, 124.67064 | Anacropora (トゲミドリイシ属) / Montipora (コモンサンゴ属) | 20.1 % |
| 11 | Magari_reef_edge | 24.636786, 124.67483 | Acropora (ミドリイシ属) | 23.65 % |
| 12 | Maedomari_east | 24.684119, 124.718539 | Acropora (ミドリイシ属) | 26 % |
| 13 | Tarama_northeast | 24.676723, 124.731388 | Acropora (ミドリイシ属) | 49.24 % |
| 14 | Tarama_east | 24.668721, 124.736149 | Acropora (ミドリイシ属) | 28.92 % |
| 15 | Futenma_port | 24.642693, 124.735633 | Acropora (ミドリイシ属) | 14.07 % |
| 16 | Uedamari_reef_slope | 24.63486, 124.720997 | Acropora (ミドリイシ属) | 16.97 % |
| 17 | Uedamari_reef_edge | 24.629848, 124.708954 | Anacropora (トゲミドリイシ属) / Montipora (コモンサンゴ属) | 28.51 % |
| 18 | Takaana_reef_edge | 24.631276, 124.69101 | Anacropora (トゲミドリイシ属) / Montipora (コモンサンゴ属) | 49 % |
The “ZOTU Top 10 Bar Graph for All Sites” shows that Acropora and Montipora are the dominant coral genera on both Tarama Island and Minna Island. However, these two genera together account for only about 50% of all corals, while the remaining 50% consists of various corals, including Pocillopora, Porites, and Paragoniastrea, suggesting that reefs of Tarama Island and Minna Island are highly diverse.
Furthermore, when viewing aerial photographs of the islands with the most dominant genera overlaid, it can be seen that Montipora dominates the western reefs of Tarama Island, whereas Acropora dominates the eastern reefs. This is exactly the opposite of the pattern observed at the tip of the Nosoko Peninsula on neighboring Ishigaki Island, where Acropora dominates on the western side and Montipora on the eastern side.
