Table 1 Difference in coastal ecosystems (coral and E. acoroides) and geographic environments between Amitori Bay and Sakiyama Bay (Kawana 1990, Shimokawa et al. 2014a, Ministry of the Environment, Government of Japan 2015, Shimokawa et al. 2016, Minami et al. 2017)

Coral

Tabular and branching corals are dominant in the bay’s mouth and inner parts, respectively. Coral diversity is the maximum in the bay’s intermediate part

Branching and massive corals are dominant in the reef edge side of the bay’s intermediate part and the coast side of the bay’s intermediate part, respectively. Coral diversity is the maximum on the bay’s reef edge

E. Acoroides

E. acoroides are rare, and no large community exists

E. acoroides is distributed over a wide area of the bay’s inner part

Bay length

Around 3.9 km

Around 1.4 km

By mouth length

Around 2.0 km

Around 1.3 km

Water depth where corals mainly exist

From a few to 6 m. The seafloor is uneven

A few meters. The sea floor is almost flat

Maximum water depth

Around 70 m at the center of the bay

Around 40 m at the outside the reef edge

Rivers

Ayanda and Udara rivers at the innermost part of the bay

Painta and Ubo rivers at the innermost part of the bay