No abstract

[1] Typhoon-generated storm waves generally cause mechanical damage to coral communities on present-day reefs, and the magnitude and extent of damage is predicted to increase in the near future as a result of global warming. Therefore, a comprehensive understanding of potential future scenarios of reef ecosystems is of prime interest. This study assesses the current status of coral communities on Ibaruma reef, Ryukyu Islands, on the basis of field observations, engineering and fluid dynamic models, and calculations of wave motion, and predicts the potential effects of a super-extreme typhoon (incident wave height, H = 20 m; wave period, T = 20 s) on the reef. On the present-day reef, massive corals occur in shallow lagoons and tabular corals occur from the reef crest to the reef slope. The observed distribution of corals, which is frequently attacked by moderate (H = 10 m, T = 10 s) and extreme (H = 10 m, T = 15 s) typhoons, is consistent with the predictions of engineering models. Moreover, this study indicates that if a super-extreme typhoon attacks the reef in the near future, massive corals will survive in the shallow lagoons but tabular corals on the reef crest and reef slope will be severely impacted. The findings imply that super-extreme typhoons will cause a loss of species diversity, as the tabular corals are important reef builders and are critical to the maintenance of reef ecosystems. Consequently, reef restoration is a key approach to maintaining reef ecosystems in the wake of super-extreme typhoons.

Coral reefs are ecologically and economically valuable. After the 2004 Indian Ocean tsunami, the damages on corals were extensively studied by various international teams. However, there is no quantitative study that evaluated the relationship between the degree of the damage on corals and the hydraulic values of the tsunami. In this study, we investigated the relationship between the coral damages by the 2004 Indian Ocean tsunami and the hydraulic value of the tsunami at Similan Islands, Thailand, based on the numerical modeling of the tsunami inundation. As a result, it was found that the current velocity of the tsunami was one of the important factors for the damage of corals.