Coral reefs have shown a decreasing trend in coral cover and reef area due to disturbances caused by climate change and human activities. However, there have been reports indicating that the rising sea levels in recent times are also prompting upward reef growth, raising interest in whether coral reefs will continue to form in the future. In this paper, I first summarize research methods using drilled core samples and raised coral reefs, which are important for reconstructing the reef formation process. In addition, while the genus and growth form of corals have been the focus in the coral reef formation process, it has become evident that coral species (key coral species) also play an important role in coral reef formation. But there is a shortage of research that specifically emphasizes key coral species, and there are numerous challenges to address, including the identification methods for these key coral species. In the future, to predict the fate of coral reefs, it is essential to meticulously clarify the conditions involved in coral reef formation. In addition to monitoring factors like coral density, it is imperative to also monitor the upward growth rate of coral reefs and the rate of sea level rise.

The frequent occurrence of coral bleaching due to rising seawater temperatures has become a major problem, and it is suggested that corals may die over a wide area in the future. In recent years, human intervention methods aimed at rescuing corals from large-scale mortality such as bleaching have been studied, and their feasibility in the field is being discussed. In this review, we introduce various approaches, such as acquiring stress tolerance through the physical environment and experienced environmental history that prevents and reduces bleaching stresses, increasing nutrition through heterotrophic food supply, and strengthening stress tolerance through the addition of metal elements like Mn. We also address bleaching as a holobiont, including bacteria and strategies for preventing bleaching utilizing genetic differences. In addition, the current status and future possibilities of human intervention in coral reef conservation efforts are discussed.

We quantitatively surveyed hermatypic corals using a one-square meter quadrat on a reef slope ranging in water depth from 3 m to 40 m at the northwestern part of Amitori Bay, Iriomote-jima, Japan. One hundred and four species of 36 genera of 12 families were recorded at the study site based mainly on underwater photos of 39 quadrats and close-up view of living corals within the quadrats. Results of cluster analyses using data on coral coverages and species compositions within the quadrats indicate that distinctive coral assemblages exhibit significant zonal (vertical) distribution patterns on the northwest reef slope of Amitori Bay. Based on differences in coverages, taxonomic groups, and growth forms of all the species recorded in this study, we defined 22 hermatypic coral assemblages that characterize the study site in the bay. It is expected that these results will not only provide ecological data for conserving the species diversity of hermatypic corals in Amitori Bay, but also serve as paleo-environmental (especially paleo-bathymetric) indicators for the Quaternary reef deposits such as the Ryukyu Limestone in the Ryukyus, southwest Japan.