We investigated the current state of the zooxanthellate scleractinian coral community in Kabira Bay, Ishigaki Island, Japan. The composition of the coral community in Kabira Bay depended on differences in topography. A greater number of internal coral species were found inside the bay. Skeletons of branch-formed and bottle wash brush-formed Acroporidae were found along the east coast of the central part of the bay probably because of coral bleaching in 2007. On the other hand, Acroporidae survived along the west coast of the inner part of the bay. In addition, turbidity was found to be higher in the inner part of the bay. It is thought that the turbidity of the inner part of the bay reduced coral bleaching.

Ministry of the Environment has carried out the coral reef monitoring survey as a part of “Monitoring sites 1000 Project” from FY 2004. The survey was conducted mainly by coral reef researchers at each site and local experts such as research institutions, local consultants, diving operators with assistance of volunteers from NGO/NPO. In 2016, Coral bleaching event occurred mainly at the area from Amami Islands to Yaeyama Islands. Severe damages by mass coral bleaching were observed at the sites of Miyako Island, Yabiji reefs, Sekisei Lagoon and Sakiyama Bay. At Yabiji reefs site, average coral bleaching rate and average coral bleaching mortality were 70.1% and 67.5%, respectively. At the sites of Sekisei Lagoon and Sakiyama Bay, average coral bleaching rate was all more than 90% and average coral bleaching mortality was 34.8-67.9%. It is thought that a primary factor of the coral bleaching event in 2016 was high water temperature in the summer.

Thermal anomaly-induced mass bleaching status of Sekisei lagoon, Okinawa was surveyed in the summer 2016. The survey focused on 11 species of major scleractinian corals including Acropora, Pocillopora, Seriatophora, Stylophora, Favites as well as massive Porites in order to evaluate the genus-specific mass bleaching impacts. The survey was conducted by visually categorizing bleaching status of more than 6400 colonies into 5 distinguished stages of bleaching at 35 sites in the Sekisei lagoon. The result showed that bleaching of 10 species reached more than 98% while massive Porites showed around 58.5% bleaching. Although, massive coral species are usually categorized into low bleaching-impacted corals, mortality rate was clearly higher in 2016 compared with the mass bleaching survey conducted in September 2007. These results strongly suggest that the 2016 mass bleaching event in Seskisei lagoon severely impacted wide range of corals with relatively high mortality of the massive coral species. Such impact may imply longer period needed for the reef scape recovery in Seskisei lagoon.

One of the major causes of rapid coral-reef decline is coral bleaching induced by anomalously high sea surface temperatures. Projections based on climate models show contrasting futures from different anthropogenic CO₂ emission scenarios, suggesting reducing CO₂ emissions is mandatory to save coral reefs. In addition to reducing the emissions, setting up adaptation measures to conserve coral reefs is needed. Both national and international conservation measures are emerging, and Japan issued “Emergency Declaration on the Large-Scale Coral Bleaching Event Conference on Emergency Countermeasures for Large-Scale Coral Bleaching” in response to the large-scale bleaching in 2016. Both mitigation and adaptation strategies for climate change are needed to save coral reefs.

Actions understood and conducted by the national government, prefectural government, private sector, researchers and residents are crucial in order to conserve the vulnerable coral reef ecosystem under the negative impacts of climate change. In this section, we introduce current status and projection of climate change in relation to coral reef ecosystems, explain potential actions to be taken by each body to reach the goal of Paris agreement, briefly explain “Action plan for coral reef ecosystem conservation 2016-2020”, and finally introduce the actions for coral reef ecosystem conservation in Iriomote-Ishigaki National Park as some of the actual actions in progress by Ministry of the Environment, Japan (MoE).

Coral reefs around Okinawa are mainly consisted by fringing type reefs adjacent to land and often characterized by relatively semi-enclosed environment. When red soil flows into the coral reef from agricultural field or development site, the coral reef becomes highly turbid for long period in which red soil tends to accumulate on the sea bed without reaching to the outer reef (open sea). Due to inflow of sewage, waste water from animal housing facilities and fertilizer from agricultural field, nutrients concentration in coral reefs might be elevated. In order to conserve the coral reef ecosystems, it is necessary to protect the hermatypic coral as the major constituent of the coral reef ecosystems. By reducing inflow of red soil and nutrients from land, and reducing the stress on the local scale, it is important to increase the resilience of the coral reef ecosystems. Regarding the measures against soil runoff, Okinawa Prefecture Red Soil Erosion Prevention Ordinance and The Master Plan of Red Soil Runoff Prevention Countermeasure have enforced, and its positive effects are expected. With regard to the nutrients load, the effect of eutrophication on the corals and reef ecosystems still remain poorly understood. However, it was suggested that eutrophication of coral reefs significantly affect the health of corals. Therefore, it is necessary to suppress excessive inflow of nutrients to coral reefs while establishing water quality guideline for reef resilience.

A correlation between the degree of coral cover, water temperature, and NO₃^－-N concentrations was identified in the peripheral sea of Yoron Island, Japan, with a numerical analysis. This analysis suggested that tidal conditions at the sea near shore and nutrients from the land, such as NO₃^－-N, influenced the coral ecosystem. Therefore, tidal and material transport models of Yoron Island must be constructed and monitored based on the management of nutrients, which is produced by the introduction of farming techniques that aims conservation of the environment. Also it’s important for people in an area of agriculture and forestry, fisheries, tourism industries to working on creation of the environment and preservation. For instance, although the watershed of the Komesu groundwater dam at Itoman city in Okinawa must be reconsidered as researchers plan the maintenance and restoration of the coral reef ecosystem, the researchers must construct a management system based on the relationships between human activities and the coral reef ecosystem as coral area to be promotion. We must recognize the importance of load reduction measures, such as reducing the nutrients entering the sea from the land, and be aware of how human activities affect the coral reef ecosystem. It is necessary to organize informed and effective countermeasures for the protection of coral reef area. People have to step forward to achieve sustainable ecosystem in the future.

Coral ecosystems nurture high biodiversity and bioproductivity, even in tropical and subtropical seas, in which nutrient levels are low. However, there is concern that these ecosystems are rapidly declining. Apart from the abnormal increase in the seawater temperature, the eutrophication of coral-supporting seawater has also drawn considerable attention, especially inside the reefs. Based on the results obtained from our previous studies of several coral islands in the Ryukyu Islands, Japan, this report shows that the uncontrolled application of fertilizer during the cultivation of sugarcane, the main crop on the islands, which is especially concentrated in the very early stage of sugarcane production, ultimately induces the eutrophication and acidification of lagoon seawater. This report also suggests an improved method of fertilizer application that will both reduce the nitrates loaded into the local environment and provide an agricultural benefit to local farmers.

Since 1998, the Onna Village Fisheries Cooperative, in Okinawa, Japan, has farmed and outplanted corals in the hope that sexual reproduction by synchronized spawning of outplanted colonies will help coral reef restoration.

One of the major techniques being employed is the coral pole culture method (Hibitate-shiki in Japanese), that is, the rearing of donor coral colonies on iron poles that are driven into sand and rubble. About 24,000 donor colonies of 54 species belonging to 15 genera and 11 families are being farmed as of the end of March, 2017. It is estimated that these coral nurseries annually release ~5.7 billion eggs, resulting in ~2.7 billion surviving larvae two days after synchronous spawning. Furthermore, the estimated number of fishes staying in the coral nurseries was approximately 670,000 belonging to 33 species, and dominated by damselfish (Family Pomacentridae). Based on microsatellite genotyping, 163 Acropora tenuis donors in coral nurseries were derived from 81 coral genets.

Mass coral bleaching was observed in the summer of 2016 in Onna Village, as in many reefs throughout the world. However, the survival rate of farmed colonies on iron poles was higher than that of outplanted corals on natural substrates and of natural colonies. Large-scale coral nurseries using the coral pole culture method might be of some help in coral reef restoration.

Coral bleaching in the summer of 2016 caused serious damage in the Sakishima Islands. In response to this event, the World Wide Fund for Nature (WWF) Japan Coral Reef Conservation and Research Center confirmed the bleaching status around Ishigaki Island. In its role as a nongovernmental organization (NGO) working together with people in various fields to tackle environmental problems, WWF Japan conducted surveys of the sea conditions and attempted to disseminate this information. On Ishigaki Island, WWF Japan conducted a joint survey of the Shiraho and Yonehara reefs with researchers, using an unmanned aerial vehicle to determine the bleaching status from an aerial perspective. It also provided information on the state of coral bleaching to researchers to allow them to analyze its spread. In collaboration with marine business operators in the area, WWF Japan established a project to disseminate information about the coral bleaching around Ishigaki and Miyako islands, and participated in and supported efforts to report the nature of the bleaching. This project successfully shared information on the coral bleaching event with many business operators and disseminated this information throughout the summer of 2016. With the objective of conserving the Sekisei Lagoon coral reef ecosystem, WWF Japan has begun surveys and studies to establish a system of environmental certification that will facilitate the conservation of coral reefs in general and the Sekisei Lagoon coral reef ecosystem in particular. The findings recommend a sustainable environmental certification system for beef cattle production, sugarcane cultivation, pineapple cultivation, fisheries, tourism, etc., to allow the conservation and restoration of the coral reef ecosystem.

Summary of private sector’s activities for massive coral bleaching event in Japan on 2016 is described. Also, coral conservation activities and coral bleaching mitigation activities are proposed.

Healthy oceans and coastal areas supply invaluable water and oxygen to people and secure eradication of poverty, supply of food, employment of people, tourism and protection from natural disasters. It is important to establish an integrated ocean and coastal management system to sustain the conservation, restoration and utilization of the ocean and coastal areas with various stakeholders’ proactive participation. Firstly, we described the status of the world and Japanese implementation of integrated ocean and coastal management, and analyzed role of the management system as means of solving problems. Secondly, taking the implementation of the basic plan of ocean policy of Taketomi Town as an example, important components for implementation of measures for the mass coral breaching were described. Those measures were, countermeasures based on sound understanding of nature, stakeholders participation and enforcement of capacity building with enforcement of institutional arrangements. Furthermore, the importance of networking efforts inside and outside the region as horizontal expansion were stressed. The measures should not be limited as regional efforts, but as a project of All-Japan as well as an advanced example of the international efforts to tackle with mass coral breaching in the world.