Indonesia is part of the coral triangle region which is known as the world’s highest marine biodiversity, including stony corals. This situation used to benefit local people by trading ornamental corals. The aims of this study are to investigate the potential stock of ornamental corals as well as the reef conditions. The study took place in Kendari, Luwuk, Sumbawa and Belitung where the ornamental coral-collecting activities used to occur. The result indicates there were approximately 110 species of corals found with the majority of coral status are common (harvest limited) and uncommon (harvest with cautions). Based on the juvenile existence, only 66 corals have potential stocks. Euphyllidae (Euphyllia glabrescens and Plerogyra sinousa) had the highest potential stock in Kendari and Luwuk, while Fungiidae (Fungia spp) held the highest potential stock in Belitung and Sumbawa. This difference is likely related to different locality or habitat type. In general, coral reefs in Kendari, Luwuk and Belitung are in good condition, while fair condition occurs in Sumbawa. To conclude, the stock of ornamental corals is still high and the reefs are generally good, suggesting the collecting activities may be allowed with proper quota and continuous monitoring habitat condition to ensure the sustainability.

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Three groups of marine biotas in the coral reef ecosystem were analyzed to determine the overall condition coral reef ecosystem in Natuna Island (coral, reef fish, and megabenthos). Nineteen sampling sites are distributed completely in Natuna Island, including Natuna Besar Island, Tiga Island, and Sedanau Island. The coral reef monitoring refers to the Underwater Photo Transect (UPT), and data processing used the Coral Point Count for excel (CPCe). The reef fish observation using the Underwater Visual Census (UVC) and megabenthos observations using the Benthos Belt Transect (BBT). The percentage of the benthic cover was analyzed for several benthic categories. The analysis for reef fish consisted of diversity and abundance for the three fish groups, including the corallivore, herbivore, and carnivore. The megabenthos community’s analysis consisted of diversity and density from eight groups, including giant clams, lobster, Drupella sp., Linckia laevigata, sea urchin, sea cucumber, trochus, and Acanthaster planci. The Coral Reef Health Index (CRHI) analysis was used to determines the coral reef condition in Natuna. Nine sites were categorized as the fair condition of live coral cover with 26.53–36.87%. The largest composition of coral reef fish groups from herbivorous groups and the highest density megabenthos was sea urchins.

This paper assesses the distribution and community structure of coral species in six locations along the west coast of Sumatra, namely Mentawai, Bengkulu, Nias, Padang Pariaman, Simeulue, and Central Tapanuli. Data collected using Line Intercept Transect (LIT) method obtained from 55 sites at six locations. The ordination analysis by using PRIMER 7 software indicates the corals do not distributed evenly. In this case, almost all of the corals distributed mainly in Central Tapanuli and followed by Bengkulu, making it the most diverse corals location in the west coast. Mentawai and Padang Pariaman were less diverse and relatively similar as clustered together, but Padang Pariaman reefs had more Montipora and Pocillopora while Mentawai reefs is mainly featured by Pavona and Psammocora. Although Nias reefs clustered into two different clusters, the main reef features were Porites and Pavona. Simeulue reefs appeared characterized by Porites and Psammocora.  Porites known as a very common genus of coral and are found in the widest area of the world's coral reefs. The within-site species richness determined by using species accumulation curve. K-dominance curve showed that Bengkulu and Mentawai seemed to have the lowest cumulative abundance but then crossed over Central Tapanuli at the third most abundance species. There were 52 genera found from six locations, eight of them distributed in all locations. Approximately 90% of which were found in Central Tapanuli. There were no differences between live coral coverage within locations, yet Caswell’s neutral model showed that Mentawai and Bengkulu had more coral species than other locations, indicating that there were likely were less stress environmental conditions occurring in these two locations.

Coral reef ecosystem is one of the coastal marine ecosystems in tropical waters. Coral reef ecosystems are vulnerable to damage mainly due to environmental factors. A fairly popular event of coral reef damage is coral bleaching. Mass coral bleaching is generally caused by changes in Sea Surface Temperature (SST). The condition of corals that have bleaching is different from the condition of corals that have died. The recovery process from coral bleaching phenomena can be effectively carried out if the surrounding environment is supportive and sea surface temperature return stable. The phenomenon of coral bleaching is a real indicator of the environmental stresses that occur on coral reefs. This paper will explain about coral bleaching, the factors that cause coral bleaching, and whether the bleaching coral reefs mean alive or dead.