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The Spratly Islands are a remote group of more than 150 coral reefs and islands scattered in the south‐central South China Sea and representing a biodiversity hotspot in the region. An integrative anthropogenic impact and increased frequency of thermal anomalies have increasingly been threatening these unique reef ecosystems over the last three decades. The repetitive surveys conducted on four coral reef sites within the Spratly Islands in 2018–2019 and in 2021 revealed a significant decrease of coral cover, particularly of acroporids, a decrease of species diversity and an outbreak of crown‐of‐thorns starfish (COTS) Acanthaster planci (the variation of starfish abundance was 1–18 starfish/100 m2). Moreover, one of two additional sites, located within the same study reefs, revealed a coral‐killing photoautotrophic cyanosponge Terpios hoshinota, covering 56.9% of all dead scleractinian colonies on the reef slope of this site. Analysis of sea surface temperature dynamics during the last 4 years (2018–2021) in the Spratly area allowed suggesting the concurrent negative effect of the COTS outbreak and the thermal anomaly of 2020 on local coral communities. This effect may have contributed to the general trends in coral reef decline in the area of the Spratly archipelago under the condition of repetitive thermal stress and increasing anthropogenic impact. [ABSTRACT FROM AUTHOR]

The distribution of dominant coral genera and their response to the recent sea temperature anomalies in the last three decades are analyzed across reefs of the Maldivian Archipelago, which spans 860 × 120 km in the central Indian Ocean. The Maldives suffered one of the worst coral mortality rates in the Indian Ocean in the 1998 warming event and experienced two sub-lethal thermal anomalies in 2003 and 2010. The results showed that the Acropora proved an important driver of post-1998 recovery and has become a major dominant genus in most Maldivian reefs at present. The average coral cover and proportion of acroporids have decreased from south to north and represent correspondently 70.6/59% for the southern atoll, 62/53% for the central atoll and 33/10.3% for the northernmost atoll. Stylophora, Seriatopora and the hydrocoral Millepora were not found and are considered candidates for local extirpation from the Maldives. Higher thermal variability and frequency of thermal stress might lead to the decrease in the abundance of susceptible taxa in the northernmost atoll. No phase-shift to algae-dominated reefs was observed in any of the three locations. Factors contributing to coral recovery and acclimatization are discussed. [ABSTRACT FROM AUTHOR]