Ocean warming is increasing the incidence, scale, and severity of global-scale coral bleaching and mortality, culminating in the third global coral bleaching event that occurred during record marine heatwaves of 2014-2017. While local effects of these events have been widely reported, the global implications remain unknown. Analysis of 15,066 reef surveys during 2014-2017 revealed that 80% of surveyed reefs experienced significant coral bleaching and 35% experienced significant coral mortality. The global extent of significant coral bleaching and mortality was assessed by extrapolating results from reef surveys using comprehensive remote-sensing data of regional heat stress. This model predicted that 51% of the world’s coral reefs suffered significant bleaching and 15% significant mortality, surpassing damage from any prior global bleaching event. These observations demonstrate that global warming’s widespread damage to coral reefs is accelerating and underscores the threat anthropogenic climate change poses for the irreversible transformation of these essential ecosystems.

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A new tribromoiododiphenyl ether (1) and eight known brominated diphenyl ethers (2–9) were isolated from the MeOH extract of the sponge Arenosclera sp. collected in Vietnam, using repeated open column chromatography and preparative thin layer chromatography. The chemical structure of the new compound 1 was determined by analyses of spectroscopic (1D‐ and 2D‐NMR, and MS) data and by comparison of our data with those reported in the literature. Compounds 1, 3, and 8 exhibited strong antibacterial activities against the Gram‐positive bacteria Bacillus subtilis and Staphylococcus aureus and the Gram‐negative bacterium Klebsiella pneumoniae with MIC values ranging from 0.8 to 6.3 μm, while compounds 5 and 7 only displayed activities against Gram‐positive bacteria with MIC values from 0.5 to 3.1 μm. Compound 2 showed activities against the four tested bacteria with MIC values ranging from 0.5 to 6.3 μm.

Coral communities in the shallow waters of Con Dao islands, located on the continental shelf of Southern Vietnam, were monitored in June 2019 when bleaching alert level 1 was announced by NOAA Coral Reef Watch (https:// coralreefwatch.noaa.gov/satellite/index.php) and the surface seawater temperature was recorded between 30-32℃ in the field. We used the ReefCheck transect method (Hodgson et al. 2006) to record cover of bleached corals and non-bleached corals at two depths (shallow: 3-5 m and deep: 6-8 m) at 5 sites (EMS Fig. 1). The study sites were characterised by the dominance of hard corals with their cover more than 50% at 4 sites and around 25% at Cua Ga. Overall, 32.5±7.5% (mean±SE) of hard corals (mean cover＝51.8%, SD＝23.7%) and 100% of soft corals (mean cover＝2.6%, SD＝4.5%) were observed to bleach. Bleaching at genus level was considered for common coral genera with their total cover (%) as follows respectively: Acropora (17.3), Montipora (9.9) Porites (4.2), Diploastrea (2.4), Pachyseris (1.7), Pavona (1.6), Fungia (1.1), Favites (1.0), Pectinia (0.8) and Galaxea (0.6). The hard coral genera with most severe bleaching (all at 100% bleached) included: Fungia (Fig. 1A), Pachyseris (Fig. 1B), Pavona (Fig. 1C), followed by Pectinia (93.8±10.2% bleached; Fig. 1B) and massive Porites (69.9±15.2% bleached; Fig. 1D). Other coral genera commonly found in Con Dao Islands were moderately bleached such as Favites (30.0±26.7%), Goniastrea (23.8±26.1%), Montipora (10.1± 5.7%; Fig. 1A). Two genera Galaxea and Diploastrea did not suffer bleaching. Acropora with most branch and tabulate colonies were less impacted both in deep and shalow waters (0.9±1.3% bleached; Fig. 1D-F). Hard corals in deeper waters exhibited a higher susceptibility to bleaching than their shallow counterparts (48% bleached in deeper transects compared with 15% in shallow transects). The findings were consistent with the higher abundance of the five most susceptible genera mentioned above in deeper (total mean cover＝17.5%) than in shallow (2.2%) transects. An earlier bleaching event at Con Dao islands in October 1998 resulted in 37.8% of hard coral colonies bleached (Vo 2000). The 2019 event had both similarities and differences in impacts. Soft corals were the most susceptible in both events (100% bleached) and Galaxea remained consistently unbleached. In 2019, Pachyseris and Fungia had much higher levels of bleaching than in 1998, when these genera were little affected (7.7% and 8.3% bleached). In contrast, Diploastrea had no bleaching compared with 14% bleached in 1998. Porites was severely impacted at both events with 57% bleached and many dead massive corals covered by filamentous algae were recorded in October 1998. Acropora were among the susceptible genera with 19% bleached colonies together with many dead colonies observed in October 1998 (Vo 2000).

The result of investigation during September and October 2015 and review of previous studies showed that 224 stony coral species, 232 coral reef fish species, 88 Mollusca and Echinoderm were found in Ly Son Marine Protected Area. The biodiversity of coral reef communities was at medium level compared with other MPAs. The coverage of stony coral and soft coral was 6.1% ± 4.2 SD and 5.6% ± 5.0 SD, respectively. The density of coral reef fishes averaged 121 ± 74.4 SD Ind./100 m2 and this density mainly focused on small size group (< 10 cm) which ocupied 69.6% of total density. The average density of macro-invertebrates was 45 ± 3.0 SD Ind./100 m2 that depended on the Echinoderm group (more than 85% of total density). The coverage of living coral was considered the lowest meanwhile the density of coral reef fishes and macro-invertebrates was at medium level compared with other MPAs. Our result showed that there were two distinguished assemblages of coral reef communities. The charateristics of coral reef fishes and macro-invertebrates communities showed the resemblance in terms of distribution in most of the study sites meanwhile the coral community revealed the separation between two types of communities.