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Mesophotic coral ecosystems (MCEs) are light-dependent communities occurring at depths of 30–150 m. They have been suggested to serve as refuge against thermal stress during heat waves for some coral species. Recent studies on MCEs have revealed a high diversity of communities, some unique, and that these ecosystems are far from being immune to anthropogenic threats. However, the depths at which these ecosystems are found make their exploration and study challenging. Consequently, most suitable environments for MCEs remain unexplored. To facilitate the detection and characterization of MCEs, we improved the methodology for mesophotic scleractinian survey by environmental DNA (eDNA) metabarcoding analysis using seawater collected by underwater mini-Remote Operated Vehicle (mini-ROV). We tested this improved approach at upper mesophotic sites in Okinawa, Japan, with different corals dominating the communities (i.e., Alveopora-dominated, Seriatopora-dominated, and Acropora-dominated communities). Despite the proximity of the different sites, our eDNA metabarcoding analyses detected the dominant coral genera specific to each site. In addition, this study detected numerous other genera present at these sites, including Acropora, Pachyseris, Galaxea, Lobophyllia, Montipora, Pocillopora, Porites, and others. Therefore, this study might support a new technical gate for comprehensive survey of MCEs using eDNA samples collected by underwater mini-ROV, although further technical improvement is required for quantitative estimation. [ABSTRACT FROM AUTHOR]

A new species of scleractinia in the genus Kuhnastraea Cuif, 1976 is described from the Upper Triassic of Sikhote-Alin. This genus includes the species K. decussata (Reuss, 1854), K. incrassata (Frech, 1890), K. cowichaenensis (Clapp et Shimmer, 1911), K. borealis (Smith, 1927), and K. rara sp. nov. [ABSTRACT FROM AUTHOR]

Scleractinian corals typically form a robust calcium carbonate skeleton beneath their living tissue. This skeleton, through its trace element composition and isotope ratios, may record environmental conditions of water surrounding the coral animal. While bulk unrecrystallized aragonite coral skeletons can be used to reconstruct past ocean conditions, corals that have undergone significant diagenesis have altered geochemical signatures and are typically assumed to retain insufficient meaningful information for bulk or macrostructural analysis. However, partially recrystallized skeletons may retain organic molecular components of the skeletal organic matrix (SOM), which is secreted by the animal and directs aspects of the biomineralization process. Some SOM proteins can be retained in fossil corals and can potentially provide past oceanographic, ecological, and indirect genetic information. Here, we describe a dataset of scleractinian coral skeletons, aged from modern to Cretaceous plus a Carboniferous rugosan, characterized for their crystallography, trace element composition, and amino acid compositions. We show that some specimens that are partially recrystallized to calcite yield potentially useful biochemical information whereas complete recrystalization or silicification leads to significant alteration or loss of the SOM fraction. Our analysis is informative to biochemical-paleoceanographers as it suggests that previously discounted partially recrystallized coral skeletons may indeed still be useful at the microstructural level.

The deep sea plays a critical role in global climate regulation through uptake and storage of heat and carbon dioxide. However, this regulating service causes warming, acidification and deoxygenation of deep waters, leading to decreased food availability at the seafloor. These changes and their projections are likely to affect productivity, biodiversity and distributions of deep-sea fauna, thereby compromising key ecosystem services. Understanding how climate change can lead to shifts in deep-sea species distributions is critically important in developing management measures. We used environmental niche modelling along with the best available species occurrence data and environmental parameters to model habitat suitability for key cold-water coral and commercially important deep-sea fish species under present-day (1951-2000) environmental conditions and to project changes under severe, high emissions future (2081-2100) climate projections (RCP8.5 scenario) for the North Atlantic Ocean. Our models projected a decrease of 28%-100% in suitable habitat for cold-water corals and a shift in suitable habitat for deep-sea fishes of 2.0°-9.9° towards higher latitudes. The largest reductions in suitable habitat were projected for the scleractinian coral Lophelia pertusa and the octocoral Paragorgia arborea, with declines of at least 79% and 99% respectively. We projected the expansion of suitable habitat by 2100 only for the fishes Helicolenus dactylopterus and Sebastes mentella (20%-30%), mostly through northern latitudinal range expansion. Our results projected limited climate refugia locations in the North Atlantic by 2100 for scleractinian corals (30%-42% of present-day suitable habitat), even smaller refugia locations for the octocorals Acanella arbuscula and Acanthogorgia armata (6%-14%), and almost no refugia for P. arborea. Our results emphasize the need to understand how anticipated climate change will affect the distribution of deep-sea species including commercially important fishes and foundation species, and highlight the importance of identifying and preserving climate refugia for a range of area-based planning and management tools.

Scleractinian corals typically form a robust calcium carbonate skeleton beneath their living tissue. This skeleton, through its trace element composition and isotope ratios, may record environmental conditions of water surrounding the coral animal. While bulk unrecrystallized aragonite coral skeletons can be used to reconstruct past ocean conditions, corals that have undergone significant diagenesis have altered geochemical signatures and are typically assumed to retain insufficient meaningful information for bulk or macrostructural analysis. However, partially recrystallized skeletons may retain organic molecular components of the skeletal organic matrix (SOM), which is secreted by the animal and directs aspects of the biomineralization process. Some SOM proteins can be retained in fossil corals and can potentially provide past oceanographic, ecological, and indirect genetic information. Here, we describe a dataset of scleractinian coral skeletons, aged from modern to Cretaceous plus a Carboniferous rugosan, characterized for their crystallography, trace element composition, and amino acid compositions. We show that some specimens that are partially recrystallized to calcite yield potentially useful biochemical information whereas complete recrystalization or silicification leads to significant alteration or loss of the SOM fraction. Our analysis is informative to biochemical-paleoceanographers as it suggests that previously discounted partially recrystallized coral skeletons may indeed still be useful at the microstructural level.

Increases in local and global stressors have led to major declines in coral populations throughout the western Atlantic. While abundances of other species have declined, however, the relative abundance of the mustard hill coral, Porites astreoides, has increased. Porites astreoides is relatively resilient to some stressors, and because of its mixed reproductive strategies, its populations often recover quickly following disturbances. The ability for P. astreoides to continue as a potential “winner” in western Atlantic reefs relies on maintaining sufficient genetic variation within populations to support acclimatization and adaptation to current and future environmental change. Without high genetic diversity and gene flow within the population, it would have limited capacity for adaptation and the species’ competitive advantages could be short-lived. In this study, we determined the genetic relatedness of 37 P. astreoides colonies at four shallow reefs along the offshore Florida Keys Reef Tract (FKRT), a region particularly hard-hit by recent disturbances. Using previously designed microsatellite markers, we determined the genetic diversity and connectivity of individuals among and between sites. Our results suggest that the FKRT likely contains a single, well-mixed genetic population of P. astreoides, with high levels of gene flow and evidence for larval migration throughout the region. This suggests that regional populations of P. astreoides likely have a higher chance of maintaining resilience than many other western Atlantic species as they face current and future disturbances. [ABSTRACT FROM AUTHOR]

Aim: Convergence, stasis and plasticity can frequently confound our understanding of species distributions in the seas. Yet delimiting species and understanding population connectivity across marine environments is mandatory for establishing appropriate management of coral reefs, which are experiencing critical declines. We test whether morphospecies from Pocillopora corals found on outer reef slopes are unique species or species complexes, in order to correctly define their respective distributions and consequently to accurately assess their population connectivity. Location: Archipelagos and islands of the Western Indian Ocean and the Southern Pacific (New Caledonia, Tonga, French Polynesia). Taxon: Pocilloporaeydouxi/meandrina and Pocillopora verrucosa morphospecies (Scleractinia). Methods: We analysed the 13‐microsatellite genotypes of 4837 colonies from six understudied ecoregions in the southern part of the genus distribution, to first explore the genetic partitioning within morphospecies. We then characterized the spatial distribution of each delimited species and analysed patterns of genetic diversity and connectivity for each species separately. Results: Both morphospecies are complexes of species, each found almost exclusively in the Indian or the Pacific Oceans. Moreover, some of these cryptic species are found in sympatry over their whole distribution, which sometimes was very restricted. However, within each species, genetic diversity and connectivity were relatively high, although some populations were found differentiated for some species, while not for others. Main conclusions: A weak connectivity was found between the Indian and Pacific Oceans, but high connectivity within both oceans, supporting the existence of a barrier impeding gene flow between both ocean basins in Pocillopora. Although constrained by the same geography and current patterns, some sympatric species present different connectivity patterns, demonstrating the importance of multi‐species connectivity models to set up appropriate management plans. [ABSTRACT FROM AUTHOR]

Anthropogenic environmental change has increased coral reef disturbance regimes in recent decades, altering the structure and function of many coral reefs globally. In this study, we used coral community survey data collected from 1996 to 2015 to evaluate reef-scale coral calcification capacity (CCC) dynamics with respect to recorded pulse disturbances for 121 reef sites in the Main Hawaiian Islands and Mo'orea (French Polynesia) in the Pacific and the Florida Keys Reef Tract and St. John (U.S. Virgin Islands) in the western Atlantic. CCC remained relatively high in the Main Hawaiian Islands in the absence of recorded widespread disturbances; declined and subsequently recovered in Mo'orea following a crown-ofthorns sea star outbreak, coral bleaching, and major cyclone; decreased and remained low following coral bleaching in the Florida Keys Reef Tract; and decreased following coral bleaching and disease in St. John. Individual coral taxa have variable calcification rates and susceptibility to disturbances because of their differing life-history strategies. As a result, temporal changes in CCC in this study were driven by shifts in both overall coral cover and coral community composition. Analysis of our results considering coral lifehistory strategies showed that weedy corals generally increased their contributions to CCC over time while the contribution of competitive corals decreased. Shifts in contributions by stress-tolerant and generalist corals to CCC were more variable across regions. The increasing frequency and intensity of disturbances under 21st century global change therefore has the potential to drive lower and more variable CCC because of the increasing dominance of weedy and some stress-tolerant corals. [ABSTRACT FROM AUTHOR]

Fluctuations of environmental factors in intertidal habitats can disrupt the trophic balance of mixotrophic cnidarians. We investigated the effect of tidal environments (subtidal, tidal pools and emerged areas) on fatty acid (FA) content of Zoanthus sociatus and Siderastrea stellata . Effect on photophysiology was also accessed as an autotrophy proxy. There was a general tendency of a lower percentage of zooplankton-associated FAs in colonies from emerged areas or tidal pools when compared with colonies from the subtidal environment. Moreover, tidal environment significantly affected the photophysiology of both species. Colonies from the subtidal generally showed lower values of α, ETR max and E k when compared with their conspecifics from tidal pools or emerged areas. However, the absence of consistent patterns in F v / F m and in dinoflagellate-associated FAs, suggest that these corals are well adapted to intertidal conditions. This suggests that intertidal pressures may disturb the trophic balance, mainly by affecting heterotrophy of these species. [ABSTRACT FROM AUTHOR]

Background Studies directed at understanding the demography and population dynamics of corals are relatively scarce. This limits our understanding of both the dynamics of coral populations and our capacity to develop management and conservation initiatives directed at conserving such ecosystems. Methods From 2012 to 2014, we collected data on the growth, survival, and recruitment rates of two common Caribbean coral species, the stress-tolerant Orbicella annularis and the weedy Porites astreoides. A set of size-based population matrix model was developed for two localities in Northeastern Puerto Rico and used to estimate population growth rates (λ) and determine the life cycle transition(s) that contribute the most to spatiotemporal differences in λs. The model was parameterized by following the fate of 100 colonies of each species at the two sites for two years. Results Our data indicate that spatial variability in vital rates of both species was higher than temporal variability. During the first year, populations of O. annularis exhibited λs below equilibrium at Carlos Rosario (0.817) and Palomino (0.694), followed by a considerable decline at both sites during the second year (0.700 and 0.667). Populations of P. astreoides showed higher λs than O. annularis during the first census period at Carlos Rosario (0.898) and Palomino (0.894) with a decline at one of the sites (0.681 and 0.893) during the second census period. Colony fate in both species exhibited a significant interaction with respect to location but not to time (G2 = 20.96; df = 3 for O. annularis and G2 = 9.55; df = 3 for P. astreoides). Discussion The similar variability of λs as well as the similar survival rates for both species during the two-year census period (2012–2014) show similar variability on demographic patterns in space and time. Our results suggest that location rather than time is important for the resiliency in coral colonies. Also, P. astreoides will show higher resistance to disturbance in the future than O. annularis.

Worldwide coral reef decline appears to be accompanied by an increase in the spread of hard coral diseases. However, whether this is the result of increased direct and indirect human disturbances and/or an increase in natural stresses remains poorly understood. The provision of baseline surveys for monitoring coral health status lays the foundations to assess the effects of any such anthropogenic and/or natural effects on reefs. Therefore, the objectives of this present study were to provide a coral health baseline in a poorly studied area, and to investigate possible correlations between coral health and the level of anthropogenic and natural disturbances. During the survey period, we recorded 20 different types of coral diseases and other compromised health statuses. The most abundant were cases of coral bleaching, followed by skeletal deformations caused by pyrgomatid barnacles, damage caused by fish bites, general pigmentation response and galls caused by cryptochirid crabs. Instances of colonies affected by skeletal eroding bands, and sedimentation damage increased in correlation to the level of bio-chemical disturbance and/or proximity to villages. Moreover, galls caused by cryptochirid crabs appeared more abundant at sites affected by blast fishing and close to a newly opened metal mine. Interestingly, in the investigated area the percentage of corals showing signs of ‘common’ diseases such as black band disease, brown band disease, white syndrome and skeletal eroding band disease were relatively low. Nevertheless, the relatively high occurrence of less common signs of compromised coral-related reef health, including the aggressive overgrowth by sponges, deserves further investigation. Although diseases appear relatively low at the current time, this area may be at the tipping point and an increase in activities such as mining may irredeemably compromise reef health.

This study tested the hypothesis that intraspecific morphological plasticity within a scleractinian coral elicits differential responses to elevated P CO2 and temperature. In Mo'orea, French Polynesia, two short-term laboratory experiments (21 and 14 days) were conducted to test the effects of P CO2 (400 vs. 700 μatm), and P CO2 (400 vs 1000 μatm) combined with temperature (27.0 vs. 29.8 °C), on branches and plates of Porites rus . Experiments employed two irradiances (~ 1000 vs 200 μmol photons m − 2 s − 1 ), which characterized the microenvironments on the shallow fringing reefs where branching and plating morphologies are common, respectively. Calcification of both morphologies was insensitive to P CO2 , as well as the combined effects of elevated P CO2 and temperature. Mean calcification rates were faster in high light than in low light for both morphologies, and biomass was greater in plates than branches in all treatments. Together, our results suggest P. rus is robust to increased P CO2 and high temperature within the constraints of the treatments applied. Morphological plasticity in this species does not mediate physiological resistance to low pH and high temperature. [ABSTRACT FROM AUTHOR]

The Gulf of Cádiz (GoC) represents an area of ecological importance within the northeastern Atlantic Ocean due to the presence of Mediterranean and Atlantic water masses, a heterogeneous seafloor and a biological confluence. Nevertheless, information on the presence of vulnerable deep-sea habitats is still very scarce and it is of importance for further habitat monitoring within the context of the Habitats and Marine Strategy Framework Directives and for improving conservation and resource extraction management. From 2010 to 2012, fluid migration and emission related edifices (e.g., mud volcanoes, diapirs) from the Spanish continental margin of the GoC have been explored using a remotely operated vehicle (ROV; Liropus 2000) and an underwater camera sled (UCS; APHIA 2012) as well as several devices for collecting sediment and fauna. Different vulnerable deepsea habitats have been observed, including anoxic bottoms with bacterial mats, sea-pen communities, sponge aggregations, antipatharian and gorgonian communities and also cold-water coral banks. Some of these habitats are included in conservation lists of the habitat directive and in international conventions (OSPAR, RAC/SPA), however some of them are located in areas of the GoC that are exposed to intense trawling. The diversity of habitats detected in the Spanish continental margin of the GoC highlights the importance of seepage related edifices as inducers of seabed and habitat heterogeneity in deep-sea areas. [ABSTRACT FROM AUTHOR]

There are concerns about the future of coral reefs in the face of ocean acidification and warming, and although studies of these phenomena have advanced quickly, efforts have focused on pieces of the puzzle rather than integrating them to evaluate ecosystem-level effects. The field is now poised to begin this task, but there are information gaps that first must be overcome before progress can be made. Many of these gaps focus on calcification at the levels of cells, organisms, populations, communities, and ecosystem, and their closure will be made difficult by the complexity of the interdependent processes by which coral reefs respond to ocean acidification, with effects scaling from cells to ecosystems and from microns to kilometers. Existing ecological theories provide an important and largely untapped resource for overcoming these difficulties, and they offer great potential for integrating the effects of ocean acidification across scales on coral reefs. [ABSTRACT FROM AUTHOR]

This study examines scleractinian zooxanthellate coral recruitment patterns in the Florida Keys to determine if differences in density or community composition exist between regions.From July to September 2002,nine patch reefs,three in each of the upper,middle and lower Keys,were surveyed for coral recruits (colonies Se examina los patrones de reclutamiento de corales escleractinios zooxantelados en los Cayos de la Florida para determinar si existen diferencias en densidad o composición de la comunidad en diferentes regiones.Entre julio y setiembre del 2002,se inventariaron los reclutas (colonias de

The effect of salinity on the elemental and isotopic skeletal composition of modern zooxanthellate scleractinian corals ( Acropora sp., Montipora verrucosa and Stylophora pistillata) was investigated in order to evaluate potential salinity proxies. Corals were cultured in the laboratory at three salinities (36, 38 and 40). The other environmental parameters were kept constant. For all species analyzed, Sr/Ca, Mg/Ca, U/Ca and Li/Ca ratios were not influenced by salinity changes. The Ba/Ca ratio also lacks a systematic relationship with salinity and exhibits high inter-generic variations, up to one order of magnitude. On the contrary, the Cd/Ca ratio decreases as a function of increasing salinity, and δO and δC also presented a significant response, but with opposite trends to salinity variations. Since Cd/Ca is usually considered as an upwelling proxy, its salinity dependence could compromise the upwelling signal, unless some corrections can be carried out. Regardless, if the dependence found in the present dataset proved to be widespread and systematic, the Cd/Ca ratio could represent a promising salinometer awaiting further investigation. This study also confirmed the reliability of the well-established temperature proxies Sr/Ca, Mg/Ca and U/Ca, as these ratios were insensitive to salinity variations. Moreover, our results showed that δO or δC can be considered as reliable temperature recorders as far as the salinity effect is removed from the parameter reconstructed (e.g., temperature). Investigating the influence of salinity on the skeletal chemistry of scleractinian corals grown under controlled environmental conditions confirmed previous results, validated isotopic corrections, and identified a promising proxy of salinity. [ABSTRACT FROM AUTHOR]

Cytochrome P450 was detected in the animal tissue of the scleractinian corals Siderastrea siderea and Montastraea faveolata collected from a reef site on the west coast of Venezuela. The concentration of P450 in these species (0.4–2.1 nmol mg–1 of microsomal protein) was similar to the levels found in other marine invertebrates, but higher than previously reported for other organisms of the phylum Cnidaria. Maximum P450 content was detected in samples collected during the reproductive season of S. siderea. These results confirm the presence of a functional cytochrome P450 in two coral species. Its usefulness as a biomarker for environmental monitoring has to be further investigated.

A nonstructural reef at Hon Nai Island in Cam Ranh Bay (southern Vietnam) was investigated. In comparison with most of the coastal continental and island coral reefs of this region, it is characterized by high species richness of reef-building corals, among them scleractinians. A total of 34 species of Acropora were found, which represent 80% of the total species composition of this scleractinian genus on the reefs of Vietnam and 25% on the reefs of the Indo-Pacific. Among 169 species of scleractinians found on the reef of Hon Nai, Favia sp. nov. was previously unknown to science. The vertical bionomic zonality of the reef corresponds to a zonal distribution of environmental factors and is similar to that on reefs of the Gulf of Siam and various areas of the Pacific and the Caribbean Basin. The thriving of the Hon Nai island reef may be connected with protective measures undertaken by the Government of Vietnam and the minimization of anthropogenic impacts due to the activities of the Sanest Co. [ABSTRACT FROM AUTHOR]

In 2010, an expedition of the Institute of Marine Biology on the R/V Akademik Oparin revisited and surveyed a number of coral reefs of Vietnam, whose species composition and structure had been first described a quarter of century ago. No substantial changes were found in the geomorphological structure of reefs of the Nam Su and Tho Chu islands in the Gulf of Siam and the Con Dao and Thu islands situated outside the gulf. Marked changes were found in the abundance of some species of associated macrobenthos. The current status of coral reefs is described and the causes of the observed changes are analyzed (anthropogenic influence, etc.). [ABSTRACT FROM AUTHOR]

The study of coral repopulation in marginal communities may provide a useful analog for understanding the dynamics of coral reefs subjected to deleterious environmental changes. Repopulation of scleractinian reef corals may strongly impact the community structure on tropical reefs; however, the extent of this process on coral communities influenced by upwelling is unknown, especially in the Caribbean. In this study, the potential for natural repopulation of coral communities subjected to wind-driven upwelling was evaluated at three sites on the island of Cubagua, Venezuela. Coral spawning behavior was recorded and both larval settlement and juvenile abundance were estimated. Upwelling did not appear to affect coral spawning behavior, since at this locality spawning occurred at dates and times similar to those reported for well-developed reefs in the Caribbean. Also, juveniles produced by brooding corals were six times more abundant than those of broadcasting species, similar to patterns on other Caribbean reefs that are not under the influence of upwelling. By contrast, mean larval settlement (4 settlers m−2) and juvenile abundance (0.1 juveniles m−2) in Cubagua were both lower than those elsewhere in the Caribbean and on Pacific reefs. Thus, the potential for repopulation of these marginal communities seems lower than for well-developed coral reefs in other regions. These results suggest that more fully developed coral reefs also may have reduced repopulation potential, as they become influenced by suboptimal environmental conditions. [ABSTRACT FROM AUTHOR]

Cytochrome P450 was detected in the animal tissue of the scleractinian corals Siderastrea siderea and Montastraea faveolata collected from a reef site on the west coast of Venezuela. The concentration of P450 in these species (0.4-2.1 nmol mg-1 of microsomal protein) was similar to the levels found in other marine invertebrates, but higher than previously reported for other organisms of the phylum Cnidaria. Maximum P450 content was detected in samples collected during the reproductive season of S. siderea. These results confirm the presence of a functional cytochrome P450 in two coral species. Its usefulness as a biomarker for environmental monitoring has to be further investigated. [ABSTRACT FROM AUTHOR]

The morphogenesis of colonial stony corals is the result of the collective behaviour of many coral polyps depositing coral skeleton on top of the old skeleton on which they live. Yet, models of coral growth often consider the polyps as a single continuous surface. In the present work, the polyps are modelled individually. Each polyp takes up resources, deposits skeleton, buds off new polyps and dies. In this polyp oriented model, spontaneous branching occurs. We argue that branching is caused by a so called “polyp fanning effect” by which polyps on a convex surface have a competitive advantage relative to polyps on a flat or concave surface. The fanning effect generates a more potent branching mechanism than the Laplacian growth mechanism that we have studied previously (J. Theor. Biol. 224 (2003) 153). We discuss the application of the polyp oriented model to the study of environmentally driven morphological plasticity in stony corals. In a few examples we show how the properties of the individual polyps influence the whole colony morphology. In our model, the spacing of polyps influences the thickness of coral branches and the overall compactness of the colony. Density variations in the coral skeleton may also be important for the whole colony morphology, which we address by studying two variants of the model. Finally, we discuss the importance of small scale resource translocation in the coral colony and its effects on the morphology of the colony. [Copyright &y& Elsevier]

Abstract: In 2015–2016, record temperatures triggered a pan‐tropical episode of coral bleaching. In the southern hemisphere summer of March–April 2016, we used aerial surveys to measure the level of bleaching on 1,156 individual reefs throughout the 2,300 km length of the Great Barrier Reef, the world's largest coral reef system. The accuracy of the aerial scores was ground‐truthed with detailed underwater surveys of bleaching at 260 sites (104 reefs), allowing us to compare aerial and underwater bleaching data with satellite‐derived temperatures and with associated model predictions of bleaching. The severity of bleaching on individual reefs in 2016 was tightly correlated with the level of local heat exposure: the southernmost region of the Great Barrier Reef escaped with only minor bleaching because summer temperatures there were close to average. Gradients in nutrients and turbidity from inshore to offshore across the Great Barrier Reef had minimal effect on the severity of bleaching. Similarly, bleaching was equally severe on reefs that are open or closed to fishing, once the level of satellite‐derived heat exposure was accounted for. The level of post‐bleaching mortality, measured underwater after 7–8 months, was tightly correlated with the aerial scores measured at the peak of bleaching. Similarly, reefs with a high aerial bleaching score also experienced major shifts in species composition due to extensive mortality of heat‐sensitive species. Reefs with low bleaching scores did not change in composition, and some showed minor increases in coral cover. Two earlier mass bleaching events occurred on the Great Barrier Reef in 1998 and 2002, that were less severe than 2016. In 2016, <9% of scored reefs had no bleaching, compared to 42% in 2002 and 44% in 1998. Conversely, the proportion of reefs that were severely bleached (>60% of corals affected) was four times higher in 2016. The geographic footprint of each of the three events is distinctive, and matches satellite‐derived sea surface temperature patterns. Our aerial surveys indicate that past exposure to bleaching in 1998 and 2002 did not lessen the severity of bleaching in 2016. This data set of aerial bleaching scores provides a historical baseline for comparison with future bleaching events. No copyright restrictions apply to the use of this data set other than citing this publication. [ABSTRACT FROM AUTHOR]