Sea surface temperatures were warmer throughout 1998 at Sesoko Island, Japan, than in the 10 preceding years. Temperatures peaked at 2.8 °C above average, resulting in extensive coral bleaching and subsequent coral mortality. Using random quadrat surveys, we quantitatively documented the coral community structure one year before and one year after the bleaching event. The 1998 bleaching event reduced coral species richness by 61% and reduced coral cover by 85%. Colony morphology affected bleaching vulnerability and subsequent coral mortality. Finely branched corals were most susceptible, while massive and encrusting colonies survived. Most heavily impacted were the branched Acropora and pocilloporid corals, some of which showed local extinction. We suggest two hypotheses whose synergistic effect may partially explain observed mortality patterns (i.e. preferential survival of thick‐tissued species, and shape‐dependent differences in colony mass‐transfer efficiency). A community‐structural shift occurred on Okinawan reefs, resulting in an increase in the relative abundance of massive and encrusting coral species.

The specific identity of endosymbiotic dinoflagellates (Symbiodinium spp.) from most zooxanthellate corals is unknown. In a survey of symbiotic cnidarians from the southern Great Barrier Reef (GBR), 23 symbiont types were identified from 86 host species representing 40 genera. A majority (Ͼ85%) of these symbionts belong to a single phylogenetic clade or subgenus (''C'') composed of closely related (as assessed by sequence data from the internal transcribed spacer region and the ribosomal large subunit gene), yet ecologically and physiologically distinct, types. A few prevalent symbiont types, or generalists, dominate the coral community of the southern GBR, whereas many rare and/or specific symbionts, or specialists, are found uniquely within certain host taxa. The comparison of symbiont diversity between southern GBR and Caribbean reefs shows an inverse relationship between coral diversity and symbiont diversity, perhaps as a consequence of more-rapid diversification of Caribbean symbionts. Among clade C types, generalists C1 and C3 are common to both Caribbean and southern GBR symbiont assemblages, whereas the rest are regionally endemic. Possibly because of environmental changes in the Caribbean after geographic isolation through the Quaternary period, a high proportion of Caribbean fauna associate with symbiont taxa from two other distantly related Symbiodinium clades (A and B) that rarely occur in Pacific hosts. The resilience of Porites spp. and the resistance of Montipora digitata to thermal stress and bleaching are partially explained by their association with a thermally tolerant symbiont type, whereas the indiscriminant widespread bleaching and death among certain Pacific corals, during El Niño Southern Oscillation events, are influenced by associations with symbionts possessing higher sensitivity to thermal stress.Cnidarians such as hard corals, soft corals, sea fans, and anemones are the principal faunal constituents of benthic AcknowledgmentsWe thank Jill Torregiani, María del Carmen Gómez-Cabrera, Paul Fisher, and Michael Stat for assisting with the collection and processing of samples, as well as M. J. Van Oppen for her help with determining the specific identity of subclades C1, C2, and C3 (Van Oppen et al. 2001).

Anomalously high water temperatures, associated with climate change, are increasing the global prevalence of coral bleaching, coral diseases, and coral-mortality events. Coral bleaching and disease outbreaks are often inter-related phenomena, since many coral diseases are a consequence of opportunistic pathogens that further compromise thermally stressed colonies. Yet, most coral diseases have low prevalence (<5%), and are not considered contagious. By contrast, we document the impact of an extremely high-prevalence outbreak (61%) of white-plague disease at 14 sites off southeastern Florida. White-plague disease was observed near Virginia Key, Florida, in September 2014, and after 12 months had spread 100 km north and 30 km south. The disease outbreak directly followed a high temperature coral-bleaching event and affected at least 13 coral species. Eusmilia fastigiata, Meandrina meandrites, and Dichocoenia stokesi were the most heavily impacted coral species, and were reduced to <3% of their initial population densities. A number of other coral species, including Colpophyllia natans, Pseudodiploria strigosa, Diploria labyrinthiformis, and Orbicella annularis were reduced to <25% of their initial densities. The high prevalence of disease, the number of susceptible species, and the high mortality of corals affected suggests this disease outbreak is arguably one of the most lethal ever recorded on a contemporary coral reef.

Thermal-stress events associated with climate change cause coral bleaching and mortality that threatens coral reefs globally. Yet coral bleaching patterns vary spatially and temporally. Here we synthesize field observations of coral bleaching at 3351 sites in 81 countries from 1998 to 2017 and use a suite of environmental covariates and temperature metrics to analyze bleaching patterns. Coral bleaching was most common in localities experiencing high intensity and high frequency thermal-stress anomalies. However, coral bleaching was significantly less common in localities with a high variance in sea-surface temperature (SST) anomalies. Geographically, the highest probability of coral bleaching occurred at tropical mid-latitude sites (15–20 degrees north and south of the Equator), despite similar thermal stress levels at equatorial sites. In the last decade, the onset of coral bleaching has occurred at significantly higher SSTs (∼0.5 °C) than in the previous decade, suggesting that thermally susceptible genotypes may have declined and/or adapted such that the remaining coral populations now have a higher thermal threshold for bleaching.

Over the past 3 decades, thermal stress events have damaged corals globally. Few studies, however, have tracked the recovery process or assessed whether winners in the short term are also winners in the long term. In the present study, we repeatedly sampled a coral assemblage over a 14 yr period, from 1997 to 2010, through 2 thermal stress events (in 1998 and 2001). Our goal was to examine the consistency of short-term winner and loser outcomes over the recovery period. Although species richness had recovered after 10 yr, the reef composition had changed, and few pocilloporids were to be found. The short-term winners were the thermally tolerant encrusting and massive coral morphologies (Porites and faviids) and Acropora colonies < 5 cm in diameter. Long-term winners were revealed as (1) thermally tolerant, locally persistent colonies, (2) remnant survivors that rapidly regrew, and (3) regionally persistent colonies that recruited. KEY WORDS: Coral bleaching · Climate adaptation · Temperature · Reefs · RecoveryResale or republication not permitted without written consent of the publisher Mar Ecol Prog Ser 434: 67-76, 2011 enced anomalous temperatures only every 50 to 60 yr (Thompson & van Woesik 2009). For example, the southern islands of Japan, the Great Barrier Reef and Micronesia all historically show low-frequency return periods (~50 yr), whereas the Galapagos Islands and Kiribati historically show high-frequency return periods (~5 yr) (Thompson & van Woesik 2009). Not only are contemporary worldwide patterns in thermal anomalies similar to those in the past, but the localities that have shown high-frequency return periods in the past few centuries have also recently experienced the most severe thermal stress (Thompson & van Woesik 2009). If these patterns persist into the near future, then some localities will receive both more intensive and more frequent thermal stress than other localities.Short-term studies suggest that some coral species are destined to become the 'winners', whereas others are destined to become the 'losers' (Loya et al. 2001). However, simply tolerating local thermal stress is not the only viable life-history strategy to persist through time. Ephemeral assemblages that are usually susceptible to local stress also survive regionally by being highly fecund and growing quickly (MacArthur & Wilson 1967, Loya 1976, Gates & Edmunds 1999. Regional persistence also depends on (1) the local survival of small fragments, which have an inherent capacity for regrowth, (2) whether corals on neighboring reefs survived through the thermal stress, (3) whether those neighboring corals have the capacity to supply recruits, (4) the survival of recruits from neighboring reefs, and (5) the return frequency and intensity of the thermal stresses.Few studies have examined the longterm recovery of coral assemblages following thermal stress. Here, we ask whether a winning species in the short term is also a winner in the long term. Previously we reported on the shortterm effects of a severe thermal s...

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In a coral-algae symbiotic system, heat-dependent photoinhibition of photosystem II (PSII) leads to coral bleaching. When the reef-building coral Acropora digitifera was exposed to light, a moderate increase of temperature induced coral bleaching through photobleaching of algal pigments, but not through expulsion of symbiotic algae. Monitoring of PSII photoinhibition revealed that heat-dependent photoinhibition was ascribed to inhibition of the repair of photodamaged PSII, and heat susceptibility of the repair machinery varied among coral species. We conclude that the efficiency of the photosynthesis repair machinery determines the bleaching susceptibility of coral species under elevated seawater temperatures.

Managing coral reefs for resilience to climate change is a popular concept but has been difficult to implement because the empirical scientific evidence has either not been evaluated or is sometimes unsupportive of theory, which leads to uncertainty when considering methods and identifying priority reefs. We asked experts and reviewed the scientific literature for guidance on the multiple physical and biological factors that affect the ability of coral reefs to resist and recover from climate disturbance. Eleven key factors to inform decisions based on scaling scientific evidence and the achievability of quantifying the factors were identified. Factors important to resistance and recovery, which are important components of resilience, were not strongly related, and should be assessed independently. The abundance of resistant (heat-tolerant) coral species and past temperature variability were perceived to provide the greatest resistance to climate change, while coral recruitment rates, and macroalgae abundance were most influential in the recovery process. Based on the 11 key factors, we tested an evidence-based framework for climate change resilience in an Indonesian marine protected area. The results suggest our evidence-weighted framework improved upon existing un-weighted methods in terms of characterizing resilience and distinguishing priority sites. The evaluation supports the concept that, despite high ecological complexity, relatively few strong variables can be important in influencing ecosystem dynamics. This is the first rigorous assessment of factors promoting coral reef resilience based on their perceived importance, empirical evidence, and feasibility of measurement. There were few differences between scientists' perceptions of factor importance and the scientific evidence found in journal publications but more before and after impact studies will be required to fully test the validity of all the factors. The methods here will increase the feasibility and defensibility of including key resilience metrics in evaluations of coral reefs, as well as reduce costs. Adaptation, marine protected areas, priority setting, resistance, recovery.