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Abstract Coral bleaching events from thermal stress are increasing globally in duration, frequency, and intensity. While bleaching can cause mortality, some corals survive, reacquire symbionts, and recover. We experimentally bleachedMontipora capitatato examine molecular and physiological differences between corals that recover (resilient) and those that die (susceptible). Corals were collected and monitored for eight months post-bleaching to identify genets with long-term resilience. Using an integrated systems-biology approach that included quantitative proteomics, 16S rRNA sequencing to characterize the coral microbiome, total coral lipids, symbiont community composition and density, we explored molecular-level mechanisms of tolerance in corals pre- and post-bleaching. Prior to thermal stress, resilient corals have a more diverse microbiome and abundant proteins essential for carbon acquisition, symbiont retention, and pathogen resistance. Protein signatures of susceptible corals showed early symbiont rejection and utilized urea for carbon and nitrogen. Our results reveal molecular factors for surviving bleaching events and identify diagnostic protein biomarkers for reef management and restoration. 

As environments are rapidly reshaped due to climate change, phenotypic plasticity plays an important role in the ability of organisms to persist and is considered an especially important acclimatization mechanism for long-lived sessile organisms such as reef-building corals. Often, this ability of a single genotype to display multiple phenotypes depending on the environment is modulated by changes in gene expression, which can vary in response to environmental changes via two mechanisms: baseline expression and expression plasticity. We used transcriptome-wide expression profiling of eleven genotypes of common-gardenedAcropora cervicornisto explore genotypic variation in the expression response to thermal and acidification stress, both individually and in combination. We show that the combination of these two stressors elicits a synergistic gene expression response, and that both baseline expression and expression plasticity in response to stress show genotypic variation. Additionally, we demonstrate that frontloading of a large module of coexpressed genes is associated with greater retention of algal symbionts under combined stress. These results illustrate that variation in the gene expression response of individuals to climate change stressors can persist even when individuals have shared environmental histories, affecting their performance under future climate change scenarios. 

Abstract Coral bleaching is the largest global threat to coral reef ecosystem persistence this century. Advancing our understanding of coral bleaching and developing solutions to protect corals and the reefs they support are critical. In the present article, we, the US National Science Foundation–funded Coral Bleaching Research Coordination Network, outline future directions for coral bleaching research. Specifically, we address the need for embedded inclusiveness, codevelopment, and capacity building as a foundation for excellence in coral bleaching research and the critical role of coral-bleaching science in shaping policy. We outline a path for research innovation and technology and propose the formation of an international coral bleaching consortium that, in coordination with existing multinational organizations, could be a hub for planning, coordinating, and integrating global-scale coral bleaching research, innovation, and mitigation strategies. This proposed strategy for future coral bleaching research could facilitate a step-function change in how we address the coral bleaching crisis. 

In 2023, a record-setting marine heat wave triggered the ninth mass coral bleaching event on Florida’s Coral Reef (FCR). We examined spatial patterns of heat exposure along the ~560-kilometer length of FCR and the mortality of two ecologically important, critically endangered reef-building corals. Sea surface temperatures were ≥31°C for an average of 40.7 days, leading to heat exposures 2.2- to fourfold higher than all prior years on record. In the Florida Keys and Dry Tortugas, 97.8 to 100% of theAcropora palmataandAcropora cervicorniscolonies died. Mortality was lower offshore southeast Florida (37.9%), reflecting cooler temperatures in this region. Since the late 1970s, multiple stressors had already reduced the ecological relevance ofAcroporain Florida, but the 2023 heat wave marks their functional extinction from FCR. 

Once one of the predominant reef-building corals in the region,Acropora cervicornisis now a focal species of coral restoration efforts in Florida and the western Caribbean. Scientists and restoration practitioners have been independently collecting phenotypic data on genets ofA. cervicornisgrown in restoration nurseries. While these data are important for understanding the intraspecific response to varying environmental conditions, and thus the potential genetic contribution to phenotypic variation, in isolation these observations are of limited use for large-scale, multi- institution restoration efforts that are becoming increasingly necessary. Here, we present theAcropora cervicornisData Coordination Hub, a web-accessible relational database to align disparate datasets to compare genet-specific performance. In this data descriptor, we release data for 248 genets evaluated across 38 separate traits. We present a framework to align datasets with the ultimate goal of facilitating informed, data-driven restoration throughout the Caribbean. 

Knowledge of multi-stressor interactions and the potential for tradeoffs among tolerance traits is essential for developing intervention strategies for the conservation and restoration of reef ecosystems in a changing climate. Thermal extremes and acidification are two major co-occurring stresses predicted to limit the recovery of vital Caribbean reef-building corals. Here, we conducted an aquarium-based experiment to quantify the effects of increased water temperatures and p CO 2 individually and in concert on 12 genotypes of the endangered branching coral Acropora cervicornis, currently being reared and outplanted for large-scale coral restoration. Quantification of 12 host, symbiont and holobiont traits throughout the two-month-long experiment showed several synergistic negative effects, where the combined stress treatment often caused a greater reduction in physiological function than the individual stressors alone. However, we found significant genetic variation for most traits and positive trait correlations among treatments indicating an apparent lack of tradeoffs, suggesting that adaptive evolution will not be constrained. Our results suggest that it may be possible to incorporate climate-resistant coral genotypes into restoration and selective breeding programmes, potentially accelerating adaptation.