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Coral bleaching, a consequence of stressed symbiotic relationships between corals and algae, has escalated due to intensified heat stress events driven by climate change. Despite global efforts, current early warning systems lack local precision. Our study, spanning 2015–2017 in the Mesoamerican Reef, revealed prevalent intermediate bleaching, peaking in 2017. By scrutinizing 23 stress exposure and sensitivity metrics, we accurately predicted 75% of bleaching severity variation. Notably, distinct thermal patterns—particularly the climatological seasonal warming rate and various heat stress metrics—emerged as better predictors compared to conventional indices (such as Degree Heating Weeks). Surprisingly, deeper reefs with diverse coral communities showed heightened vulnerability. This study presents a framework for coral reef bleaching vulnerability assessment, leveraging accessible data (including historical and real-time sea surface temperature, habitat variables, and species composition). Its operational potential lies in seamless integration with existing monitoring systems, offering crucial insights for conservation and management. A study on the Mesoamerican Reef shows that the climatological rate of seasonal warming and heat stress metrics more accurately predict coral bleaching severity than conventional indices, enhancing regional early warning systems for better conservation strategies. [ABSTRACT FROM AUTHOR]

Identifying relatively intact areas within ecosystems and determining the conditions favoring their existence is necessary for effective management in the context of widespread environmental degradation. In this study, we used 3766 surveys of randomly selected sites in the United States and U.S. Territories to identify the correlates of sites categorized as "oases" (defined as sites with relatively high total coral cover). We used occupancy models to evaluate the influence of 10 environmental predictors on the probability that an area (21.2‐km2 cell) would harbor coral oases defined at four spatial extents: cross‐basin, basin, region, and subregion. Across all four spatial extents, oases were more likely to occur in habitats with high light attenuation. The influence of the other environmental predictors on the probability of oasis occurrence were less consistent and varied with the scale of observation. Oases were most likely in areas of low human population density, but this effect was evident only at the cross‐basin and subregional extents. At the regional and subregional extents oases were more likely where sea‐surface temperature was more variable, whereas at the larger spatial extents the opposite was true. By identifying the correlates of oasis occurrence, the model can inform the prioritization of reef areas for management. Areas with biophysical conditions that confer corals with physiological resilience, as well as limited human impacts, likely support coral reef oases across spatial extents. Our approach is widely applicable to the development of conservation strategies to protect biodiversity and ecosystems in an era of magnified human disturbance. [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]

Aim Coral assemblages on Caribbean reefs have largely been considered to be biogeographically homogeneous at a regional scale. We reassess this in three taxa (corals, sponges and octocorals) using three community attributes with increasing levels of information (species richness, composition and relative abundance) across hierarchical spatial scales, and identify the key environmental drivers associated with this variation. Location Caribbean Basin. Methods We assessed reefs along 546 transects positioned within the same forereef habitat ( Orbicella reef) in 11 countries, using a consistent methodology and surveyors. Spatial variability in richness, composition and relative abundance was assessed at four hierarchical spatial scales - transects (metres), sites (kilometres), areas (tens of kilometres) and regions (hundreds of kilometres) - using permutational multivariate analysis of variance ( PERMANOVA). The relevance of contemporary environmental factors in explaining the observed spatial patterns was also assessed using PERMANOVA. Results Consistent with previous studies, species richness of coral assemblages, commonly the focus of biogeographical studies, showed little variance at large spatial scales. In contrast, species composition and relative abundance showed significant variability at regional scales. Coral, sponge and octocoral assemblages each varied independently across spatial scales. Rugosity and wave exposure were key drivers of the composition and relative abundance of coral and octocoral assemblages. Main conclusions Caribbean reef assemblages exhibit considerable biogeographical variability at broad spatial scales (hundreds of kilometres) when more responsive community attributes were used. However, the high degree of variability within sites (kilometres) highlights the relevance of local ecological drivers such as rugosity and wave exposure in structuring assemblages. The high levels of within-site variability that is not explained by environmental variables may suggest a previously unrealized contribution of anthropogenic disturbance operating at local scales throughout the region. [ABSTRACT FROM AUTHOR]

K-selected species with low rates of sexual recruitment may utilise storage effects where low adult mortality allows a number of individuals to persist through time until a favourable recruitment period occurs. Alternative methods of recruitment may become increasingly important for such species if the availability of favourable conditions for sexual recruitment decline under rising anthropogenic disturbance and climate change. Here, we test the hypotheses that asexual dispersal is an integral life history strategy not only in branching corals, as previously reported, but also in a columnar, 'K-selected' coral species, and that its prevalence is driven by the frequency of severe hurricane disturbance. Montastraea annularis is a long-lived major frame-work builder of Caribbean coral reefs but its survival is threatened by the consequences of climate induced disturbance, such as bleaching, ocean acidification and increased prevalence of disease. 700 M. annularis samples from 18 reefs within the Caribbean were genotyped using six polymorphic microsatellite loci. We demonstrate that asexual reproduction occurs at varying frequency across the species-range and significantly contributes to the local abundance of M. annularis, with its contribution increasing in areas with greater hurricane frequency. We tested several competing hypotheses that might explain the observed pattern of genotypic diversity. 64% of the variation in genotypic diversity among the sites was explained by hurricane incidence and reef slope, demonstrating that large-scale disturbances combine with local habitat characteristics to shape the balance between sexual and asexual reproduction in populations of M. annularis. [ABSTRACT FROM AUTHOR]