• Energy Research
• 2016-2025close

Predicting demographic rates is a critical part of forecasting the future of ecosystems under global change. Here, we test if growth rates can be predicted from morphological traits for a highly diverse group of colonial symbiotic organisms: scleractinian corals. We ask whether growth is isometric or allometric among corals, and whether most variation in coral growth rates occurs at the level of the species or morphological group. We estimate growth as change in planar area for 11 species, across five morphological groups and over 5 years. We show that coral growth rates are best predicted from colony size and morphology rather than species. Coral size follows a power scaling law with a constant exponent of 0.91. Despite being colonial organisms, corals have consistent allometric scaling in growth. This consistency simplifies the task of projecting community responses to disturbance and climate change.

AbstractAnthropogenic climate change is a rapidly intensifying selection pressure on biodiversity across the globe and, particularly, on the world's coral reefs. The rate of adaptation to climate change is proportional to the amount of phenotypic variation that can be inherited by subsequent generations (i.e., narrow‐sense heritability, h2). Thus, traits that have higher heritability (e.g., h2 > 0.5) are likely to adapt to future conditions faster than traits with lower heritability (e.g., h2 < 0.1). Here, we synthesize 95 heritability estimates across 19 species of reef‐building corals. Our meta‐analysis reveals low heritability (h2 < 0.25) of gene expression metrics, intermediate heritability (h2 = 0.25–0.50) of photochemistry, growth, and bleaching, and high heritability (h2 > 0.50) for metrics related to survival and immune responses. Some of these values are higher than typically observed in other taxa, such as survival and growth, while others were more comparable, such as gene expression and photochemistry. There was no detectable effect of temperature on heritability, but narrow‐sense heritability estimates were generally lower than broad‐sense estimates, indicative of significant non‐additive genetic variation across traits. Trait heritability also varied depending on coral life stage, with bleaching and growth in juveniles generally having lower heritability compared to bleaching and growth in larvae and adults. These differences may be the result of previous stabilizing selection on juveniles or may be due to constrained evolution resulting from genetic trade‐offs or genetic correlations between growth and thermotolerance. While we find no evidence that heritability decreases under temperature stress, explicit tests of the heritability of thermal tolerance itself—such as coral thermal reaction norm shape—are lacking. Nevertheless, our findings overall reveal high trait heritability for the majority of coral traits, suggesting corals may have a greater potential to adapt to climate change than has been assumed in recent evolutionary models.

Resumen El calentamiento del océano está aumentando la incidencia, la escala y la gravedad del blanqueamiento y la mortalidad de los corales a escala mundial, que culminó en el tercer evento mundial de blanqueamiento de corales que ocurrió durante las olas de calor marinas récord de 2014-2017. Si bien los efectos locales de estos eventos han sido ampliamente reportados, las implicaciones globales siguen siendo desconocidas. El análisis de 15.066 estudios de arrecifes durante 2014-2017 reveló que el 80% de los arrecifes estudiados experimentaron un blanqueamiento significativo de los corales y el 35% experimentó una mortalidad significativa de los corales. El alcance global del blanqueamiento y la mortalidad significativos de los corales se evaluó extrapolando los resultados de los estudios de arrecifes utilizando datos completos de teledetección del estrés por calor regional. Este modelo predijo que el 51% de los arrecifes de coral del mundo sufrieron un blanqueamiento significativo y una mortalidad significativa del 15%, superando el daño de cualquier evento de blanqueamiento global anterior. Estas observaciones demuestran que el daño generalizado del calentamiento global a los arrecifes de coral se está acelerando y subraya la amenaza que el cambio climático antropogénico representa para la transformación irreversible de estos ecosistemas esenciales. Résumé Le réchauffement des océans augmente l'incidence, l'ampleur et la gravité du blanchiment et de la mortalité des coraux à l'échelle mondiale, culminant avec le troisième événement mondial de blanchiment des coraux survenu lors de vagues de chaleur marines record de 2014-2017. Bien que les effets locaux de ces événements aient été largement rapportés, les implications mondiales restent inconnues. L'analyse de 15 066 enquêtes sur les récifs au cours de la période 2014-2017 a révélé que 80 % des récifs étudiés ont connu un blanchissement important des coraux et 35 % ont connu une mortalité importante des coraux. L'étendue mondiale du blanchiment et de la mortalité importants des coraux a été évaluée en extrapolant les résultats des enquêtes sur les récifs à l'aide de données complètes de télédétection du stress thermique régional. Ce modèle prévoyait que 51 % des récifs coralliens du monde souffraient d'un blanchissement important et 15 % d'une mortalité importante, dépassant les dommages causés par tout événement de blanchissement mondial antérieur. Ces observations démontrent que les dommages généralisés causés par le réchauffement climatique aux récifs coralliens s'accélèrent et soulignent la menace que le changement climatique anthropique fait peser sur la transformation irréversible de ces écosystèmes essentiels. Abstract 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. يؤدي ارتفاع درجة حرارة المحيطات إلى زيادة حدوث وحجم وشدة تبييض الشعاب المرجانية ونفوقها على نطاق عالمي، وبلغت ذروتها في الحدث العالمي الثالث لتبييض الشعاب المرجانية الذي حدث خلال موجات الحر البحرية القياسية في الفترة 2014-2017. في حين تم الإبلاغ عن الآثار المحلية لهذه الأحداث على نطاق واسع، إلا أن الآثار العالمية لا تزال غير معروفة. كشف تحليل 15,066 مسحًا للشعاب المرجانية خلال الفترة 2014-2017 أن 80 ٪ من الشعاب المرجانية التي تم مسحها عانت من ابيضاض مرجاني كبير و 35 ٪ عانت من وفيات مرجانية كبيرة. تم تقييم المدى العالمي للتبييض والوفيات المرجانية الكبيرة من خلال استقراء النتائج من المسوحات المرجانية باستخدام بيانات شاملة للاستشعار عن بعد للإجهاد الحراري الإقليمي. وتوقع هذا النموذج أن 51 ٪ من الشعاب المرجانية في العالم عانت من تبييض كبير و 15 ٪ من الوفيات الكبيرة، متجاوزة الأضرار الناجمة عن أي حدث تبييض عالمي سابق. تُظهر هذه الملاحظات أن الأضرار الواسعة النطاق للاحترار العالمي التي لحقت بالشعاب المرجانية تتسارع وتؤكد التهديد الذي يشكله تغير المناخ البشري المنشأ على التحول الذي لا رجعة فيه لهذه النظم الإيكولوجية الأساسية.

The frequency, intensity, and spatial scale of climate extremes are changing rapidly due to anthropogenic global warming.1,2 A growing research challenge is to understand how multiple climate-driven disturbances interact with each other over multi-decadal time frames, generating combined effects that cannot be predicted from single events alone.3-5 Here we examine the emergent dynamics of five coral bleaching events along the 2,300 km length of the Great Barrier Reef that affected >98% of the Reef between 1998 and 2020. We show that the bleaching responses of corals to a given level of heat exposure differed in each event and were strongly influenced by contingency and the spatial overlap and strength of interactions between events. Naive regions that escaped bleaching for a decade or longer were the most susceptible to bouts of heat exposure. Conversely, when pairs of successive bleaching episodes were close together (1-3 years apart), the thermal threshold for severe bleaching increased because the earlier event hardened regions of the Great Barrier Reef to further impacts. In the near future, the biological responses to recurrent bleaching events may become stronger as the cumulative geographic footprint expands further, potentially impairing the stock-recruitment relationships among lightly and severely bleached reefs with diverse recent histories. Understanding the emergent properties and collective dynamics of recurrent disturbances will be critical for predicting spatial refuges and cumulative ecological responses, and for managing the longer-term impacts of anthropogenic climate change on ecosystems.