• Energy Research

AbstractCoral reef ecosystems are seriously threatened by changing conditions in the ocean. Although many factors are implicated, climate change has emerged as a dominant and rapidly growing threat. Developing a long‐term strategic plan for the conservation of coral reefs is urgently needed yet is complicated by significant uncertainty associated with climate change impacts on coral reef ecosystems. We use Modern Portfolio Theory to identify coral reef locations globally that, in the absence of other impacts, are likely to have a heightened chance of surviving projected climate changes relative to other reefs. Long‐term planning that is robust to uncertainty in future conditions provides an objective and transparent framework for guiding conservation action and strategic investment. These locations constitute important opportunities for novel conservation investments to secure less vulnerable yet well‐connected coral reefs that may, in turn, help to repopulate degraded areas in the event that the climate has stabilized.

AbstractCoral reefs across the world’s oceans are in the midst of the longest bleaching event on record (from 2014 to at least 2016). As many of the world’s reefs are remote, there is limited information on how past thermal conditions have influenced reef composition and current stress responses. Using satellite temperature data for 1985–2012, the analysis we present is the first to quantify, for global reef locations, spatial variations in warming trends, thermal stress events and temperature variability at reef-scale (~4 km). Among over 60,000 reef pixels globally, 97% show positive SST trends during the study period with 60% warming significantly. Annual trends exceeded summertime trends at most locations. This indicates that the period of summer-like temperatures has become longer through the record, with a corresponding shortening of the ‘winter’ reprieve from warm temperatures. The frequency of bleaching-level thermal stress increased three-fold between 1985–91 and 2006–12 – a trend climate model projections suggest will continue. The thermal history data products developed enable needed studies relating thermal history to bleaching resistance and community composition. Such analyses can help identify reefs more resilient to thermal stress.

AbstractCoral bleaching caused by heat stress (warm water) will arguably be the greatest driver of coral reef loss in the coming decades. Understanding how corals have adapted to distinct oceanographic regimes on multiple scales can provide insight into future tolerance and persistence, information critical to directed intervention or targeted protections. The northern Line Islands span a gradient in oceanographic regimes across latitudes, with seawater becoming warmer, fresher, more oligotrophic, and more saturated with aragonite away from the equator. The combination of this regional gradient and island‐scale (local) conditions was used as a natural experiment against which to test how massive Porites corals respond to these background conditions and episodic heat stress. We found that coral condition, represented by a metric combining tissue thickness, lipids, and calcification, was similar at almost all islands, though there were differences in how corals allocate resources among these biological parameters. Corals at Teraina, the most densely inhabited island, showed evidence for reduced calcification, potentially associated with human impacts and/or outflow of freshwater from the island. In contrast, Porites corals at Palmyra, a wildlife reserve, exhibited unexpectedly high tissue‐condition metrics for its latitude, suggesting an additional food source, possibly plankton‐rich lagoonal outflow. We did not find a strong relationship between human habitation and the response of Porites corals to recent heat stress. However, differences in coral calcification rates and energy stores between observed values and those expected based solely on the regional oceanographic gradient, suggests local effects have indirect impacts on these corals.

Outbreaks of marine infectious diseases have caused widespread mass mortalities, but the lack of baseline data has precluded evaluating whether disease is increasing or decreasing in the ocean. We use an established literature proxy method from Ward and Lafferty (Ward and Lafferty 2004 PLoS Biology 2 , e120 ( doi:10.1371/journal.pbio.0020120 )) to analyse a 44-year global record of normalized disease reports from 1970 to 2013. Major marine hosts are combined into nine taxonomic groups, from seagrasses to marine mammals, to assess disease swings, defined as positive or negative multi-decadal shifts in disease reports across related hosts. Normalized disease reports increased significantly between 1970 and 2013 in corals and urchins, indicating positive disease swings in these environmentally sensitive ectotherms. Coral disease reports in the Caribbean correlated with increasing temperature anomalies, supporting the hypothesis that warming oceans drive infectious coral diseases. Meanwhile, disease risk may also decrease in a changing ocean. Disease reports decreased significantly in fishes and elasmobranchs, which have experienced steep human-induced population declines and diminishing population density that, while concerning, may reduce disease. The increases and decreases in disease reports across the 44-year record transcend short-term fluctuations and regional variation. Our results show that long-term changes in disease reports coincide with recent decades of widespread environmental change in the ocean.

La hausse de la température des océans du monde est devenue une menace majeure pour les récifs coralliens à l'échelle mondiale à mesure que la gravité et la fréquence du blanchiment massif des coraux et des événements de mortalité augmentent. En 2005, les températures océaniques élevées dans l'Atlantique tropical et les Caraïbes ont entraîné l'événement de blanchiment le plus grave jamais enregistré dans le bassin. Les outils basés sur les satellites ont fourni des avertissements aux gestionnaires de récifs coralliens et aux scientifiques, guidant à la fois le moment et l'emplacement des observations sur le terrain des chercheurs alors que des conditions anormalement chaudes se développaient et se répandaient dans la grande région des Caraïbes de juin à octobre 2005. Les enquêtes de terrain sur le blanchiment et la mortalité ont dépassé les efforts antérieurs en détail et en étendue, et ont fourni une nouvelle norme pour documenter les effets du blanchiment et pour tester les prévisions actuelles et les produits de prévision. Des collaborateurs de 22 pays ont entrepris la documentation la plus complète à ce jour sur le blanchiment à l'échelle du bassin et ont constaté que plus de 80 % des coraux blanchis et plus de 40 % sont morts sur de nombreux sites. Le blanchiment le plus sévère a coïncidé avec les eaux les plus proches d'une piscine chaude de l'Atlantique occidental qui était centrée à l'extrémité nord des Petites Antilles. Le stress thermique au cours de l'événement de 2005 a dépassé tout ce qui a été observé dans les Caraïbes au cours des 20 années précédentes, et les températures moyennes régionales ont été les plus chaudes depuis plus de 150 ans. La comparaison des données satellitaires avec les enquêtes sur le terrain a démontré une relation prédictive significative entre le stress thermique accumulé (mesuré à l'aide des semaines de chauffage de degré de NOAA Coral Reef Watch) et l'intensité de blanchiment. Ce blanchissement et cette mortalité sévères et généralisés auront sans aucun doute des conséquences à long terme sur les écosystèmes récifaux et suggèrent un avenir troublé pour les écosystèmes marins tropicaux sous un climat qui se réchauffe. El aumento de la temperatura de los océanos del mundo se ha convertido en una gran amenaza para los arrecifes de coral a nivel mundial a medida que aumentan la gravedad y la frecuencia de la decoloración masiva de los corales y los eventos de mortalidad. En 2005, las altas temperaturas oceánicas en el Atlántico tropical y el Caribe dieron lugar al evento de blanqueamiento más severo jamás registrado en la cuenca. Las herramientas basadas en satélites proporcionaron advertencias para los administradores y científicos de arrecifes de coral, guiando tanto el momento como la ubicación de las observaciones de campo de los investigadores a medida que se desarrollaron condiciones anómalamente cálidas y se extendieron por toda la región del Gran Caribe de junio a octubre de 2005. Las encuestas de campo sobre blanqueamiento y mortalidad superaron los esfuerzos previos en detalle y extensión, y proporcionaron un nuevo estándar para documentar los efectos del blanqueamiento y para probar productos pronosticados y pronosticados. Colaboradores de 22 países llevaron a cabo la documentación más completa sobre el blanqueamiento a escala de cuenca hasta la fecha y descubrieron que más del 80% de los corales blanqueados y más del 40% murieron en muchos sitios. El blanqueamiento más severo coincidió con las aguas más cercanas a una piscina cálida del Atlántico occidental que se centraba en el extremo norte de las Antillas Menores. El estrés térmico durante el evento de 2005 superó cualquier temperatura observada en el Caribe en los 20 años anteriores, y las temperaturas promedio regionales fueron las más cálidas en más de 150 años. La comparación de los datos satelitales con los estudios de campo demostró una relación predictiva significativa entre el estrés por calor acumulado (medido utilizando las semanas de calentamiento de grado de NOAA Coral Reef Watch) y la intensidad del blanqueamiento. Este severo y generalizado blanqueamiento y mortalidad sin duda tendrá consecuencias a largo plazo para los ecosistemas de arrecifes y sugiere un futuro problemático para los ecosistemas marinos tropicales bajo un clima más cálido. The rising temperature of the world's oceans has become a major threat to coral reefs globally as the severity and frequency of mass coral bleaching and mortality events increase. In 2005, high ocean temperatures in the tropical Atlantic and Caribbean resulted in the most severe bleaching event ever recorded in the basin.Satellite-based tools provided warnings for coral reef managers and scientists, guiding both the timing and location of researchers' field observations as anomalously warm conditions developed and spread across the greater Caribbean region from June to October 2005. Field surveys of bleaching and mortality exceeded prior efforts in detail and extent, and provided a new standard for documenting the effects of bleaching and for testing nowcast and forecast products. Collaborators from 22 countries undertook the most comprehensive documentation of basin-scale bleaching to date and found that over 80% of corals bleached and over 40% died at many sites. The most severe bleaching coincided with waters nearest a western Atlantic warm pool that was centered off the northern end of the Lesser Antilles.Thermal stress during the 2005 event exceeded any observed from the Caribbean in the prior 20 years, and regionally-averaged temperatures were the warmest in over 150 years. Comparison of satellite data against field surveys demonstrated a significant predictive relationship between accumulated heat stress (measured using NOAA Coral Reef Watch's Degree Heating Weeks) and bleaching intensity. This severe, widespread bleaching and mortality will undoubtedly have long-term consequences for reef ecosystems and suggests a troubled future for tropical marine ecosystems under a warming climate. أصبح ارتفاع درجة حرارة محيطات العالم تهديدًا كبيرًا للشعاب المرجانية على مستوى العالم مع زيادة شدة وتواتر أحداث ابيضاض المرجان الجماعي والوفيات. في عام 2005، أدت درجات حرارة المحيطات المرتفعة في المحيط الأطلسي الاستوائي ومنطقة البحر الكاريبي إلى أشد حدث تبييض تم تسجيله على الإطلاق في الحوض. قدمت الأدوات القائمة على الأقمار الصناعية تحذيرات لمديري وعلماء الشعاب المرجانية، حيث وجهت توقيت وموقع الملاحظات الميدانية للباحثين حيث تطورت الظروف الدافئة بشكل غير طبيعي وانتشرت في جميع أنحاء منطقة البحر الكاريبي الكبرى من يونيو إلى أكتوبر 2005. تجاوزت المسوحات الميدانية للتبييض والوفيات الجهود السابقة بالتفصيل والمدى، ووفرت معيارًا جديدًا لتوثيق آثار التبييض واختبار المنتجات الآنية والمتوقعة. أجرى المتعاونون من 22 دولة التوثيق الأكثر شمولاً للتبييض على نطاق الحوض حتى الآن ووجدوا أن أكثر من 80 ٪ من الشعاب المرجانية المبيضة وأكثر من 40 ٪ ماتوا في العديد من المواقع. تزامن التبييض الأكثر شدة مع المياه الأقرب إلى بركة دافئة في غرب المحيط الأطلسي كانت متمركزة قبالة الطرف الشمالي لجزر الأنتيل الصغرى. تجاوز الإجهاد الحراري خلال حدث عام 2005 أي حالة لوحظت من منطقة البحر الكاريبي في السنوات العشرين السابقة، وكانت درجات الحرارة المتوسطة إقليميًا هي الأكثر دفئًا منذ أكثر من 150 عامًا. أظهرت مقارنة بيانات الأقمار الصناعية بالمسوحات الميدانية وجود علاقة تنبؤية كبيرة بين الإجهاد الحراري المتراكم (الذي تم قياسه باستخدام أسابيع التسخين بدرجة ساعة الشعاب المرجانية التابعة للإدارة الوطنية للمحيطات والغلاف الجوي) وشدة التبييض. مما لا شك فيه أن هذا التبييض والوفيات الشديدة والواسعة النطاق سيكون لها عواقب طويلة الأجل على النظم الإيكولوجية للشعاب المرجانية وتشير إلى مستقبل مضطرب للنظم الإيكولوجية البحرية الاستوائية في ظل مناخ دافئ.

AbstractIncreasingly frequent severe coral bleaching is among the greatest threats to coral reefs posed by climate change. Global climate models (GCMs) project great spatial variation in the timing of annual severe bleaching (ASB) conditions; a point at which reefs are certain to change and recovery will be limited. However, previous model-resolution projections (~1 × 1°) are too coarse to inform conservation planning. To meet the need for higher-resolution projections, we generated statistically downscaled projections (4-km resolution) for all coral reefs; these projections reveal high local-scale variation in ASB. Timing of ASB varies >10 years in 71 of the 87 countries and territories with >500 km2 of reef area. Emissions scenario RCP4.5 represents lower emissions mid-century than will eventuate if pledges made following the 2015 Paris Climate Change Conference (COP21) become reality. These pledges do little to provide reefs with more time to adapt and acclimate prior to severe bleaching conditions occurring annually. RCP4.5 adds 11 years to the global average ASB timing when compared to RCP8.5; however, >75% of reefs still experience ASB before 2070 under RCP4.5. Coral reef futures clearly vary greatly among and within countries, indicating the projections warrant consideration in most reef areas during conservation and management planning.