(Last Updated: December 5, 2017)
In the central equatorial Pacific, all of CRW's 5km Regional Virtual Stations have decreased to Bleaching Watch or No Stress status. This includes the Samoas, which suffered multiple weeks of Alert Level 2 heat stress (associated with widespread coral bleaching and significant mortality) in early to mid-2017, with confirmed reports of bleaching of both shallow and deeper corals. Note, however, that multiple coral reef areas throughout the region are expected to return to Alert Level 1 heat stress (associated with significant coral bleaching) shortly, including Tuvalu in the next 5-8 weeks and the Samoas, Wallis and Futuna, Northern Tonga, Southern Tonga, and the Austral Islands in the coming 9-12 weeks.
The Main Hawaiian Islands (MHI), which observed record levels of bleaching in 2014 and static Alert Level 2 bleaching heat stress in October and November 2015, experienced only low-level heat stress during summer 2017, although there had been concerns in August, September, and October that Alert Level 2 stress would develop. The Northwestern Hawaiian Islands (NWHI), which sustained high, prolonged levels of bleaching heat stress in 2014 and some subsequent coral death, returned to Alert Level 1 bleaching conditions from mid-September to mid-October 2017, but have since decreased to a level of No Stress. CRW continues to collect data from field partners, including Hawai'i's Eyes of the Reef (EOR) volunteer community reef monitoring program, concerning the extent and severity of coral bleaching and mortality in the MHI and NWHI since 2014.
CRW's 5km Regional Virtual Stations in Micronesia have all returned to a Bleaching Watch or No Stress status. Note, however that Alert Level 1 heat stress is expected again in the next 5-8 weeks in the Eastern Federated States of Micronesia (FSM), which suffered Alert Level 2 bleaching stress from mid-September to late-November 2017 (and were previously at Alert Level 2 bleaching conditions from mid-August to early December 2016). The Northern Mariana Islands and Guam (which has been hit by severe coral bleaching for five consecutive years) have returned to Bleaching Watch status, after suffering severe Alert Level 2 heat stress from mid-August to mid-October 2017. Alert Level 2 bleaching conditions also dominated the Western FSM throughout September and October and Palau during much of October.
In Micronesia's Phoenix Islands, in particular, as noted in multiple articles below and by numerous news outlets worldwide, in Kiribati, persistent elevated ocean temperatures (as high as 31.4-degrees Celsius) in 2015-2016 killed most of the corals in the region. Photos taken by scientists surveying the reef damage, especially around Kiritimati (Christmas Island), where more than 80% coral mortality has been documented, are gruesome. The high bleaching heat stress in Kiribati was tied to the very strong El Niño that dissipated in late 2016 but whose effects lasted for multiple additional months in the southern hemisphere. It is estimated that only 1-5% of Kiribati's reefs will survive and recover from this severe bleaching heat stress event.
Continuing further west, heat stress is building again in Melanesia. Alert Level 1 bleaching stress arrived in West Papua and Papua New Guinea at the end of November 2017 and is expected to continue for the next 9-12 weeks. Alert Level 1 stress also is expected in the Solomon Islands and in Vanuatu in 5-8 weeks' time, and in Fiji, Eastern New Caledonia, Western New Caledonia, and in the Chesterfield Islands in 9-12 weeks' time.
The Coral Triangle also continues to heat up. In addition to multiple of the aforementioned Melanesian islands, many of CRW's 5km Regional Virtual Stations in the Coral Triangle are registering a Bleaching Warning. Although it appears the Philippines (which suffered severe Alert Levels 1 and 2 bleaching stress throughout much of June and July 2017) will escape this round of high heat stress, Alert Level 1 bleaching stress is expected in Maluku, Indonesia, West Nusa Tenggara, East Nusa Tenggara, West Timor, and Timor-Leste in the next 5-8 weeks, and in South Sulawesi and East Java and Bali in 9-12 weeks' time. CRW continues communicating with local field partners to try and assess the status of local reefs throughout the Coral Triangle impacted by severe bleaching heat stress during and since the Third Global Coral Bleaching Event.
Severe heat stress (Alert Levels 1 and 2) persisted for many weeks in East Asia in summer 2016. Significant coral bleaching was reported in multiple reef areas, including Hainan Island, China, Northern Vietnam, Dongsha, Taiwan, and in the Ryukyu Islands, Japan - where extensive (over 90%) bleaching was observed in the region's largest coral reef (Sekiseishoko Reef) as of July 2016, resulting in 70% mortality. Prolonged, severe Alert Levels 1 and 2 heat stress returned to the Ryukyu Islands, Japan, Taiwan, Vietnam, and China from mid-August to mid-October 2017, dissipating with the onset of late Autumn in the region. CRW continues communicating with local coral reef management and research partners to determine the extent of the damage to the region's coral reefs during and since the Third Global Coral Bleaching Event.
In Southeast Asia, all of CRW's 5km Regional Virtual Stations have returned to a level of either Bleaching Watch or No Stress.
After multiple weeks of severe (Alert Levels 1 and 2) heat stress along much of the GBR, especially the central GBR, in March 2017 (the Reef's unprecedented, second consecutive year of confirmed mass bleaching), cooler waters finally arrived in the region in mid-April. All of CRW's 5km Regional Virtual Stations for the GBR region returned to a level of No Stress. As of early December 2017, with the approaching summer, Alert Level 1 heat stress is expected again in the Torres Strait, throughout the GBR, and in the Northern Coral Sea Islands and the Southern Coral Sea Islands in the next 5-8 weeks. CRW's near-real-time satellite monitoring and modeled predictions of environmental stress during and since the Third Global Coral Bleaching Event have been critical in helping local management and research partners plan effectual in-water and aerial surveys of the GBR. We recommend coral reef managers and other stakeholders continue to closely monitor CRW's website for the most up-to-date information on environmental conditions on the GBR.
In mid-May 2017, cooler waters arrived along the western coast of Australia, in the Indian Ocean. Since that time, CRW's 5km Regional Virtual Stations throughout the region had been at a level of No Stress. However, as of early December and the approaching Austral summer, Alert Level 1 bleaching heat stress has arrived at Scott to Ashmore Reefs. Alert Levels 1 and 2 heat stress also are expected in the next 5-8 weeks from the Gulf of Carpentaria west to North Western Australia, and at Rowley Shoals, in Central Western Australia, in Moreton Bay, and at Lord Howe Island in 9-12 weeks' time.
It is important to note that even though widespread coral bleaching was not confirmed throughout the Indian Ocean in the first half of 2017, in the Middle East, severe Alert Level 2 bleaching heat stress was present throughout September 2017 in multiple coral reef areas, including in the Western Persian Gulf and Bahrain. As of this writing in early December, CRW's 5km Regional Virtual Stations throughout the region are all at a level of No Stress.
In the Gulf of Mexico, multiple months of high heat stress in the Flower Garden Banks, Texas and Yucatan Peninsula dissipated in mid-September and late-October 2016, respectively. Again in 2017, Alert Level 1 heat stress was predicted at all three 5km Regional Virtual Stations for the Gulf region through early August; however it only materialized in the Yucatan Peninsula. In mid-September, the high heat stress increased further, elevating to Alert Level 2 bleaching conditions, which remained until the end of October 2017.
A strong bleaching season in 2015 impacted coral reefs throughout the Caribbean. Bleaching of Caribbean corals at a number of reef locations (e.g., Cuba, the Turks and Caicos, the Bahamas, Haiti, the Dominican Republic, and Mexico) in 2015, as reported by partner organizations with divers working on affected reefs, including the XL Catlin Seaview Survey and Reef Check, led to NOAA's declaration of the Third Global Coral Bleaching Event on record (after the 1998 and 2010 global events). In early November 2016, high levels of bleaching heat stress returned to the eastern and southern portions of the Caribbean basin. Bleaching conditions remained until late December 2016. As of early October 2017, Alert Levels 1 and 2 heat stress were present at more than one-half of CRW's 5km Regional Virtual Stations in the Caribbean, especially in the southern portion of the basin; this severe heat stress remained throughout the month. As of early December 2017, Alert Level 2 bleaching stress remains only in Nearshore Venezuela and is expected to decrease finally in the coming week. CRW continues seeking data and observations from field partners concerning the extent and severity of coral bleaching and mortality throughout the Caribbean since 2015.
Click here to access the most recent Pacific Climate Update from NOAA CRW.
In 2016, we wrote in Reef Encounter about the ongoing Third Global Coral Bleaching Event, which was forecast to continue into 2017 (Eakin et al. 2016). As predicted, the 2015-16 strong El Niño formed, worsening the bleaching, and was followed by a La Niña event. Despite the end of the La Niña, high temperatures persisted into 2017. At least half of the world's coral reef areas bleached in two or all three years of the event, and many suffered the worst bleaching ever documented. As of June 2017, the three-year-long, Third Global Coral Bleaching Event has most likely ended (National Oceanic and Atmospheric Administration (NOAA) 2017) but remains the longest, most widespread, and probably the most destructive ever recorded.
Recap: Bleaching in 2014
In June 2014 coral bleaching began in Guam and the Commonwealth of the Northern Mariana Islands (CNMI, Heron et al. 2016), and it looked like an El Niño was predicted to form but never did. Papaha̅naumokua̅kea Marine National Monument, the Main Hawaiian Islands (DAR 2014, Bahr et al. 2015), southeastern Florida and the Florida Keys (FRRP 2015a) saw bleaching in August and September, while the Republic of the Marshall Islands (Fellenius 2014, Eakin et al. 2016) saw bleaching from September-November.
Recap: Bleaching in 2015
Bleaching worsened as heat stress moved into the southern hemisphere in late 2014/early 2015, striking in the South Pacific, large areas of the Indian Ocean, and parts of Southeast Asia - including severe localized bleaching in Dongsha Atoll in June 2015 (DeCarlo et al. 2017). With the onset of the 2015-16 El Niño, the heat stress focused on the central and eastern Tropical Pacific. The heat stress spread northward, causing the worst bleaching on record in the Main Hawaiian Islands in October 2015 (TNC 2015, Eakin et al. 2016, Kramer et al. 2016, Rodgers et al. 2017, Rosinski et al. 2017). In the Atlantic, September-October brought moderate to severe coral bleaching (and disease) and low to moderate mortality to Florida's coral reefs for the second year in a row (FRRP 2015b, FRRP 2016a); bleaching at varying severities and scales was then reported from multiple locations across the eastern and western Caribbean through October. As of October 2015, with widespread bleaching in each of the Indian, Pacific, and Atlantic basins, NOAA declared that the Third Global Coral Bleaching Event was underway. By the end of 2015, 41% of global coral reefs had been exposed to heat stress of 4°C-weeks or more (measured by NOAA Coral Reef Watch's Daily Global 5km Degree Heating Week version 3 - DHW) and almost all of the world's reefs had exceeded their normal warm-season temperatures.
Figure 1. NOAA Coral Reef Watch Maximum Bleaching Alert Area map for January-December 2016. Severe coral bleaching was reported in all areas circled in white on map and listed below the map. Data from Coral Reef Watch Daily Global 5km Coral Bleaching Heat Stress Monitoring Product Suite version 3 (Liu et al. 2017).
Bleaching in 2016
As the El Niño continued to strengthen, heat stress and bleaching returned to the Southern Hemisphere. Heat stress in 2016 was much more widespread than in 2015, encompassing 51% of global coral reefs (measured by Coral Reef Watch's DHW product). Even more important was the severity. The El Niño resulted in continuous heat stress in the Central Pacific from April 2015 to May 2016. The Northern Line Islands heat stress values were the highest Coral Reef Watch has ever documented (DHW > 25°C-weeks) and caused the worst bleaching-related mortality ever reported. By May 2016, this included 80% of total coral cover dead and an additional 15% bleached in Kiritimati (Harvey 2016), as well as 98% total coral cover dead at Jarvis Island with substantial reduction to reef structural complexity (investigation into the mechanism of this rapid erosion is underway). Severe heat stress in Fiji's lagoons caused sudden and widespread coral death in February just weeks before Cyclone Winston cooled ocean temperatures. Bleaching in New Caledonia in March caused wide swaths of lagoon corals, especially Acropora, to fluoresce in multi-colored pastels. The first major bleaching ever documented on the Northern and Far Northern sectors of the Great Barrier Reef (GBR) peaked in March (Hughes et al. 2017). This was the worst bleaching ever seen in the GBR resulting in 29% mortality of shallow-water corals across the entire reef (GBRMPA 2017). Coral bleaching started in the Western Indian Ocean in January and peaked by May (CORDIO-EA), with bleaching in the Seychelles ranging from 69-99% resulting in a subsequent 50% reduction in hard coral cover (SIF 2017). Bleaching in Southeast Asia caused Thailand to close many of its coral reefs to recreational diving activities in May (AFP 2016). Bleaching in Guam, especially Tumon Bay, returned for the fourth year in a row.
In the boreal summer, bleaching returned to the Northern Hemisphere, with extensive (over 90%) bleaching observed in the largest coral reef in the Ryukyu Islands, Japan starting in July, resulting in 70% mortality (Harvey 2017). The heat stress then brought bleaching back to the western Atlantic, Gulf of Mexico, and Caribbean from September through November, with the western Caribbean hit hardest. Florida suffered only mild to moderate bleaching in summer 2016 but was struck by another round of coral disease, including the loss of 95% of pillar coral (Dendrogyra cylindrus) across the state (FRRP 2016b). October brought the worst bleaching ever to the Flower Garden Banks, while patchy bleaching was reported from the eastern Caribbean. Moderate to severe bleaching (generally more severe than in 2015) also was reported in parts of the Mesoamerican Barrier Reef in October and November, with deeper reefs being impacted moreso than shallow. The year culminated in a return of bleaching to the Republic of the Marshall Islands by November 2016. Figure 1 (above) shows the total extent of heat stress in 2016 and regions with confirmed coral bleaching reports.
Figure 2. NOAA Coral Reef Watch Maximum Bleaching Alert Area map for January-May 2017, with coral reef areas with reports of bleaching circled in white. Data from Coral Reef Watch Daily Global 5km Coral Bleaching Heat Stress Monitoring Product Suite version 3 (Liu et al. 2017).
As of September 2017, NOAA's El Niño-Southern Oscillation Alert System has issued a La Niña Watch, with a 55-60% chance of La Niña formation during late 2017. NOAA Coral Reef Watch's Four-Month Coral Bleaching Heat Stress Outlook indicates that bleaching is much less likely in most of the Northern Hemisphere this summer (Figure 3). However, the Outlook through December 2017 does indicate a potential for significant bleaching and coral mortality in the western Pacific Ocean (from Guam through Micronesia); in the eastern portion of the Papaha̅naumokua̅kea Marine National Monument; and in the Caribbean Sea.
While more coral bleaching may still occur in 2017, the absence of widespread coral bleaching in the Indian Ocean appears to signal that the three-year-long global event has ended.
Figure 3. Map of areas where 60% or more of the model ensemble members were predicting heat stress at each of NOAA Coral Reef Watch's bleaching heat stress alert levels through December 2017 (as of September 12, 2017). Data from Coral Reef Watch Four-Month Coral Bleaching Heat Stress Outlook version 4 (Liu et al. 2017).
A special issue or portion of an issue of the International Society for Reef Studies journal Coral Reefs will focus on this event. This will be an opportunity for you to publish more detailed studies on coral health, bleaching, disease, and mortality in your country or region associated with the Third Global Coral Bleaching Event.
Since our last update (Eakin et al. 2016), filmmakers at Exposure Labs completed a 90-minute documentary on their efforts to capture time-lapse imagery of coral bleaching during the Third Global Coral Bleaching Event. The film includes many of your contributions to their global call for bleaching reports and part was shot at the 13th International Coral Reef Symposium in Honolulu, Hawaii. The resulting film, Chasing Coral, just premiered on Netflix on July 14, 2017 (see two more detailed articles about the film in the August 2017 edition of Reef Encounter).
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The scientific results and conclusions posted on this web page, as well as any views or opinions expressed herein, are those of the author(s) and do not necessarily reflect the views of NOAA or the Department of Commerce.