Coral bleaching occurs when heat or other stress causes coral to expel the symbiotic algae living in its tissues, turning the coral white. A bleached coral is not dead: it can recover if the stress is brief, but prolonged loss of its algae leaves it starved and more vulnerable to disease, and eventually to death, and rising ocean temperature from climate change is the leading cause.
Facts
PeriodicityIncreasingly frequent since the early 1980s; on the Great Barrier Reef, bleaching is projected to recur three times a decade if global warming holds at 1.5 degrees Celsius, rising to every other year at 2 degrees. 1 ScaleIndividual coral polyps and colonies, scaling up to entire reef systems during mass bleaching events 2 First DescribedSixty major coral bleaching episodes were recorded between 1979 and 1990, but the first globally recognized mass bleaching event, driven by an especially strong El Nino, took place in 1998, when 21 percent of the world's reefs experienced bleaching-level heat stress. 1 Connections
Demonstrated By
Source National Oceanic and Atmospheric Administration
Source Coral Bleaching (Wikipedia)
Source National Oceanic and Atmospheric Administration
Elkhorn coral's critically-endangered status is tied in part to repeated bleaching from warming Caribbean waters.
Source Coral Bleaching (NOAA Ocean Service)
The Great Barrier Reef has suffered repeated mass bleaching events during marine heatwaves.
Source Coral Bleaching (NOAA Ocean Service)
Source Coral Bleaching (Wikipedia)
Although Red Sea reefs are unusually heat tolerant, episodes of coral bleaching still occur there during periods of elevated sea surface temperature.
Source Encyclopaedia Britannica
Open Questions
Source Coral Bleaching (NOAA Ocean Service)
Sources
1. Coral Bleaching (Wikipedia)
WikipediaMass bleaching events section
The first globally recognized bleaching event took place in 1998 and 21% of reefs experienced bleaching-level heat stress.
Trends due to climate change section
Bleaching is predicted to occur three times a decade on the Great Barrier Reef if warming is kept to 1.5 °C, increasing to every other year at 2 °C.
View the Source 2. Coral Bleaching (NOAA Ocean Service)
National Oceanic and Atmospheric AdministrationQuote
When a coral bleaches, it is not dead. Corals can survive a bleaching event, but they are under more stress and are subject to mortality.
National Oceanic and Atmospheric Administration
National Oceanic and Atmospheric Administration- Demonstrated By: Coral Sea
- Demonstrated By: Chagos Archipelago
View the Source Encyclopaedia Britannica
Encyclopaedia Britannica, Inc.Demonstrated By: Red Sea Coral ReefView the Source Open Questions (1 open question)
How fully can a coral reef recover from a severe bleaching event if ocean warming continues?
Bleached coral can survive and recover if the stress is brief, but scientists are still working out how repeated, prolonged heat stress under continued warming affects a reef's long-term capacity to bounce back.
What would resolve this Long-term monitoring of reef recovery trajectories across repeated bleaching events under different warming scenarios, tied to disease-susceptibility research.
Marine biology and coral reef ecologyCoral Bleaching (NOAA Ocean Service)
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