Coral reefs are among the most vibrant and diverse ecosystems on Earth, often called the "rainforests of the sea." But today, many of these magnificent structures are under threat—one of the most alarming signs being coral bleaching, where corals lose their brilliant colors and turn ghostly white. But what causes this to happen, and why should we care?
What Is Coral Bleaching?
Coral bleaching occurs when corals, under stress, expel the symbiotic algae (called zooxanthellae) that live in their tissues. These algae provide up to 90% of the energy corals need to grow and also give corals their stunning colors. Without them, corals turn white and become much more vulnerable to disease and death. 
Why Do Corals Bleach?
The most common trigger for coral bleaching is rising ocean temperatures, often caused by global warming. Even a sustained increase of just 1–2°C above normal can stress corals enough to bleach them.
Other causes include:
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Ocean acidification from increased CO₂ levels
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Pollution from coastal development and agriculture
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Overexposure to sunlight
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Changes in salinity
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Overfishing that disrupts reef balance
According to the National Oceanic and Atmospheric Administration (NOAA), bleaching events are becoming more frequent and severe due to climate change (NOAA, 2023).
Is Bleaching the Same as Death?
Not necessarily. Corals can recover from bleaching if stress conditions subside in time. However, if bleaching is prolonged, the coral may starve and die. The Great Barrier Reef, for example, experienced mass bleaching events in 2016, 2017, 2020, and 2022, with significant coral loss (Australian Institute of Marine Science, 2023).
Why Coral Health Matters
Healthy coral reefs:
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Provide shelter for 25% of all marine life
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Support fishing industries and tourism
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Protect coastlines from erosion and storms
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Are sources of potential new medicines
When reefs die, the impact ripples across entire ecosystems and human communities.
What Can We Do to Help?
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Reduce carbon emissions to combat global warming
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Support reef-safe tourism and sunscreen products
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Avoid buying coral or marine life souvenirs
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Support marine conservation groups
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Educate others about reef protection
Even small lifestyle changes can help preserve the beauty and function of coral reefs for future generations.