Widespread Coral Bleaching (I)

 What is Coral Bleaching?

Coral bleaching is a phenomenon that occurs when coral polyps expel algae called zooxanthellae from their tissues. This gives the coral a stark white appearance, resembling bleached or dead coral. Coral bleaching is caused by abnormally warm ocean temperatures, usually during prolonged periods of warmer weather. When water temperatures rise just 1-2°C above the normal local seasonal maximum, corals become stressed. They react by ejecting the symbiotic algae living inside their tissues. These algae normally provide up to 90% of the coral's energy through photosynthesis. Without them, the coral loses its major energy source and turns translucent and white, revealing the stark white calcium carbonate skeleton beneath. This bleached appearance signals that the coral is severely stressed and at risk of death.

Causes of Coral Bleaching

Coral bleaching is primarily caused by increased ocean temperatures. When water temperatures rise, corals become stressed and expel the symbiotic algae that gives them their color, causing them to turn white. This bleaching makes it harder for corals to survive. Several factors contribute to increased ocean temperatures and coral bleaching:

Increased Ocean Temperatures - Warming oceans are the main driver of mass coral bleaching events. Even an increase of just 1-2°C can cause bleaching.

El Niño Weather Patterns - El Niño brings warmer water temperatures to tropical and cold-water regions, causing bleaching. The strong 2015-2016 El Niño triggered severe bleaching at reefs around the world.

Climate Change and Global Warming - Climate change is increasing average ocean temperatures, making bleaching events more frequent and severe. Since the 1980s, mass bleaching events have occurred during most El Niño years.

Pollution - Pollution from agricultural runoff and coastal development can further stress corals, increasing their vulnerability to bleaching.

Overfishing - Overfishing key herbivorous fish can allow algae to overgrow and outcompete corals. This added pressure makes it harder for corals to recover from bleaching.

Rising ocean temperatures due to human-caused climate change are the primary driver of increased coral bleaching worldwide. El Niño and local stressors like pollution magnify the impacts of warming seas. Reducing carbon emissions and local threats are key to coral reef conservation.