What Is Coral Bleaching?

I was recently reading an article about coral reefs and their importance  in our ecosystem.  The article mentioned coral bleaching, which I had not heard of before.  Here's a little about coral bleaching that I found interesting.

Warmer water temperatures can result in coral bleaching. When water is too warm, corals will expel the algae (zooxanthellae) living in their tissues causing the coral to turn completely white. This is called coral bleaching. 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.

In 2005, the U.S. lost half of its coral reefs in the Caribbean in a single year due to a massive bleaching event.

Comparison of satellite data from the previous 20 years confirmed that thermal stress from the 2005 event was greater than the previous 20 years combined.


There are other factors that can produce coral bleaching as well. In January 2010, cold water temperatures in the Florida Keys caused a coral bleaching event that resulted in some coral death. Water temperatures dropped 12.06 degrees Fahrenheit lower than the typical temperatures observed at this time of year. Researchers will evaluate if this cold-stress event will make corals more susceptible to disease in the same way that warmer waters impact corals.

Coral reefs are vital to our ecosystem. Reefs cover an area of over 280,000 km and support thousands of species in what many describe as the “rainforests of the seas”.
Coral reefs benefit the environment and people in numerous ways.

• Protect shores from the impact of waves and from storms;
• Provide benefits to humans in the form of food and medicine;
• Provide economic benefits to local communities from tourism.

They also yield more than $30billion annually in global goods and services, such as tourism and food, and coastline protection. In the past few years, global threats to coral reefs have been of increasing concern.  The coral reefs are the undersea equivalent of rainforest trees.  Through the photosynthesis carried out by their algae, coral serve as a vital input of food into the marine food chain.  The reefs provide  home and shelter to over 25%of fish in the ocean and up to two million marine species.  Eliminate the undersea trees, which mass coral bleaching is in the process of doing, and you'll eliminate everything that depends on it for survival.