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Coral Crisis: Why Coral Bleaching Is a Big Problem

The world’s coral reefs are in poor condition. A major reason for this is a process called coral bleaching whereby healthy, vibrantly coloured coral turn shockingly white and subsequently die. This past year, it is estimated that approximately 12% of the world’s coral reefs have been bleached, a record high for one year.

The Great Barrier Reef in Australia has been particularly badly affected this past year, as almost half of coral there have died to date due to adverse environmental conditions.

What is coral bleaching?

When coral become stressed by conditions in their environment, such as a change in temperature, nutrients or light, they expel a symbiotic algae (zooxanthellae) living within their tissues. As a result, the coral turn completely white. Although the coral is still alive at this point, bleached coral is under significant stress and as a result subject to much higher mortality rates. Scientists cite climate change, ocean acidification and the El Nino effect as the main causes of the ocean conditions leading to coral bleaching.

Although this year has set records, the phenomenon is not new, nor is it limited to the Great Barrier Reef.

The National Ocean Service reports that in 2005, the United States lost approximately half of its coral reefs in the Caribbean region due to a bleaching outbreak. Satellite imagery showed that this particular bleaching event cause more coral loss in 2005 than in the previous 20 years combined.

Making the phenomenon more complex, unusually cold water in the Florida Keys in 2010 also caused a significant bleaching event the lead to high coral death rates.

The fall out from bleaching: 

While coral bleaching may appear very strangely beautiful, it is a big problem. Not only does coral bleaching have a cascading effect on the ecosystem, but also a detrimental effect on those who economically depend upon the health of coral reefs. Nexus Media reports that half a billion people rely on coral reefs for their livelihood with $30 billion (USD) of income at risk.

Nexus Media has produced an incredible video for explaining and showing the coral bleaching. You can watch it here.

All images via Justin Marshall/