Coral Bleaching

Causes of Coral Bleaching

Approximately 1% of the world's population has chosen to learn scuba diving and interact with the amazing aquatic marine life that lies beneath our Oceans.

The creations that divers can see include hard and soft coral formations, which display some of the unique colors, and patterns that cannot be found elsewhere on earth.


It's widely accepted that most reefs are disappearing at an alarming rate due to coral bleaching and other stress factors.

Coral bleaching is a process that causes coral to lose its normal colour.

Even though inexperienced divers may admire the apparent snow-like environment, it's a sign that the coral is distressed.

Coral is a living polyp, which surrounds a hard shell of calcium carbonate.

The coral polyps also share their calcium shell with zooxanthellae algae, which converts energy from the sun into an energy form that polyps need to stay alive.

The coral polyp is a clear transparent formation. The algae that live with the coral create the vibrant colors that divers thrive to see.

If the algae die, the result is a distinct lack of colour, leaving the skeletal remains of the coral polyps white and colorless.


The reason why this happens is usually one of the following or a combination of several and the largest reasons are often preventable.

Foreign objects and contaminants Coral and algae are extremely sensitive to their surrounding environment and if foreign objects and/or contaminants such as oil and garbage are present on the reef, the algae can often die if the conditions are too difficult for them to exist.

Inorganic nutrients Inorganic nutrients are nutrients that are not normal to the corals' ecosystem, which can lead to a higher concentration of zooxanthellae than normal.

Rainwater run-off causes this type of pollution, which tends to lower the immune system of the coral much like large numbers of people spreading colds and flu.

Water Temperature If the ocean temperature increases, the algae begin to die because they need normal temperatures to function properly.

Coral reefs have an extremely small tolerance for changes in temperatures, typically (+/-) 1-3 degrees change.

Therefore, raised water temperatures commonly causes coral bleaching particularly during summer months.

These are the most common reasons that coral bleaching occurs and usually the most preventable. We should stop introducing waste products into the oceans. We need more education and awareness to the plight of the earth's ecosystems.

Many countries have laws that ban the emptying of garbage and chemicals from factories into our water systems. The production of unregulated greenhouse gases, causes the temperature of the sea to rise.

Without alternatives to these preventable causes of coral bleaching, we risk losing a precious multi-coloured world of ocean coral reefs.


The underwater world needs caring divers and non-divers to conserve the fragile aquatic ecosystems.

Coralline Systems |> Artificial Reefs |> Coral Reef Systems |> Underwater Pollution |

Join the actions of concerned individuals, by discovering some of the most pressing problems facing these vulnerable environments and help to protect and conserve them. The Project AWARE course is informative, interesting and most importantly, you can make a difference.

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