Climate change problems: coral bleaching
Coral bleaching due to temperature rise, Indo-Pacific Ocean.
© WWF-Canon / Jürgen FREUND
© WWF-Canon / Jürgen FREUND
How does coral bleaching occur?
The beautiful and varied colours of corals come from algae living symbiotically in their tissue. Called zooxanthellae, these algae provide the coral with food, in return for protection and access to light provided by the coral.
Environmental stresses such as increased water temperatures cause the zooxanthellae to leave the coral tissue. This exposes the white, calcium carbonate skeletons of the coral and is what we call coral bleaching.
Other reef animals that have a symbiotic relationship with zooxanthellae also suffer from bleaching, such as giant clams and some sponges.
Environmental stresses such as increased water temperatures cause the zooxanthellae to leave the coral tissue. This exposes the white, calcium carbonate skeletons of the coral and is what we call coral bleaching.
Other reef animals that have a symbiotic relationship with zooxanthellae also suffer from bleaching, such as giant clams and some sponges.
One of the most visually dramatic effects of climate change is coral bleaching, a stress response caused by high water temperatures that can lead to coral death.
Recent years have seen widespread and severe coral bleaching episodes around the world, with coral mortality reaching 70% in some regions.The worst of these events occurred when the effects of an El Niño - a periodic natural weather cycle originating in the Pacific Ocean that causes water temperatures to rise and extreme weather (hurricanes, droughts, and floods) around the world - were superimposed on sea temperature rises due to global warming.
A recent WWF report warns that the frequency and severity of coral bleaching caused by global warming will increase worldwide in the coming decades. The report predicts that less than 5% of the coral on Australia’s Great Barrier Reef will remain by 2050 if we fail to curb climate change. The loss of the coral would destroy the entire reef ecosystem.
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