How is global warming responsible for the death of corals?
Submitted by: Ng Jing Yi
Global warming has increased the temperature of our tropical oceans by about a degree over the last hundred years. This has increased the chance that corals will undergo something called coral bleaching, which is where the plant-like symbionts inside corals (also called zooxanthellae) leave their tissues. The symbionts are important to corals because they give them energy (trapped from our Sun) which they use to grow and maintain themselves. When they bleached, and loose the symbionts, they are more susceptible to disease and death.
Since 1979, there have been six episodes of mass coral bleaching across the planet. There are none reported before 1979. They have all been driven by small stressful temperatures, often only 1-2oC above the long-term summer maxima. In some episodes, such as that that happened in 1998, over 16% of the world’s corals have died. Given that corals build the habitat in which over one million species live, this is a very worrying impact of global warming on the planet’s tropical oceans.
Answer by: Prof.Ove Hoegh-Guldberg, Director, Centre for Marine Studies, University of Queensland, Australia. Deputy Director, ARC Centre for Excellence in Coral Reef Studies; BLOG: www.climateshifts.org