What is coral bleaching?
Coral bleaching is a serious problem facing corals all over the world. It is a general stress response of corals, and is the result of several different factors, especially increasing sea temperature. This causes the zooxanthellae, or symbiotic algae that live with the coral, to be expelled. The coral becomes white or “bleached”, and is unable to obtain the nutrients it needs, as it relies on its photosynthetic zooxanthellae.
Increasing sea temperatures are the cause of mass bleaching, but the following threats are responsible for small-scale bleaching:
- Decline in zooplankton, causing starvation.
- Ocean acidification.
- Bacterial infections.
- Changes in ocean salinity.
The most severely affected coral reefs include the Great Barrier Reef, reefs in the Indian Ocean, around the Maldives, Seychelles, and Hawaii. Up to 90% of corals have been lost from these locations.
A huge range of sea life depends on coral reefs for survival, so the disappearance of the corals would have a dire effect on the oceans. In turn, this would impact on many people who rely on the sea for their food and livelihoods.
Photo: John Pascal.