Coral bleaching can be defined as “When corals are stressed by changes in conditions such as temperature, light, or nutrients, they expel the symbiotic algae living in their tissues, causing them to turn completely white.” It can occur in oceans all over the world, usually caused by warming water temperatures by 1-2°C. When the ocean water heats up, the corals will eject a type of algae, which resides in their tissues, known as zooxanthellae.
This causes the coral to become white, which is the why the term ‘bleaching’ is used. Coral bleaching doesn’t always permanently destroy the corals but they become subjected to increased stress, and increase their vulnerability to mortality. This can cause the corals to starve following bleaching and only a few can feed themselves. Fortunately there is the small chance that conditions can turn to normal and corals can recuperate the algae to gain their colour and health.
Despite the small percentage of corals amongst the Earth’s undersea ecosystems, they are of great importance, both environmentally and economically. There is even evidence that corals may be of specific significance relative to medical research! However, corals are a main source of protection, sheltering 25% of marine species and protecting shorelines. Furthermore they influence the human economic commerce by supporting fishing industries and being used as major tourist destinations such as in Australia’s Great Barrier Reef.
Coral Bleaching has been extremely prominent in the Great Barrier Reef where in 1998, a global mass-bleaching event caused 50% of the reefs to suffer from bleaching and this was reported as a result of extreme climate change. Following this event in 2002 was an even larger coral bleaching event to where 60% of the reefs were damaged. These two events together caused around 10% of the coral reefs to face severe damage.
By Chantelle Levy
CORAL BLEACHING
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