The Great Barrier Coral Reef Bleaching

By Ian Teñido

Coral bleaching in March at Lizard Island on the Great Barrier Reef– Google Image

As the climate change dynamics take shape and toll on different physical environments, the ocean is not left behind particularly the coral reefs. Coral Reef Bleaching is predicted to be on the increase and its frequency will become severe if bleaching agents are not controlled. Science shows that sea temperature increases will intensify the stress on the coral reefs; an aspect that increases vulnerability to bleaching. Almost all types of coral reefs have a symbiotic co-existence with tiny algae normally called zooxanthellae. These algae live, actively, in the coral’s tissue and are very efficient and effective in food production. Basically they provide over 90% of energy that corals require in order to grow and reproduce.

Coral bleaching occurs when the relationship between these active algae and the corals are jeopardized. The zooxanthellae give the corals much of their color and thus, without its active presence and residence within the corals, their tissues appear transparent and the white bright skeleton of the corals are revealed. This is what is referred to as coral bleaching and once bleaching sets in, the corals begin to starve. Although some of the corals can be able to feed themselves, most of the colony members struggle to survive without their zooxanthellae.

Normally, if the conditions return to normal when the bleaching agents are rectified, most corals would retain their zooxanthellae and thus will get back to their normal color and survive. However, after going through the stress, the corals are likely to experience reduced reproduction and growth and they will be highly susceptible to diseases. Persisting stress kills the corals; it should be known that the coral reefs with high rates of coral deaths following bleaching can take many years to recover and actually, this is the tragedy that has befallen most coral reefs around the globe. Even of more concern today is the fact that some of the bleaching agents such as climate change seem to be uncontrollable in the short-term and this may lead to erosion of tons of thousands of coral reefs in the world’s waters.

Google Image

Under the radar here is the Great Barrier Coral Bleaching. In April 2016, the Australian Scientists revealed that the full extent of coral bleaching that is unfolding on the Great Barrier Reef was catastrophic and urgent strategies to preserve and sustain its existence must be laid. The results of the extensive aerial and underwater surveys showed that over 93% of the reefs are affected (Cressey, 2016). Along stretch of 2300 KM length, the images show moderate, little damage to severe destructions on the reef.

The main cause of the coral bleaching is the heat stress that result from the high sea temperatures. Scientists have proven that a one degree Celsius temperature increase within four weeks can trigger bleaching events on the coral reefs and if such temperatures persist any longer, then the coral reefs begin to die. This therefore, implies that high water temperatures as a result of the increased global warming can cause a devastating global coral reef bleaching, an aspect that will severely affect the marine life and all its dependents including humans.

To this end, it should be noted that the Great Barrier Reef has experienced mass coral reef bleaching events in the past. In 1998, there was a massive bleaching on the Great Barrier Reef where more than 50% of the reefs suffered bleaching. During this time of bleaching, it was also at a time when the temperatures over the reef were the highest recorded in its history. Another mass bleaching occurred in 2002 with over 60% of the reefs affected at that time and this went down in history as the largest ever single bleaching to have happened. In both events of 1998 and 2002, about 5% of the coral reefs on the Great Barrier Reefs were severely damaged (Normile, 2016).



Cressey, D. (2016). Coral Crisis: Great Barrier Reef Bleaching is “the worst we’ve ever seen.” Retrieved from on October 1st, 2016.

Normile, D. (2016). Survey Confirms Worst-ever Coral Bleaching at Great Barrier Reef. Retrieved from on October 1st, 2016.

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