Coral Reef Bleaching

Coral reefs are large structures, found in deep seawater which is made up of skeletons of the marine specie called coral (a class of marine invertebrates). Generally, hard corals (hermatypic) forms reefs by extracting calcium carbonate from the sea to create a rigid, long-lasting exoskeleton for the protection of their soft sac-like body. These invertebrates are always in a symbiotic relationship between photosynthetic algae. The coral reefs are often referred as rainforests of the sea due of its diversity. The great barrier reef, one among the seven wonders of the world, is a remarkable site in the northeast coast of Australia, which contains the world’s largest coral reef collection. The great barrier reef is considerably larger than the Great Wall of China and is the only living thing in the world which is visible from space. It is also popular for the presence of endangered species like the large green turtle and sea cow (dugong). Great barrier reef is found in the Southwestern Pacific Ocean.
Recently, climate change in the regions of the northeast coast of Australia is becoming dangerously high to the corals. The intensity of the heat makes the corals eject the colourful, vibrant microscopic zooxanthellae algae from their surface leaving their symbiotic relationship. The ejection of algae causes coral bleaching, where the colourful coral turns into stark white colour structures. If the temperature lasts for a long period, the algae won’t able to get back to the corals and eventually the coral will die. The coral reefs play an important role in supporting the survival of most marine diversities including species like fish, crabs, shrimps, starfish, turtles etc. These reefs serve as the ground for spawning, act as a shield from predators and become shelters for many species. In addition to these, it also helps the organisms at the base of the food chain. Coral bleaching not only affects the marine ecosystem, but it also causes impacts on the livelihood, safety and food security of the people.

One of the main reasons for the coral bleaching in the Great barrier reef is the unpredictable climatic change caused by greenhouse gases. The bleaching undergone by these coral reefs were more rapid and severe than predicted by the marine scientists .The threats to reefs can be reduced by controlling the global temperature and greenhouse gases. The rapid climatic changes increase the temperature and acid level of the seawater which in turns reduces the capacity of corals to form the skeletons which are a key habitat for the marine life of the reefs. Besides the high temperature, the low pH due to the acidification of the ocean make the corals more vulnerable to destruction factors. The oceans are polluted by the excess production of carbon dioxide from anthropogenic activities and the 30 %of the atmospheric carbon dioxide is absorbed by the ocean. When the seawater absorbs this CO 2 , acidification occurs which reduce the pH level.

Pollution and poor water quality are yet another threat to the Great barrier reefs. The sea water easily gets contaminated by the rivers containing wastes of pesticides, fertilizers, etc from agricultural sites. The crown thorn starfish, which preys on coral species is also considered as a form a threat, besides overfishing of large fishes (which feeds on these star fishes) can also cause an increase in the number of starfishes.

The coral bleaching can be prevented by the following ways :

  • The area covering a large area from the reef must reduce the use of fertilizers andpesticides. Because the nutrients from the fertilizers and can cause significant harm to the corals.
  • Dumping trashes to the seawater should be stopped.
  • Recycling of trashes can reduce coral destruction.
  • Reduction in the release of greenhouse gases to the atmosphere can become a major reason for sustaining coral reef ecosystems.Lowering of temperature through reduced deforestation and global warming can prevent corals from bleaching.


The Great barrier Reef is a remarkable site that contains the world’s largest coral reef collection, and one of the major tourist spots in Australia. If the reefs are not maintained properly, there will be a decrease in the number of species that depends on these reefs for survival. In addition to the reduction in species diversity, the economic growth of the country can get fluctuated, since the great barriers have that much importance in the perspectives of tourism. So the protection of Great barrier reefs from all kinds of destruction is an inevitable factor in all means.


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