Coral Reefs and Coral Bleaching

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What are Coral reefs?

  • It is underwater marine ecosystem characterized by reef-building corals.
  • Reefs are formed of colonies of coral polyps held together by calcium carbonate.
  • Corals secrete hard carbonate exoskeletons that support and protect them.
  • Most coral reefs are built from stony corals, whose polyps cluster in groups.
  • Coral belongs to class Anthozoa in animal phylum Cnidaria, which includes sea anemones and jellyfish.
  • Corals are often called “rainforests of the sea” as they form some of Earth’s most diverse ecosystems.
  • They occupy less than 0.1% of world’s ocean area, but provide a home for at least 25% of all marine species.
  • Tiny differences in the anatomy of each polyp species mainly affect the shape of their shells and produce the exotic shapes of each reef.

Conditions required for growth of corals:

  • Warm tropical oceans with minimum temperature of 20 degree.
  • They are primarily located between 30 degree north and 25 degree south latitudes where water temperature favours the growth of coral organisms;
  • Transparent parts of ocean bodies;
  • Oceanic water must be free of sedimentation;
  • It should have relatively low salinity.
  • They are most commonly found at shallow depths in tropical waters, but deep water and cold water coral reefs exist on smaller scales in other areas. 

What is coral bleaching?

  • Coral bleaching causes corals to expel tiny photosynthetic algae, draining them of their colour.
  • It calcifies the corals to  turn into white.
  • Algae are vital to the coral, which uses the organic products of photosynthesis to help it grow.
  • The loss of algae makes it vulnerable to disease and it will eventually die.
  • When a coral bleaches, it is not dead. They can recover if the water temperature drops and the algae are able to re-colonise them.

How bleaching occurs?

  • Bleaching occurs when abnormal environmental conditions, such as warmer sea temperatures, cause corals to expel tiny photosynthetic algae, draining them of their colour.
  • Algae are vital to the coral, which uses the organic products of photosynthesis to help it grow. The loss of algae makes the host vulnerable to disease and means it will eventually die.

Can coral recover?

Yes. Coral can recover if the water temperature drops and the algae are able to recolonise them.

 
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