Natural colour of corals is white but we see colourful and bright corals.

The algae that live within the coral’s tissues give them vibrant colours and make them look bright.

Coral bleaching is the term used for the fading of colour of the corals due to the discharge of algae from their tissues. This happens when the rate of photosynthesis carried by algae is decreased. Corals are sensitive to the change in their environment.


The discharge of algae may occur due to

  • Rise in temperature of water body
  • Water pollution
  • Sedimentation of water bodies
  • Eutrophication
  • Threat from invasive species
  • Disturbance in habitat


The prolonged algae loss may result in dead coral host, which affects the marine system as they constitute a major in marine food chain. Coral reefs also provide safe refuge to many marine animals.

Coral bleaching can be seen among corals in Indian Waters, Great Barrier Reef, Queensland.