Coral reefs

Coral reefs are among the most diverse and productive communities on earth and are referred as ‘tropical rain forests of oceans’. They are found in the warm, clear, shallow waters of tropical oceans worldwide.

Coral polyp lives in symbiotic relationship with unicellular algae zooxantheallae. Algae assist the coral in nutrient production through its photosynthesis activity; in return coral polyp provides a protected environment to live.


Functions performed:

• Provide food and shelter to fish and invertebrates
• Protect shore from erosion e.g. Great Barrier Reef protects Australia’s eastern coast
• Important source for natural product based drugs and medicines
• Forms various islands in tropical areas e.g. Maldives, Lachdives in Indian Ocean
• Tourism attraction due to beauty of coral reefs


Coral Bleaching: 

  • Because many coral reef organisms can tolerate only a narrow range of environment conditions, reefs are sensitive to damage from env. changes. Coral reef bleaching results from the loss of symbiotic zooxantheallae. Coral reef bleaching is caused by various anthropogenic (overexploitation, overfishing, increased sedimentation, nutrient overload) and natural variations in reef environment like violent storms, high and low temperature extremes, flooding, El-Nino, sub aerial exposure, solar irradiance, inorganic nutrients.
  • Coral reef bleaching events have been increasing in both frequency and extents worldwide in the last 20 years. Nearly all the world’s major coral reef regions – Caribbean Sea, eastern and western Pacific, Indian Ocean, Arabian Gulf, and Red Sea experienced some degree of coral bleaching and mortality since 1980s.
  • It has been hypothesized that bleaching is an adaptive mechanism which allows corals to be repopulated with a different type of zooxantheallae, possibly having greater stress resistance.


Coral Triangle:

  • Coral triangle geographical, refers to a roughly triangular area of the tropical marine waters of Indonesia, Malaysia, Papua New Guinea, Philippines, Solomon Islands and Timor-Leste that contain at least 500 species of reef-building corals. The Coral Triangle is recognized as the global centre of marine biodiversity and a global priority for conservation.

In extreme cases, bleaching can lead to a reduction in species and a reduction in species diversity and loss of relief framework.


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