Coral and Coral reef

  • The International Union for Conservation of Nature (IUCN) has released the report at UN climate talks in Bonn, Germany.
  • According to the report, the number of UNESCO natural sites at risk has grown to 62 from 35 in 2014.
  • Among the ecosystems most threatened by global warming are coral reefs which bleach as oceans heat up and glaciers which melt.
  • The three World Heritage-listed coral reefs that have been affected by “devastating” bleaching events over the last three years are:
  1. The Aldabra Atoll in the Indian Ocean
  2. The Belize Barrier Reef in the Atlantic
  3. Australia’s Great Barrier Reef


Coral and Coral reef

  • Corals are animals related to jellyfish and anemones. They ingest tiny organism called plankton.
  • An individual coral is known as a polyp
  • Thousands of identical polyps live together and colony.
  • Each polyp excretes a calcium carbonate exoskeleton beneath it and over long periods of time, the skeletons of many coral colonies add up to build the structure of a coral reef.
  • Many other species – fish, invertebrates, algae and microorganisms – make their homes on and around this reef.
  • Reefs only occur in shallow areas that are reachable by sunlight because of the Symbiotic relationship between coral and algae.
  • Coral reefs are found all around the world in tropical and subtropical oceans.
  • They are found in shallow areas at a depth of less than 150 feets, sometimes they can go to a depth of 450 feets deep.




There are many problems which corals are facing today. Some of them are:

1. Warm water 

  • Rising seawater temperature as a result of climate change is one of the most serious causes of stress to corals throughout the world.
  • When temperature is too high, the relationship between corals and their symbiotic microalgae breaks down.
  • The algae are what give corals some of their bright colours (red,orange,yellow etc) so when this happens, corals appear white or bleached.
  • Just one degree above the typical summer temperature is enough to bleach many corals.
  • High temperature allows corals to become sick more easily, a sick coral’s appearance, like black band, white band, white spots.


2. Ocean Acidification

  • Carbon dioxide (CO2) also has adverse effects on the oceans.
  • Recently, ocean acidification has emerged as another potential serious threat to coral reefs. Seawater absorbs some of the excess CO2 from the atmosphere, causing the oceans to become more acidic.
  • These acidic conditions dissolve coral skeletons, which make up the structure of the reef and make it more difficult for corals to grow.


3. Other threats

Coral reefs are also being degraded by many other factors. The list of problems can seem endless:

  • Overfishing
  • Fishing using cyanide and dynamite
  • Pollution from sewage and agriculture
  • Massive outbreaks of predatory starfish and invasive species
  • Sedimentation from poor land use practices.


4. Global Warming

  • Global warming is rising of earth’s temperature. It occurs when Carbon Dioxide (CO2) and other air pollutants and greenhouse gases collected in the atmosphere and absorb sunlight and solar radiation that have bounced back by the earth’s surface.
  • Normally, these radiation would escape into space—but these pollutants,trap the heat and cause the planet to get hotter. That’s what’s known as the greenhouse effect.
  • The earth’s rising temperature is fuelling longer and hotter heat waves, more frequent droughts, heavier rainfall, and more powerful hurricanes.


Efforts to protect

  • Corals face many risks. Fertilizers, pesticides and oil pollution harm the corals and lower their resilience to high temperatures.
  • There is a need to join forces within various countries to protect the corals (by lower their contribution of green house gases in the atmosphere) since the reefs have no borders.
Section : Environment & Ecology