Note4Students

From UPSC perspective, the following things are important :

Prelims level: Coral bleaching

Mains level: Coral reefs and their significance

A survey has found record sea temperatures had caused the third mass bleaching of the 2,300-kilometre Great Barrier Reef system in just five years.

When corals face stress by changes in conditions such as temperature, light, or nutrients, they expel the symbiotic algae zooxanthellae living in their tissues, causing them to turn completely white.
This phenomenon is called coral bleaching.
The pale white colour is of the translucent tissues of calcium carbonate which are visible due to the loss of pigment-producing zooxanthellae.

The Great Barrier Reef is the world’s largest coral reef system composed of over 2,900 individual reefs and 900 islands.
It is stretched for over 2,300 kilometres over an area of approximately 344,400 square kilometres.
The reef is located in the Coral Sea, off the coast of Queensland, Australia.

Coral reefs are some of the most diverse and valuable ecosystems on Earth.

They support more species per unit area than any other marine environment, including about 4,000 species of fish, 800 species of hard corals and hundreds of other species.
This biodiversity is considered key to finding new medicines for the 21st century. Many drugs are now being developed from coral reef animals and plants as possible cures for cancer, arthritis, human bacterial infections, viruses, and other diseases.
Healthy coral reefs support commercial and subsistence fisheries as well as jobs and businesses through tourism and recreation.
Local economies receive billions of dollars from visitors to reefs through diving tours, recreational fishing trips, hotels, restaurants, and other businesses based near reef ecosystems.
Coral reef structures also buffer shorelines against 97 percent of the energy from waves, storms, and floods, helping to prevent loss of life, property damage, and erosion.
When reefs are damaged or destroyed, the absence of this natural barrier can increase the damage to coastal communities from normal wave action and violent storms.

Coral reefs are built by and made up of thousands of tiny animals—coral “polyps”—that are related to anemones and jellyfish.
Polyps are shallow water organisms which have a soft body covered by a calcareous skeleton. The polyps extract calcium salts from sea water to form these hard skeletons.
The polyps live in colonies fastened to the rocky sea floor.
The tubular skeletons grow upwards and outwards as a cemented calcareous rocky mass, collectively called corals.
When the coral polyps die, they shed their skeleton on which new polyps grow.
The cycle is repeated for over millions of years leading to accumulation of layers of corals shallow rock created by these depositions is called reef.

Third mass bleaching of Great Barrier Reef

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