5th Mass bleaching event hits Great Barrier Reef (GBR) in 8 years

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Before this event, GBR has suffered mass coral bleaching in 1998, 2002, 2016, 2017, 2020, and 2022.
Bleaching occurs when healthy corals become stressed by spikes in ocean temperatures, causing them to expel algae living in their tissues, which drains them of their vibrant colours.

Causes of Mass Bleaching events
- Climate change induced warming. Example, Current underwater heatwave is most intense in southern GBR, which is most affected by bleaching.
- Rising frequency of El Nino increases frequency and severity of mass-bleaching events.
- Lack of wind and currents may result in less mixing of water layers, clearer seas, and deeper penetration of solar irradiance, which can intensify bleaching.
- Other causes: Extremely low tides, Pollution, Overexposure to sunlight, etc.

GBR stretches for more than 2,300 kilometres along the northeast coast of Australia.
- It is the world's largest coral reef complex, located in Pacific Ocean.
- It was declared a World Heritage Area in 1981.
- This reef structure is composed of and built by billions of tiny organisms, known as coral polyps.

They are made up of colonies of thousands of tiny individual corals, called polyps. These marine invertebrate animals have hard exoskeletons made of calcium carbonate.
In India, Coral reefs are present in Gulf of Kutch, Gulf of Mannar, Andaman & Nicobar, Lakshadweep Islands and Malvan (in Maharashtra).