Australia Declares ‘Mass Bleaching’ At Great Barrier Reef (Gbr).

Why in news?

• It is reported that GBR, which is the world’s largest coral reef system is suffering a “mass bleaching event, the fourth since 2016.
• GBR has suffered three mass bleaching events during heatwaves in 2016, 2017 and 2020.
• GBR stretches for more than 2,300 kilometres along the northeast coast of Australia.
• It was declared a World Heritage Area in 1981 because of its ‘outstanding universal value.
• This reef structure is composed of and built by billions of tiny organisms, known as coral polyps.
• 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.
• This is despite the cooling effect of the La Nina weather phenomenon which is currently influencing Australia’s climate.

About Corals

• Coral reefs are large colonies of invertebrate, tiny soft-bodied animal called Coral polyps, that live in symbiotic relationship (mutually beneficial) with small algae like organism called zooxanthellae.
• Coral polyps provide protection to zooxanthellae in return of nutrient. Zooxanthellae also provide them the colourful hues.
• India has 4 coral reef areas: Gulf of Mannar, Andaman and Nicobar Islands, Lakshadweep islands and Gulf of Kutch.
• Coral reefs are some of the most bio diverse and productive ecosystems.
• They act as natural barriers to shorelines, protecting them from damage and flooding from storms, hurricanes, and cyclones.