CORAL BLEACHING (Syllabus: GS Paper 3 – Env and Eco)

Context: Recently, along coastlines stretching from Australia to Kenya to Mexico, numerous colorful coral reefs worldwide have recently turned ghostly white, marking what scientists describe as the fourth global bleaching event in the past three decades.

oIt has triggered the fourth global mass coral bleaching event, according to the US National Oceanic and Atmospheric Administration (NOAA).

Coral Bleaching

• About: When corals are stressed by changes in conditions such as temperature, light, or nutrients, they expel the symbiotic algae microscopic algae called zooxanthellae living in their tissues, causing them to turn completely white.
• Causes: 
• Temperature Sensitivity: A mere one-degree Celsius increase in temperature over a four-week period can trigger coral bleaching events.
• Transparency and Skeleton Exposure: Bleached corals become transparent, exposing their white skeletons as a result of expelling algae.
• Additional Stress Factors: Apart from temperature, changes in water quality, increased sun exposure, and extreme low tides can also induce coral bleaching.

Mass Coral Bleaching

• First Mass Bleaching: The 1998 event occurred due to the El Niño weather pattern, heating up sea surfaces in the Pacific Ocean.

oResulted in the death of 8% of the world’s coral.

• Second Mass Bleaching: Occurred in 2002, showing a trend of increasing frequency.

oSignaled a shift towards more closely spaced bleaching events.

• Third Mass Bleaching: Affected reefs across regions including Guam, the Western Pacific, North and South Pacific, and the Indian Ocean.

oThe global temperature in 2017 reached the third-highest recorded level.