An “unprecedented” mass bleaching event has been recorded off Australia’s western coast, scientists said on March 26, 2025, turning huge chunks of a celebrated reef system a sickly dull white.
Key Points
- As per scientists, a months-long marine heatwave had cooked” the sprawling Ningaloo Reef, part of a world heritage-listed marine park renowned for vibrant corals and migrating whale sharks.
- Branching through shallow waters along Australia’s western coast, the 300-km Ningaloo Reef is one of the largest “fringing reefs” in the world.
What is Bleaching?
- Bleaching occurs when corals lose the algae that give them their colour and most of their nutrients if ocean waters get too warm.
- Bleaching is a sickness, but it does not mean outright death. If bleaching is not severe, corals can recover, but studies show they are less able to reproduce and are more susceptible to disease.
Degree heating weeks (DHW)
- Coral reef experts use a metric known as degree heating weeks (DHW) to show how much heat corals have accumulated. Generally, corals begin to bleach at about 4DHW, and 8DHW can kill heat-sensitive corals.
(Sources: TH & The Guardian )
