'Deathly silent': world heritage reef decimated by heatwave

Almost two out of three corals across popular tourism spots at the world heritage-listed Ningaloo reef died after an unprecedented marine heatwave hit the Western Australia region, scientists have said.

- Graham Readfearn

The areas in Ningaloo's northern lagoon had undergone a “profound ecological simplification” with coral species that were keystones to the habitat among those killed.

The marine heatwave swept across the Western Australian coastline last summer and autumn, turning corals white from heat stress.

When corals sit in unusually warm water for too long they separate from the algae that give them much of their colour and nutrients, leaving behind a translucent flesh revealing the white skeleton.

About 90% of the extra heat on the planet has been taken up by the ocean.

Zoe Richards, a coral scientist and associate professor at Curtin University, had in March surveyed 1,600 corals at sites spanning 40km when the bleaching event was peaking.

“The bleaching was so confronting because it was so expansive,” she said.