'Extremely unusual': Hottest ocean temperature in 400 years threatens the Great Barrier Reef

The Great Barrier Reef is now facing the hottest sea surface temperatures in four centuries, a new study finds. The rapid warming is causing massive coral bleaching which threatens the marine ecosystem and biodiversity, the scientists warned. 

"The world is losing one of its icons," study lead author Benjamin Henley, a paleoclimatologist at the University of Melbourne, Australia, said at a news conference Tuesday (Aug. 6). "We will sadly see the demise of one of Earth's most spectacular natural wonders."  

The Great Barrier Reef, off the coast of Queensland, is home to the world's largest collection of coral reefs, stretching for more than 1,400 miles (2,253 kilometers), and covering an area greater than 134,000 square miles (348,000 square kilometers). 

In a new study published Wednesday (Aug. 7) in the journal Nature, scientists revealed that the sea surface temperature in the first three months of 2024 is the warmest ever recorded in 400 years, reaching 0.34 degrees Fahrenheit (0.19 degrees Celsius) above the previous record high. 

This unprecedented high temperature is the key driver of coral bleaching, the scientists said. 

Related: Great Barrier Reef Again Hit by Severe Coral Bleaching

Coral bleaching occurs when environmental stress, such as heat and pollution, causes a coral to expel the colorful algae — its primary food source — that live inside it. When the algae leave, the coral loses its vibrant colors and turns white. Bleached corals are more susceptible to disease and death.