May 12, 2022
Warming sea temperatures threaten to wipe out huge amounts of Australia’s famed Great Barrier Reef, scientists say. The evidence? Bright colors have disappeared from much of the world’s largest coral reef system.
In fact, experts say, about 90% of the 133,000-square-mile Great Barrier Reef has suffered “bleaching.” That happens when sea temperatures rise. The higher temperatures cause corals to expel algae that the reefs need to live. The reefs then turn white. Bleaching results mostly from climate change. And that’s driven by the release of greenhouse gases.
This is the sixth “mass bleaching” event on the reef system since 1998, according to Australia’s Climate Council. Three have occurred since 2016, the council said. It called for action to slow climate change.
“The science is very clear: In order to save the world’s reefs from total destruction, we must dramatically reduce emissions in the 2020s,” the council’s research director said.
According to the National Oceanic and Atmospheric Association, at least 75% of the world’s tropical coral reefs have suffered bleaching. In 30% of them, the heat killed the coral.
Coral reefs play a critical role in our ecosystem. They provide habitat and spawning areas for marine life. The reefs also protect thousands of species from predators.
Fishers and those who work in tourism also rely on the reefs. That's how they make their living. In addition, reefs provide natural barriers. They protect coastal areas by absorbing the force of waves and storm surges.
Photo from UNESCO World Heritage Convention.
Interactive Exploration of Coral Bleaching
In this interactive video, students will learn about the symbiotic relationship between corals and zooxanthellae and how changes in ocean temperatures can cause corals to expel zooxanthellae resulting in coral bleaching.
The Magic of Coral Elementary Lesson Plan
This lesson plan and supporting materials cover the importance and benefits of coral, coral bleaching, coral ecosystems, and how human activity impacts coral.
This page on ocean warming presents interactive graphs of ocean heat content over time.