A healthy section of the Great Barrier Reef

Gary Bell/Oceanwide/Minden Pictures (healthy reef); Shutterstock.com (fish)

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In Hot Water

Record-setting ocean temperatures are putting the Great Barrier Reef at risk.

December 2, 2024
By Talia Cowen

As You Read, Think About: How can endangered coral reefs affect other species?

Jim McMahon/Mapman®

Ben Henley was 7 years old when he saw a coral reef for the first time. His father had taken him scuba diving in the Coral Sea, off the east coast of Australia. They explored one of Earth’s most spectacular natural wonders: the Great Barrier Reef. 

“It’s such a huge and beautiful place,” says Henley. He is a scientist at the University of Melbourne in Australia.

The Great Barrier Reef stretches more than 1,400 miles along the ocean floor. It’s the largest system of coral reefs in the world. And it’s in danger of disappearing. 

According to a study released in August, temperatures in the Coral Sea are higher than they have been in 400 years. This is putting the Great Barrier Reef at risk. It’s not the only reef that’s in trouble. 

“All coral reefs around the world are in trouble from climate change,” says Henley, an author of the study.

Reefs at Risk

Coral reefs can be found in every ocean in the world. They cover only about 1 percent of the ocean floor. But these ecosystems are home to one-quarter of all underwater species. More than 9,000 unique species live in the Great Barrier Reef alone, from turtles and sharks to seahorses and eels.

Although corals look like plants, they’re tiny animals that live in huge colonies. They have hard outer skeletons that form reefs. Healthy corals come in every color of the rainbow. 

They get their bright colors from small plantlike organisms called algae. Algae also produce food for corals. 

When oceans get too warm, corals release algae and turn white. This process, called coral bleaching, can kill corals. More than 70 percent of the Great Barrier Reef has been affected by bleaching, according to a study done in April. Some corals can recover as waters cool in the winter, but not all do.

“If corals die, the reef structures they build can crumble away,” Henley says. “In the future, there will probably be fewer places for fish and other animals to live.”

Brett Monroe Garner/Getty Images

Bleached corals in the Great Barrier Reef

Saving Corals

Bleaching isn’t affecting corals only in the Great Barrier Reef. About 77 percent of the world’s reefs have experienced some bleaching over the past year and a half.

“Large-scale coral bleaching events are now far more common and more severe than even a decade ago,” Henley says.

Henley says human activity is largely responsible for warming oceans. For example, we burn fossil fuels to create electricity and power our cars. That releases extra greenhouse gases, which are gases that trap heat in Earth’s atmosphere. This is contributing to Earth’s rising temperatures.

Scientists are working hard to protect reefs. For instance, they are developing corals that can live in high temperatures. 

Henley wants the Great Barrier Reef to be around for future generations.

“Everything we can do to slow climate change will help the coral reefs of the world,” he says. “And that is a very good thing.”

1. Why is “In Hot Water” a good title for the article?

2. Based on the article, what is a main cause of the warming of oceans?

3. How does warmer ocean water affect corals?

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