Thousands of tourists visit Hawaii each year to experience its spectacular marine life. Waters off the islands contain coral reefs bursting with bright colors and exotic fish. But these reefs—and others like it around the globe—are in danger. The U.S. National Oceanic and Atmospheric Administration says that right now reefs worldwide are experiencing the longest coral bleaching event on record, which started in 2014. Coral bleaching is when reefs lose their color and become vulnerable to disease.
Hawaii’s reefs aren’t the only ones being affected. A recent survey found that 93 percent of the Great Barrier Reef off the coast of Australia is suffering from devastating bleaching. The Great Barrier Reef, which stretches some 2,000 kilometers (1,200 miles) long, is Earth’s largest coral reef ecosystem—a community of organisms interacting with their physical environment.
Coral reefs are made up of colonies of small marine animals that build hard skeletons around themselves. Tiny plantlike creatures, called algae, live inside corals’ tissues. Corals provide the algae with a safe place to live, while the algae make food the corals can eat. This is an example of mutualism—a close relationship between two different organisms where each benefits.
Bleaching occurs when waters surrounding reefs become too warm. This causes corals to expel the algae living inside them and turn white. Scientists blame the recent worldwide coral bleaching event on climate change —a change in global climate patterns—as well as a particularly strong El Niño, a warm climate pattern that affects the Pacific Ocean every few years.
The longer bleaching goes on, the more likely corals are to die from its effects. Reefs can survive bleaching, but they need help. It’s important to keep pollution, which can further damage corals, from entering the ocean while reefs recover. That includes things like fertilizers added to lawns and soap used to wash cars.
Countries are also taking steps to protect the many animals that call reefs home. In Hawaii, for example, “There are now strict fishing regulations, and it is illegal to harm endangered species, such as the Hawaiian green sea turtle, Hawaiian humpback whales, and Hawaiian monk seals,” says Roxie Sylva, the Maui Marine Program Coordinator for The Nature Conservancy, a nonprofit organization.