The Effect of Increasing Water Temperature on Zooxanthellae and Coral Bleaching

This infographic describes the effect of increasing water temperature on the microscopic algae called zooxanthellae that live in coral tissue.

This infographic was made in collaboration with the University of Maryland Center for Environmental Science Integration and Application Network.

Visit the National Coral Reef Monitoring Program's page for all U.S. coral reef status reports.

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Infographic Transcript: The Effect of Increasing Water Temperature on Zooxanthellae and Coral Bleaching

Healthy corals have a symbiotic relationship with microscopic algae called zooxanthellae that live in their tissue. These algae produce the coral's primary food source and give them their color. When ocean water is too warm, corals expel their algae, rendering the coral tissue translucent and making the animal's white skeleton clearly visible. These events are called coral bleaching because its now stark white appearance makes it look as the coral has been “bleached” of color (in addition to having lost its main food source). Corals can survive a bleaching event and recruit new algae, but repeated events cause stress and decrease colony healthy, leading to coral death.