Why Do Corals Bleach?

Duration: 3 minutes
Grade Level: Appropriate for all ages; content connects to NGSS standards for grades 5 and above

Shallow reefs are particularly sensitive to increasing temperatures. Warming water can cause coral bleaching, when an entire colony of coral polyps loses its color. In this clip, you'll visit the interior of an individual polyp to see how this happens.

Bleached corals are sick, but not dead. Bleached reefs can recover, which is why it's imperative we slow the pace of rising ocean temperatures.

With the help of new technology, scientists are gaining unprecedented insights into a process that is changing both the face and function of our planet’s coral reefs: coral bleaching.  Coral bleaching is when corals expel their colorful—and life-sustaining—algae as a result of stress. In this immersive article from bioGraphic, you can dive into a coral polyp to see both how and why this happens.

How does water temperature affect the health of coral reefs?

In this lesson for grades 9-12, students will examine real water temperature data for San Juan, Puerto Rico to identify patterns and make predictions about the effects of prolonged increased water temperatures on coral reefs.

While this video doesn't necessarily cover the following standards in depth, it is a compelling resource you can use to supplement your curriculum that does.

Disciplinary Core Ideas

• MS-LS2-3 Considering the relationship between coral cells and zooxanthellae, how can you explain the pattern of interaction among these organisms?
• HS-ESS2-2 How do Earth’s surface processes and human activities affect each other? How does one change to Earth’s surface create feedback that causes changes to other Earth systems?

Crosscutting Concepts

• Stability and Change