Two Views of Coral Reefs: Thriving and Threatened

Coral reefs are beautiful, vibrant ecosystems that house roughly one quarter of all marine species and provide billions of dollars in products and services to humans each year. But they are also vulnerable to human activities – both direct disturbances and small, indirect effects that build up over time. Read about why it's important for coral to be resistant and resilient, in a blog post by Smithsonian marine scientist Dr. Nancy Knowlton.

A bluefin trevally swims in Hawaii’s Maro Coral Reef, part of the Papahānaumokuākea Marine National Monument.
Compare the healthy coral on the left with the bleached coral on the right.Close-up photograph of translucent coral polyps, showing the symbiotic algae living inside.Photo of coral polyp, with a single bleach polyp.Rockfish, anemones and other invertebrates inhabit this deep-sea coral reef in Cordell Bank National Marine Sanctuary. These corals are dead—smothered in sediments and overgrown with algae.A red snapper hunts for prey on Kingman’s Reef, a healthy reef in the Line Islands.Algae has overtaken this coral reef off heavily populated Kiritimati, or Christmas Island.A variety of organisms make their home on this tropical coral reef in Indonesia.These bleached corals in the Gulf of Mexico are the result of increased water temperatures.A diver cares for the reef by cleaning up discarded fishing gear and garbage.