Coral reef ecosystem at Palmyra Atoll National Wildlife Refuge. Photo credit: Jim Maragos/U.S. Fish and Wildlife Service

Did you know that coral reefs cover less than 1 percent of the seafloor but provide food, shelter and safe breeding areas for 25% of marine species? More than 4,000 species of fish and thousands of other plants and animals call reefs their home.

Meet the Architects of the Coral Reefs

Hard polyps, or individual corals, use calcium carbonate to create a hard shell (exoskeleton) around their soft bodies (which don’t have a backbone). When individual polyps die, they leave their exoskeleton while new polyps add their own exoskeleton thus growing the reef.

Tiny algae called zooxanthellae add color to the corals by forming a partnership with the clear polyps and their white exoskeletons. Algae get shelter and take up nutrients not needed by the corals like carbon dioxide and nitrogen while polyps get nutrients and the calcium carbonate they need for their exoskeleton. https://oceanservice.noaa.gov/education/kits/corals/coral02_zooxanthellae.html

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Threats toThe Coral Reefs

1, About a fifth of all coral in the world has died in the past three years. Some experts believe that there is now just half the amount of coral that was in the oceans 40 years ago.