Feature

Reef rehab could help threatened corals make a comeback

Solutions for threatened reefs vary by location and damage done

REEF REHAB A coral fluoresces purple (left), perhaps as a sunscreen defense for colorless polyps, in a photo taken September 12 of a bleached reef near Okinawa, Japan.

Coral reefs are bustling cities beneath tropical, sunlit waves. Thousands of colorful creatures click, dash and dart, as loud and fast-paced as citizens of any metropolis.

Built up in tissue-thin layers over millennia, corals are the high-rise apartments of underwater Gotham. Calcium carbonate skeletons represent generations of tiny invertebrate animals, covered in a living layer of colorful coral polyps. Their structures offer shelter, and for about 114 species of fish and 51 species of invertebrates, those coral skyscrapers are lunch.

Important as they are, corals are in jeopardy. Warming oceans are causing more and more corals to bleach white and become vulnerable to destruction. A prolonged spike in temperatures, just 1 to 2 degrees Celsius, is enough to kill the marine animals. Greenhouse gas emissions also acidify the water, dissolving the calcium skeletons. In some countries, fishermen use dynamite to catch fish, leaving behind coral rubble. Today, more than 60