Table coral, Acropora cytherea, discovered off O'ahu in Hawaii

Given its common name due to its flat-topped, table-like shape, table coral (Acropora cytherea) is one of the primary reef-building corals throughout most of the tropical Pacific, but it has never been observed in waters off O'ahu -- until now, researchers said. The coral, estimated to be 14 years old, was found at a depth of 60 feet during a training dive.

"This discovery represents a significant contribution to the diversity of O'ahu reefs," said Daniel Wagner, Ph.D., NOAA research specialist with Papahānaumokuākea Marine National Monument. "Hawai'i may be in the process of being colonized by table coral from Johnston Atoll or other neighboring tropical archipelagos."

Table coral is abundant at Johnston Atoll, 800 miles southeast of Honolulu. However, it is rare in Hawai'i, where its distribution is limited to French Frigate Shoals and neighboring atolls in the Northwestern Hawaiian Islands.

The coral colony was discovered by scientists last November during survey dives using closed-circuit rebreathers off the south shore of O'ahu. Rebreathers recycle the gases that divers breathe, removing carbon dioxide and actively managing oxygen levels, thereby allowing for extended dive times and more efficient decompression at depths not accessible using conventional SCUBA.