WASHINGTON — El Nino’s super warm water has turned what had been one of the world’s most lush and isolated tropical marine reserve into a coral graveyard, federal scientists said Wednesday.

Researchers finishing an emergency undersea expedition found 95 percent of the coral dead around Jarvis Island in the Pacific Remote Island Marine National Monument. In November, much of the coral had bleached white but was alive.

“There’s hardly anything left on the bottom in terms of the coral. It basically looks like a graveyard,” said the expedition chief scientist Bernardo Vargas-Angel of the National Oceanic and Atmospheric Administration. “The skeletons are still there but they are covered with algae.”

The algae was red, and below it was a sea of dead coral, he said, returning from a 10-day diving expedition to the region along the equator, 1,400 miles southwest of Hawaii.

Scientists say the area around Jarvis Island normally looks like something out of a technical movie, vibrant with coral, plankton, fish and sharks. A unique current normally brings cold water up from the deep, making it teem with life, said Woods Hole Oceanographic Institution scientist Anne Cohen.

“It’s like the Super Bowl of coral reefs, this place,” Cohen said.

The coral can survive short bouts of warm water but the water just got too warm for too long, scientists said.