Large sections of coral reef on windward Oahu and parts of Kauai are continuing to suffer from high ocean temperatures, raising the risk that they will die, scientists said Friday.

Corals stressed by warm waters continue to expel algae, which the coral rely on for survival. These conditions are expected to continue for another four weeks.

The more resilient corals will likely bounce back but the more sensitive ones will die, said Amy Apprill, an assistant scientist with the Woods Hole Oceanographic Institution in Massachusetts who is visiting Hawaii to study the bleaching.

"You’re going to have this sort of phase shift in the coral species distribution. We’re not sure right now what these events are going to look like," she said.

Coral reefs provide habitat for shrimp, crab, fish and other species. They support the state’s biggest industry, tourism, as many visitors snorkel and dive to see the coral and the fish that live among them.

Anne Rosinski, a marine resources specialist at the state Department of Land and Natural Resources, said the current bleaching event is more serious than the last one to occur in Hawaii, in 1996.

Scientists who witnessed that one say this current event is both more severe and covers a larger area, she said.

The most serious bleaching is currently at Kaneohe Bay off Oahu, where 75 percent of the dominant coral species surveyed has starting to lose color or has turned completely white.

The department has set up a program to monitor the coral there for signs of recovery but hasn’t seen any yet. Officials are also monitoring waters off Kauai’s Lepeuli, Anahola Beach Park and Anini.

Richard Vevers, the director of the Catlin Seaview Survey, an international project to film coral reefs, said he saw 10-foot wide head of coral in waters off Lanikai that had turned bright white. He estimated the coral was 200 to 300 years old.

The temperatures have risen past the point corals are able to tolerate, he said.

"It’s the big wakeup call to climate change. It’s the most visual manifestation of climate change at the moment," Vevers said.