The hot, muggy weather that’s stifled Hawaii in recent weeks appears to have spurred widespread coral bleaching across the state, and researchers say it’s the most severe degradation of coral that they’ve ever observed in Hawaii waters.
The worst of the bleaching so far has been found on Oahu’s Windward Coast, state officials say. In dives conducted there earlier this week, 75 percent of the coral surveyed in Kaneohe Bay ranged from having early signs of bleaching to being "100 percent white," meaning they’re about to die or are already dead, officials with the state Division of Aquatic Resources said Monday.
Divers also found severe coral bleaching in the shallows off Lanikai and Waimanalo.
The problem is that the onslaught of hotter air and sparse tradewinds is warming the local sea surface to temperatures far higher than the average for this time of year, researchers said during a news conference Monday at Heeia Kea Small Boat Harbor, where fleeting clouds and trades swiftly gave way to more of the intense sun and heat.
The hotter conditions, they added, are likely pushing local corals already stressed by pollution, runoff, water sports and other man-made factors past the point of what they can survive.
Excessive coral bleaching is also being found at popular visitor sites such as Hanauma Bay and Waikiki — as well as off Maui, Hawaii island and even the Northwestern Hawaiian Islands, said Frazer McGilvray, the division’s administrator.
"It’s the most extreme event that we’ve seen since people have been studying corals in Hawaii," said Cynthia Hunter, an associate biology professor focusing on coral reef ecology and director of the Marine Option Program at the University of Hawaii at Manoa.
"It’s unprecedented for everyone who’s studied this in the past," added Zac Forsman, a coral recovery specialist with the Division of Aquatic Resources.
The weather that’s threatening the local coral could last another four to six weeks, added Anne Rosinski, also with the division. That agency and researchers say they plan more dives to keep a close eye on how the coral is faring and to do more surveys.
They’re hoping that much of the coral might rebound and survive.
To lose it all would be "catastrophic," McGilvray said.
"The corals are the foundation of the habitat of the bay," he said Monday, referring to Kaneohe. "This is the foundation of this ecosystem, is the coral."
Some of the coral species most crucial to building reefs are also the most sensitive and susceptible to this bleaching, said Ruth Gates, a researcher at the Hawaii Institute of Marine Biology. Those species include Montipora capitata — what’s commonly known as "rice coral," she said.
Some of the coral affected by the bleaching is "hundreds of years old," and even if a particular coral survives, its ability to reproduce could be hindered in future years, Gates added.
"Corals can withstand slight excursions above their normal range," Gates said. "What they don’t like is when the temperature stays high for an extended period of time. What we want is for the tradewinds to return."
In the meantime, Gates said, she and her colleagues can use what they learn to search for a solution.
The public can pitch in somewhat to help the situation, Rosinski said. She encouraged anyone who sees coral bleaching while surfing or snorkeling to send photos to the Eyes of the Reef Network, a statewide volunteer group that trains people to identify such problems.
She further encouraged the public to try to avoid any activities that would add further stress on local coral.
Temperatures in the water around Coconut Island have peaked at 86 degrees, Hunter said, even though they typically don’t exceed about 80 degrees in that general area.
"We’re way over what the normal would be," Hunter said. "They’re responding to a stressful situation."
Meanwhile, September saw the second-hottest air temperatures on record locally since the 1940s, McGilvray said.
Researchers and state officials at Monday’s conference said that local, widespread coral bleaching due to rising sea temperatures could be a recurring problem in the future as the effects of global climate change intensify.
For more on Eyes of the Reef, visit eorhawaii.org.
