Bleaching didn't kill Hawaii's coral reefs,
but global warming, and
overuse still loom

By Joan Conrow
Star-Bulletin

But that doesn't mean the state's extensive living reef system, which spans nearly 1,052 miles of tidal coastline, is immune to threats.

Overfishing. Overuse. Global warming and depletion of the ozone layer.

"It's really a global-scale phenomenon," said Paul Jokiel, associate researcher with the Hawaii Institute of Marine Biology.

"It's an ecosystem that's being affected by a change in the whole planetary system, and that's pretty profound."

By Bruce Carlson, special to the Star-Bulletin
Looking much like bleached coral, this healthy coral, photographed at
South Point, Kona, provides food and shelter for thousands of species.

Other scientists called him alarmist, but Jokiel's predictions proved true last summer, when coastal waters reached their highest temperatures ever and the state experienced its first massive bleachings.

Corals from Kaneohe to Johnston Atoll were affected, he said, but then the waters cooled again and the episode passed without extensive mortality of reef corals.

"All of this is consistent with global warming," Jokiel said.

"If this warming trend is here to stay, we will see the bleaching more often."

Scientists aren't sure why this happens, and some theorize that the reefs could adapt as temperature-resistant forms of algae quickly evolve.

But if corals are the key players in this symbiotic relationship, Jokiel said, it could take hundreds of thousands of years for them to adapt through natural selection. And they may not have that much time if global temperatures rise as rapidly as some scientists predict.

Researchers also are finding that corals are greatly affected by the interaction between higher water temperatures and other factors, such as high light levels and ultraviolet radiation penetration that are linked to weakening of the ozone layer, and reduced salinity caused by massive flooding.

"These factors are much more stressful if working together than independently," Jokiel said. And corals are even more susceptible if they are already stressed by the presence of sewage, sedimentation and other forms of pollution.

Stricter local grading laws and the demise of sugar also have led to a reduction in the amount of sediment being dumped on reefs. That's long been a problem in Hawaii, where sugar cultivation and processing sent massive amounts of soil and bagasse into the ocean, where it accumulated on nearshore reefs.

Studies have shown that reefs can quickly recover once the sedimentation stops, but that's only true of open coastlines subject to wave and current actions, Jokiel said.

"But inshore, such as in bays, that isn't going to happen. Once you get burials or substantial deposits that can't be removed, that's irreparable," he said.

Hawaii also has taken strides to reduce the effects of sewer and power-plant outfalls on reefs, and it doesn't have much of the heavy industry associated with marine pollution. Still, problems are lurking, such as the potential for massive damage from oil spills, coral diseases and the introduction of alien species.

"Everything's interrelated," said Richard Brock, a researcher and fisheries expert with the University of Hawaii's Sea Grant Program. "If you upset the balance between the species, there could be tremendous changes occurring in other living components of the reef."

An explosion in water sports prompted by expanding tourism and public recreation is also taking a toll on local reefs. Intense pressures on Hanauma Bay prompted the city to control access to what is arguably Hawaii's most popular coral reef. State officials, meanwhile, are installing moorings at some of the most popular dive spots to reduce coral damage from boat anchors.

"I think there's an increased interest as people have become more aware of what human impacts on the reefs are," said Sherwood Maynard, director of the University of Hawaii's Marine Option program. "And there's been a growing concern and realization we need to do something to protect them to ensure they're here for future generations."

Still, Jokiel said, "what's going on here is not at all typical of what's happening in the rest of the world." Coral reefs in South America, Africa, Southeast Asia and the Philippines are threatened by skyrocketing human populations, raw sewage, siltation caused by deforestation, agricultural runoff and fishing practices that employ the use of deadly cyanide.

International scientists say that at the rate the world's reefs are being degraded, 40 percent of them will be destroyed beyond recovery in 20 years.