Ocean warming and intrusions by humans threaten coral reefs worldwide, with alarming ramifications for other sea life. A U.S. task force will address the issue, but some fear it may be too late. 

Rising ocean temperatures are causing unprecedented damage to coral reefs from the western Pacific to the Caribbean, according to marine scientists monitoring the teeming, fragile underwater ecosystems. 

The damage from warming waters, coupled with disease and human-caused destruction, threaten the survival of much of the world's coral. At the present rate of decline, as much as 70 percent of the world's coral reefs may be killed in the next two to four decades, some scientists predict. 

Coral reefs -- home to nearly 25 percent of all marine life -- are the tropical rain forests of the ocean, providing food and shelter for a million species of sea creatures and plants. They have become an important source of new medicines for bone grafts and treatment of leukemia and skin cancer. 

Reefs also are vital to fishermen, tourists and coastal communities. Worldwide, about 10 percent of the annual fisheries catch comes from reefs, and coral reefs are central to multibillion-dollar marine recreation industries in such places as the Florida Keys, the Caribbean, Hawaii, Australia, Indonesia and the South Pacific. And they serve as protective barriers for low-lying islands and coastal areas. 

Now, in tropical waters around the globe, snorkelers and scuba-divers are seeing colorful reefs turn white and die. And where reefs die, the rich sea life soon dwindles. 

Ocean waters warmed by climate changes and the recent El Nino have caused widespread coral bleaching, a phenomenon in which the coral loses its characteristic color. Coral can frequently recover from moderate bleaching, but sustained and severe bleaching can kill the coral, leaving behind a white skeleton that is soon overgrown by underwater plants. 

To try to halt the decline of coral reefs, a federal task force will convene today in Key Biscayne, Fla. It's the first meeting of federal agencies on the issue since President Clinton created the task force last June. Clinton directed the agencies to develop coordinated plans for restoring damaged reefs in U.S. waters. 

Clinton administration officials say they will seek millions from Congress to hire "reefkeepers" and to fund research aimed at protecting reefs from such threats as fishing, sewage, and pollution. 

Reefs are "the underwater equivalent of Yellowstone," said Interior Secretary Bruce Babbitt, who will lead the meeting. "They're under seige all over the world, from climate change and land use, among other things. And they have not had the attention they deserve." 

Babbitt said coral bleaching showed "the extraordinary consequences of putting more carbon dioxide into the air and letting global warming go unchallenged. This could simply drive coral reefs to extinction." 

Given the effects of climate change, many experts are not optimistic about the future of the reefs. 

"The global phenomenon seems to be making our efforts futile," said Tim McClanahan, a World Conservation Society scientist who has spent 18 years studying corals and helping establish coral reef preserves. 

Coral bleaching involves a breakdown in the normal life of coral. Corals are composed of tiny creatures, called polyps, that form enormous colonies; each polyp is essentially a transparent, hollow cylinder, connected to its neighbors by the gut cavity. 

Many of the splendid colors of corals come from algae that live within the polyps in a symbiotic relationship. The algae produce most of the food for the coral, and the coral provide the algae with nutrients as well as housing. The algae and polyps are also food for grazing fish, who are prey for larger fish. 

The polyps are very sensitive to changes in light, water quality, and temperatures. When waters get too warm, coral expel their algae, leaving behind the transparent tissue, through which the white, calcium carbonate skeleton is visible. The coral is deprived of most of its food and goes into a dormant state and dies if algae do not return. 

Reefs have been threatened for years by such human activities as fishing with explosives and poisons, water pollution and sedimentation, careless boating and diving, and dredging and trawling. Human population growth and further development on land have increased the pressures on coral reefs, which grow only in shallow, tropical water. 

Now, there is the added threat of rising ocean temperatures. Because of increases in "greenhouse gases" such as carbon dioxide from auto and industrial emissions, and the recent El Nino weather pattern, seawater temperatures are at or near record levels in many locations. 

Sustained temperatures above 86 degrees Fahrenheit can cause bleaching. Scientists are also concerned about another effect of climate change: Increasing levels of carbon dioxide in the atmosphere collect in seawater, where it is expected to slow the ability of coral to calcify and build their skeletal reefs of calcium carbonate. 

"These things are in trouble -- they're headed downward, and I, quite frankly, don't see a turnaround," said Robert W. Buddemeier, chairman of a scientific working group on coral reefs and global change, sponsored by Scientific Committee on Oceanic Research and the Land-Ocean Interactions in the Coastal Zone. "I'm fairly pessimistic about being able to manage and preserve reefs, at least the ones that are at all near people." 

Satellite monitoring by the National Oceanic and Atmospheric Administration showed high temperatures -- and an unprecedented round of bleaching -- this year in the Indian Ocean reefs of Seychelles, Kenya, Reunion, Mauritius, Somalia, Madagascar, Maldives, Indonesia, Sri Lanka, Gulf of Thailand, Andaman Islands, Malaysia, Oman, India, and Cambodia. 

Unusually warm waters are now being reported in the Caribbean and the Atlantic, in such places as the Cayman Islands and Belize. NOAA satellites show current "hot spots" -- where temperatures are at least 1.8 degrees Fahrenheit above the average annual maximum -- stretching from Mexico's Yucutan peninsula across the Atlantic to the African coast of Mauritania. 

"About 85 to 90 percent of all our hard coral is bleached," said Tim Austin, assistant director of the Cayman Islands' Department of the Environment. "It's certainly the highest we've ever seen." Austin said it's too soon to tell how much coral will recover, but noted "we already are starting to see some dying." 

"It's a cumulative thing . . . much of the coral had bleached last year, and had only just recovered from that," he said. 

On Glover Reef, 20 miles off the coast of Belize, "nearly everything is bleached, all the way down to 30 meters," said McClanahan, the Wildlife Conservation Society scientist. "I was out there today, and I think we're probably going to see 40 to 50 percent mortality." 

The last two years have seen "the most geographically widespread bleaching ever recorded," says a new report prepared by the scientific group International Society for Reef Studies. "In the present bleaching episode, the response has been exceptionally severe with a large number of corals . . . subsequently dying." 

Another study, by the Global Coral Reef Alliance, said, "Coral reef health worldwide has entered a catastrophic decline due to global threats to their survival which are affecting even the most remote and previously untouched reefs. 

"Bleaching and diseases have certainly killed more corals in the last two years than all previous human damage," the report says. "Unless they are controlled, all efforts at reef protection will be futile." 

One of the report's authors, Thomas J. Goreau, said most Indian Ocean corals have already been killed "stone cold dead" by high temperatures, and he predicted "catastrophic biodiversity declines for over 100 countries" if the decline of coral reefs is not halted. 

John Ogden, director of the Florida Institute of Oceanography and a professor of biology at the University of South Florida, said he considers Goreau's assessment "too apocalyptic," but agreed that coral reefs are threatened on many fronts. 

"We can't evaluate the mortality [ from bleaching ] yet, it's too soon," Ogden said. "In past bouts of bleaching, we've had more recovery than death." 

High water temperatures are not the only causes of coral bleaching. Disease, excess shade, increased ultraviolet radiation, pollution, sedimentation, and changes in salinity can also cause the phenomenon. 

But even in protected areas, where most other factors have been avoided, too-warm water has been devastating. 

In Kenya's 20-year-old Kisite Marine National Park, one of East Africa's most colorful coral ecosystems, virtually all of the coral bleached and died this year, McClanahan said. 

"It was shocking to see this jewel of management and natural beauty looking like a dead piece of rock," he said. "It's rather depressing to think about the future." 

©1998 Philadelphia Newspapers Inc. 

[ and - two prior articles on diseased coral]