ST. CROIX - When the rains and winds came back to the territory last October - ending months of stagnant heat - National Park Service fisheries biologist Jeff Miller breathed a sigh of relief.

As ocean temperatures dropped, the bone-white coral reefs that had been cooking in the overheated waters for more than 10 weeks began to regain their critical algae partners - green creeping back into the transparent tissue wrapped over ivory-colored skeletons.

Biologists like Miller fought to contain their excitement - publicly expressing cautious optimism but privately celebrating what looked like the first stage of a recovery from the coral bleaching event.

The celebrations, however, have now turned to alarm.

"We were thrilled. We thought we had dodged a major bullet," Miller said. "But now, we think we were wrong."

Only weeks after the corals recolored, patches of dead tissue began appearing. A disease - which seems to be a variant of "white plague" - began to take hold on reefs across the territory and the results, according to Miller, have been devastating.

White plague - whose causes are still unknown - destroys the tissue of the coral, leaving only the white skeleton behind. It has a similar appearance to bleaching, but in bleaching events the polyp tissue is transparent and alive. In corals affected by white plague, the tissue is dead. White plague is thought by scientists to be contagious, spreading from coral to coral, but that theory has not yet been conclusively proven.

"This is unprecedented in its scale of mortality," Miller said. "We've been monitoring these sites since 1997 and I've never seen anything this devastating."

Speaking at a three-day conference on coral bleaching held at the Nature Conservancy in Estate Little Princess, Miller and colleague Erinn Muller painted a grim picture of coral health following the summer and fall bleaching.

Miller said the recently discovered disease is now killing coral colonies that have grown at a rate of the width of a dime per year for millennia.

"We're losing colonies that took thousands of years to grow - in weeks," he said. "It's really depressing."

Miller said he had not yet analyzed enough data to accurately assess the extent of the disease, but he said it was present at every one of the Park Service's monitoring sites in St. John and St. Croix. The Park Service does not have monitoring sites on St. Thomas.

"I can't give you a number," he said of the percent of coral affected. "But it's a lot. It's very prevalent."

Incontrovertible evidence linking the disease to the stress caused by the bleaching has not yet been found, but Miller said that bleaching and disease is likely linked to a host of factors, from ocean temperature to human-generated pollution and sediment.

While environmental managers can do nothing about ocean heat and disease, Miller reiterated the call from many of the scientists at this week's conference to reduce the stresses posed by humans and give the corals their best chance to battle the natural threats.

Scientists also are working to gain a historical picture of coral growth and decline. Without knowing the fate of past coral colonies, it can be difficult to place the recent bleaching events and disease die-offs in perspective. Are these events truly unprecedented, or are scientists simply glimpsing one end of a long-term cycle for the first time?

No one yet knows the answers to these questions.

Scientists looking for explanations have turned to reef cores, studying the layers laid down by corals year after year. By drilling into the coral and extracting a cylinder, the scientists can examine the growth over centuries. Similar to the rings of a tree, scientist can chart years of growth and death in the corals.

What caused any deaths within the cores, however, remains a mystery.

"All it can tell you is that there is dead coral," said Bob Ginsburg, a scientist working out of the University of Miami who attended the conference. "It can't tell you anything about how they died."

The puzzles of the past can do little to help save the territory's corals now affected by disease, and Miller admits that any treatment for the disease is "a couple of bends down the road."

For now, scientists can only watch and wait and continue to urge the public to do what they can to help the coral through the current crisis.

"We know that anchors hurt corals and we are the ones dropping the anchors," Miller said. "We know that sediments hurt corals and we are the ones doing the development" that causes erosion and leads to sediments. "We need to reduce the human stressors."

- Contact Patrick Joy at 774-8772 ext. 458 or e-mail pjoy@dailynews.vi.