But the reefs are in trouble.
     For the past two summers, the water temperature has climbed above 86 degrees Fahrenheit, the “thermal maximum” for many of the delicate corals that form the Keys. The warmer water can bleach the colorful algae from the corals, leaving a white skeleton instead of the pastel robes that normally cloak the reef.
     “We've never had two years (of dangerously high temperatures) in a row before,” says Steven L. Miller, the associate director of the Aquarius underwater lab off Florida's Key Largo.
     The warmer water stresses the corals, and “they don’t grow as quickly, and they don’t reproduce as well,” he says. “If the event is not too serious they can recover, but sometimes they die.
     “Corals are animals,” Miller says, “with algae that live in their tissue. During the day, through photosynthesis, they capture light energy,” allowing them to grow and provide energy to the coral polyps.

Turn Down the Heat
It all works well when the water temperature remains below 86 degrees Fahrenheit, but above that, the corals get stressed, shedding the algae.
    The years when the water is warm enough to cause bleaching are becoming more frequent, not only in Florida but around the world.
     “Is this a signal of global warming?” asks Miller, a coral reef ecologist at the University of North Carolina at Wilmington. The university runs the Aquarius program, the world's only underwater lab, for the National Oceanic and Atmospheric Administration.
     “Coral reefs may be the first ecosystem that is giving us a signal that the oceans are warming. Perhaps it’s a signal of things to come.”
     In July, scientists from across the country will arrive in Key Largo to get ready for more experiments aboard the Aquarius, nestled on a sand pocket 63 feet below the surface of the Atlantic.
     Scientists and students and other interested folk can share in the discoveries. Images, research data, video clips, audio and even diaries from the those aboard the 81-ton undersea habitat will be posted on the project’s Web site.
     “We will have lesson plans for teachers built around the mission,” Miller says, “and students can pose questions.”

An Underwater Abode
The 43-foot long Aquarius looks sort of like a cross between an overgrown oil barrel and a motor home. From it, scuba-diving scientists can venture onto the reef for up to nine hours of research without fear of the bends, compared to less than an hour if they had to dive from the surface.
     The Aquarius has seen 22 10-day missions between 1993 and 1996, studying such things as the effects of water pollution, with six planned for this year.
     A key part of the next mission will be studying bleaching, which is threatening the very life of the reef.
     Aside from too-warm water, coral may also be bombarded by ultraviolet light because of the thinning of the ozone layer. Scientists also worry that all of these individual stresses may somehow work together to make the environment even tougher for corals.
     Peter Edmonds, a coral reef expert at the University of California at Northridge, will venture onto the reef to test whether increased UV radiation and temperature extremes work together to degrade the coral. For example, he'll expose some small areas to higher levels of UV and varying temperatures, while monitoring the results.

Before It’s Too Late
The goal of all of the research is to better understand these delicate ecosystems before it’s too late.
     Economics may also play a role.
    Pharmaceutical companies look to reefs as possible sources of new drugs. The chemicals and mechanisms that corals use to protect themselves from predators might someday help humans fight disease.
     Aside from all that, there is the majesty of these underwater treasures.
     “You can put on a snorkel and the entire system unfolds beneath you,” says Miller, who has been an “aquanaut”—a resident of the Aquarius lab.
     “You see the fishes and you see the corals and you view a spectacular ecosystem. It’s quite an opportunity to study and explore the tremendous diversity that we have on this planet.”
     But because most people are disinclined or unable to strap on a snorkel and visit the reefs, they remain out of sight. And out of sight, Miller says, “makes it easy for them to be out of mind as well.”