In habitats, the pressure was matched to the pressure of the depth at which the habitat was placed, enabling divers to come and go as they pleased. Such advantages notwithstanding, habitats gradually fell out of favor. Currently the only underwater habitat devoted to science is Aquarius . Since 1993 it has operated off Key Largo, Fla., as the centerpiece of a research program focusing on the state s fragile and economically important coral reefs. The marine analogue of the terrestrial rain forest, coral reefs are home to between 20 and 40 percent of the 160,000 known marine species.
Coral reefs are also among the earth s most threatened ecosystems.
But the reefs are significant for more than their biodiversity and their status as endangered ecosystems -there are economic reasons for their study as well. Reefs also help to maintain beaches through cycles of growth and erosion and the development of seagrass and mangrove ecosystems are linked to reefs as well. In contrast to its predecessors, Aquarius is really more a laboratory than a habitat. In addition to a comfortable living environment, Aquarius provides enough space to conduct experiments and includes computer and electronic capabilities to permit research that could not be accomplished any other way. Scientists spend six to nine hours a day in the water and often venture out at night as well.