The number of areas with diseased coral increased by 276 percent during the past year and the number of coral species affected by disease increased 211 percent, according to a major study of the reef tract. 

The findings were to be presented to ecologists at the Smithsonian Institution's American History Museum in Washington, D.C. on Tuesday. 

"We are concerned,'' Fred McManus, Florida Keys coordinator for the U.S. Environmental Protection Agency, said. "The incidence of disease has nearly quadrupled in frequency.'' 

The study was conducted at 29 reef locations in the Florida Keys, a chain of low-lying islands off the southern tip of the state. 

It is the largest and most complex reef in North America and a mecca for fishermen and scuba divers. The 2,800-square-mile national sanctuary was created to protect the delicate coral. 

The EPA-funded study found signs of disease at 94 of 160 monitoring stations this year, compared to 25 last year. The number of species showing signs of disease rose from nine to 28 during the same period. 

Researchers said not all of the diseases had been identified and they were not certain of their origins. Scientists have long believed the burgeoning population in the Florida Keys and resulting pollution could be damaging the reefs. 

"At this time, it is unknown whether these diseases are the expression of a naturally occurring short-term event with limited impact to the coral reef communities or a human-induced degradation with more serious long-term ramifications,'' McManus 
said. 

Coral reefs are constructed by tiny creatures called coral polyps which secrete calcium carbonate, the basic building block of the reef. 

Researchers found at least one reef where 80 percent of Elkhorn coral, the species primarily responsible for reef building, was killed within a three-year period. 

Scientists and divers have seen an increase in coral bleaching, a whitening of the usually colorful corals, in recent years. 

"Coral bleaching is a sign of stress,'' McManus said. ''When they become stressed, they become more susceptible to disease.'' 

05:20 PM ET 11/17/97 

[ A prior article on diseased coral]