Coral reefs in U.S. waters and the Pacific are under stress from both humans and nature, according to a national assessment released yesterday by the National Oceanic and Atmospheric Administration.

A combination of overfishing, pollution, disease and climate change is threatening the health of coral reefs everywhere from the Florida Keys to Palau, said the report, which covers 14 areas in the United States and its territories.

"We see a decline in our overall ecosystems," said Mark Monaco, biogeography program manager for NOAA's Ocean Service. "We're very concerned about the future of these delicate ecosystems."

Reefs nearest populated areas, such as the Florida Keys, are under increasing stress, researchers found, whereas more remote areas, including the northwestern Hawaiian Islands, are doing better. In Hawaii, federal officials have removed fishing nets and other debris that had been damaging the reefs and are considering making much of the area off-limits to fishing and other human activities.

"There's a lot of good management going on," said Jeannette Waddell, a NOAA marine biologist, noting that the government is collecting coral reef data from federal, state, territory and local partners. "Now we can really begin to understand what's out there."

Some reef managers are struggling to combat natural forces, such as coral bleaching, as well as human influences. (Bleaching occurs when warmer seas drive out tiny, one-celled algae that live within the coral and help sustain it.)

Billy Causey, superintendent of the Florida Keys National Marine Sanctuary, said the area suffered from two serious episodes of bleaching, in 1997 and 1998, followed by damage from Hurricane Georges in 1998. The reef lost 30 percent of its living coral as a result.

"The good news is, we have not seen an appreciable decline since then. The bad news is, we have not seen an increase," Causey said. "Coral reefs are showing the greatest amount of damage in our lifetime compared to any other marine environment."

Sanctuary officials, he added, are doing a better job of anticipating strains on the reef, using an early detection system for coral bleaching developed by Mote Marine Laboratory in Sarasota, Fla. They now alert area dive shops that swimmers need to take precautions when reefs are under stress.