A DIE-OFF of unprecedented proportions has blighted coral in Caribbean waters in recent months ? but Bermuda's reefs are holding up well.

Dr. Ross Jones, a research associate scientist at the Bermuda Biological Station For Research (BBSR), said 14 years of monitoring had shown no change in the percentage cover of coral in Bermuda's reefs.

In contrast, many other parts of the world have seen 50 per cent or more of their coral killed off by a combination of rising ocean temperatures, disease and pollution.

Dr. Jones, who heads the BBSR Marine Environmental Programme (MEP), put the local reefs' survival success down to hardier species of coral and clean water.

Researchers in the Caribbean estimated this week that around one third of coral in official monitoring sites in Puerto Rico and the US Virgin Islands had recently died off.

"It's an unprecedented die-off," US National Park Service fisheries biologist Jeff Miller told the Associated Press, after he checked 40 stations in the US Virgin Islands. "The mortality that we're seeing now is of the extremely slow-growing reef-building corals. These are corals that are the foundation of the reef.

"We're talking colonies that were here when Columbus came by have died in the past three to four months."

Some of the devastated coral can never be replaced because it only grows the width of one dime a year, Dr. Miller said.

The extent of the coral death has been put down to unusually high sea temperatures in the Caribbean and the Gulf of Mexico last year, which caused widespread "bleaching".

Bleaching happens when the heat causes the symbiotic algae that provides food for the coral to die and turn white. That leaves the coral in a severely weakened state, ripe for disease to move in and finish it off.

New National Oceanic and Atmospheric Administration (NOAA) sea surface temperature figures show the sustained heating in the Caribbean last summer and fall was by far the worst in 21 years of satellite monitoring, Mark Eakin, of the NOAA said.

"The 2005 event is bigger than all the previous 20 years combined," he added.

Dr. Jones said the MEP was constantly monitoring for any changes happening in the island's reefs, but said the Caribbean horror story had not been echoed here.

"The MEP is funded by the Government and we monitor the reefs and water temperatures closely," Dr. Jones said.

"The water temperature was high last year ? although it was higher in 2003 ? and we saw no change in the percentage coral cover.

"I think one of the reasons our coral is faring better than many parts of the world is that we have tougher species, big brain corals that are a bit more temperature-resistant."

Coral reefs are a major economic asset to the island, boosting the tourism and fishing industries, as well as providing protection for the island from the eroding effects of storm-induced high seas.

Formed by colonies of tiny, living organisms, they are very sensitive to environmental change. Bermuda's isolation is both a help and a hindrance to its reefs.

"Bermuda's reefs are very healthy compared to those in the Caribbean," Dr. Jones said. "One reason for that is we have very, very clean seawater.

"We are not in a region where we have to worry about a near neighbour putting pollutants into our water. Also Bermuda has no rivers. Rivers are bad for carrying pesticides and pollutants from far inland and putting them into the sea."

However, geographical isolation means that the arrival of other corals from reefs further south, which can strengthen our own reefs, is already rare. But with the recent devastation of Caribbean coral it will become rarer, Dr. Jones said.

"It means that Bermuda's reef will becomes more and more self-reliant, so it's going to be a case of protecting what we've got," added the scientist.

"Overall, the outlook is very good. In other areas, their coral coverage is 50 per cent down and more, but we've not seen that type of thing here. We've been monitoring some areas for 14 years and we've seen no change at all and they've probably remained the same for 25 years.

"But the warning bells are sounding in the rest of the world and we will keep monitoring our reefs very closely."