The coral reef off southeast Florida is experiencing an unprecedented and potentially deadly level of bleaching this summer because of rising ocean temperatures caused by climate change, federal scientists said Thursday.

Some sites around the Florida Keys, a coral cay archipelago, are being exposed to twice the amount of heat stress that causes corals to die, and earlier in the year than ever before, scientists from the U.S. National Oceanic and Atmospheric Administration (NOAA) said in a telephone news conference. They said the phenomenon is likely to affect the Caribbean very soon and a global bleaching event could be just around the corner.

"We are quite concerned and worried and stressed about this event," said Ian Enochs, a research ecologist at NOAA's Atlantic Oceanographic & Meteorological Laboratory. "It's not a normal thing."

Warming ocean threats coral reefs

Ocean surface temperatures off the Florida coast have risen to above 32 degrees Celsius this summer, but scientists said they won't know the extent of damage until early next year.

Coral reefs are made up of tiny organisms that link together. The reefs get their color from the algae that live inside them and are the corals' food. When temperatures get too high, the corals expel the algae, making the reefs appear bleached or white. That doesn't mean they are dead, but the corals can starve and are more susceptible to disease.

Already, there is coral bleaching along the Pacific coasts of Colombia, Costa Rica, El Salvador, Mexico and Panama, as well as along the Atlantic coasts of Belize, Cuba, Puerto Rico and the U.S. Virgin islands. Sharks have disappeared off the coast of Oaxaca, Mexico, because of the water temperature.

"Florida is just the tip of the iceberg," said Derek Manzello, coordinator of NOAA's Coral Reef Watch Program. "The scale of this event is very alarming. We are talking about thousands upon thousands of miles of coral reefs undergoing bleaching from severe heat stress."

At this point, a tropical storm or hurricane – although undesirable for other reasons – would be the best way to cool the waters and limit the damage, Manzello said.

"Unless we have significant changes in weather patterns, we are marching toward heat stress for the Caribbean in a matter of days or weeks," he said.

Relocation of coral reefs

Up and down the chain of islands that form the Florida Keys, coral rescue groups and government and academic institutions have mobilized to save the corals by relocating them to land-based facilities where they can be studied. The goal is to figure out which coral types are best at surviving heat stress and then using them to build a more resilient reef, said Andy Bruckner, research coordinator for NOAA's Florida Keys National Marine Sanctuary.

Though the ecological collapse of the reef system is possible, Bruckner said he is optimistic that restoration efforts can keep that from happening.

"I think we are near a tipping point, and how this event unfolds will tell us if we are there," Bruckner said. "But I don't feel it's too late."

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