Florida ocean temps surge to 100 degrees as mass coral bleaching event is found in some reefs

An urgent rescue operation is underway to save Florida coral species from extinction as a mass bleaching event and die-off from unprecedented water temperatures spreads across reefs in the the Florida Keys.

Multiple reefs around the Florida Keys are now completely bleached or dead in a grim escalation that took place in as little as two weeks, coral experts told CNN.

Experts now say they expect "complete mortality" of the bleached reefs in just a week, and worry reefs at greater depths could face the same fate if the unprecedented ocean warmth continues to escalate.

Extreme heat and a lack of rain and wind pushed water temperatures around Florida to some of the highest levels ever observed anywhere. A buoy in the Florida Bay hit 101.1 degrees Fahrenheit at a depth of 5 feet Monday, in an area where coral is scant. Many other stations in the area topped 96 degrees, including one that hit 99 degrees, according to the National Data Buoy Center.

The most significant concentration of coral isn't located in the shallower Florida Bay, where the readings were taken, but that matters little for coral around the Florida Keys baking in water temperatures topping 90 degrees.

Coral is extremely sensitive to temperature changes. Temperatures that are too hot for too long cause coral to bleach and turn white as they expel their algal food source and slowly starve to death. The water is typically in mid-80s in the region, experts said.

Temperatures at a reef managed by the Florida Aquarium were 91 degrees on July 6. The coral was completely healthy then, but when aquarium teams returned on July 19, all of the coral was bleached and an estimated 80% of it was dead. Another report from the Coral Restoration Foundation found "100% coral mortality" at Sombrero Reef off the coast of Marathon in the Florida Keys.