Scientists use dire language to describe an ecological disaster under way off Florida's coast. A blistering marine heat wave this summer created record-high sea temperatures near South Florida — home to a 350-mile barrier reef, largest in the continental United States. The result is extensive coral bleaching – potentially fatal whitening of fragile formations that are habitats for fish and lobsters, as well a living buffer against coastal storms and erosion. Weak or dead ones get chewed up by waves. "Off the charts," "disastrous" and "the worst bleaching event that Florida has ever seen" are among reactions from specialists quoted by The Washington Post. "The ocean is getting too hot for coral to live there," The New York Times suggested recently.

The surface water temperature reached 101 degrees off Manatee Bay in late July and hovered around 90 degrees near other parts of the Florida Keys, an island chain south of Miami. Rising temperatures trigger whitening by causing coral to expel algae that lives within its tissue and provide it with food. (Ideal water temperatures for coral are 73-84 degrees.) The situation may get worse before it gets better, with much of the Caribbean projected to see coral-damaging temperatures in the coming weeks, according to the National Oceanic and Atmospheric Administration (NOAA). Most reefs in the Keys are under the highest stress level, with "severe coral bleaching and significant coral death," the federal agency says. Since the late 1970s, the Florida Keys have undergone a 90% decline in healthy coral cover.

Concern extends more widely as about 44 percent of global oceans are in a heat wave. The world's seas have absorbed 90 percent of the additional heat created by people burning fossil fuels and razing forests, experts say. Coral reefs support a quarter of all marine life.

"Coral bleaching does not automatically mean coral death," says diver Katey Lesneski, who helps monitor the status for NOAA. "Corals can recover from bleaching if environmental conditions improve." Otherwise, she warns, "ecological collapse and severe economic losses" are possible. In response, NOAA teams are moving some coral out of the Atlantic and Caribbean and into cooler "quarantine tanks" at two sites in Florida that serve as gene banks for an envisioned restoration effort. It’s a "last-ditch sort of insurance policy," says Jennifer Moore of agency's Southeast region. "God forbid everything dies in the water, we still have not lost those."

Researcher says: "I was crying for nearly the entire dive because I realized that I would likely never see these hundred-plus-year-old colonies alive again." -- Katey Lesneski of the Florida Keys National Marine Sanctuary after a reef visit off Key Largo

Nonprofit leader says: "I don't really know how to process it. I keep thinking, what's it going to take to get people's attention?" – Ken Nedimyer, founder of Reef Renewal USA in Tampa, Fla.

Federal official says: "I fear for the worst." -- Derek Manzello, coordinator of NOAA’s Coral Reef Watch program