Florida Keys coral reefs are already bleaching due to rising water temperatures, experts say

FORT LAUDERDALE, Fla. — Some reefs in the Florida Keys are losing color weeks earlier than usual this summer due to record-high water temperatures, which means the reefs are under stress and their health may be at risk, federal scientists said.

Corals should be vibrant and colorful at this time of year, but they quickly turn white, says Katie Lesneski, research and monitoring coordinator for Mission: Iconic Reef, a program launched by the National Oceanic and Atmospheric Administration to protect Florida’s coral reefs.

“The coral is pale and seems to have lost its color,” said Lesneski, who spent several days on the reef over the past two weeks. “And there are some who are all white. And we’re still getting more.

NOAA scientists this week upgraded the Coral Bleaching Warning System in the Keys region to Alert Level 2, the highest of five heat stress levels. This level is reached when average surface temperatures are about 1°C above normal maximum temperatures for eight consecutive weeks.

Ground temperatures around the Keys average about 33 degrees Celsius, well above the normal mid-July average of 29.5 degrees Celsius, said Jacqueline de LaCour, operations manager for NOAA’s reef monitoring program. The previous alert level 2 was reached in August.

Coral reefs are made up of small organisms linked together. The color of coral reefs comes from the algae that live in them and that the corals feed on. When temperatures get too hot, corals expel algae, making the reef appear white. That doesn’t mean the corals are dead, but they can starve and become more susceptible to disease.

Andrew Bruckner, research coordinator for the Florida Keys National Marine Sanctuary, said some reefs began showing the first signs of bleaching two weeks ago. And in the last few days, some coral reefs have completely lost their color. This had never been recorded before August 1st. Peak bleaching usually occurs in late August or September.

“We’re at least a month ahead of schedule, if not two months,” Bruckner said. “We are not yet at the stage of confirming any cases of albinism mortality. There are still a small number of completely white individuals of certain species, but that is much earlier than we expected.”

Still, de la Cour and Bruckner said it’s hard to predict what will happen for the rest of the summer. Rising water temperatures are likely to continue, which can be devastating, but tropical storms and hurricanes can stir and cool the water. As dusty air from the Sahara Desert sinks across the Atlantic Ocean and over Florida, it weakens the sun’s rays and can cool temperatures.

Climate change and other factors have caused the Keys region to lose 80 to 90 percent of its coral over the past 50 years, Bruckner said. This affects people as well as marine life that depends on coral reefs for survival. Coral reefs provide a natural buffer against storm surges caused by hurricanes and other storms. There are also economic implications, as tourism industries such as fishing, scuba diving and snorkeling rely heavily on coral reefs.

“People go into the water, fish, dive, and that’s why it’s so important to protect Florida’s reefs,” de la Cour said.

Both scientists said the current situation is not “all hopeless and bleak”. A massive 20-year effort is underway to restore Florida’s corals to about 90% of their 50-year-old state. Professor Bruckner said scientists are breeding corals that can withstand the heat and are using simple things like sunshades and underwater fans to cool the water so the corals can survive.

“We’re looking for answers and trying to do something instead of just looking away,” Bruckner said.

Coral breeding may promote heat tolerance in future generations of animals, said Jason Spadaro, reef restoration program manager at the Mote Marine Institute & Aquarium in Sarasota, Florida. It may be essential to save them, he said.

Spadaro and his colleagues, who visited the reef, said they found coral bleaching worse in the Lower Keys than in the northern part of the region. Keys has had severe albinism in years past, but this year it’s “really aggressive, really persistent,” he said.

“This is going to be a tough year for coral reefs, and we are keenly aware of the need to continue this important effort,” he said.

Early bleaching occurs in years when water temperatures spike faster than normal, said research biologist Ross Canning of Chicago’s Shedd Aquarium. Water temperatures are above 32 degrees Celsius at the Keys, he said, which normally doesn’t happen until August or September.

Canning said it could cause “disastrous bleaching” if the hot water is not reduced.

“We’re seeing temperatures even higher than normal peaks right now, which makes this particularly frightening,” Canning said.

De La Cour said there was no doubt that rising ocean temperatures are being caused by man-made global warming and that corals need to fix that if they are to survive.

“If we don’t reduce the amount of greenhouse gases we emit, and if we don’t reduce the amount of greenhouse gases that are already in the atmosphere, no matter what we do, we will end up with a world where coral reefs cannot exist,” she said.