An outbreak of paralyzing algae known as red tide is killing manatees by the dozens in Florida.

Florida wildlife officials report that 149 of the gentle giants have been killed by red tide this year in just two and a half months, making it almost certain that the state will pass the record of 151, set in 1996.

The bloom of algae this year covers a 70-mile stretch of the west coast of Florida, roughly from Sarasota to Fort Myers. That makes it particularly dangerous for the blimp-shaped, endangered mammals because they congregate in the warm water there for winter.

The algae contain a toxin that can stop the breathing of manatees when they eat it, and particles seep into sea grass, which manatees also eat. So the killing will probably continue for two months after the red tide dissipates.

“They’re basically paralyzed, and they’re comatose,” Virginia Edmonds, animal care manager of Florida mammals for the Lowry Park Zoo in Tampa, told the Tampa Bay Times. “They could drown in 2 inches of water.”

Eleven manatees, often called sea cows, have been rescued and taken to the zoo for treatment this year. Workers there take three-hour shifts standing in a water tank and holding a manatee’s head out of the water so it can breathe until it recovers and can breathe on its own.

“We just keep taking them in,” Edmonds told the newspaper. “We want to save as many as we can.”

The algae develop naturally, and when water temperature, salt content and nutrients are just right, they can bloom in an outbreak that turns the water reddish-brown. Red tide develops all over the world, including off California and throughout the Gulf of Mexico.

Scientists say some studies have linked red tide to global warming because algae thrive in warmer water.

Adult manatees average about 10 feet long and glide through the water, steering with their flippers, at about 5 mph. They have to come to the surface every few minutes to breathe.

Florida has an estimated 4,000 to 5,000 manatees. The most common cause of death is not red tide but collisions with boats, according to the Florida Fish and Wildlife Conservation Commission. Watercraft killed almost 800 manatees from 1995 to 2005.