A red algae bloom, also known as Red Tide, is currently killing a record number of manatees living off the coast of Florida.Last week, the Florida Fish and Wildlife Conservation Commission ( FWC ) found an average of 10 dead manatees a day and some observers said the phenomenon doesn't appear to be receding. A toxin produced by the red algae affects the nervous system of the manatees causing them to drown."This is probably going to be the worst die-off in history," said Martine DeWit, veterinarian with the FWC.DeWit noted that a confluence of factors has caused the animals to swim into a precarious situation."It's a very large bloom that persisted through the winter and there are lots of manatees in the same area," she said. "They all aggregated to the warm-water side, and that put them in the wrong place at the wrong time."As of Friday, state officials had this year's number of manatee casualties pegged at 149, just two animals short of the record high mark of 151 set by a Red Tide in 1996.The FWC and conservation groups have been racing to locate and save the slow moving marine mammals. So far, 11 manatees have been rescued and taken to Lowry Park Zoo in Tampa for treatment and resuscitation. To revive manatees that have been afflicted by the red algae toxins, zookeepers have been standing in the manatees' tank and holding the animals' heads out of the water so they can breathe."They're basically paralyzed and they're comatose," said Virginia Edmonds, the zoo's animal care manager for Florida mammals. "They could drown in 2 inches of water."The zookeepers have also been using flotation devices to keep the manatees from drowning. However, because the manatees often suffer from seizures in these conditions - the zoo staff made the decision to schedule three-hour shifts dedicated to holding the manatees' heads up.Zoo spokeswoman Rachel Nelson told the Tampa Bay Times that one particular manatee that was brought in Thursday took a long time to recover, meaning that "for 29 hours our keepers held a manatee's head out of the water."Although manatees in the zoo are safe for now, officials are trying to decide what to do once they make a full recovery from the algae toxin."We're making arrangements to move them to other places and stabilize them and keep them there until the Red Tide goes away," Pat Rose, executive director of the Save the Manatee Club , told the Tampa Bay Times.Every few years, the red algae population off the coast of Florida mysteriously explodes and the resulting bloom floods the immediate area with deadly toxins - killing off manatees and fish that live in the area.The current Red Tide, which has been floating on the water since last fall, affects about 70 miles of the southwest Florida coast. Widespread manatee deaths were not seen until last month, according to DeWit."We'll just keep taking them in," Edmonds said. "We want to save as many as we can."