MIAMI-A record number of manatees died in Florida waters this year and the leading killer of the endangered mammals was a toxic algae bloom in the Gulf of Mexico, according to the state’s Fish and Wildlife Conservation Commission. The commission’s research institute said it documented 803 manatee deaths in state waters between January 1 and December 13, the most for any year since record-keeping began in 1974.

That was more than double the 392 manatee deaths in Florida in 2012 and up sharply from the 453 deaths recorded in 2011. “The previous record was 766 manatee deaths and that was in 2010,” commission spokesman Kevin Baxter said on Friday.  “That was a year when cold weather was a major factor,” he added. Baxter said a Red Tide that killed 276 manatees in the Gulf, in an area centered largely off Ft. Myers, was the single leading cause of death in 2013. Naturally occurring algae sometimes grow out of control for unknown reasons, turning the water red and producing a suite of neurotoxins deadly to fish, sea turtles, birds and marine mammals.  The algae settles on the sea grasses that manatees eat, affecting their nervous system.