On Friday the number reached 149 so far this year. By the end of the weekend, that number could pass the record set in 1996 at 151 deaths.
"This is probably going to be the worst die-off in history," said Martine DeWit, a veterinarian who oversees the state's marine mammal pathology laboratory.
Nearly a dozen manatees have been rescued and are being treated at the Lowry Park Zoo in Tampa. SeaWorld has taken two and Homosassa Springs Wildlife State Park will probably get four, said Virginia Edmonds, the zoo's animal care manager for Florida mammals.
Biologists say it's unclear if the algae bloom will let up any time soon.
Red Tide has plagued Florida's gulf coast beaches for centuries. The algae bloom turns the water into a rust color, releasing large amounts of toxins. This is very harmful and even fatal to people, fish, shellfish, marine mammals and birds in high concentrations.
Scientists at the National Ocean Service have been monitoring and studying this phenomenon for a number of years to determine how to detect and forecast the location of the blooms.
The goal is to give communities advance warnings so they can adequately plan for and deal with the adverse environmental and health affects associated with these Red Tide events.
The current bloom affects 70 miles of the southwest Florida coast, from Sarasota through the middle of Lee County.