Sometime this weekend, the record for manatee deaths caused by Red Tide will be broken.

A Red Tide bloom has been killing 10 or more manatees a day and the deadly algae bloom shows no sign of letting up any time soon, say state biologists.

"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.

The record for manatees killed by Red Tide was set in 1996, with 151 killed by a toxin in the algae bloom. As of Friday, the number killed this year had hit 149, DeWit said, which means the record is likely to fall by today.

Eleven manatees have been rescued, alive but ailing, and taken to Lowry Park Zoo in Tampa for treatment. The treatment requires having zookeepers stand in the manatees' water tank and hold the manatee's head up out of the water so it 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."

Although the zoo does have flotation devices to support the manatees' heads, said zoo spokeswoman Rachel Nelson, "they tend to have seizures, which makes them drown." So each staffer takes a three-hour shift holding the manatees' heads up, she said.

One that was brought in Thursday took a long time to recover and start breathing on its own. That meant that "for 29 hours our keepers held a manatee's head out of the water," Nelson said.

The problem is what to do with them once they've recovered, noted Pat Rose, executive director of the Save the Manatee Club.

"Right now we just have full pools," Edmonds said.

Releasing the recovered manatees back into the wild where the Red Tide is would just sicken them all over again.

"We're making arrangements to move them to other places and stabilize them and keep them there until the Red Tide goes away," Rose said.

SeaWorld has taken two, Edmonds said, and Homosassa Springs Wildlife State Park will probably get four. But after that, no one is sure what will happen.

"We'll just keep taking them in," she said. "We want to save as many as we can."

Red Tide has plagued Florida's beaches for centuries. Spanish explorers recorded blooms in the 1500s. Karenia brevis — named for retired biologist Karen Steidinger, who spent decades studying its properties at the state's marine science laboratory in St. Petersburg — lives in the Gulf of Mexico all year long, usually without causing anyone any problems.

But every now and then the algae population just offshore explodes into something called a bloom, staining the water a rust color and releasing large amounts of toxins. No one knows what spurs those blooms or how to stop them, but they can wreak havoc with the state's fishing and tourism industries by causing massive fish kills.

The current Red Tide bloom affects about 70 miles of the southwest Florida coast, extending along the shores of Sarasota County south through the middle of Lee County. It has been floating out there since last fall, hanging on despite changes in the weather, but it did not begin killing off manatees in earnest until last month, DeWit said.

Roughly 40 percent of the state's estimated manatee population of 4,000 to 5,000 animals lives in southwest Florida from Tampa Bay down to the Ten Thousand Islands. Virtually all of the manatees killed by the Red Tide have turned up in the center of that stretch, in Lee County.

During the winter, manatees tend to congregate in areas where they can stay warm, such as springs and the outfalls of power plants. One of the most used of those refuges is in Lee County, where the Caloosahatchee and Orange rivers flow together.

DeWit said biologists figure the manatees that were huddled up in the rivers during the winter have left it and ventured out into the wider waterways — and run into the Red Tide.

In 1996, biologists were at first baffled about what was killing so many manatees. Eventually, once the Red Tide bloom dissipated, the die-off ended, which helped solve the mystery. Biologists figured out that the manatees were breathing in the toxins from the algae bloom, producing the spasms and paralysis that led to their death.

This time, Dewit said, scientists believe the toxins have settled onto the sea grass that the manatees eat, so when they feed they become paralyzed and drown.

Unfortunately, she said, that means that even after the Red Tide bloom ends, the sea grass beds are likely to retain their poisonous coating for another two months, extending the die-off that much longer.

Craig Pittman can be reached at craig@tampabay.com



Up to

5,000

Estimated statewide manatee population

392

Manatees killed last year from all causes

151

Manatees killed by Red Tide in 1996 (record)

146

Manatees killed by Red Tide in 2013 (as of Friday)



About Red Tide

Red Tide is a higher-than-normal concentration of microscopic algae. The blooms stain the water a rusty tint and can kill fish, manatees, dolphins and other marine creatures. The algae contains at least 12 different toxins that can also be harmful to humans, particularly those with respiratory problems. No one knows what spurs the algae growth that produces a Red Tide bloom, but it can wreak havoc with the state's fishing and tourism industry.