By Saundra Amrhein
TAMPA, Florida (Reuters) - A deadly algae bloom that killed a record number of manatees has dissipated, though the death toll for the endangered sea mammals continues to rise, Florida wildlife officials said on Thursday.
Red Tide has killed 241 manatees this year as of Wednesday, said Kevin Baxter, spokesman for the Florida Fish and Wildlife Research Institute in St. Petersburg, Florida. The figure already surpasses the highest number of Red Tide manatee deaths on record in Florida - 151 in 1996.
This year's fatalities from Red Tide will likely continue into the spring because the algae bloom's deadly toxins have settled on the sea grasses that the manatees eat, Baxter said.
"In the past, when we've seen Red Tide-related deaths, they've continued on for a month or two after the Red Tide bloom is no longer detected," he said.
Naturally occurring algae sometimes grow out of control for unknown reasons, turning the water red and producing high concentrations of toxins that can harm people, fish, birds, sea mammals and shellfish.
This recent Red Tide bloom began last fall in the Gulf of Mexico in a 70-mile (113-km) swath of southwest Florida's coast from Sarasota County to Lee County - home to a large share of the state's estimated 5,000 manatees.
The toxins are usually inhaled by manatees when they come up for air, typically every 20 minutes. Because the toxins settled into the sea grasses, the manatees were ingesting them as well.
Inhaling or eating the toxins can spark seizures and paralyze the manatees, causing them to drown as they struggle to breathe or surface for air.
Meanwhile scientists are trying to discover the cause of the mysterious deaths of 85 manatees since July on Florida's Atlantic coast in the Indian River Lagoon in Brevard County, Baxter said.
While Red Tide was not present, experts believe that consecutive algae blooms of another sort had destroyed sea grasses, possibly forcing the manatees to turn to other food sources.
"We're looking at changes in their feeding patterns from the loss of sea grass," Baxter said.
A total of 463 manatees have died this year as of March 29, Baxter said, though that number will go up because it doesn't include the most recent Red Tide-related deaths. The record year for manatee deaths was 2010, when 733 died, including about 300 from record cold temperatures.
Back on the Gulf Coast, 12 manatees that were rescued and brought to Tampa's Lowry Park Zoo for treatment for Red Tide poisoning will stay in their temporary homes until the coast is clear to return them to the wild. Of those 12, two were sent to Sea World in Orlando and three others went to Homosassa Springs Wildlife State Park.
The rest remain at the zoo, where they had been brought by a rescue team from the Florida Fish and Wildlife Conservation Commission. The rescued manatees' treatment included an immediate injection of the anti-toxin atropine and the first of three possible antibiotic injections.
In the initial hours after the manatees' arrival, staff members in the zoo's manatee hospital stood in shallow pool water around the clock to help keep the manatees' heads above the water.
The manatees were put on floatation devices and the pools' elevated hydraulic floors so that their bodies were kept moist but their noses were out of the water in the treatment pools.
Many recovered quickly, and after a week, with the toxins passed out of their systems, the manatees were in good condition, said zoo spokeswoman Rachel Nelson. The manatees rescued from Red Tide have settled in with the zoo's several other patients undergoing treatments for other ailments.
"They are doing great," Nelson said.
(Editing by Jane Sutton and Phil Berlowitz)