The Red Tide algae bloom blamed for killing more than 200 manatees this year appears to have finally dissipated, according to state wildlife officials.
However, the manatee deaths are likely to continue for a while, said Kevin Baxter of the Florida Fish and Wildlife Research Institute in St. Petersburg.
"Once the bloom has disappeared we typically see manatee deaths from Red Tide continue for a couple of months," Baxter said.
That's because the toxins in the Red Tide settle onto sea grass eaten by the manatees, biologists say.
This year's deaths broke the record for manatees killed by Red Tide, set in 1996, with 151.
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 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. The bloom that killed off so many manatees this year appeared last fall along 70 miles of the southwest Florida coast, extending along the shores of Sarasota County south to Lee County, and hung on until March.
Meanwhile, even though there is no Red Tide bloom on Florida's Atlantic Coast, another 80 or so manatees have died in the Indian River Lagoon in Brevard County. Scientists have been searching for the cause, Baxter said.
They suspect the deaths may be connected to back-to-back blooms of a harmful algae, one that has stained the Indian River Lagoon a chocolate brown. Over two years the blooms wiped out some 31,000 acres of sea grass in the 156-mile-long lagoon that stretches along the state's Atlantic Coast. Manatees eat sea grass, but with the grass gone, they may have turned to less healthful sources of nutrition.
It's possible they won't be able to figure it out, said Pat Rose, a manatee biologist and president of the Save the Manatee Club.
"Occasionally things will just stop and you don't know the cause," he said.
The 207 Red Tide deaths and the deaths in the Indian River Lagoon have pushed the total number of manatee deaths this year to 426 as of Friday, Baxter said. That's roughly 10 percent of the estimated manatee population in Florida.
Whether the number of manatee deaths this year breaks the record "depends on how the whole year goes," Baxter said.
The number so far this year has already topped the number of manatees that died all of last year. The deadliest year on record, 2010, saw 766 manatees killed, nearly 300 of them by a record cold snap.
Manatees have been on the federal endangered species list since the list was created in 1967 — although a libertarian group, the Pacific Legal Foundation, working on behalf of the antiregulation group Save Crystal River, has petitioned for the U.S. Fish and Wildlife Service to downgrade their status to threatened. Manatees have been protected by state law since 1893.
Craig Pittman can be reached at [email protected]