Hakai Magazine

Coastal science and societies

Loggerhead turtle (Caretta caretta)
Loggerheads and other sea turtles are among the marine life affected, and sometimes killed, by blooms of toxic marine algae. Photo Doug Perrine/Minden Pictures

In Florida, Turtles Poisoned by Red Tide Are Getting a New Treatment

Animal rehabilitation experts are looking to a human overdose therapy to treat sea turtles poisoned by toxic marine algae.

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by Amelia Urry

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It was evening when the patient came in. He’d been spotted floating in the surf off a beach in Captiva, Florida, unresponsive and immobile, and was rushed to the nearest clinic. A large adult male at well over 135 kilograms, he was so big that it took several volunteers and staff members to carry the stretcher into the clinic. They had just gotten him into the lobby when his body suddenly stiffened and his eyes began to twitch and roll back into their sockets.

Even after months of back-to-back emergencies, Robin Bast, a veterinarian at the Clinic for the Rehabilitation of Wildlife (CROW), a nonprofit wildlife rehabilitation center in southwest Florida, had never seen anything quite like this before. “None of us had seen a turtle that big have a seizure that long,” she says. “It was sobering.”

The staff at CROW continued to treat the loggerhead turtle throughout the night. But it was too late. The sea turtle, decades old and bigger than a bathtub, did not survive.

Though the loggerhead was the largest patient that Bast and her colleagues treated last summer, it was one of dozens of similar cases. All these endangered sea turtles were suffering from brevitoxicosis, the result of poisoning by a neurotoxin released when a species of algae reproduces quickly and blooms, causing a red tide. Since the current bloom off Florida’s Gulf Coast began in October 2017, more than 300 turtles have been reported dead in the state. CROW alone has taken in more than 50 suffering from the effects of brevetoxin—more than three times the number of turtles they treat in a typical year.

But a treatment borrowed from human medicine may soon give wildlife veterinarians a new tool to deal with these increasingly common red tide poisonings. Treating sick turtles quickly and effectively can be critical for the entire population, Bast says. “It’s really important for these species to breed,” she explains. “So the best thing we can do is get them back out into safe waters as quickly as possible.”

Red tide poisoning affects species from sardines to seabirds. Turtles—including loggerheads and the smaller Kemp’s ridley and green turtles, all federally listed endangered species in the United States—are especially hard hit when a bloom coincides with nesting season, as it did in Florida last year.

The usual treatment for turtles with brevetoxin poisoning is intravenous fluids to help flush the toxin from the kidneys and liver. Antibiotics are often necessary to treat secondary infections. This is reasonably effective, Bast says, as long as the animal receives treatment before too much damage has been done. “The first 24 hours that they’re here are usually the most critical,” she says. CROW’s turtle survival rate last year was just over 60 percent.

Charles Manire, director of research and rehabilitation at the Loggerhead Marinelife Center in Juno Beach, Florida, thinks he might be able to improve that survival rate with a treatment more commonly used in humans suffering from anesthetic overdoses: intravenous lipid emulsion (ILE), a treatment that uses an injection of fatty acids that bind to toxic compounds. “It basically acts like a sponge that soaks up the toxins,” says Manire. Rendered harmless by the ILE, the brevetoxin can then be safely filtered by the liver.

Manire and collaborators at Florida Atlantic University first tested this treatment on red-eared sliders—a common species of freshwater turtle that is not endangered. Just as they’d hoped, the turtles that received ILE were able to recover from brevetoxin poisoning almost immediately.

Last summer, Manire collaborated with CROW, as well as several other marine research centers in Florida, to try the new treatment on suffering sea turtles. “It’s very preliminary at this point,” Manire says, “but it seems like it’s going to be more effective than current treatment standards.”

If it is, ILE will likely become a regular part of Florida’s wildlife veterinarians’ toolkit as they face down future algal blooms, Bast says. CROW treated around 20 turtles with ILE last summer, and the injections are also being tested on seabirds.

The bloom in southwest Florida appears to be waning after more than 14 months, but red tides have been known to last nearly two years. Bast says all of the clinic staff had an exhausting summer struggling to keep up with daily cases of animals suffering and dying. But despite the grim toll, 2018 wasn’t all bad news for Florida’s sea turtles: in red tide hotspot Collier County, for example, nearly twice as many turtle nests had hatchlings compared to the previous year. That’s twice as many chances for the future survival of the species. And every successful release that CROW facilitates, Bast notes, is a victory, too: “Every individual is important for the continuation of the species.”