Things are grim in southwest Florida. A toxic algal bloom is poisoning one of most biodiverse regions in the United States. Hundreds of manatees, turtles and dolphins have washed up dead in the worst red tide since 2006.
Perhaps the most tragic casualties of the algal bloom are the Kemp’s ridley sea turtles, which are not only the most endangered turtle in Florida but also the rarest species of sea turtle in the world. More than 200 Kemp’s ridleys have been stranded in the red tide, and the mortality rate among those is nearly total.
“When we get a deceased sea turtle in, our stranding investigations program here at Mote conducts a thorough necropsy and learns as much as they can about the animal,” said Hayley Rutger at the Mote Marine Laboratory. “Right now, it’s very strongly believed that the Florida red tide is playing a role in the sea turtle mortalities.”
Nearly 100 manatees are dead since January, the result of suspected exposure to red tide toxin, according to Florida Fish and Wildlife Conservation Commission, or FWC. This week alone, responders recovered 12 dead bottlenose dolphins, including one newborn.
“It’s alarming. I think we will see long-lasting effects from this event,” said Gretchen Lovewell, the manager of Mote’s stranding investigations program.
Mote and FWC collect and test the bodies they find. But they also try to save animals on the brink of death. If the animals are recovered alive, they can be housed in rehab facilities until the toxin has passed through their system. Veterinarians use life jackets and pool noodles to keep manatees afloat so they can breathe at the surface of the rehab pools.
The toxic algae settles on the sea grass, the manatee’s main food. Even after the bloom is gone, the toxin may remain in the environment and continue to harm manatees for weeks afterward, according to Martine deWit, a manatee veterinarian at the FWC.
Sea turtles ingest the toxic algae in a similar fashion. Both the turtles and manatees become paralyzed by the algae’s neurotoxin, and their tissues can swell. Because they breathe air, the paralysis prevents them from reaching the surface to breathe. They usually drown, Lovewell said.
The situation in Florida is heartbreaking, but the whiskered faces of surviving manatees, swaddled in red life jackets, gives hope.
“We do this work because there are success stories. You can make difference,” deWit said.
The red tide has fouled the Florida waters since the fall. This red tide is caused by a tiny algae called Karenia brevis, which produces an often-deadly toxin. Algae is an important part of the marine ecosystem, but blooms can get out of control. Red tide starts offshore, but once moved to the coast can be exacerbated by natural or human-caused nutrients, like fertilizer runoff.
“People have really beautiful yards in Florida, and we want to have all of these really nice things,” Lovewell said. “But you know all of this comes at a price.”
Scientists say it’s difficult to know how much longer the bloom will persist. The longest recorded bloom lasted more than a year, from 2005 to 2006.