A mysterious disease that causes fishing in the Florida Keys to spin in circles has sparked a frantic race to find the cause and save an endangered species before it’s too late.
After eight months of hunting scientists, some think a prime suspect has emerged: toxins from algae colonizing the seabed may be causing neurological problems in some species of fish.
Fishermen noticed the bizarre behavior in October, according to Ross Boucek, a fisheries ecologist with the Bonefish & Tarpon Trust, a nonprofit conservation and fisheries group.
“When they turned on the lights, the fish turned upside down and spun all the way to the bottom,” he said.
In the following months, Boucek received reports of stingrays upside down and lemon sharks spinning violently in the mud. Dozens of species have been affected, including the critically endangered sawfish, known for its flat snout with teeth that look like a saw blade.
At least 47 sawfish died, although the number is likely higher, said Michael Crosby, president and CEO of Mote, a nonprofit marine laboratory and aquarium. The price is profound, given that there can only be several hundred fish left in US waters.
An emergency response to rescue the affected sawfish was launched in early April, involving government agencies and non-profit partners. Meanwhile, scientists at several laboratories are trying to figure out what is causing the widespread suffering of marine life.
Recently, tests by researchers identified a cocktail of natural toxins both in seawater and in the tissues of some affected fish.
“The hypothesis I’m working on right now is that the combination of these various benthic algal toxins is coming together to create the phenomenon we’re seeing,” said Alison Robertson, senior marine scientist at the Dauphin Island Sea Lab.
But that’s not a confirmation, she added, and researchers don’t know what caused the algae bloom or toxins. What’s more, other experts are less convinced.
“I honestly don’t think anything can reasonably be ruled out at this point,” Crosby said.
Whatever the researchers ultimately conclude, it could determine what’s on the plates of some Florida restaurants, how fishermen make a living and whether tourists come to visit. The Keys have already suffered several ecological shocks: Hurricane Irma in 2017, record sea surface temperatures last year and mass coral death.
“We’ve been jumping from crisis to crisis here,” Boucek said.
Allison Delashmit, executive director of a fishing group called the Lower Keys Guides Association, said “there’s a lot at stake.”
“Our economy is built on tourism. It’s not a good idea to have a fish spinning in the water and broadcast it without answers as to what it is,” she said.
This puts local scientists under intense pressure to provide answers.
Is it the algae’s fault?
It’s been a grueling eight months for Boucek, whose freezer at home is full of dead fish that he plans to send off for testing. He compared the effort to “a final exam that you forgot and never studied for before, and you have two hours to learn everything.”
When work began, he said, the most likely explanations for the fish’s bizarre behavior did not materialize. Oxygen levels in the water were normal. There were no signs of red tide. Pollutant tests found nothing out of the ordinary.
Boucek calculated that the exposure was likely due to the water, and when he removed spinner fish from the ocean and placed them in tanks with clean water, some recovered in just 25 minutes.
The only clue was elevated background levels of a genus of algae called Gambierdiscus in water samples.
That clue caught the attention of Michael Parsons, a professor of marine sciences at Florida Gulf Coast University and an algae expert who has been collecting algae in the Keys for more than a decade. In February, Parsons discovered that Gambierdiscus cell levels were about four times higher than he had ever recorded.
Robertson, an environmental toxicologist, refocused his lab to respond to the crisis and has been working seven days a week. She estimates that her team has performed more than 5,000 analyzes of algae, seawater and the muscles, livers, kidneys and stomachs of a variety of affected fish species.
Their work revealed toxins known to affect fish behavior, as well as some potential new toxins that had never been seen before in the Keys.
“The things we found in benthic algae we also found in many fish samples,” Robertson said.
She suspects that a “cocktail” of deep-sea algae toxins, potentially from multiple species, is combining to cause the fish’s strange behavior, although she said there is “no definitive proof yet.” The toxins may also be interacting with other environmental toxins, she said.
Efforts to save the sawfish
Meanwhile, other scientists rush to help the struggling sawfish.
In early April, the Mote team rescued a 12-foot male sawfish that was swimming in circles in Cudjoe Bay. They loaded the fish onto a boat, took it to a quarantine facility with clean, filtered seawater and infused it with antibiotics, lipid compounds and other treatments, according to Crosby.
“If you can put it in human terms, a patient was taken to intensive care,” he said.
The fish stabilized and “was starting to swim in a more natural pattern,” Crosby said.
But two weeks later, the animal’s health deteriorated and it had to be euthanized.
“We were clearly moving in a positive direction, but the internal organs were very worn out,” Crosby said.
He added that he hasn’t seen enough evidence to convince him that algae is to blame. The results of the necropsy (an animal’s autopsy) are still pending, but could offer important information because researchers were able to perform tests soon after death. Mote also plans to try to rescue more sawfish.
There are other reasons for hope too.
Robertson said this episode doesn’t seem to represent the downfall of an entire ecosystem.
Other important species are doing well, including barracuda, bonefish and tarpon, which appear to be unaffected, Boucek said.
Florida lawmakers also agreed to spend $2 million on fish research in the Keyswhich could help scientists get answers faster.
“As so many scientists are coming together to solve this issue, we will be able to figure out what is going on and find mitigation strategies and solutions,” Robertson said.
This article was originally published in NBCNews. with
