FORT MYERS, Fla. — Southwest Florida is no stranger to harmful algal blooms, including a recent one in Gator Slough. Now, new research on dolphins in the Indian River Lagoon on Florida's east coast suggests these blooms may be connected to neurological diseases such as ALS, Parkinson's, and Alzheimer's.
The study, led by Dr. David Davis from the University of Miami's Miller School of Medicine, examined what long-term exposure to algal toxins may be doing to marine life — and what that could mean for humans living near the water.
Dolphin brain tissue shows high levels of neurotoxin
Researchers analyzed brain tissue from beached dolphins collected between 2010 and 2019, comparing samples taken during algal bloom season with those from non-bloom periods.
"What's very interesting is seeing how algal toxins that we know produce neurological effects impact dolphins and their brains," Davis said.
One of the most concerning findings involved a toxin called 24DAB, which acts like an inhibitory amino acid and can interfere with how neurons communicate.
Davis found that concentrations of 24DAB were 2,900 times higher in dolphins stranded during bloom season. His team also discovered changes in gene expression resembling those found in human Alzheimer's patients.
"We saw that dolphins stranded during algae season had an increased signature of Alzheimer's disease-related genes," Davis said.
"We also found that the expression of some of these genes correlated with toxin concentrations," he said.
Possible implications for humans
While Davis cautions that dolphin findings cannot be directly applied to humans, his team is exploring whether similar exposure risks exist for people — especially those who live close to waterways in Florida.
A similar South Florida study examined human brains donated to science. Those who lived near the water had olfactory nerves saturated with algal toxins.
"We measured three algal toxins in that study," Davis said.
"The striking thing was that individuals with early-stage Alzheimer's, who were still active and out in the community, had much higher toxin levels than those in late stages," he said.
With Florida's large elderly population, Davis says these findings highlight a potential environmental risk that deserves further investigation.
"These types of environmental exposures are probably not good for people at risk of developing neurological diseases or those already living with Alzheimer's," he said.
Why dolphins may be stranding
The team is still studying how exactly these toxins impact dolphin behavior, but one leading theory is that neurotoxins may disrupt how dolphins hear and use sonar — possibly contributing to strandings during bloom events.
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