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5 hours ago
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Scientists have uncovered a disturbing link between stranded dolphins and a toxin known to trigger Alzheimer's-like brain damage, which could have implications for millions of people along the US coast.
Researchers examined 20 dolphins that washed up along Florida's Indian River Lagoon and found high levels of a brain-damaging chemical produced by cyanobacteria, also called blue-green algae.
These microscopic organisms release compounds that are highly toxic to nerve cells, damaging the brain regions responsible for memory, thinking and communication.
Dolphins stranded during peak algae blooms had up to 2,900 times more of the toxin than those found at other times of the year.
Their brains also showed hallmark signs of Alzheimer's disease, including sticky protein clumps and tangled fibers, which impair brain function and can lead to memory loss and confusion.
Dr David Davis of the University of Miami's Miller School of Medicine explained: 'Since dolphins are considered environmental sentinels for toxic exposures in marine environments, there are concerns about human health issues associated with cyanobacterial blooms.'
In 2024, Miami-Dade County recorded the highest prevalence of Alzheimer's disease in the nation, highlighting a potential connection between human exposure and these harmful toxins.
'While Alzheimer's likely has many causes, cyanobacterial exposure is increasingly emerging as a significant risk factor,' Davis added.
Scientists have discovered a link between stranded dolphins and a toxin known to trigger Alzheimer's-like brain damage (STOCK)
Scientists found the hallmarks of Alzheimer's in the brains of all the dolphins tested, including misfolded tau proteins (center), amyloid plaques (left) and tangled fibers (right) that destroy neural connections
Cyanobacteria, also known as blue-green algae, are microscopic organisms that thrive in warm, nutrient-rich waters, especially where agricultural runoff and sewage introduce high levels of nitrogen and phosphorus.
During 'blooms,' these organisms multiply rapidly, turning waterways bright green or blue-green and releasing toxins into the surrounding water.
While these blooms may look harmless, they produce a range of toxins, including β-N-methylamino-L-alanine (BMAA) and its chemical relatives 2,4-Diaminobutyric acid (2,4-DAB) and N-2-aminoethylglycine (AEG), which are highly toxic to nerve cells.
Researchers noted that over time, the exposure can lead to the same type of brain changes seen in Alzheimer’s disease, including misfolded tau proteins, amyloid plaques and tangled fibers that destroy neural connections.
The link between these toxins and neurodegenerative disease is not just theoretical.
'Research involving residents of Guam has shown that people who regularly consume foods containing cyanobacterial toxins are more likely to develop the same brain abnormalities seen in Alzheimer's disease,' the team shared in a press release.
The brains of affected individuals showed the same protein misfolding and plaque formation that occurs in Alzheimer’s patients worldwide.
Experiments in laboratory animals have confirmed these findings, demonstrating that prolonged exposure to BMAA can induce cognitive decline and brain lesions virtually identical to those observed in Alzheimer’s disease.
The team studied 20 dolphins stranded on the shores of Florida 's Indian River Lagoon, finding they all had signs of Alzheimer's
In dolphins, the situation is particularly alarming, as top predators in marine ecosystems, dolphins are highly susceptible to bioaccumulation, the process by which toxins build up in the bodies of animals at the top of the food chain.
Small fish and invertebrates ingest cyanobacterial toxins, and these compounds gradually concentrate as they move up the chain. By the time they reach dolphins, the levels can be extremely high.
Researchers at the Hubbs-SeaWorld Research Institute in Melbourne Beach, Florida, along with collaborators at the University of Miami and the Blue World Research Institute, analyzed the brains of 20 bottlenose dolphins stranded from 2010 to 2019.
They found dolphins that washed ashore during periods of peak algae blooms had up to 2,900 times more 2,4-DAB in their brains than dolphins stranded at other times of the year.
The brains displayed many hallmark signs of Alzheimer’s disease, including sticky β-amyloid plaques, hyperphosphorylated tau proteins and TDP-43 protein inclusions, a marker of more aggressive neurodegenerative forms.
Scientists also identified changes in 536 genes that correspond to patterns associated with Alzheimer’s in humans.
The problem is worsening with climate change and increased nutrient runoff, as warmer water temperatures and prolonged sunlight create ideal conditions for cyanobacteria to bloom more often and for longer periods.
In Florida, water released from Lake Okeechobee into the St Lucie River and Indian River Lagoon has repeatedly carried high concentrations of cyanobacteria downstream, creating large areas of toxic water.
For dolphins navigating these waters, long-term exposure is practically unavoidable.
'Since dolphins are considered environmental sentinels for toxic exposures in marine environments, there are concerns about human health issues associated with cyanobacterial blooms,' Davis said.
