Some dolphins found stranded on beaches may have ended up their because they suffer from a form of Alzheimer’s disease linked to toxins in the water.
This is the conclusion of a study led by researchers from Florida’s Hubbs-SeaWorld Research Institute, who suspect that—just like some adult humans with dementia are occasionally found wandering far from their homes—dolphins may become similarly disoriented when suffering from Alzheimer’s.
Their findings, published in the journal Communications Biology, point to chronic exposure to toxins produced by microorgansims known as cynobacteria—which are frequently found in freshwater, estuarine and marine waters—as a possible trigger.
The cyanobacterial toxin β-N-methylamino-L-alanine (BMAA), as well as its isomers 2,4-diaminobutyric acid (2,4-DAB), and N-2-aminoethylglycine (AEG), have been found to be extremely toxic to neurons.
BMAA triggers Alzheimer’s-like neuropathology and cognitive loss in experimental animals. These toxins can be biomagnified as they accumulate up the food chain in the marine ecosystem towards top predators like dolphins.
The resarcher’s study, which involved 20 common bottlenose dolphins stranded in the Indian River Lagoon in eastern Florida during the summer cyanobacterial bloom season, identfied markers of Alzheimer’s disease.
The duration of cyanobacterial blooms is increasing due to climate change and nutrient pollution from agricultural runoff and sewage discharges. Cyanobacterial-laden waters have often been released down the St. Lucie River from Lake Okeechobee into the Indian River Lagoon, intensifying exposure risks even in humans.
“Since dolphins are considered environmental sentinels for toxic exposures in marine environments, there are concerns about human health issues associated with cyanobacterial blooms,” said paper author and neuropathologist Dr. David Davis of the University of Miami said in a statement.
Studies of villagers on the island of Guam show that chronic dietary exposure to cyanobacterial toxins are associated with misfolded tau proteins and amyloid plaques characteristic of Alzheimer’s disease.
“Among Guam villagers, exposure to cyanobacterial toxins appeared to trigger neurological disease,” explained Dr. Paul Alan Cox, of the Brain Chemistry Labs in Jackson Hole, in a statement.
In 2024, Miami Dade County had the highest prevalence of Alzheimer’s disease in the United States.
“Although there are likely many paths to Alzheimer’s disease, cyanobacterial exposures increasingly appear to be a risk factor,” adds Dr. Davis.
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