Toxic Algal Blooms Linked To Alzheimer's-Like Brain Changes In Dolphins


Rachel Baxter

Copy Editor & Staff Writer

The researchers studied a mixture of common dolphins (pictured) and bottlenose dolphins. COULANGES/Shutterstock

Toxic algae could be having a worrying effect on dolphins’ brains. A recent study found that a majority of dolphins washed up on America’s East Coast had high levels of algal toxins in their brains, accompanied by signs of neurodegeneration similar to that seen in human patients with Alzheimer’s disease.

Toxic algal blooms contain a neurotoxin called β-methylamino-L-alanine (BMAA), which has previously been linked to β-amyloid, a protein involved in Alzheimer’s, in nonhuman primates. What’s more, signs of BMAA have also been spotted in the brains of deceased people who suffered from Alzheimer’s and amyotrophic lateral sclerosis (ALS), a neurodegenerative condition often referred to as motor neurone disease or Lou Gehrig’s disease.


Publishing their findings in the journal PLOS ONE, a team led by the University of Miami examined the brains of 14 stranded dolphins. Thirteen of them contained noticeable levels of BMAA. The animals also showed signs of Alzheimer’s-like neurodegenerative changes, which may be linked to the build-up of toxin in their brains.

The researchers note that Florida’s dolphins are often exposed to harmful algal blooms both directly and via eating creatures that have been exposed to the algae’s toxins. Half of the dolphins tested were found on Florida’s coastline at sites known for experiencing recurring algal blooms. The remaining seven dolphins were found washed up in Massachusetts. The animals were a mixture of bottlenose (Tursiops truncates) and common (Delphinus delphis) dolphins.

The quantity of BMAA found in the dolphins’ brains was 1.4 times greater than levels observed in the brains of human patients with Alzheimer’s and ALS. The Florida dolphins also contained three times as much BMAA as the Massachusetts cetaceans, which may be down to differences in their diets or a greater presence of harmful algal blooms in Florida’s waters.

It’s important to note that the findings don’t imply that BMAA causes neurodegeneration in dolphins, but there may be a link between the two. The researchers point out that as our climate continues to warm, the issue could be exacerbated as toxic algal blooms are becoming more frequent and lasting longer, particularly in North America and eastern China. What’s more, the results indicate that humans exposed to BMAA, such as those living near water, could suffer a similar fate.


“This isn’t animals being fed a certain dose over a certain amount of time. It’s naturalistic exposure,” lead author David Davis told the Miami Herald. “If you have these ... dolphins feeding in the same marine food web as humans, potentially eating the same things as humans, that’s why we say it serves as a sentinel.”

Future research will hopefully reveal more about the risks associated with BMAA for both humans and animals living in areas where toxic algae thrive.