Researchers have linked brain degeneration in stranded bottlenose dolphins to toxins from ocean blooms, mirroring Alzheimer’s disease in humans. The study, focusing on dolphins from Florida’s Indian River Lagoon, highlights the role of climate change and pollution in worsening these blooms. This discovery raises concerns for both marine life and human health.
For decades, scientists have puzzled over why dolphins and whales strand on beaches, often appearing disoriented. A new study suggests that bottlenose dolphins may suffer from an Alzheimer’s-like condition caused by exposure to cyanobacterial toxins. These microscopic organisms thrive in warm, nutrient-rich waters, producing harmful compounds that accumulate in the marine food chain and reach top predators like dolphins.
The research team, including experts from the Hubbs-SeaWorld Research Institute in Melbourne Beach, Florida, the University of Miami Miller School of Medicine, and Brain Chemistry Labs in Jackson Hole, Wyoming, examined the brains of 20 bottlenose dolphins that stranded along Florida's Indian River Lagoon. They detected significant levels of β-N-methylamino-L-alanine (BMAA) and its relatives, 2,4-diaminobutyric acid (2,4-DAB) and N-2-aminoethylglycine (AEG). Dolphins stranding during peak cyanobacterial bloom periods had up to 2,900 times more 2,4-DAB than those from other times.
The dolphins' brains showed pathological features akin to human Alzheimer’s, including β-amyloid plaques, hyperphosphorylated tau proteins, and TDP-43 protein inclusions. Additionally, 536 genes were expressed in patterns consistent with the disease. Cyanobacterial blooms are lengthening due to climate warming and nutrient pollution from agricultural runoff and sewage, often releasing toxin-laden waters from Lake Okeechobee into the Indian River Lagoon via the St. Lucie River.
"Since dolphins are considered environmental sentinels for toxic exposures in marine environments," explained Dr. David Davis at the University of Miami Miller School of Medicine, "there are concerns about human health issues associated with cyanobacterial blooms." In 2024, Miami-Dade County reported the highest Alzheimer’s prevalence in the United States. "Although there are likely many paths to Alzheimer’s disease, cyanobacterial exposures increasingly appear to be a risk factor," Dr. Davis added. Dr. Paul Alan Cox of Brain Chemistry Labs noted, "Among Guam villagers, exposure to cyanobacterial toxins appeared to trigger neurological disease."
The findings were published in Communications Biology on October 11, 2025.