They are intelligent, social and able to orient themselves with surprising precision. Yet, more and more often, dolphins end up stranded on the coasts of Florida, disoriented or already lifeless. For years, scientists have wondered why. Now research published in Nature Communications Biology suggests an explanation: these animals could become ill with a form of Alzheimer’s, triggered by toxins produced by algal blooms.
The research team, coordinated by David A. Davis of the University of Miami together with the Brain Chemistry Labs in Wyoming, analyzed the brains of twenty bottlenose dolphins found dead along the Indian River lagoon, a large coastal area subject to cyanobacterial blooms for years. The findings tell us that during peak flowering periods, dolphin brains contained up to 2,900 times more 2,4-diaminobutyric acid (2,4-DAB), a neurotoxin produced by microscopic algae, than in non-flowering months.
This substance, chemically similar to β-N-methylamino-L-alanine (BMAA), is known for its effects on the nervous system. In the dolphins analyzed, the researchers observed β-amyloid plaques, tangles of tau proteins and TDP-43 inclusions: the same abnormalities found in the brains of humans suffering from Alzheimer’s. Furthermore, 536 altered genes were identified, many of which are involved in synaptic functions, the blood-brain barrier and neuronal inflammation mechanisms.
Cyanobacterial blooms — phenomena that color water green and release toxic compounds — intensify with rising temperatures and excess nutrients from agricultural and urban waste. In an environment like the Indian River lagoon, heated and rich in nitrogen and phosphorus, algae proliferate rapidly, releasing substances into the sea that accumulate in the food chain until they reach top predators, such as dolphins.
“These animals are true environmental sentinels,” Davis explained. “They show us how toxic substances present in marine ecosystems can affect the health of organisms, including humans.”
Global warming and water pollution are therefore creating a dangerous biological entanglement. Warmer seas encourage toxic blooms, toxins accumulate in fish and marine mammals, and long-term damage affects the brain.
The study does not prove that algal toxins are the sole cause of Alzheimer’s, but indicates that they may be an environmental risk factor.
