A new study conducted by researchers at the University of Miami Miller School of Medicine identified clear biomolecular markers of neurodegeneration in dolphin brains, including elevated levels of specific neurotoxins and misfolded proteins typically associated with human dementia. The work focused on dolphins found in the Indian River Lagoon, where harmful cyanobacterial blooms are common during warmer months.
These strandings have long been a mystery. While many assume disorientation or illness, the full causes are rarely understood. Dolphins are considered a sentinel species—organisms whose health reflects the state of the environment—and so this discovery has implications not just for marine biology, but for public health and environmental policy as well. The study suggests that neurotoxins produced by algae may not just harm marine life, but could potentially signal larger risks to humans exposed to the same waters.
Toxic Bloom Season Linked to Brain Changes
The research team, at the University of Miami Miller School of Medicine, examined 20 common bottlenose dolphins stranded between 2010 and 2019, focusing on brain tissue collected during both bloom and non-bloom seasons. The results revealed that dolphins exposed to cyanobacterial blooms carried 2,900 times more of the neurotoxin 2,4-diaminobutyric acid in their cerebral cortex compared to those found during non-bloom periods. According to Earth, this toxin was found to align with significant shifts in gene activity associated with Alzheimer’s pathology.
The dolphins’ brains also contained amyloid beta plaques and abnormal tau proteins, both considered hallmarks of human Alzheimer’s disease. Additionally, the team detected TDP-43 inclusions—a protein tied to faster cognitive decline in human patients, as highlighted in previous neurological reviews. These inclusions were consistently found in the brain samples from the stranded animals.
Disrupted Brain Function in Stranded Dolphins
Beyond chemical exposure, the study published in Nature revealed that neural communication systems in these dolphins were significantly impacted. Researchers noted that genes regulating the GABAergic system, which controls inhibitory synapses, showed marked changes during bloom seasons. This suggests a destabilization of the brain’s ability to manage nerve signal flow, potentially leading to cognitive and motor dysfunctions.
Also affected were the basement membranes—structures supporting blood vessels in the brain and controlling what crosses into brain tissue. According to the researchers, weakening of these protective barriers may lead to leaks, inflammation, and neural damage, compounding the effects of environmental toxin exposure.
Laboratory studies cited also show that 2,4-diaminobutyric acid interferes with nerve cell development in other vertebrates. That, combined with the observed biomolecular signatures, paints a concerning picture for dolphin health in toxin-rich environments.
Environmental Warnings from Sentinel Species
Dolphins occupy a top position in the coastal marine food chain and share close proximity to human coastal activity, making them effective indicators of ecosystem health. According to Dr. David A. Davis, the lead author of the study, the neurological effects observed in dolphins raise public health concerns, particularly in regions frequently affected by harmful algal blooms.
While the study does not claim a definitive cause-and-effect relationship between cyanobacterial exposure and Alzheimer’s disease, it shows a tight seasonal correlation that warrants further investigation. The findings underscore the urgency of monitoring toxin levels during bloom periods and reinforce the need for stronger coastal management strategies, such as improving wastewater and agricultural runoff controls.
The team carried out their research under federal permits, carefully selecting stranded animals and focusing on high-quality RNA samples to ensure robust genetic analysis. The study spanned multiple Florida sub-basins, offering a broad regional view of how environmental stressors might influence marine mammal health.