Dolphins may be getting an Alzheimer’s-like disease due to this neurotoxin
For marine biologists, dolphins are often considered sentinel species, or animals that shed light on the health of the ocean. Along with whales, porpoises and other cetacean species, dolphins are one way researchers know how to sound the alarm about environmental dangers that could affect the ocean as a whole and potentially humans.
In this context, researchers linked neurotoxins from algal blooms to brain changes associated with Alzheimer’s-like disease in Florida dolphins. This link does not bode well for human communities exposed to these same substances.
“These findings are concerning because dolphins share coastal waters with humans and face the same environmental risks as we do,” Wendy Noke Durden, a researcher at the Hubbs-SeaWorld Research Institute’s Florida laboratory, said in an emailed statement to Popular science.
Algae are tiny photosynthetic organisms that live in natural bodies of water, and an algal bloom occurs when the density of algae increases rapidly. Some types of algae produce toxic substances called toxins. Among these, neurotoxins specifically impact the body’s nervous system.
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In a study published in the journal Communication biologyDurden and colleagues show that dolphins found stranded during an algae bloom in the Indian River Lagoon along Florida’s Atlantic coast had an alarming amount of a neurotoxin called 2,4-diaminobutyric acid (2,4-DAB) in their brains. University of Miami neurotoxicologist and study co-author David Davis says Popular science that 2,4-DAB has a chemical structure similar to BMAA, a cyanobacterial neurotoxin associated with neurodegeneration. It’s also important to note that although cyanobacteria are often called “blue-green algae,” they are not actually algae. Davis says harmful algal blooms are a broad term that includes different species.
Dolphins that stranded during the summer algae bloom season had 2,4-DAB concentrations 2,900 times higher than those in non-bloom seasons. Those who had a higher concentration of this neurotoxin also had more severe changes in their brain chemistry and tissues, associated with the early stages of Alzheimer’s disease. These include an unusual accumulation of insoluble proteins and alterations in important genes linked to memory, brain health and Alzheimer’s disease risk. Additionally, these results were consistent for dolphin strandings for almost a decade, and the changes were more drastic with each algal bloom season.
Given dolphins’ identity as a sentinel species, “there are concerns about human health issues associated with cyanobacteria blooms,” Davis explained. “While there are likely many pathways to Alzheimer’s disease, exposure to cyanobacteria increasingly appears to be a risk factor.”
Additionally, global warming, nutrient pollution and sewage will continue to intensify these harmful algal blooms, he adds. There is therefore a need for more research into the consequences of harmful algal blooms and exposure to their toxins.
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