Study shows how algal toxin damages sea lions’ brains and behavior

A new study shows that a neurotoxin produced by algae disrupts the memory of California sea lions, animals that rely heavily on recall of food-rich locations to forage.

Brain scans on 30 California sea lions found damage in the part of the brain that handles memory and helps with navigation. Peter Cook, lead author of the study and now a postdoctoral researcher at Emory University, started studying domoic acid nearly a decade ago as a graduate student at the University of California at Santa Cruz.

Thousands of sea lions have turned up on West Coast beaches in bad condition this year. The result of the study showed that domoic acid may be to blame for the dozens of sea lions and pups that seemingly have a poor spatial memory. Their blooms – a term used to describe rapid spread of algae – have grown more frequent and severe. The algal blooms that produce this toxin, called domoic acid, flourish under the warmer waters brought about by climate change.

According to UC-Davis professor and co-researcher Charan Ranganath, the study serves as the “missing link” between environmental degradation that causes toxic algal blooms and incidences of sea lions getting beached, or stranded.

“Every year since – for the last 17 years – there have been sick and dying sea lions, sometimes in the hundreds”, Kathi Lefebre of the National Oceanic and Atmospheric Administration said according to The Guardian.

“We didn’t know exactly why the algae lead to strandings”.

“This is the first evidence of changes to brain networks in exposed sea lions, and suggests that these animals may be suffering a broad disruption of memory, not just spatial memory deficits”, Cook said. They found that the animals had suffered significant damage in the hippocampus, the region of the brain associated with memory and spatial navigation. They even found negative effects on interactions between the hippocampus and other brain structures of the sea lions. Here, the toxin can lead to seizures, which then harms the brain.

Basically, the sea lions have no sense of where to go and have difficulty finding food, which obviously threatens the creature’s survival.

Shawn Johnson, who serves as the Marine Mammal Centre’s director of veterinary science but wasn’t involved in the study, explained that the rescue group has seen some freakish things in recent years.

The algal toxin affects not only sea lions, but dolphins, fur seals, sea otters, and other species. “Sea lions navigate a complex and changing environment, and if their spatial memory is impaired, it’s bound to affect their ability to survive in the wild”.

“The guys with hippocampal damage were sort of lost at sea”, Cook says.

Still researchers are not sure how heavy and how often exposure to algan toxic cause this kind of brain damage.

Only one human has ever developed temporal lobe epilepsy following exposure to domoic acid.