Emaciated and disoriented sea lion pups have been rescued by the dozen from the beaches of California. Many are taken to a rehabilitation center in Sausalito. Photo by Marine Mammal Center
DAVIS, Calif., Dec. 15 (UPI) -- Seal lions along the coast of California are suffering permanent brain damage as a result of exposure to toxins from algae blooms. Researchers believe the damage may explain the uptick in sea lion strandings over the last year.
The revelations are a result of brain scans and behavioral research conducted by scientists at the Marine Mammal Center, University of California, Davis and the University of California, Santa Cruz. Researchers published their findings in a new study, published this week in the journal Science.
Algae blooms can produce a number of toxins, but domoic acid is the one of concern. Its presence off the California coast has forced regulators to put an indefinite hault on the state's crab harvest, and now brain scans show the toxin may be responsible for brain lesions among sea lions.
To measure how lesions may be affecting sea lions, researchers developed maze-like behavioral tests similar to those used to measure the memory abilities of rats.
"In this study, we were able to correlate the extent of hippocampal damage to specific behavioral impairments relevant to the animals' survival in the wild," study author Peter Cook, a former Santa Cruz grad student now at Emory University, said in a press release.
The results showed sea lions with hippocampus damage performed poorly on short- and long-term spatial memory testing. This may explain why sea lions are increasingly found disoriented on California beaches, and are being found in areas where sea lions are rarely seen.
Researchers likened the combination of structural damage and behavioral symptoms observed in affected sea lions to Alzheimer's disease.
The brain scans also showed that in addition to hippocampus damage, exposure to domoic acid hampered connections between the hippocampus and other parts of the brain.
"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.
