A deadly algae toxin called domoic acid is doing some serious damage to sea lions along California’s coast. A group of scientists has found that the toxin is causing permanent behavioral and neurological changes in sea lions. It impairs the marine animals’ ability to navigate and survive out in the wild. The discovery explains why hundreds of sea lions are found stranded on California beaches every year.
The algae see the largest bloom on record
Findings of the study were published Monday in the journal Science. The stranded animals showed signs of domoic acid poisoning. Scientists believe that thousands of these animals have been exposed to the toxin. Microscopic algae called Pseudo-nitzschia bloom in coastal waters. Though the toxic algae usually bloom in the spring and fall, their blooms have become more severe and frequent in recent years.
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This year, the toxic algae witnessed the largest bloom on record, extending from Santa Barbara to Alaska. Researchers also believe that rising ocean temperatures and pollution from chemicals contribute to the algal bloom size and frequency. Scientists led by Peter Cook of Emory University, who worked on the study while at the UC-Santa Cruz, studied 30 sea lions undergoing care and rehabilitation at the Marine Mammal Center in Sausalito.
It affects sea lions’ ability to survive in a complex environment
They performed brain scans and various behavioral tests to assess the animals’ spatial memory and the extent of brain damage. Scientists found that the affected animals’ hippocampus was severely damaged. The hippocampus is a part of the brain associated with spatial navigation and memory. Sea lions navigate in a changing and complex environment. So, impaired spatial memory affects their ability to survive in the wild.
The affected sea lions showed impaired performance on long-term as well as short-term spatial memory tasks. The connectivity between hippocampus and thalamus, which is responsible for sensory perception and regulation of motor functions, was also greatly reduced. Domoic acid accumulates in fish and shellfish that consume algae. And then sea lions and other marine animals consume these shellfish and fish.