Wildlife

Toxic Marine Algae Causing Brain Damage In California Sea Lions

Massive blooms of toxic algae, also known as red tides, may have led to brain damage contributing to the stranding of thousands of sea lions on California beaches, researchers say.

The algal bloom that has spread from California waters all the way to northern Washington is releasing domoic acid, which can be toxic to humans and to marine mammals who consume concentrations of it in crabs, oysters, mussels, sardines and anchovies, they explain.

Sea lions exposed to the neurotoxin can suffer damage to their spatial memory, leading to them becoming confused and lost as they search for increasingly diminishing sources of food, the researchers report in the journal Science.

They conducted a series of tests on 30 sea lions that had been rescued after being stranded on state beaches, putting them through a simple maze to see if they could navigate it to find a food reward.

The animals exhibited a significant loss in spatial memory, the researchers found.

The massive blooms of algae are occurring in waters off the California coast that are as much as 6 degrees warmer than usual, the researchers say, and climate change is likely an important factor.

The first signs that California's sea lions were being affected by the algae toxin came in 1998 when hundreds washed ashore in Monterey Bay, and strandings of the marine mammals, often showing signs of confusion and seizures, have been seen almost every year since then.