Dozens of sick sea lions found off the Monterey coast are being treated at the Marine Mammal Center. The culprit, officials say, is domoic acid.
Domoic acid is naturally occurring in algae blooms. Scientists say it's all part of the food chain - certain species of phytoplankton need the acid to survive. But now researchers say there may be some indication that humans may also be causing domoic acid to be produced in higher concentrations
At least 35 sick sea lions were found stranded on the Monterey Bay. They were convulsing with seizure-like symptoms. Biologists say that's just one side effect to high concentrations of domoic acid. The neurotoxin is produced by a specific phytoplankton species.
"Lab studies show that this domoic acid actually serves a function of their lives, for example acquiring limited amount of iron that's in the water that they need for growth, or detoxifying copper so that they can grow," said John Ryan, biological oceanographer with the Monterey Bay Aquarium Institute.
Ryan says the high amount of the toxin in the ocean could be natural.
"However, researchers are also finding that affects of human waste runoff for example, can affect the degree to which these microscopic algae become toxic and produce domoic acid," said Ryan.
Scientists at the Sausalito-based Marine Mammal Center said most of the sick sea lions they are seeing are treatable. They say the mammals are primarily poisoned by eating anchovies and sardines, which consume the algae that has the acid. Doctors say the toxin attacks parts of the brain, which causes seizures.
"Their whole body convulses uncontrollably," said Ryan.
Researchers say the acid can have the same effect on humans. Ryan says a lot of the research underway now will help them learn more about the high concentration of acid and where its coming from.
"(Then we will) move towards prediction, and eventually in places where we understand it well enough-- toward mitigation and management, (and) reducing its impacts," he said.
State public health officials say humans shouldn't be eating sardines or anchovies caught off the Monterey Bay because of the high levels of domoic acid. An advisory was set in place two weeks ago warning people not to eat anchovies, sardines or recreationally harvested bivalve shellfish from Monterey or Santa Cruz counties.
The Marine Mammal Center said this year, it's seen a record number of animals needing to be treated. Still, the center was able to release five treated sea lions back out to the bay Monday.