San Diego sea lions continue to be affected by neurotoxins from an unusually large algae bloom.
The bloom that created the domoic acid appears to have occurred in the open ocean off the Santa Barbara and Ventura County coasts. The Channel Islands Marine & Wildlife Institute had more than 1000 reports of sickened or dead sea lions in that region in early June.
Locally, SeaWorld’s marine mammal rescue team has taken in more than 20 sea lions suffering after ingesting the toxin.
Rescuers picked up the sick animals after being contacted by people who noticed them acting strangely.
Domoic acid can create seizures, sluggish behavior and aggression in the affected animals. It can also cause death.
Half of the federally-protected marine mammals that were rescued in San Diego did not survive.
“The care teams find a little bit of comfort in the fact that we’re doing everything we can to help them and we know that we’re going to lose some,” said Kelsey Herrick, a SeaWorld veterinarian.
Herrick said the toxin can create permanent damage to the part of the brain that impacts memory making it impossible for the marine mammals to survive in the wild.
Some of the sea lions in SeaWorld’s care were euthanized to prevent suffering.
Federal officials warn beachgoers and onlookers to give animals that appear to be sick plenty of room because the sea lions can be dangerous.
“When they’re affected by the toxin they can act very weird,” Herrick said. “They can act really disoriented. They can act overly aggressive. They can act like they don’t even see you. They can act blind.”
SeaWorld officials said people should be wary around sea lions that look sick or are acting in an unusual way. People who see a sick animal should call the marine mammal rescue center at SeaWorld so the mammal can be taken into custody for treatment.
The toxin comes from a large, fast-growing algae bloom in the open ocean.
The rapid growth of the algae Pseudo-nitzschia creates a neurotoxin that damages the brains and hearts of infected animals.
Smaller fish and squid eat the poisonous algae and those smaller animals pass the toxin up the food chain when dolphins and sea lions feed on them.
Sea Lions can eat large quantities of infected animals in a relatively short period of time, and the more toxins they consume, the sicker they get.
“It really started offshore, which we knew because we didn’t see it at any of our nearshore monitoring sites,” said Clarissa Anderson, executive director of Southern California Coastal Ocean Observing System.
Scientists noticed the outbreak in early June around the Ventura and Santa Barbara county shores.
“The bloom may have been in the water for weeks before we started seeing animals strand,” Anderson said. “There is this kind of delay because they’re feeding on animals that are feeding on other animals and it does take time for that to propagate up and throughout a food web.”
Because the bloom was so large, the poisoning of sea lions spread to the Los Angeles and San Diego coast in later June.
The toxic blooms are typical in the spring because of sunshine, warmer ocean waters, and upwelling which brings nutrients that feed the algae closer to the surface.
The ocean conditions that are ripe for the blooms do change in the summer.
“For Southern California in particular, as we move into July, upwelling should go down quite a bit,” Anderson said. “I would just say in terms of the seasonal climatology we should be starting to move out of the time where these blooms are particularly common.”
Even though the offshore bloom might be subsiding, the impact on local marine mammals could linger through the summer.
Anderson said scientists do not fully understand why large blooms happen but a warming ocean could lead to an increasing number of toxic algae blooms in coming years.
