Hundreds of sea lions treated for domoic acid poisoning in Santa Barbara and Ventura Counties
A bloom of harmful algae is causing hundreds of sea lions to wash up on shore from poisoning in Santa Barbara and Ventura counties.
A harmful algal bloom, or HAB, is when types of algae rapidly grow and cause harmful effects on marine life and people. Central Coast sea lions in particular are affected by a neurotoxin produced by the algae, called domoic acid, which accumulates in shellfish and causes marine mammals to have seizures.
“They can have acute exposure to high levels of toxin that's present and in their food,” said National Centers for Coastal Ocean Science NCCOS Research Scientist Maggie Broadwater, “When they're brought in (to marine rehabilitation facilities), they're provided a clean food source, as they process the toxin and excrete it through urine and feces.”
According to Southern California Coastal Ocean Observing System Executive Director Clarissa Anderson, the diatom pseudo-nitzschia threatens marine ecosystems by producing high levels of domoic acid.
“What makes it a crisis now is we have a particularly acute event that has gone on for many weeks, where the algae continues to bloom and produce this toxin that gets into the base of the food web,” said Anderson.
The toxin is ingested by fish, after which it spreads to sea lions and other marine mammals. Under certain circumstances, it can even pose a risk to humans. Eating contaminated shellfish can cause people to develop amnesic shellfish poisoning, an illness that causes short term memory loss, brain damage, and in severe cases, death.
“It can kill you, and in fact we first realized what this toxin was in the environment in 1987,” said Anderson, “It had killed 10 people who consumed wild caught mussels in Prince Edward island, which is up in Canada.”
However, the current risk for human domoic acid poisoning is low, as the state strictly monitors seafood for biotoxins.
Harmful algal blooms mostly happen as a result of weather conditions and “overfeeding” from land-based nutrients flowing into the ocean. As for the Central Coast, Anderson says it is uncommon for a HAB event on this scale to occur on the Santa Barbara Channel this late in the year.
Researchers are still trying to figure out what is causing this late-September toxic bloom. Climate change and recent heat waves may exacerbate the problem, although that is hard to determine, as many factors contribute to HABs.
“It’s not an easy question to answer. As the temperature goes up, the growth rate increases, but at some point it gets too hot for them, and they stop growing,” said NCCOS Senior HAB Scientist Quay Dortch.
“And then on top of that there are all sorts of things that affect toxicity, like how much rainfall there is and how much nutrients are coming into the coastal zone with the rainfall.”
When it comes to HAB events, there are good and bad years. One of the worst was a domoic acid outbreak during the marine heat wave of 2015 that spread from California all the way up to the coast of Washington.
“It was not just sea lions, it was a whole variety of organisms that got the toxin in them and it had major effects,” said Dortch. “They had to close the Dungeness crab fishery for a long period of time which had major economic impacts.”
Anderson said her team’s research data has found that domoic acid events seem to be worsening in California.
“They’ve gotten bigger, more toxic certainly. When they bloom the toxins just seem to be produced at higher concentrations,” said Anderson.
While humans can do little to stop HABS from running their course, researchers have gotten better at predicting them.
NASA and the National Oceanic and Atmospheric Administration developed C-HARM, a domoic acid forecasting technology. Marine rescue centers consult C-HARM maps to evaluate the risk of marine domoic acid poisoning in their area.
“We are able to bring in lots of different information from satellites, from models, and from our water sampling to create a forecasting system that is real time that looks like a weather map,” said Anderson.
In the Central Coast, the nonprofit Channel Islands Marine and Wildlife Institute is currently treating sea lions. They are accepting donations to help fund their rehabilitation services.