Then marine mammals — mostly California sea lions — began showing up disoriented and sick like the pelicans on the beaches of the Central California coast. Some of them also wound up dying.
More and more stories of these unfortunate sick and dying creatures are increasing, especially since the beginning of this century. Now, sea lions are showing up at the Marine Mammal Center,
in Sausalito, California, in huge numbers. Testing was definitely in order — blood tests, urine and fecal tests were done, and the environment and prey of these animals were also tested. The results showed what many already suspected. The marine mammals were being poisoned by domoic acid — a deadly neurotoxin.
What is domoic acid?
“It’s a bio-toxin produced by diatoms
such as Pseudonitzschia australis
says Frances Gulland, a senior scientist at the center. Domoic acid is often called a “red tide,” but this is somewhat of a misnomer as the diatoms, which are one-celled algae are often colorless or have other colors that aren’t red. Pseudonitzschia is a natural part of the environment, but sometimes it “blooms” in excessive numbers and releases the toxin. This is when the problem begins. The toxin accumulates in shellfish, sardines and anchovies and as it travels up the food chain it becomes more and more concentrated. It targets the brain, specifically the hippocampus,
and sea mammals such as California sea lions and sea otters become sick when they eat prey that has been feeding on the algal blooms. If severe enough, it can cause seizures and other serious problems in the central nervous system and even death.
A definitive diagnosis of domoic acid poisoning is tricky because toxicity of algal blooms can vary and the timing of domoic acid outbreaks can be unpredictable and other factors have to be ruled out, according to the Santa Cruz Sentinel.
In 2014, the Marine Mammal Center has treated 35 California Sea lions for domoic acid poisoning. Treatment includes plenty of fluids and diazepam (Valium), Gulland said, in an interview with Digital Journal.
Researchers say that the outbreak is the worst they’ve ever seen and there’s evidence to suggest that the problem may become worse, the Sentinel reports.
Concerns about this prompted California’s Department of Public Health to warn people against eating sardines and anchovies from Monterey Bay late last month. Domoic acid poisoning can cause serious problems in humans as well. In high concentrations, the toxin can cause amnesic shellfish poisoning.
There’s even evidence to suggest that small amounts of this toxin can cause kidney damage. The warning was eventually downgraded, but it applied to the organs of anchovies, sardines and crabs, and recreationally harvested clams, mussels and other types of bivalves.
Researchers don’t know why the algae produce these toxins, Tenaya Norris, a marine scientist at the Marine Mammal Center told the Sentinel.
“They can be in the water and not producing this toxin, and they can be out in the water and raging,” she said.
Researchers at the University of California Santa Cruz
have been trying to get a better handle on the problem by taking weekly water samples from a local harbor for the past 14 years, then sharing the results with public health officials, the Sentinel reports. They have even been taking samples of underwater sediment, and these samples show high levels of the toxin in the ground. The latest results are the highest ever recorded.
The waters off of the coast of California are rich in nutrients, Gulland says, making it easier for the toxic algae to proliferate. Scientists believe that Pseudonitzschia
likes products that are rich in nitrogen-rich waste products such as agricultural runoff, nitrates and other waste products because they act like fertilizers. Maps have demonstrated that algal blooms often occur at the mouths of rivers and other areas where waste accumulates. When the algae dies or is eaten by animals the acid is released. Increased oxygenation of the water due to pollution is exacerbating the situation, Toxipedia
reports. This means that human activity may well lead to worsening blooms of this toxic algae, thus affecting the health of sea lions, other marine mammals, and birds, the center reports.
By mimicking glutamic acid, the toxin binds to glutamate receptors — especially in the nervous system and the heart. In so doing, it kills the cells it attaches to, the Sentinel reports.
Brown pelicans have been hit particularly hard. Poisonings have been occurring regularly since 2001, but in 2006, large numbers of the birds began falling out of the sky, according to the International Bird Rescue Research Center,
in San Pedro, California. Disoriented, the birds flew inland, fell from the sky and flipped onto their backs once they were on the ground. One disoriented pelican was even picked up in Burbank, some 25 miles from the coast.
The birds arrived at the Center in varying stages of illness. Once there, they were given massive amounts of fluid therapy, and those that were in the earliest stages of illness had the best chances of survival. From the early part of April through May in 2006, more than 80 pelicans wound up at the shelter. Unfortunately, out of that number, 18 were dead on arrival, and 12 died during their stay.
The first reported outbreak of this nasty toxin occurred in 1987 on Prince Edward Island,
Canada when three people died after eating toxic shellfish, the IBRRC reports. Starting in 1991, dead and dying seabirds began washing up on the beaches off of Santa Cruz and Monterey Bay, California after eating anchovies contaminated with the toxin. In May and June of 1998, 400 California sea lions died due to domoic acid poisoning.
By May 2002, domoic acid poisoning had claimed the lives of thousands of birds and mammals, the IBRRC reports. This included dolphins, sea lions, seabirds and the endangered brown pelican.
Once again, human activity is creating a deadly harvest — one that appears to be occurring in unprecedented numbers. By poisoning the world’s oceans in so many ways, we are sending scores of helpless creatures to their deaths, and in so doing, we are going along for the ride.