A beautiful walk on the beach is abruptly interrupted when you spot a sea lion in distress. The creature struggles to get onto shore as it bobs its head up and down and foams from the mouth. You can call a marine mammal center to help, but unfortunately, it may be too late.
Although devastating, the scene is becoming a more common one along the coast of California due to toxic algae blooms. The toxin they release, domoic acid, can be devasting to marine mammals — leading to thousands of sick animals and often several deaths.
What is Domoic Acid and Why is it in Southern California?
Domoic acid is a neurotoxin produced by algae. The acid can be produced by a variety of species of algae, but the main source in California comes from Pseudo-nitzschia. The toxin often accumulates in shellfish, sardines, and anchovies which eat the algae. As a result, marine mammals and humans can be poisoned when they eat these foods, even though they are not directly consuming the algae.
The production of Domoic acid is often hard to predict due to the variability in conditions preferred by Pseudo-nitzschia. While the algae seem to prefer colder temperatures, the presence of toxic algae blooms is increasing with warming waters. Additionally, several other factors aside from temperature can contribute to the blooms.
For the past 20 years or so, toxic algae blooms of Pseudo-nitzschia have been relatively common in Southern California, typically in the spring and summer. Changes in run-off of fertilizer increases in upswells, and warmer temperatures can lead to variation in the occurrence of events.
For example, in 2015 one of the largest toxicity events due to Pseudo-nitzschia occurred in Monterey Bay. During the event, scientists determined that a large upswelling in March of 2015, accompanied by a low ratio of silicate to nitrate allowed the bloom to become more toxic.
These events are not uncommon, as demonstrated in 1991, 1998, 2015, and several other years. The question is why there is a large toxic bloom occurring this year, especially after just having another major toxic event in the prior year. Much of this is thought to be related to warming temperatures and an adapted version of Pseudo-nitzschia that is more heat tolerant. With the El Nino taking place in the US, California has become the perfect breeding ground for the algae.
How is Domoic Acid Poisoning Affecting Marine Mammals?
While technically any animal that eats algae is at risk for domoic acid poisoning, marine mammals, specifically sea lions are the most affected. This is primarily due to their diet, which is how they become exposed.
The fish, specifically sardines and anchovies, eat the algae. While they don’t always become sick from the algae, animals that eat an abundance of these items, like sea lions or seals, accumulate enough of the toxin to become very ill.
Domoic acid is a neurotoxin, which means it primarily affects the nervous system. As a result, when marine mammals are exposed to it, they can begin to experience neurological dysfunction, which can lead to seizures, disorientation, and confusion. The neurotoxin can also cause lesions to form on the brain and spinal cord.
Aside from neurological issues, domoic acid can also lead to a variety of other health issues in marine mammals, especially if they are exposed to concentrations of domoic acid repeatedly. Some of the other well-known health issues include heart failure and lesions on the heart (especially in sea otters), premature births and stillbirths, and developmental issues.
While marine mammals can often flush out the toxin over time, sometimes the health effects can cause them to strand on the beach or be unable to surface for air underwater, which oftentimes will lead to death.
Why Does This Matter?
While domoic acid poisoning can be very sad, especially because it involves our well-loved marine mammals, you might wonder why you personally should care about this issue, especially since it is a naturally occurring event. The biggest reason is because it can affect you personally.
Pseudo-nitzschia, the toxic algae, not only causes domoic acid poisoning in animals but can also cause amnesiac shellfish poisoning in humans, which can have some severe side effects. When there are increases in domoic acid poisoning in marine mammals, it signals to scientists that something may be up and gives them a warning to close fisheries that could potentially expose humans to the toxin.
Domoic acid poisoning is also a reminder that we need to be careful with fertilizers use and application. While it may be a naturally occurring event, there has been a huge increase in the size of the mass mortality events associated with neurotoxins, largely due to fertilizers and nutrients getting into the ocean and worsening the algal blooms. It may not change the occurrence of a bloom, but fertilizers can make the blooms more intense with greater spread.
Additionally, you should care about this problem because many marine mammals are endangered and have decreasing population sizes. Continuous mortality events, like the one we are seeing with domoic acid, may put them at further risk for extinction. This is not only an issue for the specific species affected, but the entire ecosystem as it can disrupt the food web.
So now that we understand the problem and how it is impacting marine mammals, what can you do to help?
How You Can Participate
The biggest way you can help marine mammals with domoic acid poisoning is by calling in experts. If you see an animal that is swaying its head, bobbing, and looking disoriented you can call the NOAA animal stranding hotline for your region. The hotline number for California is (866) 767–6114. This will lead to NOAA sending marine mammal rescue teams in to assist the animal.
Additionally, it is important that if you do see this, you stay back and try to remain quiet. While you may want to push the animal back into the ocean or try to help it, that is actually illegal under the Marine Mammal Protection Act and could cause more harm than good.
Another way you help is by making sure to properly dispose of fertilizers and other nutrients. This could help prevent the algal blooms from worsening.
Overall, domoic acid poisoning may seem like a devastating, yet rare occurrence, but understanding the issue and being aware of it when it happens is critical for prevention and mitigation.
