Toxic algae is causing normally gentle sea lions to become aggressive

Warm temperatures and favourable water conditions have created an environment for the toxic algae to flourish.

Toxic algae is quickly spreading along sections of the Southern California Coast, fueled by warm temperatures, favourable wave and water conditions, and an excess of agricultural chemicals, among other factors.

The conditions may be behind the deaths of hundreds of sea lions and nearly six dozen dolphins in the first week of June, NOAA reports.

Between June 8 and 14, the Channel Islands Marine & Wildlife Institute fielded more than 1,000 reports of sick or dead marine mammals.

Aggressive sea lions

Sea lions affected by the neurotoxins in the algae are becoming aggressive, with wildlife officials receiving more than 20 reports of sea lions biting beachgoers as of late June.

They appear to have fallen ill after consuming large quantities of domoic acid, present in fish via the algal blooms.

"Sea lions and dolphins eat mostly sardines, anchovy and hake, which are concentrating this toxin," Alissa Demming, Vice President of Conservation Medicine and Science at the Pacific Marine Mammal Center, told NPR.

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"We think we're seeing these domoic acid blooms more frequently as well as lasting longer and potentially even producing a higher level of toxin that's resulting in worse clinical signs."

Domoic acid can have an effect on various mammal species. In 1961, dozens of seabirds began acting strangely in Monterey Bay due to an algal bloom, although the cause of their behaviour wasn't known at the time. It is said to be the inspiration behind Alfred Hitchcock's iconic 1963 film The Birds.

Demming told NPR domoic acid can impact brain or heart receptors, causing overexcitement that can lead to seizures or heart damage.

“It literally affects their brains, and the behaviour of sea lions—especially when the concentrations of domoic acid are quite high—is drastically changed,” John Warner, the CEO of the Marine Mammal Care Center, told NBC News.

“They become symptomatic in ways that are just unpredictable in terms of their behaviour—aggressiveness that we don’t normally see.”

The Marine Mammal Centre is just one of several local rescue organizations under strain due to the influx of sick marine animals.

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Experts are quick to point out that while beachgoers should be cautious around sea lions, their current behaviour is atypical - under normal circumstances, sea lions are usually gentle creatures that prefer to nap near the shore.

"I don't want people to think sea lions are the new Jaws because they're not," Warner said.

VIDEO: Giant seaweed blob continues to bloom

Headline image courtesy of Canva