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Warmer Oceans Increase Likelihood Of Toxic Shellfish, Study Finds

Thanks for the poison lobster, El Niño.

12/01/2017 7:33 AM AEDT | Updated 12/01/2017 7:33 AM AEDT
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A cook at Nick's Lighthouse prepares Dungeness crab on November 5, 2015 in San Francisco, California. The California Fish and Game Commission suspended recreational Dungeness crab fishing for 180 days in 2015 due to high levels of domoic acid, a neurotoxin.

The neurotoxin domoic acid inspired Alfred Hitchcock’s “The Birds” after hundreds of sooty shearwaters ingested the poison in the summer of 1961 and, well, lost their minds.

The crazed birds likely consumed domoic acid via small fish like anchovies and sardines. It also tends to collect in shellfish, like clams, crabs and lobsters. And, according to a study published Tuesday in the Proceedings of the National Academy of Sciences, it may become more prevalent as oceans warm, threatening birds and humans alike.

Researchers at Oregon State University, the University of Oregon, the National Oceanic and Atmospheric Administration, and the Oregon Department of Fish and Wildlife studied the prevalence of domoic acid over the past 20 years in the Pacific Northwest, and found it strongly correlated with water temperatures that are warmer than normal.

For now, warmer waters typically stem from events like El Niño and a decades-long climate cycle called “Pacific decadal oscillation,” the study found. It isn’t yet clear how climate change, which also warms the oceans, might affect the toxin’s prevalence.

“When water’s unusually warm off our coast, it’s because the circulation and patterns in the atmosphere has changed, bringing warm water from elsewhere — and this is happening at the same time that we also see high domoic acid in shellfish,” Morgaine McKibben, a doctoral student at Oregon State and the study’s lead author, told E&E News.

“It has a very strong mechanistic connection,” McKibben added.

The toxin is produced by some species of Pseudo-nitzschia ― a type of phytoplankton ― during warm algae blooms, and gets passed up the food chain by animals that eat it. Sea lions, otters, dolphins (and other cetaceans) and humans all are at risk, notes the Marine Mammal Center.

While some animals can eventually cleanse themselves of the toxin, the threat can persist long after the warm water recedes.

“For example, razor clams are filter-feeders that bioaccumulate this toxin in their muscles, so they take much longer to flush it out than other shellfish,” McKibben said in a statement. “The higher the toxin levels, the longer it takes for razor clams to be safe to eat again, perhaps up to a year after warm ocean conditions have subsided.”

Animals poisoned by domoic acid tend to become lethargic and disoriented, and experience seizures and death. Symptoms in humans include vomiting, nausea, diarrhea and abdominal cramps, according to the Washington Department of Fish and Wildlife. Severe cases can lead to headache, dizziness, confusion, loss of short-term memory, motor weakness, seizures, profuse respiratory secretions, cardiac arrhythmia and coma.

It isn’t just a health risk. An Oregon State University statement notes that officials have to shut down shellfish harvests when domoic acid levels are high, causing economic harm.

Since health officials first identified domic acid as a health threat in 1987, Pacific Northwest shellfish harvests have been halted in 2003, 2015, and 2016. The West Coast crab industry took an estimated $100 million hit in 2015 alone, Oregon State University said.

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