Warming Oceans Could Make These Seafood Favorites Toxic

New study links rising temperatures to dangerous toxins

dungeness crabs
Fred Benenson via Flickr

In recent years, scientists have warned that climate change could have a disastrous effect on the ocean’s ecosystems as the world’s waters get warmer. But now, a new study suggests that widespread die offs of ocean-going species isn’t the only thing that warmer waters could cause: It might also make some seafood favorites too toxic to eat.

Chances are, most people haven’t heard of domoic acid, but it’s something that could be making more headlines soon enough. That’s because it’s a neurotoxin that can build up in sea creatures that are popular on the dinner table, like Dungeness crab, mussels, clams and anchovies, Clare Leschin-Hoar reports for NPR. And, according to a new study published in the Proceedings of the National Academy of Sciences, warmer waters lead to algae blooms that can cause elevated levels of this toxin in many of the ocean's critters.

“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. It has a very strong mechanistic connection,” Morgaine McKibben, study author and Oregon State University doctoral student tells Kavya Balaraman for Scientific American.

Domoic acid is produced by some kinds of algae, in particular one called pseudo-nitzschia. These microorganisms are the basis of the underwater food chain and thrive in warm waters, but can build up in sea life, causing serious health issues for humans and animals alike. As Leschin-Hoar explains, domoic acid first became known as a health threat in 1987, when an outbreak in Canada killed three people and sickened more than 100 with symptoms including vomiting, diarrhea and cramps. In serious cases, domoic acid poisoning can even cause seizures, numbing and memory loss.

Since then, officials have monitored domoic acid levels along the western North American coastline—and it’s been steadily rising over time. McKibben’s study looked at more than two decades worth of data gathered in the region and found a strong correlation between rising water temperatures and rising domoic acid levels, Stephanie Bucklin reports for LiveScience.

These elevated levels of domoic acid are already starting to affect the seafood business. In 2015, officials shut down Dungeness crab fisheries from Alaska to California for several months because of high domoic acid content, Balaraman reports, and similar shutdowns were enacted in 2016. This left the seafood industry in Washington state $9 million in the hole. To make matters worse, the toxin can linger in fisheries for as long as a year.

“If they've already made their harvest and then there's a closure, they can't distribute to the public—so they lose money on the effort to harvest as well as the product. There's further money lost to the shellfish industry as these closures last,” McKibben tells Balarama.

While health officials can test for the the toxin in seafood and keep contaminated fish and molluscs away from store shelves and dinner plates, McKibben hopes that this study could help officials predict when and where blooms will occur, Leschin-Hoar reports. At the same time, McKibben says it’s important for states whose economies rely on fishing and seafood harvesting prepare for the increased risk of domoic acid contamination by conducting more thorough testing.

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