Steady warming on Earth is affecting the quality and safety of shellfish.

Researchers recently linked warmer ocean to increased, potentially more dangerous levels of domoic acid, a potent neurotoxin found in shellfish and other marine creatures that can spell illness and even death.

The team from Oregon State University and other organizations pored over data from 1991 to 2015, comparing ocean water conditions off the Oregon coast with domoic acid levels in the state’s razor clams. They used climate variability measures such as the Pacific Decadal Oscillation, which focuses not just on temperatures but also factors such as ocean water movement and currents.

According to the results, the five years with the most annual domoic acid levels in the clams were also the years with the warmest ocean conditions.

Domoic Acid Concerns

Domoic acid is produced by certain marine algae and accumulates in animals consuming those algae, at pronouncedly higher levels up the food chain. In humans, it can cause poisoning known as amnesic shellfish poisoning, with symptoms like stomach ache, seizures, memory loss, and even death in rare cases.

First noted as a public health threat back in 1987, domoic acid poisoning has led to mass death events in marine animals as well as closures of beaches in the Pacific Northwest in 2003, 2015, and last year that have led to massive economic setbacks.

In 2015, DAP-induced closures in coastal towns affected the Dungeness crab trade on the West Coast.

As of last year, a bit over 70 percent of the estimated 1,500 razor clams tested in Oregon since 1992 had levels of the toxin below 20 parts per million, lead author Morgaine McKibben said in a Live Science report.

Standard tests prevent the harvesting of toxic shellfish, effectively translating to no documented domoic acid-related illness or death in Oregon.

New Predictive Model

The team also devised a model that tracks climate conditions, in aid of predicting large increases in the toxin levels. They intend to make this model publicly available to assist authorities in crafting guidelines and decisions on fisheries in Oregon as well as Washington and California.

While strongly predictive of toxic level increases, the model could still miss a pertinent event occasionally or produce a false positive.

Study co-author Matt Hunter of the Oregon Department of Fish and Wildlife noted, however, that advance warnings of domoic acid levels remain “extremely helpful.”

"The biggest takeaway is that the ocean temperatures are changing, and that has the potential for more frequent and more extreme harmful algal blooms,” he warned.

A similar warning was issued by a study last year, which found that longer and more frequent toxic algal blooms along the Pacific coast of Canada may occur due to climate change. The researchers, probing the carcasses of over 900 Alaskan marine animals, looked for signs of domoic acid and saxitoxin.

It appeared that the toxic blooms have shifted North, with low domoic acid levels found in all 13 Alaskan mammal species and saxitoxin found in 10 species in the study. Both were unexpected to be seen in all the studied animals everywhere.

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