January 10, 2017 — A mysterious, potentially deadly neurotoxin that poisons humans by way of shellfish has now been linked to warming ocean waters. The new findings could help fisheries predict spikes of this substance in their catches, allowing them to protect human consumers and mitigate their own financial losses. But one question remains unanswered: as climate change edges ocean temperatures higher and higher, will blooms of the dangerous neurotoxin follow suit?
Domoic acid is natural, but it ain’t pretty. It’s a substance produced by tiny algae called phytoplankton—but no one is quite sure why.
“The shellfish that eat these algae blooms don’t seem to be affected by the toxin,” Morgaine McKibben, a PhD student at the University of Oregon, tells PopSci. But while the algae’s direct predators are seemingly impervious to the substance, the animals that eat them can suffer terrible consequences: domoic acid mimics a neurotransmitter called glutamate, and does a better job of binding with the brain than the real thing. It essentially kicks the neurotransmitter out of place, causing symptoms like seizures and memory loss. Some research suggests the toxin is causing an Alzheimer’s-like illness in sea lions, and it’s been blamed for the mass deaths of everything from whales to seabirds. It’s killed humans, too.
“Why do these little bitty single-celled creatures in the ocean make a toxin that only works a couple levels up the food chain? It could be an accident. We don’t have a good answer yet,” McKibben says.
But while the evolutionary purpose behind this sinister trick of the food web is still a mystery, McKibben and her colleagues have started to answer another important question: how can we predict increases in domoic acid to keep the substance off of human dinner plates? In a study published Monday in the Proceedings of the National Academy of Sciences, McKibben presents over two decades worth of evidence that warmer oceans can trigger domoic acid production.