Mercury levels in fish are on the rise

Add another item to the ever-growing list of the dangerous impacts of climate change: Warming oceans are leading to an increase of the harmful neurotoxicant methylmercury in popular seafood, including cod, Atlantic bluefin tuna and swordfish, according to research led by researchers at Harvard University.

Human exposure to mercury through seafood is predicted to increase. Photo: Harvard SEAS

The scientists developed a first-of-its-kind, comprehensive model that simulates how environmental factors, including increasing ocean temperatures and overfishing, affect levels of methylmercury in fish. The researchers found that, while the regulation of mercury emissions has successfully reduced methylmercury levels in fish, spiking temperatures are driving those levels back up and will play a major role in the methylmercury levels of marine life in the future.

"This research is a major advance in understanding how and why ocean predators, such as tuna and swordfish, are accumulating mercury," said Elsie Sunderland, senior author of the paper.

"Being able to predict the future of mercury levels in fish has been difficult to answer because, until now, we didn't have a good understanding of why methylmercury levels were so high in big fish," said Amina Schartup, first author of the paper.

Based on the new model, the researchers predict that an increase of 1 degree Celsius in seawater temperature, relative to the year 2000, would lead to a 32% increase in methylmercury levels in cod and a 70% increase in spiny dogfish. (National Science Foundation)

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