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Arctic narwhal tusk study reveals increased mercury content present due to climate change

Published: Apr. 22, 2021 at 4:21 PM AKDT
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FAIRBANKS, Alaska (KTVF) - Climate change and pollution are the biggest threats to many animal species here in the arctic according to many researchers. In response to the decline of sea-ice, top predator species like narwhals are affected by changes in their diets and exposure to pollution.

Jean-Pierre Desforgesis is a Post Doctoral Research Fellow at McGill University, and part of an international team of researchers who have studied narwhals to determine whether human emissions have led to a sharp rise in the presence of mercury in the oceans over the last few decades.

“In this project we use narwhal tusks as a tool to investigate kind of the history of narwhal feeding and exposure to mercury. What we’ve been able to show is that going back to the 1960s, climate change is having major impacts on the way that narwhal are feeding. So they’re changing what they’ve been feeding on over the past decades. But it’s also changing how these animals are being exposied to potentially toxic compounds like mercury,” said Desforgesis.

Narwhal’s spiraled tusks are cut open to reveal the individual layers of growth in the tusk, similar to the rings that develop in trees. Desforgesis explained, “The tusk is essentially an extended tooth much like our own teeth, which grow in incremental layers. So every year an additional ring is added, and then over the lifespan of the animal you can just count up these rings. What we’ve been able to show is that mercury changes throughout the full lifetime of these animals. Because some of them live over 50 years, we can go back 50 years in time to look how the levels of mercury have changed.”

Heavy metals like mercury and other contaminants accumulate at each link in the food chain. The higher an animal is in the food chain, the more mercury it can accumulate in its body throughout its life. Elevated amounts of heavy metals in the body are toxic and can affect the neurochemistry of animals, including behavior and the ability to reproduce.

“And essentially what we’ve shown is that mercury levels vary predictably with the diet over the past half century, with the exception of the most recent decades where mercury levels start to rise much higher than they have in the past. We’re linking this to things like increased emissions of mercury globally, through things like fossil fuel combustion, coal use in a lot of developing countries, as well as things like forest fires, the melting of permafrost, glaciers and things like that,” said Desforgesis.

These research findings show that each layer of the narwhal’s tusk can offer valuable information on both the animals’ living conditions, and provide a window into climate developments in the Arctic.

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