Mercury Contamination in Beluga (Not Caviar)

Junko Kimura via ABCNews.com

In 2005, Lockhart et al reported upon mercury contamination in beluga whales in the Canadian Arctic from 1981 to 2002.  The team reported a steep increase in mercury levels in the marine mammals that did not seem to correlate with the relatively steady mercury levels measured in Arctic environments. 

PLOS Biology today published Arctic Sentinels as a summation of their follow up work to  determine the source of the “extra” mercury.  Interestingly, the team may have evidence to suggest that climate change increased accumulation of mercury in whales, seals, fish, and other top Arctic predators. 

Some mammals in the Canadian Arctic have shown 10-fold increases in mercury levels since the end of the 19th century. Of particular concern are the steep increases of mercury—a potent neurotoxin—in beluga whales and other marine mammals that have been hunted for food by northern peoples for centuries.

Gary Stern, a researcher with the Department of Fisheries and Oceans and a professor at the University of Manitoba, and his colleagues measured mercury levels in samples of liver, kidney, muscle, and muktuk—frozen whale skin and blubber, frequently eaten by the Inuit—taken from beluga whales from the Mackenzie Delta between 1981 and 2007. Stern says the highest mercury concentrations were measured in animals from the mid-1990s. The levels have since declined a bit, but they remain higher than they were in the 1980s [1], even though global atmospheric mercury has been in decline since the 1980s. And in the high Arctic, where scientists have been measuring atmospheric mercury levels since 1995, mercury levels have remained stable, and may be decreasing. “We didn’t see an increase in mercury that could explain the mercury concentration in the biota,” says Wang.

Because of the complex mercury cycle within the high Arctic it is very hard to pinpoint the exact source of the mercury contamination although researchers estimate: “that there are more than 47 metric tons of abiotic methylmercury in the upper ocean and 450 metric tons in the entire Arctic Ocean, but only 4.5 metric tons of methylmercury in the marine biota.”  The researchers also suggest that rising temperatures may actually increase areas of new sea ice formation – where mercury contamination may start. 

The article goes on to discuss the impacts of this type of mercury contamination and its relevance for Inuit cultures which rely upon marine mammals and Arctic fish species as the bulk of their traditional diet.  (Yes, traditional cultures are still allowed to hunt marine mammals even within United States waters where all marine mammals are protected.  A provision in the Marine Mammal Protection Act of 1972 – which had its 36th anniversary today – allows for indigenous people to continue traditional hunting practices.)

However.. what we’re in no way prepared to answer are questions concerning the impact that methylmercury contamination may have upon the health and reproductive capacities for the marine mammals!  If the belugas are carrying mercury loads high enough to endanger humans when consumed then perhaps these levels also alter normal health and physiology for the whales. 

It would be incredibly interesting to study rates of birth defects and other physical abnormalities in the wild populations of belugas, polar bears, ringed seals, and walrus.  (That is, if it were truly possible.)  The NRDC lists symptoms of mercury poisoning including: hair loss, vision and hearing disruptions, headaches, seizures, delayed learning, memory loss and others. 

I wonder which, if any, of these symptoms might also be observed in marine mammals?  Or if mercury poisoning, given the potential alterations to human senses, might impact a marine mammal’s use of echolocation or migration patterns?  Either way it seems we need more information in order to understand fully our impact and chart a path to better protect arctic species.   

Speaking of protecting Arctic species, if you’re a voter in the US you might be interested to know about a certain VP candidate’s position on beluga whale conservation.  Don’t forget to make your voice heard on or before Election Day. 

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