For years, scientists have been concerned about the substantial increase of mercury concentrations in Arctic marine mammals such as polar bears, beluga whales, and seals. In some places in Canada, for example, levels of mercury in the tissue of marine mammals has quadrupled in the last twenty-five years. Mercury is a potent neurotoxin that can result in a wide variety of health effects in animals and people, and pose a particular risk to pregnant women and young children. Most global mercury pollution comes from coal fired power plants, which release mercury into the air. Other significant sources are industrial processes such as chemical manufacturing, battery production, and gold mining.
Today's Winnipeg Free Press reports that changes to the Arctic's food web, such as melting sea ice caused by global warming, may be one of the primary causes of mercury contamination of marine mammals.
[R]esearchers now believe the increasing levels found in beluga whales are actually due to rising temperatures and disappearing sea ice, which have boosted the productivity of the northern seas by creating a warmer, brighter and more nutrient-rich environment for tiny plants and animals to grow.
According to the theory, new sources of food in an increasingly ice-free Arctic are forcing larger predators to change their feeding behavior, creating more links in the Arctic food chain.
That means more mercury gets concentrated at the top of the food chain, even though the overall amount of mercury in the ecosystem has not increased very much.
This research is intriguing and is consistent with predictions in other studies. Of course, the problem of mercury pollution and global warming goes hand-in-hand: ultimately, the best way to decrease global mercury pollution is to reduce our dependence on dirty sources of fuel like coal. If we did that, we would also be taking a big step toward controlling global warming, thus slowing down the very changes to the Arctic ecosystem that may be driving up mercury contamination of marine mammals. Another thing we can do here in the United States is to follow the example of the European Union and ban on the export of mercury. A bill to do just that has already passed the U.S. House of Representatives and companion legislation is awaiting action in the Senate.