A study conducted by the U.S. Geological Survey over eleven years concluded that mercury concentrations in the water of two lakes in Voyageurs National Park, Lake Peary and Lake Ryan, have declined by 50 and 43% respectively. The study also found that mercury concentrations had fallen in young Yellow Perch by a mean of 34.5% between the two lakes.
While only two of the four lakes tested in the study showed significant decline in the mercury concentration of its fish and water, the study did find that the declines observed corresponded with a 32% decline in rates of wet mercury deposition from 1998 to 2012.
In other words, less mercury has been falling from the sky into our northern lakes, and, consequently, the fish of these lakes are experiencing less contamination.
Furthermore, Mark Brigham, one of the leaders of the study, attributes the decline in mercury deposition to a decrease in mercury emissions from coal-fired power plants.
“…we’re starting to tackle emissions from coal-fired power plants, and the results are showing up. Reducing emissions of mercury into the atmosphere appears to be causing a measurable decrease in mercury that falls to the earth.” said Brigham in an interview with MinnPost released on June 5th.
These results mean hopeful news for those who have been fighting mercury emissions and coal burning, for those who are concerned about the health of Minnesota’s aquatic ecosystems, and for those who regularly eat game fish up north. As mercury travels from organism to organism up the food chain, it undergoes a process known as “biomagnification”, in which it increases significantly when absorbed by a new organism, according to a 2009 U.S. Geological Survey Publication. This means that even very small amounts of mercury deposited into lakes can pose serious risks to the ecosystem of lakes and ecosystems which depend on lake organisms.
There is still significant progress to be made world-wide when it comes to the control of mercury emission and migration, but this study indicates that local efforts to limit and contain mercury have made a tangible difference in its presence in some of our lakes.