A team of scientists from the US, Russia and Canada has compared mercury concentrations in burbot (Lota lota) from 20 locations along the Pasvik river on the Norwegian-Russian border and along the Mackenzie River in Canada with findings from the Lena and Mezen rivers in Russian Arctic.
Lena is the easternmost of the three great Siberian rivers that flow into the Arctic Ocean, while Mezen runs through the Komi Republic and Arkhangelsk regions and flows into the White Sea.
Decades of studies from Norway and Canada have found high levels of mercury that make the fish unsafe, but further understanding has been limited by a lack of studies in Russia. The research team determined that burbot fish in the two Russian rivers are safe to eat.
Mercury concentrations in burbot in the Lena and Mezen Rivers also were found to have been declining at an annual rate of 2.3% while they have been increasing in the Mackenzie River Basin at annual rates between 2.2 and 5.1% during roughly the same time period.
Atmospheric mercury comes largely from mining and ore processing. Under certain water conditions, mercury is converted to a special form that can be absorbed by living organisms. Until the 1970s, atmospheric mercury were on the rise as a result of industry in Europe and in North America, but began to decline from those sources due to emission controls, with Asia coming on line as a source, the paper explains.
In Russia, metallurgic industries in the Murmansk region and smelter companies in the Pasvik watershed explain high levels of atmospheric mercury in the Pasvik River. The economic decline near the watersheds of the Lena and Mezen lowered polluting activity there.
A confounding factor has been climate change. In burbot in the Canadian Arctic, mercury concentrations in fish tissue have increased despite declining atmospheric concentrations because rising temperatures appear to increase availability of mercury to fish populations.