Researchers assumed the entire Arctic's fish population was contaminated with mercury because North American and European Arctic species had tested positive; new research suggests that assumption was incorrect.
Researchers found that mercury contaminations varied throughout the Arctic based on "atmospheric, geological, and biological conditions," a Virginia Tech news release reported.
"It turns out that the economic decline of the former Soviet Union, which collapsed in 1991, appears to have been good for the Arctic environment in that part of the world," Leandro Castello, an assistant professor of fish and wildlife conservation in the College of Natural Resources and Environment at Virginia Tech, said.
Most aquatic mercury contamination comes from ore processing and mining. In specific water conditions the mercury can be converted into a substance that can be absorbed by living species through a process called methylation.
"Methylmercury is highly toxic," Castello said.
The team found fish in the Russian Lena and the Mezen rivers were safe to eat while Pasvik River ("on the Norwegian-Russian border) fish and those living in the Canadian Mackenzie River were highly contaminated.
Burbot fish are a non-migrating species.
"The burbot fish was chosen because they are top predators that integrate many bio-geo-chemical processes in the river watersheds," Castello said. "The fish were collected downstream of the watersheds, so that they would present everything that happened upstream."
The fish were tested for mercury contamination using an ice-fishing method.
"We developed and led an initiative of biological monitoring of the water quality of major rivers of Russia in 1980 and continued to do it until 2001, because we knew it could provide useful information one day. In 2002 the funding was cut and the program was closed. Unfortunately we have no funding to continue collecting such interesting data," co-author Alexander V. Zhulidov of the South Russian Centre for Preparation and Implementation of International Projects, said.
The team found the Lena river had one of the lowest contamination levels.
"Good news since the Lena River is one of the largest watersheds in the world," Castello said.
Mercury levels started to significantly rise in the 1970s because of industry in Europe and North America, but emission control started to reduce the trend. Russian metallurgic industries in the Murmansk region help explain the contamination in the Pasvik River, but economic issues around the Lena and Mezen rivers slowed the pollution rate.
The team suggested global warming could be exacerbating the problem because it makes mercury more available to fish.
"There are no ancillary environmental data from the time period of the study in Russia, [but the differences across the Arctic] may be explained by differences in water quality, geological bedrock formations, and proximity to polluting sources," Castello said.
