Study traces mercury pollution in fish

A new environmental study proves atmospheric mercury emissions end up in fish in as little as three years, and concludes that if mercury emissions from coal-fired power plants and other industrial activities were cut immediately, the amount of mercury in fish would begin to go down within a decade.

"Before this study, no one had directly linked atmospheric deposition (mercury emissions) and mercury in fish," said University of Alberta biological sciences professor Vincent St. Louis, a principal investigator in the study, who helped design the complex, experiment.

Called METAALICUS - Mercury Experiment to Assess Atmospheric Loading in Canada and the United States - the research fills a major gap in scientists' understanding of how mercury moves from the atmosphere, through forests, soils, lakes and into the fish that people eat.

The study's immediate value is that it provides undeniable proof of a direct link, said St. Louis, who specializes in what is called whole-ecosystem experimentation. What seemed intuitive is now backed up by hard science.
The findings should spur policy-makers to write regulations for more rapid reductions in mercury emissions by industry, St. Louis said.

"We can say conclusively that if you reduce mercury emissions it will result in less mercury in fish. The METAALICUS experiment underscores the importance of immediately reducing atmospheric mercury releases."

The research findings will appear in the Proceedings of the National Academy of Sciences of the United States of America online edition this week.

The research took place in the Experimental Lakes Area in northwestern Ontario from 2001 - 2003, and is ongoing. Jennifer Graydon, a U of A PhD student and study co-author, was also part of the research team and worked closely with St. Louis.

Over the course of the study, the scientists introduced small amounts of mercury - not enough to initiate a toxic response - to one of the lakes in the remote area.

She and St. Louis spent months at a time at the site, but fortunately they didn't have to rough it. A government-run, permanent field camp there is equipped with dorms, a kitchen and a $1-million lab.

The research team employed a spray plane to spike the forest canopy with mercury. Other mercury "spikes" went into the wetlands and directly into the lake, simulating atmospheric depositions.

Graydon said the novel approach in this experiment, and the key to its success, was the use of three identifiable, stable forms of mercury (isotopes) distinguishable from other forms of mercury already present in the lake environment. She said the team was able to isolate and trace these isotopes over an extended period of time as the isotopes made their way through the ecosystem.

The Experimental Lakes Area was set aside by government several decades ago for just such large-scale research projects.

"Being able to study the whole ecosystem this way is an extremely powerful tool," she said.

The U of A's role was to follow the mercury when it was deposited onto the forest canopy, passed through the trees and onto the ground vegetation. The United States Geological Survey then took over, analyzing the soil and runoff. Other agencies and universities played other roles in the complex experiment.

The team was astonished to discover how quickly mercury introduced from the atmosphere into the lake ended up in fish - in three years or less. The researchers also concluded that it takes much longer for mercury to get into the lake via the forest canopy and runoff.

Monitoring at the lake will go on for many years. Now that the experimental additions of mercury have stopped, the next phase of the experiment will involve finding out how long it takes for the heavy metal to decline in fish.

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Study traces mercury pollution in fish