Why is METAALICUS Necessary?
This brochure describes research that will directly answer for the first time what happens to fish mercury concentrations when there is a change in atmospheric mercury deposition. Despite the massive amounts of scientific information published on mercury contamination of ecosystems, there remain very basic questions about the environmental behavior and effects of this element. A critical uncertainty is whether a reduction in atmospheric mercury emissions will reduce mercury concentrations in fish. It is important to answer this question now because controls on industrial emissions of mercury have been proposed that will cost billions of dollars per year if implemented, yet the effectiveness of these controls is unknown.
|Mercury is the most common contaminant in fish
in the United States and Canada. Forty-two states have advisories against
fish consumption due to high mercury levels, and unacceptable fish mercury concentrations
exist in all Canadian provinces and the Northwest Territories, including remote
"pristine" lakes. Ninety-seven percent of closures to fishing in Ontario are due
to mercury contamination.
Mercury is a neurotoxin. There is a particular concern for prenatal life and infants, for whom safe levels of mercury exposure are lower than in adults. Concern also exists regarding the toxic effects of mercury on reproduction, behavior and survival in fish-consuming birds and marine mammals.
Experts agree that the relationship between atmospheric mercury deposition and the mercury in fish can not be understood by examining historical or regional data. This is mainly because empirical attempts to isolate the effects of mercury loading on fish mercury levels are confounded by other environmental factors which cause variations in fish mercury concentrations in lakes. These factors include a wide range of local site conditions and annual weather variability, often combined with poorly documented mercury loads. By contrast, this experiment provides the control necessary to examine the effects of one critical factor: mercury loading. Furthermore, this experiment will also allow us to distinguish newly deposited mercury from background mercury that has accumulated over hundreds of years.
What is METAALICUS?
METAALICUS is a whole-ecosystem experiment in which mercury inputs to a headwater lake (example Lake 658, Figure 1) and its watershed will be increased experimentally. An ecosystem approach will be used because the complex pathway of mercury from the atmosphere to fish cannot be simulated in laboratory experiments.
The mercury will be added as stable, non-radioactive isotopes of inorganic mercury (Hg(II)). The power of using isotopes lies in the ability to follow the newly deposited mercury separately from the background mercury.
Different mercury isotopes will be added to the upland, wetland and the lake surface to determine if the route of entry affects how much is accumulated in the fish (Figure 2).
|Figure 2. Using stable mercury isotopes to evaluate the contributions of direct deposition, upland runoff and wetland outflow to fish mercury levels.|
Comprehensive field studies will be carried out to establish site conditions and mercury concentrations in all compartments in the lake and watershed, and how they change with time. Detailed process studies will also be carried out. Movement of the mercury and transformations between mercury forms will be followed through the watershed and lake. Production of methylmercury (MeHg) will be studied in the lake sediments, upland and wetland, as will the bioaccumulation of MeHg into benthic organisms, plankton and fish. Methylmercury will be followed specifically because it is the dominant form in fish and the most toxic form of mercury in the environment.
This process-based approach will allow us not only to document what happens, but also to understand why. This is essential if we are to use the results of the study to make predictions for other locations. The approach will also provide critical information for an existing model that predicts fish mercury concentrations in lakes and the effects of remedial actions such as reductions in mercury loading.
The study will be carried out in two phases over a 5-year period. Phase 1 has started and involves a series of pilot studies, and background information on the study site. In Phase 2, the mercury loading to the whole ecosystem will be increased.
The Experimental Lakes Area (ELA) is situated in Northwestern Ontario. ELA lakes have been used over the past 30 years to provide leading limnological studies in freshwater lakes, including landmark whole-lake studies of the effects of nutrients, acidification and reservoir construction.
Other mercury studies at ELA include the completed Experimental Lakes Area Reservoir Project (ELARP) and the ongoing Flooded Uplands Dynamics Experiment (FLUDEX). These experiments are investigating mercury cycling in natural boreal ecosystems and in experimentally flooded wetlands and uplands.
How Much Hg will be Added?
|Figure 3. Proposed addition of stable Hg(II) isotope during METAALICUS|
Not much. ELA is a low deposition area for mercury, with approximately 3 ug/m2/yr of wet mercury deposition. The low mercury deposition rate at ELA means that adding the equivalent of about half a teaspoon of mercury over the entire 5 year study is enough to increase the atmospheric load to a 50 ha system by 4 to 5 times. This amount of mercury addition will result in a mercury deposition rate to the experimental system that is equivalent to rates currently observed in the Northeastern US (Figure 3).
A general research plan was drafted at two workshops in Toronto, Ontario in 1998 and in Washington, D.C. in 1999. It was decided that initial pilot scale studies are essential to refine the analytical methods and to ensure that the effects of the additions proposed will be measurable during the full-scale study. Pilot studies undertaken during 1999 include:
Figure 4. Fish sampling during baseline METAALICUS studies.
The pilot studies have confirmed that the analytical techniques are sufficiently sensitive to detect the small additions of added isotope, and that the general research design is viable.
Future Activities and Schedule
In 2000 we will continue baseline studies and begin an aquatic mesocosm experiment with different Hg doses. The full-scale addition experiment is planned to start in 2001 and will run for three years. Mercury will be added at intervals to mimic natural seasonal deposition patterns. Initial full-scale results will emerge in 2001. 2004 will be dedicated to final reporting and publishing for the study. If appropriate, less intensive sampling in the longer term will be considered.
The Study Team
The project team (Table 1) includes leading mercury researchers from the United States and Canada. We also have an international advisory committee from Sweden, the USA and Canada (Table 2). The team has extensive experience with whole ecosystem mercury experiments and a history of successful collaboration.
|Mr. Reed Harris, P. Eng.||Tetra Tech Inc.|
|Dr. John Rudd||Canadian Department of Fisheries and Oceans (DFO)|
|Dr. Carol Kelly||DFO|
|Dr. Holger Hintelmann||Trent University, Ontario|
|Dr. Marc Amyot||INRS, Université du Québec|
|Dr. R.A. (Drew) Bodaly||DFO|
|Mr. Ken Beaty||DFO|
|Dr. Paul Blanchfield||DFO|
|Dr. Brian Branfireun||University of Toronto|
|Dr. David Findlay||DFO|
|Dr. Cynthia Gilmour||Academy of Natural Sciences, MD|
|Dr. Andrew Heyes||Academy of Natural Sciences, MD|
|Dr. James Hurley||University of Wisconsin/Wisconsin DNR|
|Dr. David Krabbenhoft||U.S. Geological Survey|
|Dr. Karen Kidd||DFO|
|Dr. Lyle Lockhart||DFO|
|Dr. Vince St. Louis||University of Alberta|
|Dr. Steven Lindberg||Oak Ridge National Laboratory, TN|
|Dr. Michael Paterson||DFO|
|Dr. Cheryl Podemski||DFO|
|Dr. Robert Flett||Flett Research Ltd.|
|Dr. Åke Iverfeldt||Swedish Environmental Research Institute (IVL)|
|Dr. John Munthe||Swedish Environmental Research Institute (IVL)|
|Dr. Edward Swain||Minnesota Pollution Control Agency|
|Dr. Ray Hesslein||Canadian Department of Fisheries and Oceans|
To ensure timely dissemination of research results we will employ different means of communications: a) annual workshops for government, industry and team members, b) publications in newsletters and primary research journals throughout the study, and c) general information distribution via the world-wide-web (address below).
METAALICUS Status and Funding
Funding for the METAALICUS study is about half complete. We presently have funding from the Canadian Department of Fisheries and Oceans, the Electric Power Research Institute, the U.S. EPA, the USGS, the Wisconsin DNR, the National Sciences Engineering and Research Council of Canada, and the U.S. Department of Energy.
For more information:
Contact Reed Harris or Dr. John Rudd:
Dr. John Rudd