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A survey of four lake basins and fish in three Alaska national park units has detected measurable levels of mercury, pesticides and other airborne contaminants. The study also found airborne contaminants in other western United States national parks.
The primary Alaska surveys took place at Denali National Park & Preserve, Gates of the Arctic National Park & Preserve, and Noatak National Preserve. Contaminant concentrations were measured mainly in lake trout, a species present in all three parks.
Contaminants such as mercury and the insecticide dieldrin were likely carried to the Alaska ecosystems in the air from distant sources like Europe and Asia, indicating a global background signal. In the Lower 48, the other western parks studied receive global inputs but also receive contaminant loads from local agricultural sources (those within 150 km), or local industrial sources.
Findings are the result of the Western Airborne Contaminants Assessment Project (WACAP), a six-year, multi-agency study funded primarily by the National Park Service. Results of the project add considerably to the state of the science concerning contaminant transport and the subsequent biological and ecological effects in remote areas of Alaska and the Lower 48. “These well-documented and carefully analyzed data will provide a basis for evaluating future changes in the status of these ecosystems,” said Dr. Dixon Landers, the U.S. Environmental Protection Agency (EPA) scientist who headed the study. National park managers in Alaska said they anticipate continuing the assessment work by sampling more lake trout and other fish species in other locations.
State and federal researchers familiar with the results noted that lake trout are a relatively longlived fish species at the top of the food web, and as such are more likely to biomagnify mercury and other toxins over their life spans. For the most part, they are not consumed in great quantities by either sport or subsistence fishermen. The risk to people is therefore likely low, but is variable given location and frequency of fish consumption. However, the extent of the effects on fish-eating birds and mammals that depend on these resources for survival is unknown.