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The Mercury Paradox

Bacteria living in aquatic sediments can convert mercury into methylmercury, a more toxic form of the heavy metal. As this substance accumulates in marine animals it can lead to elevated mercury levels in fish. However, Marc Beutel of Washington State University is working with the Colville Confederated Tribes to better understand how adding oxygen to lakes affects mercury levels in fish. While field data indicates that oxygen addition represses methylmercury accumulation in bottom waters, mercury levels remain elevated in lake animals and fish.

These preliminary findings have major implications for the practice of adding oxygen to lakes to manage mercury uptake in fish. The goal is to lower mercury levels in fish because mercury can pose a health risk to fish-eating wildlife and humans.

Methylmercury tends to build up in the bottom water of lakes with no oxygen. The researchers anticipated that adding oxygen to lakes would impede methylmercury accumulation in bottom waters and its subsequent uptake into fish. While oxygen addition has decreased methylmercury accumulation in bottom waters, preliminary results suggest that mercury uptake into aquatic animals may be higher under oxygenated versus non-oxygenated conditions, which is the exact opposite of what was expected.

This study, and the unraveling of this apparent "mercury paradox," will expand the knowledge-base related to actively managing mercury pollution in lakes.

Images (1 of )

  • researchers sample water at north twin lake
  • graduate students haul mercury monitoring gear to north twin lake
Researchers sample water at North Twin Lake for mercury.
Marc Beutel, Washington State University
Graduate students haul mercury monitoring gear to the center of North Twin Lake.
Marc Beutel, Washington State University

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