Is Mercury the Achilles Heel of the Restoration Effort?

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Part 2: What is the Cause of the South Florida Mercury Problem?

What are the most significant sources of mercury to the Everglades? How does new or recycled inorganic mercury become methylmercury? More than 95% of the new mercury added to the Everglades each year comes from atmospheric deposition. But the mercury that has already accumulated in Everglades soil can also be released from storage by soil bacteria for recycling back into the aquatic ecosystem. Inorganic mercury in storm runoff, rainfall, or soil is transformed by natural (sulfate-reducing) bacteria into methylmercury. This generally occurs in flooded soil and always occurs in the presence of sulfate and the absence of dissolved oxygen.

What makes methylmercury so dangerous?

Methylmercury is rapidly taken up but only slowly eliminated from the body by fish and other aquatic organisms, so each step up in the food chain (bio)magnifies the concentration from the step below. Bioaccumulation factors (BAF's) of up to 10 million in largemouth bass have been reported for the Everglades. Fish-eating birds, otters, alligators, raccoons and panthers can have even higher bioaccumulation factors. Methylmercury in the organs and tissues causes birth defects & disorders of the brain, reproductive system, immune system, kidney, and liver at extremely low levels in food.

Next: Multi-agency strategy for understanding and solving the Everglades mercury problem