USGS science is increasing our understanding of mercury pollution affecting a vital wildlife and human resource

When people talk about mercury contamination warnings in fish, they are talking about the compound methylmercury. Methylmercury can be stored in an organism’s body — and this amount gets passed onto larger organisms that eat them. Methylmercury “biomagnifies” in animal protein, meaning that concentrations increase in animal tissue with each step up the food chain.
The bacteria involved in the mercury methylation process are naturally occurring, and their ability to produce methylmercury is known to scientists and managers of natural and agricultural wetlands. The current challenge, however, is to make accurate predictions of methylmercury production, export, and bioaccumulation in wetland environments.
http://www.usgs.gov/blogs/features/usgs_top_story/growing-science-in-agricultural-wetlands/