How do methylmercury levels increase from new hydroelectric developments?

• If a hydroelectric development creates a new or enlarged reservoir through flooding, the production of methylmercury may increase
• This occurs as flooded vegetation in the new reservoir decomposes, stimulating the conversion of existing inorganic mercury into methylmercury by bacteria. (Figure 1)
  
• Methylmercury can then start to build up in the food chain.
• The percentage of new flooding compared to the total reservoir area is an important factor in determining the extent to which methylmercury concentrations may increase.
• Wetland areas are known to be a greater source of methylmercury thanupland areas.