“Seeing” Mercury Methylation in Progress

Mercury in the environment can easily reach toxic levels. In a process called methylation, Hg is transformed into a form that can be accumulated in the muscle and fatty tissue of fish. Accumulated levels of methylmercury become higher as the fish grow, and levels are magnified up the food web as larger fish eat smaller fish, a process called biomagnification. As a result, mercury concentrations in fish can be millions of times higher than in surrounding waters [1]. Fish advisories have been set to limit consumption of certain fish higher up on the food web, especially for pregnant women and small children (see Figure 1).