Environmental concentrations of mercury (Hg) have increased three-fold globally due to human industrial activities. This inorganic mercury enters ecosystems through the air (e.g., from coal-fired power plants and incinerators), water (e.g., from chlor-alkali facilities and artisanal small- scale gold mining), and land (e.g., from landfills and other contaminated sites). The world’s freshwater ecosystems, estuaries and oceans are primary reservoirs where mercury is deposited. Once in the environment, mercury can be converted by bacteria and other microbes to its organic form, or methyl mercury. Methyl mercury is toxic, and can accumulate in the tissues of fish, wildlife, and humans, causing numerous negative health effects.
Monitoring mercury in biota (plants and animals) provides a pathway for understanding spatial gradients, temporal trends, and environmental magnitude of concern that cannot be ascertained in air, water, or sediment. Emphasizing upper trophic level biota for monitoring (i.e., trophic level 4 or higher) ultimately provides a confident ability to assess whether the global input of anthropogenic mercury into the environment is safe.
