Mercury as a pollutant in aquatic ecosystems Mercury is a highly toxic pollutant that rapidly spreads all over the world from its natural and anthropogenic sources. Although atmospheric mercury concentrations have been decreased by 20 to 38% since 1996 (Slemr et al. 2011), mercury pollution is still a severe threat to aquatic ecosystems. Recent causes of mercury pollution in aquatic ecosystems include oil and coal combustion, agricultural drain water and atmospheric deposition from electric power