The Chemical Cycle and Bioaccumulation of Mercury

Abstract

Because it is very toxic and accumulates in organisms, particularly in fish, mercury is an important pollutant and one of the most studied. Nonetheless we still have an incomplete understanding of the factors that control the bioconcentration of mercury. Elemental mercury is efficiently transported as a gas around the globe, and even remote areas show evidence of mercury pollution originating from industrial sources such as power plants. Besides elemental mercury, the major forms of mercury in water are ionic mercury (which is bound to chloride, sulfide, or organic acids) and organic mercury, particularly methylmercury. Methylmercury rather than inorganic mercury is bioconcentrated because it is better retained by organisms at various levels in the food chain. The key factor determining the concentration of mercury in the biota is the methylmercury concentration in water, which is controlled by the relative efficiency of the methylation and demethylation processes. Anoxic waters and sediments are an important source of methylmercury, apparently as the result of the methylating activity of sulfatereducing bacteria. In surface waters, methylmercury may originate from anoxic

Trophodynamics of inorganic pollutants in a wide-range feeder: The relevance of dietary inputs and biomagnification in the Yellow-legged gull (Larus michahellis)

“…In particular, several studies have previously reported on the influence of particular dietary contributions on THg and Se concentrations (Bergeron et al, 2007;Loseto et al, 2008;Ramos et al, 2009a). In addition, many other studies have already reported on biomagnification of these elements throughout foodwebs, considering d 15 N as a measure of trophic positions (Atwell et al, 1998;Becker et al, 2002;Cabana and Rasmussen, 1994;Jarman et al, 1996;McIntyre and Beauchamp, 2007;Morel et al, 1998). Some of these studies even found this positive pollutante d 15 N relationship at intra-specific level (Ramos et al, 2009a).…”

“…Since Cabana and Rasmussen (1994) questions related to biomagnification of contaminants to deleterious levels in biota, have largely been addressed by considering species' trophic positions (Becker et al, 2002;McIntyre and Beauchamp, 2007;Morel et al, 1998;Stewart et al, 2004). However, direct trophic transfer of pollutants derived from local feeding opportunities and individual feeding behaviours is also considered an important pathway for contaminant acquisition (Bearhop et al, 2000;Bergeron et al, 2007;Loseto et al, 2008;Ramos et al, 2009a), adding complexity to the study of pollutant trophodynamics.…”

Monitoring the Response to Changing Mercury Deposition

“…Ancillary information on fish length, weight, sex, and age is required to provide a more statistically defensible, normalized MeHg value. Other factors, such as nutrient input, watershed land use change, fluctuations in water levels in shallow ecosystems, overfishing, changes in food chain structure, and variations in species competition, can also alter fish MeHg concentration (9,27,30). Because MeHg is the dominant form in fish, measurement of total mercury is an adequate metric.…”

Mercury Levels in Pristine and Gold Mining Impacted Aquatic Ecosystems of Suriname, South America

“…Aquatic microorganisms transform metallic mercury into the extremely toxic methylmercury (Morel et al 1998) which is assimilated rapidly by aquatic biota and accumulates in the food chain: the bio-accumulation factor (BAF) for piscivorous fish calculated by the US EPA (1997) is 6 800 000.…”