2009) and continue to increase presently in some regions of the Arctic ( Rigét et al. Furthermore, there is evidence that MeHg concentrations in many marine mammals and birds have increased since industrialization ( Dietz et al. In some Greenland communities where diets are comprised predominantly of traditional foods, average Hg concentrations up to 40 µg L −1 have also recently (2000–2007) been observed in pregnant women, mothers, and women of child bearing age ( AMAP 2011). Environmental Protection Agency’s recommended blood Hg level of 5.8 µg L −1 in several northern populations ( AMAP 2011), which is very high compared to the 50 th percentile for American females of 0.720 µg L −1 ( Department of Health and Human Services 2012). In fact, >50% of mothers and women of child bearing age exceed the U.S. Monomethylmercury (MeHg), a potent vertebrate neurotoxin that is readily bioaccumulated and biomagnified, is present in numerous Arctic marine mammals, such as ringed seals ( Phoca hispida) and beluga whales ( Delphinapterus leucas), at concentrations high enough to pose health risks to Northern Peoples consuming these animals as traditional country foods ( AMAP 2011). Map of the Arctic Ocean including major seas and ocean currents (arrows warm currents = red, cold currents = black), as well as median sea ice extent between 1979–2000 (blue line), and minimum sea ice extent in 2010 (shaded area). These stressors include health issues associated with an increased reliance on processed foods from the south and exposure to multiple contaminants, such as Hg and persistent organic pollutants, through the consumption of traditional foods ( AMAP 2011). Many changes have recently occurred in communities across the Arctic, and Northern Peoples are now experiencing a combination of complex stressors. The Arctic is also inhabited by Northern Peoples, such as Inuit, who harvest and rely on marine mammals and fishes for subsistence, adding a very important human dimension to the issue of Hg contamination of Arctic marine ecosystems. A large percentage of the Arctic Ocean is ice covered for much of the year, which alters many aspects of the Hg cycle (e.g., rates of ocean-atmosphere Hg exchange and photochemical processes) and makes access for scientific study more logistically challenging. Furthermore, atmospheric processes that are unique to polar regions play an important role in controlling the deposition of atmospheric Hg to this region. Firstly, due to its extremely remote location, virtually all anthropogenic Hg inputs to the Arctic Ocean originate from long-range transport rather than point source emissions, making source attribution more challenging than in other systems. The Arctic Ocean ( Figure 1), including its coastal seas, has many features differentiating it from the rest of the world’s marine ecosystems that can affect the fate of mercury (Hg) and how issues surrounding Hg contamination are viewed. Finally, although some Northern Peoples have high mercury concentrations of mercury in their blood and hair, harvesting and consuming traditional foods has many nutritional, social, cultural and physical health benefits which must be considered in risk management and communication. Mercury concentrations in biological organisms have increased since the onset of the industrial age and are controlled by a combination of abiotic factors (e.g., monomethylmercury supply), food web dynamics and structure, and animal behavior (e.g., habitat selection and feeding behavior). While many knowledge gaps exist limiting our ability to make strong conclusions, it appears that the long range transport of mercury from Asian emissions is an important source of atmospheric Hg to the Arctic and that mercury methylation resulting in monomethylmercury production (an organic form of mercury which is both toxic and bioaccumulated) in Arctic marine waters is the principal source of mercury incorporated into food webs. The cycling of mercury in Arctic marine systems is reviewed here, with emphasis placed on the key sources, pathways and processes which regulate mercury levels in marine food webs and ultimately the exposure of human populations to this contaminant. The reliance of Northern Peoples on traditional foods, such as marine mammals, for subsistence means that they are particularly at risk from mercury exposure. Mercury in the Arctic is an important environmental and human health issue.
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