'Integrating Knowledge to Inform Mercury Policy'

• Mercury isotopes reveal more about sources of mercury to fish in the open Ocean [Senn et al (2010)]
• Agricultural wetlands may be an important hotspot for methlymercury bioaccumulation [ Ackerman and Eagles-Smith (2010)]
• Sources of Mercury Exposure for U.S. Seafood Consumers: 
Implications for Policy [Selin et al. (2009)]
• Mercury contamination of tuna in the Pacific Ocean, why its likely to worsen [Sunderland et al (2009)]
• Global warming may result in higher mercury levels in Arctic seals [Gaden et al (2009)]
• Study reveals new mercury risks for fish and birds [Eagles-Smith and Ackerman (2009)]
• The availability of mercury in streams and how it makes its way into fish and other life-forms [ ES&T Environmental news, 2009]

Mercurial tuna: Study explores sources of mercury to ocean fish (Mar 9 2010 environmental research web) In the current study, the researchers wanted to know if tuna and other open-ocean fish pick up methylmercury by eating contaminated fish that live closer to shore or by some other means.  Chemical signatures in the fish suggest coastal and open ocean fish feed from different food webs.  The authors suggest the most likely reason is that there is deposition and methylation of mercury in the open ocean.  One of the biggest differences the researchers found between coastal and open-ocean fish was in their mercury “fingerprint.”   The researchers found that open-ocean fish have mercury with different isotopic properties than coastal fish, a discovery that opens the door to new ways of analysing human exposure to mercury. Environmental Science & Technology Senn et al (2010)

Agricultural Wetlands as Potential Hotspots for Mercury Bioaccumulation.  Wetlands are investigated as a source of methylmercury by introducing caged fish to monitor their response in natural wetlands and rice fields.   Mercury was higher in fish in agricultural fields than those in the permanent wetlands. The results indicate that shallowly flooded rice fields are potential hotspots for MeHg bioaccumulation and, due to their global prevalence, suggest that agricultural wetlands may be important contributors to methyl mercury contamination.  Environmental Science & Technology Ackerman and Eagles-Smith (2010)

Sources of Mercury Exposure for U.S. Seafood Consumers: 
Implications for Policy. (Editor’s summary) Efforts to reduce human exposure to methylmercury have focused on dietary recommendations and policies to reduce emissions from anthropogenic sources. Selin et al. (2009) note that current and future exposures are also a function of historical anthropogenic emissions and argue that a comprehensive evaluation of mercury dynamics in aquatic and atmospheric systems, bioaccumulation in food webs, and patterns of human food consumption is needed to predict the potential impact of emissions reductions on human exposure over time. They estimate that North American emissions controls may reduce mercury exposure by up to 50% in certain highly exposed groups but note that potential effects on populations consuming marine fish are uncertain. The authors conclude that a combination of North American and international emissions controls and dietary adaptation strategies are needed to manage methylmercury risks across population subgroups.   Environmental Health Perspectives Selin et al. (2009)

How mercury emissions reach tuna and other seafood, and why mercury contamination is likely to worsen.  (May 3, 2009 Science Daily) A new landmark study documents for the first time the process in which increased mercury emissions from human sources across the globe, and in particular from Asia, make their way into the North Pacific Ocean and as a result contaminate tuna and other seafood. Because much of the mercury that enters the North Pacific comes from the atmosphere, scientists have predicted an additional 50 percent increase in mercury in the Pacific by 2050 if mercury emission rates continue as projected.  Global Biogeochemical Cycles Sunderland et al (2009)

Mercury Levels In Arctic Seals May Be Linked To Global Warming. (May 5 2009 Science Daily)  Higher seal mercury concentrations may follow relatively short ice-free seasons due to consumption of older, more highly contaminated Arctic cod while relatively long ice-free seasons may promote increased survival and abundance of Arctic cod with the overall result of more fish consumption and greater exposure to mercury. Longer ice-free seasons resulting from a warming Arctic may therefore result in higher mercury levels in ringed seal populations as well as their predators (polar bears and humans).  Environmental Science & Technology Gaden et al (2009)

Mercury in small fish peaks when fish-eating birds are breeding in the San Francisco Bay estuary.  (Nov 11, 2009 ES&T Environmental news)  A time-series study of mercury levels in two small fish species was performed in the San Francisco Bay estuary representing benthic and pelagic food webs.  Mercury levels in the fish fluctuated significantly in a very short period of time, increasing by 40% from March to May, then decreasing 40% from May to July.  Environmental Science & Technology Eagles-Smith and Ackerman (2009)

How mercury flows downstream. A comprehensive study shows the correlations among landscape, mercury, and the life in streams and rivers. Researchers from the U.S. Geological Survey have published a suite of papers in ES&T that elucidate the availability of mercury in streams and how it makes its way into fish and other life-forms in these dynamic ecosystems.  The researchers tracked proxies for mercury availability and methylation,  and looked at mercury concentrations in different predator fish by moving up the food chain from algae to the insects and small fish the predators eat.  ES&T How mercury flows downstream