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New study identifies source of methylmercury in Southern Ocean sea ice


Mercury is a global pollutant entering the environment mainly from fossil fuel combustion, cement production and waste incineration. Once emitted to the environment, mercury can be methylated by microbes to methylmercury which can be accumulated in organisms and biomagnified along the food chain. The main exposure of humans to methylmercury is through the consumption of marine fish and especially predatory species such as tuna or swordfish. Once taken up from food it can be transported by the blood stream, cross the blood-brain-barrier and reach the central nervous system, severely affecting neural development in fetuses and damaging brain, heart, kidney, lung and immune functioning in adults.

The new study:
Led by Caitlin Gionfriddo and Dr. John Moreau from the University of Melbourne, an international team of scientists from the Center for Systems Genomics at the University of Melbourne, the US Geological Survey, and Lawrence Livermore National Laboratory, have become the first to find that sea ice bacteria can change mercury into methylmercury.

photo of the mountains in Antarctica
Photo: The Southern Ocean and the mountains of Antartica (Public Domain via Pixabay)

In order to find out how methylmercury enters the arctic marine environment and eventually ends up in the food-web, Ms Gionfriddo spent two months aboard the icebreaker Aurora Australis to collect samples of Antarctic sea ice during an expedition mounted by the Australian Antarctic Division. After collection, the sea ice samples were analysed for the presence of different mercury species by the US Geological Survey, while DNA and proteins from sea ice microorganisms were studied at the University of Melbourne and the Lawrence Livermore National Lab.

Using metagenomic analysis of whole-community microbial DNA from Antarctic snow, brine, sea ice and sea water, the research team confirmed the presence of bacteria in the sea ice with the genetic ability to convert mercury into its more toxic form, methylmercury.

"These results are the first to identify a particular genus of bacteria, called Nitrospina, as capable of producing methylmercury in Antarctic ice," Dr Moreau said. Especially interesting was the absence of any anaerobic bacteria known to methylate mercury in the samples studied.


Reprinted from materials provided by University of Melbourne. Note: Materials have been edited for content and length.

The cited study:

  Caitlin M. Gionfriddo, Michael T. Tate, Ryan R. Wick, Mark B. Schultz, Adam Zemla, Michael P. Thelen, Robyn Schofield, David P. Krabbenhoft, Kathryn E. Holt, John W. Moreau, Microbial mercury methylation in Antarctic sea ice, Nature Microbiol., 1 (2016) #16127. doi: 10.1038/nmicrobiol.2016.127

Used analytical techniques:

Cold vapour atomic fluorescence spectrometry

Related studies (newest first):

Lars-Eric Heimbrger, Jeroen E. Sonke, Daniel Cossa, David Point, Christelle Lagane, Laure Laffont, Benjamin T. Galfond, Marcel Nicolaus, Benjamin Rabe, Michiel Rutgers van der Loeff, Shallow methylmercury production in the marginal sea ice zone of the central Arctic Ocean. Sci. Rep., 5 (2015) 10318. doi: 10.1038/srep10318

Mircea Podar, Cynthia C. Gilmour, Craig C. Brandt, Allyson Soren, Steven D. Brown, Bryan R. Crable, Anthony V. Palumbo, Anil C. Somenahally, Dwayne A. Elias, Global prevalence and distribution of genes and microorganisms involved in mercury methylation, Sci. Adv., 1 (2015) e1500675. doi: 10.1126/sciadv.1500675

Sarah A. Beattie, Debbie Armstrong, Amanda Chaulk, Jerome Comte, Michel Gosselin, Feiyue Wang, Total and methylated mercury in arctic multiyear sea ice, Environ. Sci. Technol., 48 (2014) 55755582. doi: 10.1021/es5008033.

Jerry M. Parks, Alexander Johs, Mircea Podar, Romain Bridou, Richard A. Hurt Jr., Steven D. Smith, Stephen J. Tomanicek, Yun Qian, Steven D. Brown, Craig C. Brandt, Anthony V. Palumbo, Jeremy C. Smith, Judy D. Wall, Dwayne A. Elias, Liyuan Liang, The genetic basis for bacterial mercury methylation, Science, 339 (2013) 13321335. doi: 10.1126/science.1230667

Cynthia C. Gilmour, Mircea Podar, Allyson L. Bullock, Andrew M. Graham, Steven D. Brown, Anil C. Somenahally, Alex Johs, Richard A. Hurt, Jr., Kathryn L. Bailey, Dwayne A. Elias, Mercury methylation by novel microorganisms from new environments, Environ. Sci. Technol., 47 (2013) 1181011820. doi: 10.1021/es403075t

Daniel Cossa, Lars-Eric Heimbrger, Delphine Lannuzel, Stephen R. Rintoul, Edward C.V. Butler, Andrew R. Bowie, Bernard Averty, Roslyn J. Watson, Tomas Remenyi, Mercury in the southern ocean, Geochim. Cosmochim. Acta, 75 (2011) 40374052. doi: 10.1016/j.gca.2011.05.001

I. Lehnherr, V.L. St. Louis, H. Hintelmann, J.L. Kirk, Methylation of inorganic mercury in polar marine waters, Nature Geosci., 4 (2011) 298302. doi: 10.1038/ngeo1134

Annette K. Mller, Tamar Barkay, Waleed Abu Al-Soud, Sren J. Srensen, Henrik Skov, Niels Kroer, Diversity and characterization of mercury-resistant bacteria in snow, freshwater and sea-ice brine from the High Arctic, FEMS Microbiol. Ecol., 75 (2011) 390401. doi: 10.1111/j.1574-6941.2010.01016.x

Catherine Larose, Aurlien Dommergue, Martine De Angelis, Daniel Cossa, Bernard Averty, Nicolas Marusczak, Nicolas Soumis, Dominique Schneider, Christophe Ferrari, Springtime changes in snow chemistry lead to new insights into mercury methylation in the Arctic, Geochim. Cosmochim. Acta, 74 (2010) 62636275. doi: 10.1016/j.gca.2010.08.043

Alexandre J. Poulain, Sinad M. N Chadhain, Parisa A. Ariya, Marc Amyot, Edenise Garcia, Peter G.C. Campbell, Gerben J. Zylstra, Tamar Barkay,  Potential for mercury reduction by microbes in the high arctic, Appl. Environ. Microbiol., 73 (2007) 22302238. doi: 10.1128/AEM.02701-06

V.L. St Louis, H. Hintelmann, J.A. Graydon, J.L. Kirk, J. Barker, B. Dimock, M.J. Sharp, I. Lehnherr, Methylated mercury species in Canadian high Arctic marine surface waters and snowpacks, Environ. Sci. Technol., 41 (2007) 64336441. doi: 10.10217es070692s

Related EVISA Resources

Brief summary: Atomic Fluorescence Spectrometry as a Detection System for Speciation Analysis
Brief summary: GC-ICP-MS: A very sensitive hyphenated system for speciation analysis
Brief summary: Chemical speciation analysis for nutrition and food science
Brief summary: Speciation and Toxicity
Link database: Toxicity of Organic mercury compounds
Link database: Human exposure to methylmercury via the diet
Link page: All about Atomic Spectrometry

Related EVISA News

September 2, 2014: Man is significantly contaminating oceans with mercury
September 14, 2013: Toxic Methylmercury-Producing Microbes More Widespread Than Realized
August 6, 2013: Bacterial methylation of mercury not only starting from oxidized mercury
February 8, 2013: ORNL scientists solve mystery about mercury methylation
June 17, 2012: Factors Affecting Methylmercury Accumulation in the Food Chain

last time modified: August 3, 2016


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