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Reducing mercury pollution entering lakes quickly lowers how much harmful mercury is found in fish


Every year, about 2000 tons of gaseous mercury are released into the atmosphere by human activities such as coal power plant operation, waste incineration or cement production. The harmful substance than is partly transformed to various species as it circulates between the air, soil and water in a complex biogeochemical cycle. Reaching the aquatic environment, it gets particularly dangerous, entering the food web where it accumulates in fish in the form of methylmercury. Human exposure is mainly via the consumption of contaminated fish, creating adverse effects on brain development in children or causing cardiovascular diseases in adults. Simply avoiding fish is not a good solution, since Fish is a source of high-quality protein that is beneficial to many people, providing that it is low in methylmercury.

The Minamata Convention on Mercury is an international treaty that aims to protect human health and the environment from adverse effects of methylmercury by controlling mercury emissions, which should then decrease deposition and loading of anthropogenic mercury to aquatic environments. Since the biogeochemical cycling of mercury in the environment is rather complex, influenced by many environmental and anthropogenic factors, little is known about how quickly fish contamination will decline following reductions in anthropogenic mercury emissions.  

The new study:

The study was carried out at IISD Experimental Lakes Area (IISD-ELA) in Ontario, Canada, which is one of the only facilities in the world where lakes and their watersheds can be experimentally manipulated to determine the many ways in which humans are impacting lakes.  

“Showing that reducing mercury inputs to a lake will lower mercury concentrations in fish sounds simple,” said Dr. Paul Blanchfield of Fisheries and Oceans Canada and Queens University and a lead investigator of the Mercury Experiment to Assess Atmospheric Loading in Canada and the United States (METAALICUS).  

“But it required a dedicated team effort, including academic, government and NGO researchers from across North America, during the 15-year whole-ecosystem study to arrive at this conclusion.”

An airplane that sprays mercury into the experimental lake area
Photo: An airplane that sprays mercury into the experimental lake area (Credit: IISD Experimental Lakes Area)

The team applied about one teaspoon of an isotopically enriched mercury to a lake and its watershed, at a cost of over one million CAD. They were able to measure this mercury as methylmercury in the ecosystem and to track its rapid decline in fish once they stopped adding it to the environment.

“Whole-ecosystem experiments are incredibly powerful because they examine the effects of a single factor at a time and provide solutions to globally-important issues in a real-world setting,” said Dr. Carol Kelly, who has spent decades conducting research on the experimental lakes.   

Part of that real-world setting was working with natural fish populations.  

“Studying fish only in laboratories was not revealing the full story,” said Lee Hrenchuk, a Biologist with IISD-ELA. “Individual fish retain mercury they have previously accumulated for a long time, and so it could be assumed that decreasing mercury input to a lake might not be very beneficial. However, we discovered that the hatching of new fish into a lower mercury environment was sufficient to lower the mercury level of the population as a whole in a short period of time”.

“The near-term value of reducing mercury inputs to freshwater lakes was not a sure thing, because large masses of old mercury always exist in lakes from decades past,” said Mr. Reed Harris, of Reed Harris Environmental, one of the founders of the study.  

“So, it was critical for the experiment that isotopic form of mercury we added could be distinguished from older mercury in the ecosystem.” As new mercury inputs to the experimental lake were increased and then decreased in a controlled manner, the methylmercury in the lake water, surface sediments, invertebrates and fish both increased and decreased quickly. This was true whether the mercury ‘rained’ directly onto the lake surface or entered the lake from the surrounding watershed in streams.

“While mercury exported to lakes from their watersheds may not decline exactly in step with lowering atmospheric deposition rates, this experiment clearly demonstrates that any reduction in the amount of mercury entering lakes will have immediate benefits to fish consumers,” said Dr. John Rudd, former Chief Scientist at the Experimental Lakes Area and a principal investigator on the study.  

This article has been republished from material presented by IISD. Note: material may have been edited for length and content.

The original publication

Paul J. Blanchfield, John W.M. Rudd, Lee E. Hrenchuk, Marc Amyot, Christopher L. Babiarz, Ken G. Beaty, R. A. Drew Bodaly, Brian A. Branfireun, Cynthia C. Gilmour, Jennifer A. Graydon, Britt D. Hall, Reed C. Harris, Andrew Heyes, Holger Hintelmann, James P. Hurley, Carol A. Kelly, David P. Krabbenhoft, Steve E. Lindberg, Robert P. Mason, Michael J. Paterson, Cheryl L. Podemski, Ken A. Sandilands, George R. Southworth, Vincent L. St Louis, Lori S. Tate, Michael T. Tate, Experimental evidence for recovery of mercury-contaminated fish populations. Nature. 601 (2022) 74-78. DOI: 10.1038/s41586-021-04222-7

Instrumentation used:

Micromass Platform ICP-MS
PerkinElmer Elan DRC II ICP-MS System

Related studies (newest first):

C.P. Madenjian, S.R. Chipps, P.J. Blanchfield, Time to refine mercury mass balance models for fish. FACETS 6, 272–286 (2021). DOI: 10.1139/facets-2020-0034

Vincent L. St. Louis, Jennifer A. Graydon, Igor Lehnherr, Helen M. Amos, Elsie M. Sunderland, Kyra A. St. Pierre, Craig A. Emmerton, Ken Sandilands, Michael Tate, Alexandra Steffen, and Elyn R. Humphreys. Atmospheric concentrations and wet/dry loadings of mercury at the remote Experimental Lakes Area, Northwestern Ontario, Canada. Environ. Sci. Technol., 53 (2019) 8017–8026. DOI: 10.1021/acs.est.9b01338

Celia Y. Chen, Charles T. Driscoll, Collin A. Eagles-Smith, Chris S. Eckley, David A. Gay, Heileen Hsu-Kim, Susan E. Keane, Jane L. Kirk, Robert P. Mason, Daniel Obrist, Henrik Selin, Noelle E. Selin, Marcella R. Thompson. A critical time for mercury science to inform global policy. Environ. Sci. Technol. 52 (2018) 9556–9561. DOI: 10.1021/acs.est.8b02286

C.J. Oswald, A. Heyes, B.A. Branfireun, Fate and transport of ambient mercury and applied mercury isotope in terrestrial upland soils: insights from the METAALICUS watershed. Environ. Sci. Technol., 48 (2014) 1023–1031. DOI: 10.1021/es404260f

J.L.A. Van Walleghem, P.J. Blanchfield, L.E. Hrenchuk, E. Hintelmann, Mercury elimination by a top predator, Esox lucius. Environ. Sci. Technol., 47 (2013) 4147–4154. DOI: 10.1021/es304332v

David C. Depew, Neil M. Burgess, M. Robin Anderson, Randy Baker, Satyendra P. Bhavsar, R.A. (Drew) Bodaly, Chris S. Eckley, Marlene S. Evans, Nikolaus Gantner, Jennifer A. Graydon, Kevin Jacobs, Jason E. LeBlanc, Vincent L. St. Louis, and Linda M. Campbell, An overview of mercury concentrations in freshwater fish species: a national fish mercury dataset for Canada. Can. J. Fish. Aquat. Sci., 70 (2013) 436–451. DOI: 10.1139/cjfas-2012-0338

Jennifer A. Graydon, Vincent L. St. Louis, Steve E. Lindberg, Ken A. Sandilands, John W. M. Rudd, Carol A. Kelly, Reed Harris, Michael T. Tate, Dave P. Krabbenhoft, Craig A. Emmerton, Hamish Asmath, Murray Richardson , The role of terrestrial vegetation in atmospheric Hg deposition: Pools and fluxes of spike and ambient Hg from the METAALICUS experiment. Global Biogeochem. Cycles, 26 (2012) GB1022. DOI: 10.1029/2011GB004031

L.E. Hrenchuk, P.J. Blanchfield, M.J. Paterson, H.H. Hintelmann, Dietary and waterborne mercury accumulation by yellow perch: a field experiment. Environ. Sci. Technol., 46 (2012) 509–516. DOI: 10.1021/es202759q .

Ken A. Sandilands, Carol A. Kelly, John W.M. Rudd, Michael T. Tate, Holger Hintelmann, Brian Dimock, Reed Harris. Application of Enriched Stable Mercury Isotopes to the Lake 658 Watershed for the METAALICUS Project, at the Experimental Lakes Area, Northwestern Ontario, Canada, 2001−2007. Can. Tech. Rep. Fish. Aquat. Sci. vol. 2813 (Fisheries and Oceans Canada, 2008). https://publications.gc.ca/collections/collection_2014/mpo-dfo/Fs97-6-2813-eng.pdf

Reed C. Harris, John W. M. Rudd, Marc Amyot, Christopher L. Babiarz, Ken G. Beaty, Paul J. Blanchfield, R. A. Bodaly, Brian A. Branfireun, Cynthia C. Gilmour, Jennifer A. Graydon, Andrew Heyes, Holger Hintelmann, James P. Hurley, Carol A. Kelly, David P. Krabbenhoft, Steve E. Lindberg, Robert P. Mason, Michael J. Paterson, Cheryl L. Podemski, Art Robinson, Ken A. Sandilands, George R. Southworth, Vincent L. St. Louis, and Michael T. Tate, Whole-ecosystem study shows rapid fish-mercury response to changes in mercury deposition. Proc. Natl Acad. Sci. USA, 104 (2007) 16586–16591. DOI: 10.1073/pnas.0704186104

George Southworth, Steven Lindberg, Holger Hintelmann, Marc Amyot, Alexandre Poulain, MaryAnna Bogle, Mark Peterson, John Rudd, R. Harris, Kenneth Sandilands, David Krabbenhoft, Mark Olsen. Evasion of added isotopic mercury from a northern temperate lake. Environ. Toxicol. Chem., 26/1 (2007) 53–60. DOI: 10.1897/06-148R.1

J.L.A. Van Walleghem, P.J. Blanchfield, H. Hintelmann, Elimination of mercury by yellow perch in the wild. Environ. Sci. Technol., 41 (2007) 5895–5901. DOI: 10.1021/es070395n.

C.S. Eckley, H. Hintelmann, Determination of mercury methylation potentials in the water column of lakes across Canada. Sci. Total Environ., 368 (2006) 111–125. DOI: 10.1016/j.scitotenv.2005.09.042

Michael J Paterson, Paul J Blanchfield, Cheryl Podemski, Holger H Hintelmann, Cynthia C Gilmour, Reed Harris, Nives Ogrinc, John WM Rudd, and Ken A Sandilands. Bioaccumulation of newly-deposited mercury by fish and invertebrates: an enclosure study using stable mercury isotopes. Can. J. Fish. Aquat. Sci., 63 (2006) 2213–2224. DOI: 10.1139/f06-118

Ken A. Sandilands, John W.M. Rudd, Carol A. Kelly, Holger Hintelmann, Cynthia C. Gilmour, Michael T. Tate. Application of Enriched Stable Mercury Isotopes to the Lake 658 Watershed for the METAALICUS Project, at the Experimental Lakes Area, Northwestern Ontario, Canada. Can. Tech. Rep. Fish. Aquat. Sci., 2597 (2005). https://publications.gc.ca/site/eng/429104/publication.html

P. Sellers, C.A. Kelly, J.W.M. Rudd, Fluxes of methylmercury to the water column of a drainage lake: The relative importance of internal and external sources. Limnol. Oceanogr. 46 (2001) 623–631. DOI: 10.4319/lo.2001.46.3.0623

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last time modified: November 26, 2023


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