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Elephant seals’ fur as a source for methylmercury in coastal sea water


When mercury, generated by industrial pollution, reach the ocean, microbes transform the toxic metal species into an even more dangerous compound called methylmercury. Methylmercury accumulates in marine organisms and its concentration gets biomagnified along the food chain.

Male and female elephant seals
Photo: Male and female elephant seals
Elephant seals consume mercury through the marine species they feed and can accumulate levels of mercury to 10 million times more than that found in the surrounding seawater. Therefore, often animals are used as bioindicators for monitoring the contamination of their environment.

The new study:
Researchers from the University of California - Santa Cruz found that Elephant seals are not only a bioindicator for their environment but a significant source for methylmercury themselves. Methylmercury, previously taken up by the animals is returned to the water with the seals’ excreta and fur during the molting season, which contributes to the high levels of mercury in the in coastal waters near the elephant seal rookery at Año Nuevo State Reserve.

"Many studies have looked at biomagnification up the food chain, and we took that a step further to see what happens next. Mercury is an element, so it never breaks down and goes away -- it just changes forms," Jennifer Cossaboon, first author and graduate student in environmental health at San Diego State University, said in a news release. “Elephant seals undergo a catastrophic moult (which) comes off in big sheets of fur and the top few layers of skin”, explaines Jennifer Cossaboon.

A 1981 study by coauthor Russell Flegal, professor of microbiology and environmental toxicology at UC Santa Cruz, had found elevated mercury concentrations in mussels near large colonies of seals and sea lions at Año Nuevo and San Miguel Island.

"At that time, we didn't have the analytical instruments to detect mercury at the concentrations found in seawater, so we used mussels, which filter seawater, as sentinel organisms," Flegal said. "In the new study, we were able to look at seasonal changes in the water, and during the elephant seal molting season the levels of methyl mercury really took off."
Compared to other coastal sites, the concentration of methyl mercury in the seawater at Año Nuevo was twice as high during the breeding season and 17 times higher during the molting season.

Source: Press release University of California - Santa Cruz from Sep. 7, 2015

The original study

Jennifer M. Cossaboon, Priya M. Ganguli, A. Russell Flegal, Mercury offloaded in Northern elephant seal hair affects coastal seawater surrounding rookery, Proc. Nat. Acad. Sci. USA, 2015: doi: 10.1073/pnas.1506520112

Related studies (newest first)

Nicole David, Lester J. McKee, Frank J. Black, A. Russell Flegal, Christopher H. Conaway, David H. Schoellhamer, Neil K. Ganju, Mercury Concentrations and Loads in a Large River System Tributary to San Francisco Bay, California, USA, Environ. Toxicol. Chem., 28/10 (2009) 2091–2100. available from USGS

Christopher H. Conaway, Frank J. Black, Thomas M. Grieb, Sujoy Roy, A. Russell Flegal, Mercury in the San Francisco Estuary, Rev. Environ. Contam. Toxicol., 194 (2008) 29-54. doi: 10.1007/978-0-387-74816-0_2

Laszlo Magos, Thomas W. Clarkson, The assessment of the contribution of hair to methyl mercury excretion, Toxicol. Lett., 182 (2008) 48–49. doi: 10.1016/j.toxlet.2008.08.010 

Fernando Elorriaga-Verplancken, David Aurioles-Gamboa, Trace Metal Concentrations in the Hair of Zalophus californianus Pups and their Relation to Feeding Habits, Biol. Trace Elem. Res., 126 (2008) 148–164. doi: 10.1007/s12011-008-8186-8

Elsie M. Sunderland, Robert P. Mason, Human impacts on open ocean mercury concentrations, Global Biogeochem. Cycles, 21 (2007) GB4022.  doi: 10.1029/2006GB002876

Tiffini J. Brookens, James T. Harvey, Todd M. O'Hara, Trace element concentrations in the Pacific harbor seal (Phoca vitulina richardii) in central and northern California, Sci. Total Environ., 372 (2007) 676–692.  doi: 10.1016/j.scitotenv.2006.10.006

Francois M.M. Morel, Anne M.L. Kraepiel, Marc Amyot, The Chemical Cycle and Bioaccumulation of Mercury, Annu. Rev. Ecol. Syst., 29 (1998) 543–66. doi: 10.1146/annurev.ecolsys.29.1.543

M.C. Fossi, L. Marsili, M. Junin, H. Castello, J.A. Lorenzani, S. Casini, C. Savelli, C. Leonzio, Use of nondestructive biomarkers and residue analysis to assess the health status of endangered species of pinnipeds in the south-west Atlantic, Mar. Pollut. Bull., 34/3 (1997) 157–162. doi: 10.1016/S0025-326X(96)00073-2

C. Wenzel, D. Adelung, H. Kruse, O. Wassermann, Trace Metal Accumulation in Hair and Skin of the Harbour Seal, Phoca vitulina, Mar. Pollut. Bull., 26/3 (1993) 152-155. doi: 10.1016/0025-326X(93)90126-5

A.R. Flegal, G.J. Smith, G.A. Gill, S. Sañudo-Wilhelmy, L.C.D. Anderson, Dissolved trace element cycles in the San Francisco Bay estuary,  Mar. Chem., 36/1–4 (1991) 329-363. doi: 10.1016/S0304-4203(09)90070-6 

G.J. Bacher, Mercury Concentrations in the Australian Fur Seal Arctocephalus pusillus from SE Australian Waters, Bull. Environ. Contain. Toxicol. (1985) 35:490-495. doi: 10.1007/BF01636543

A.R. Flegal, M. Stephenson, M. Martin and J.H. Martin, Elevated Concentrations of Mercury in Mussels (Mytilus californianus) Associated with Pinniped Colonies, Mar. Biol., 65 (1981) 45-48. doi: 10.1007/BF00397066

Related EVISA Resources

Link Database: Toxicity of Organo-mercury compounds
Link Database: Mercury exposure through the diet
Link Database: Environmental cycling of methylmercury
Link Database: Environmental cycling of inorganic mercury
Link Database: Environmental pollution of methylmercury
Link Database: Environmental pollution of inorganic mercury
Link Database: Toxicity of mercury
Brief summary: Atomic Fluorescence Spectrometry as a Detection System for Speciation Analysis
Brief summary: Gas chromatography for the separation of elemental species

Related EVISA News

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June 17, 2012: Factors Affecting Methylmercury Accumulation in the Food Chain
August 16, 2010: Methylmercury: What have we learned from Minamata Bay?
June 28, 2010: New Study Examines Why Mercury is More Dangerous in Oceans
August 21, 2009: USGS Study Reveals Mercury Contamination in Fish Nationwide
May 5, 2009: Ocean mercury on the rise
February 11, 2009: Mercury in Fish is a Global Health Concern
October 30, 2008: Precautionary approach to methylmercury needed
March 11, 2007: Methylmercury contamination of fish warrants worldwide public warning
October 9, 2006: Linking atmospheric mercury to methylmercury in fish
September 23, 2006: Report Finds Mercury Contamination Permeates Wildlife Systems
August 16, 2006: Mercury pollution threatens health worldwide, scientists say

last time modified: July 22, 2020


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