From: Woods Hole Oceanographic Institution
Published August 6, 2014 05:29 PM

Mercury in the oceans increasing

Although the days of odd behavior among hat makers are a thing of the past, the dangers mercury poses to humans and the environment persist today.

Mercury is a naturally occurring element as well as a by-product of such distinctly human enterprises as burning coal and making cement. Estimates of "bioavailable" mercury - forms of the element that can be taken up by animals and humans - play an important role in everything from drafting an international treaty designed to protect humans and the environment from mercury emissions, to establishing public policies behind warnings about seafood consumption.

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Yet surprisingly little is known about how much mercury in the environment is the result of human activity, or even how much bioavailable mercury exists in the global ocean. Until now.

A new paper by a group that includes researchers from the Woods Hole Oceanographic Institution (WHOI), Wright State University, Observatoire Midi-Pyréneés in France, and the Royal Netherlands Institute for Sea Research appears in this week's edition of the journal Nature and provides the first direct calculation of mercury in the global ocean from pollution based on data obtained from 12 sampling cruises over the past 8 years. The work, which was funded by the U.S. National Science Foundationand the European Research Council and led by WHOI marine chemist Carl Lamborg, also provides a look at the global distribution of mercury in the marine environment.

Analysis of their results showed rough agreement with the models used previously - that the ocean contains about 60,000 to 80,000 tons of pollution mercury. In addition, they found that ocean waters shallower than about 100 m (300 feet) have tripled in mercury concentration since the Industrial Revolution and that the ocean as a whole has shown an increase of roughly 10 percent over pre-industrial mercury levels.

"With the increases we've seen in the recent past, the next 50 years could very well add the same amount we've seen in the past 150," said Lamborg. "The trouble is, we don't know what it all means for fish and marine mammals. It likely means some fish also contain at least three times more mercury than 150 years ago, but it could be more. The key is now we have some solid numbers on which to base continued work."

"Mercury is a priority environmental poison detectable wherever we look for it, including the global ocean abyss," says Don Rice, director of the National Science Foundation (NSF)'s Chemical Oceanography Program, which funded the research. "These scientists have reminded us that the problem is far from abatement, especially in regions of the world ocean where the human fingerprint is most distinct."

Photo shows a CTD (conductivity, temperature, depth) rosette being lowered over the side of R/V Knorr during the North Atlantic GEOTRACES cruise in 2011. Data and water samples collected during the cruise contributed to the study of mercury in the global ocean led by Carl Lamborg. (Photo by Brett Longworth, Woods Hole Oceanographic Institution)

Read more at Woods Hole Oceanographic Institution.

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