Featured Research

from universities, journals, and other organizations

Mercury In Ocean Fish May Come From Natural Sources, Not Pollution

Date:
December 5, 2003
Source:
American Chemical Society
Summary:
Mercury levels in yellowfin tuna caught off the coast of Hawaii have not changed in 27 years, despite a considerable increase in atmospheric mercury during this time, according to a new study. The findings suggest that the high levels of mercury that have been found in tuna and other ocean fish may not be coming from pollution, but from natural sources.

Mercury levels in yellowfin tuna caught off the coast of Hawaii have not changed in 27 years, despite a considerable increase in atmospheric mercury during this time, according to a new study. The findings suggest that the high levels of mercury that have been found in tuna and other ocean fish may not be coming from pollution, but from natural sources.

Related Articles


The report will appear in the Dec. 15 edition of Environmental Science & Technology, a peer-reviewed journal of the American Chemical Society, the world's largest scientific society.

Nearly all fish contain trace amounts of mercury, but longer-lived predators — like tuna, swordfish and sharks — generally have higher levels. The U.S. Food and Drug Administration warns pregnant women against eating large amounts of fish to avoid harming an unborn child's developing nervous system.

Mercury enters the environment naturally and through industrial pollution, mostly from coal-fired power plants. Scientists have estimated that the amount of mercury in the atmosphere today is about two to three times what it was 150 years ago.

"People have assumed that the high mercury in fish must be from pollution," says Franηois Morel, Ph.D., a professor of geochemistry at Princeton University and an author of the study. "We have about tripled the mercury in the atmosphere, and therefore it should be tripled in the ocean, right? But maybe mercury that occurs in fish is a natural thing, and it may have been there all along."

The first step in exploring this assumption is to clarify the chemical nature of mercury in the environment. "The question is not where mercury is coming from, but where methylmercury is coming from," Morel says. Mercury concentrations in the air are of little concern, but when mercury enters water, microorganisms transform it to a highly toxic form — methylmercury — that builds up in fish.

Unfortunately, scientists are not yet able to measure methylmercury in ocean surface waters, so Morel and his coworkers approached the problem from a different angle. They measured methylmercury levels in yellowfin tuna caught off the coast of Hawaii in 1998 and compared the numbers to a similar study from the same area in 1971.

They found no change in methylmercury levels in the tuna over that 27-year period.

The researchers predicted that mercury in the surface waters should have increased by up to 26 percent during this time, according to a computer model. The model took account of the change in atmospheric mercury, the sub-equatorial Pacific waters and the potential for mixing in the"thermocline" — a transition layer in the ocean where temperature changes rapidly.

The findings imply that the high levels of methylmercury in these fish are not coming from increased pollution, but from a natural source. The specific source is not yet clear, Morel says, but he suggests it could be hydrothermal vents and deep ocean sediments.

The research should also extend to other ocean-going predatory fish, like swordfish and sharks, according to Morel, which could mean that whatever is passing the mercury up to the tuna is probably doing the same to these other fish.

Morel is more cautious, however, about extending the findings to coastal fish. Bluefish, for example, run up and down along the eastern coast of the United States feeding on the continental shelf, and they may be taking up human pollution there. Lake fish are also a different situation, Morel says, since scientists have established a strong link between pollution and mercury levels in lakes.

The U.S. EPA and the U.S. Tuna Foundation provided support for this research.


Story Source:

The above story is based on materials provided by American Chemical Society. Note: Materials may be edited for content and length.


Cite This Page:

American Chemical Society. "Mercury In Ocean Fish May Come From Natural Sources, Not Pollution." ScienceDaily. ScienceDaily, 5 December 2003. <www.sciencedaily.com/releases/2003/12/031205053316.htm>.
American Chemical Society. (2003, December 5). Mercury In Ocean Fish May Come From Natural Sources, Not Pollution. ScienceDaily. Retrieved January 25, 2015 from www.sciencedaily.com/releases/2003/12/031205053316.htm
American Chemical Society. "Mercury In Ocean Fish May Come From Natural Sources, Not Pollution." ScienceDaily. www.sciencedaily.com/releases/2003/12/031205053316.htm (accessed January 25, 2015).

Share This


More From ScienceDaily



More Plants & Animals News

Sunday, January 25, 2015

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Florida Might Legalize Black Bear Hunting

Florida Might Legalize Black Bear Hunting

Newsy (Jan. 24, 2015) — A string of black bear attacks has Florida officials considering lifting the ban on hunting the animals to control their population. Video provided by Newsy
Powered by NewsLook.com
Ebola Killing Large Portion Of Ape Population

Ebola Killing Large Portion Of Ape Population

Newsy (Jan. 23, 2015) — Experts estimate Ebola has wiped out one-third of the world&apos;s gorillas and chimpanzees. Video provided by Newsy
Powered by NewsLook.com
Controversy Shrouds Captive Killer Whale in Miami

Controversy Shrouds Captive Killer Whale in Miami

Reuters - Light News Video Online (Jan. 23, 2015) — Activists hope the National Oceanic and Atmospheric Agency (NOAA) will label killer whales endangered, allowing lawyers to sue a Miami aquarium to release an orca into the wild after 44 years. Jillian Kitchener reports. Video provided by Reuters
Powered by NewsLook.com
‘Healthy’ Foods That Surprisingly Pack on Pounds

‘Healthy’ Foods That Surprisingly Pack on Pounds

Buzz60 (Jan. 23, 2015) — Some &apos;healthy&apos; foods are actually fattening. Fitness and nutrition expert John Basedow (@JohnBasedow) shines a light on the sneaky foods like nuts, seeds, granola, trail mix, avocados, guacamole, olive oil, peanut butter, fruit juices and salads that are good for you...but not so much for your waistline. Video provided by Buzz60
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:

Strange & Offbeat Stories

 

Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins