Seals and Mercury ??

[Hoser John]

Wow...
The Marine Mammal Polluting the Ocean With Toxic Mercury

.


By Katharine Gammon | Takepart.com
17 hours ago

TakePart.com











. ˠ
➕
✕
.





..
.




The Marine Mammal Polluting the Ocean With Toxic Mercury
.
View photo

The Marine Mammal Polluting the Ocean With Toxic Mercury

.


Año Nuevo State Reserve sits on a wild stretch of the California coast 60 miles south of San Francisco, far from power plants and other sources of pollution. So when researchers found 35 times more mercury in mussels there than at other sites, they wondered: why so much toxic contamination in such a pristine place?

They may have found their answer: elephant seals, which accumulate the metal in the food they eat and slough off mercury when they shed fur and hair each year.





That’s a previously unknown source of mercury in the environment, said Jennifer Cossaboon, who led the study as an undergraduate at the University of California, Santa Cruz, and is now a graduate student in environmental health at San Diego State University. At the time of the first study, in the 1980s, the analytical tools didn’t exist to detect trace amounts of mercury in seawater.

Cossaboon and her colleagues took samples of seawater at Año Nuevo during different times of year, along with samples at seven other coastal sites without high numbers of marine mammals. They found that the concentrations of methylmercury—that’s the powerful neurotoxin that can impair brain function—were 17 times higher at Año Nuevo during the molting season and twice as high during breeding season compared with sites without seals. The research was published Monday in the journal Proceedings of the National Academy of Sciences.

Mercury is emitted into the atmosphere from the burning of coal and falls into the ocean. Bacteria and plankton ingest mercury, and when fish eat them, the metal accumulates and continues up the food chain. Elephant seals store some of the metal in their fur and skin. When seals undergo what’s called a catastrophic molt—losing fur and the top layer of their skin to help them regulate their temperature—they shed the mercury into coastal waters.

RELATED: Much More Toxic Mercury Is Blowing In From Asia Than Thought

An 880-pound elephant lion will lose about 30 pounds of hair and skin. With 4,000 seals living together in a colony, molting results in 120,000 pounds of metal-laden tissue and fur into the water.

Scientists don’t know how much of the methylmercury will contaminate mussels or small fish. “There isn’t really any research on how methylmercury breaks down out of hair,” said Cossaboon. “We do know that if mercury is sediment-bound, then it does assimilate in mussels and fish, but it’s hard to extrapolate the human health effect.”

There is also uncertainty about the effects of mercury on the elephant seals themselves, as it’s difficult to assess seals’ neurological function, according to Cossaboon. A previous study found that 99 percent of the elephant seals studied in the North Pacific Ocean had blood mercury levels that exceeded the threshold for clinical neurotoxicity in humans.

The amount of mercury in the marine environment has increased two to four times over preindustrial levels and is expected to keep climbing for the next few decades.

“Mercury never fully breaks down; it just changes form,” said Cossaboon. “The best thing we can do is cut emissions—and also get educated about the fish we’re eating.”