Elephant Seals Can Increase Concentrations of Toxic Mercury

Written by on September 11, 2015 in Marine Life, Seals, Sea Lions & Sea Otters

A new study from UC Santa Cruz shows that elephant seals contribute a large amount of mercury to coastal waters.

Elephant Seal.

Elephant Seal. Photo credit: NOAA.

We often hear about the potential dangers of mercury poisoning from consuming top predators like tuna. That’s because mercury is a toxic metal that can build up quickly in marine food webs. Concentrations in tuna and other large, predatory fish can be dangerous because of a process called biomagnification, where concentrations of mercury start out small, but become more and more concentrated as it passes up the food chain. It can be so concentrated, in fact, that mercury concentrations in top predators can be up to 10 million times higher than levels found in surrounding sea water.

This study went beyond biomagnification to look at what happens with mercury next.

“Mercury is an element, so it never breaks down and goes away — it just changes forms,” first author Jennifer Cossaboon explained in a news release.

Elephant seals are top predators that have been known to accumulate high concentrations of mercury in their bodies. They also happen to undergo an annual “catastrophic molt” (which isn’t as bad as it sounds) during which they shed their outer layer of skin and hair.

So what happens to the mercury in their skin and hair once it’s shed? Well, it ends up right back in the water. The researchers found that during the molting season, coastal waters near the rookery in the Año Nuevo State Reserve experienced elevated mercury concentrations.

When compared to other coastal sites, the concentration of methylmercury in Año Nuevo was twice as high during breeding season and 17 times higher during molting season.

The amount of mercury being added to marine environments from industrial emissions (mostly from coal burning) has increased dramatically over the last century.

“This internal recycling back into the coastal environment just adds to the problem,” said coauthor Russell Flegal.

To learn more:

Copyright © 2015 by Marine Science Today, a publication of Marine Science Today LLC.

About the Author

About the Author: Emily Tripp is the Publisher and Editor of MarineScienceToday.com. She holds marine science and biology degrees from the University of Miami's Rosenstiel School of Marine and Atmospheric Science and a Master of Advanced Studies degree in Marine Biodiversity and Conservation from Scripps Institution of Oceanography. When she's not writing about marine science, she's probably running around outside or playing with her dog. .


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