Study of whale earwax sheds light on the health of the oceans

WACO, TX—Like many mammals, whales have wax in their ears. And, given how large they are—blue whales can grow to nearly 100 feet in length and weigh close to 200 tons—it’s not surprising that they pack a lot of earwax.

Whether it interferes with their hearing is hard to say; it doesn’t seem that any marine audiologists have tested whales for conductive hearing loss. And even if their hearing was impaired by wax, they would probably have to live with it. Trying to clean whale ears would be difficult, not to mention dangerous.

However, Sascha Usenko, an environmental scientist at Baylor University, and colleagues have found that whale earwax can serve a valuable purpose, namely to provide a record over time of the level of pollution in the oceans.

For their research, Usenko and his colleagues analyzed a column of wax, nearly a foot in length, extracted from a blue whale. The carcass of the giant sea creature had washed ashore on the California coast in 2007. Scientists at the Santa Barbara Museum of Natural History had collected the wax from inside the skull of the dead whale and preserved it. Subsequently, Usenko, who specializes in include tracking the human-caused contaminants in aquatic ecosystems, and colleagues have spent years studying the material.

 

FINDINGS PUBLISHED

In an article published last month in the Proceedings of the National Academy of Sciences, Usenko and five co-authors discussed their findings and their significance.

They noted that it is very rare to be able to obtain a chemical profile of an animal over an extended life span, from birth to death. However, in the case of the wax from the whale, not only was the material very old—blue whales have life spans similar to humans and are not known to get their ears cleaned–it contained many layers, each of which corresponded to about six months of a whale’s life. By analyzing the wax, layer by layer, the scientists could tell what chemicals the whale was exposed to and when and thereby get a picture of the changing pattern of ocean pollution.

They found that the whale had been exposed to pollutants throughout its lifetime, including DDT (dichlorodiphenyltrichloroethane). Even though this once widely used insecticide was banned 30 years ago, Usenko and colleagues found high levels of the deadly substance in the earwax.

Usenko et al. wrote, “We anticipate that this technique will fundamentally transform our ability to assess human impact on these environmental sentinels and their ecosystems.” To continue this research, Usenko has asked scientists to start collecting earwax from dead beached whales the world over and mail the samples to him. He can b e-mailed at sascha_usenko@baylor.edu.