An illustrated blue whale embryo. [Image credit: Biodiversity Heritage Libraries via Flickr Creative Commons]
Inside the ear of a blue whale, lies a record of the fluctuating ocean.
Last year, the fatality of a 2007 ship strike provided scientists with a 10-inch column of informative earwax. The victim’s wax was composed of fatty, alternating dark and light layers, each distinctly spaced to depict the highs and lows of food availability during seasonal migrations of a 12-year life. Within these layers, researchers found handfuls of historically used chemicals — of the most concerning, perhaps, were high levels of the long outlawed chemical DDT.
DDT, the global insecticide of choice until the ‘70s, was banned in the U.S. in 1972 for its serious threats to wildlife and human health (it’s still used in malaria-plagued countries). For instance, blood samples of human infants born in the ‘60s reveal that those with mothers exposed to the chemical were much more likely to be born prematurely or with a low weight.
In the dead whale’s ear, this potent pesticide was discovered in greatest concentration in the layers of wax that aligned with infancy — when the whale was less than six months old and still young enough to nurse. The whale’s mother, the study postulates, must have transferred her own ocean absorbed pesticides over to the new baby. This unsettling finding validates prior hypotheses, the study continues, that large marine mammals can pass organic contaminants from mother to baby, through either pregnancy or by nursing.
As the myriad of DDT’s effects remain unknown to science, the whale study cannot confirm how the chemical load influenced the young whale and other animals like it. The authors suggest that the chemical may be related to increased levels of the hormone cortisol, a telltale sign of stress. And, unfortunately, the case of the blue whale is not a lone one. To this day traces of DDT are still found in people and wildlife across the globe — living records of the man-made toxin — stuck in the ears of hundred ton cetaceans, the flesh of farmed salmon, the brains of songbirds, and the milk of a mother feeding her baby.