Elephant seals are some of the planet’s most elite diving animals. In fact, until about a year ago, they held the mammal record for both longest and deepest dive. Researchers have now recruited these blubbery foragers to help them investigate the accumulation of pollutants in the deep ocean. Their blubber and blood reveal the presence of long-banned chemicals such as the pesticide DDT, according to new findings published in Science of The Total Environment.

As top predators in the northeast Pacific Ocean, northern elephant seals (Mirounga angustirostris) are ingesting various kinds of contaminants from their environment. These likely include persistent organic pollutants (POPs), which hang out for long periods of time. The use of DDT, for example, was (mostly) banned in the U.S. in 1972. And PCBs, which are found in products ranging from electronics to plastics, were banned in the U.S. in 1979.

To find out where and what these massive mammals are picking up, a team led by Sarah Peterson of UC Santa Cruz examined the blubber and blood of free-ranging northern elephant seals before and after their 7-month-long foraging trip. For 24 adult females, the before-and-after samples were obtained from the same seals, who were also satellite tagged. For adult and sub-adult males, 14 were sampled before, and 15 different seals were sampled after. Each time, the researchers sedated the seals and applied a local anesthetic, Science describes, before they took a sample from the hind flank with a small biopsy punch.

The found that all of the elephant seals had detectable concentrations of DDT, PCBs, and other POPs, including PBDEs, which are used as flame retardants.

Their concentrations, however, varied depending on factors such as sex, geography, and diving behavior. Males had higher concentrations of all the chemicals compared to females. And seals that hunted farther from shore – and away from populated areas – had lower levels of most chemicals. Although, they still absorbed high concentrations of PCBs, Science reports, which suggests this chemical likely spreads farther through the ocean than the others.



S.H. Peterson et al., Science of The Total Environment 2015