In 2007, scientists recovered a blue whale earplug off Santa Barbara; its 24 wax layers archived 12 years of hormones, mercury, and man-made pollutants

Ear wax may not seem like a fascinating subject for a scientist. But a 10-inch plug that came out of the ear canal of a 70-foot male blue whale that was struck by a ship and washed up dead near Santa Barbara in 2007 contained a more complete and more honest record of a whale's life. For years it lay forgotten in storage until it was finally identified as the diary the whale had never planned to write.

Baylor University researchers divided that plug into cross-sections and discovered 24 light and dark layers, deposited about every six months like tree rings, and thus formed a chemical autobiography of the animal's life that spanned 12 years, from birth to death. According to a 2013 study titled “Blue whale earplug reveals lifetime contaminant exposure and hormone profiles,” published in the Proceedings of the National Academy of Sciences, the wax contains surges of the stress hormone cortisol, spikes in the levels of testosterone associated with sexual maturity, and a toxic combination of pesticides, flame retardants and mercury, which the whale ingested by just being in the modern ocean. This is an interesting find in itself.

The whale's body was keeping receipts


The pollution was highest during the whale's first six months of life, the period when a blue whale calf nurses exclusively on its mother's milk and hasn't yet started feeding itself. That's exactly what makes the spike notable: through a process called "maternal transfer," a mother's lifetime accumulation of contaminants gets concentrated in her fat-rich milk and passed to the calf, so the calf inherits a dose of pollution before it has ever fed itself at all. The wax also indicated that the animal's level of stress rose by about 50% each year for 12 years, and that its level of testosterone rose markedly as it neared maturity at about nine years.

Cortisol, meanwhile, roughly doubled over the whale's lifetime compared with its baseline level near birth, a steady rise across 12 years, not a runaway year-over-year compounding of stress. There was no exotic contamination from some distant industrial catastrophe. Only common chemicals of modern life: the DDT breakdown products that have been in the environment for decades, the flame retardants that used to be a standard part in the furniture and electronics industry, and mercury that cycles through the air, water, and food chain, were found.

It's not just what's in the water; it's how loud it is

The Santa Barbara earplug is a chemical record from one Pacific blue whale, but it points to a wider pattern that shows up in a completely separate line of research on a different species and ocean. A 2012 study titled “Evidence that ship noise increases stress in right whales,” published in Proceedings of the Royal Society B and led by Rosalind Rolland of the New England Aquarium, found that the stress hormone levels of right whales significantly decreased when the amount of shipping noise underwater decreased shortly after 9/11. Taken together, the two studies, one chemical and one acoustic, on two different whale populations, point to the same underlying idea: these animals are not only consuming our runoff, but also our racket, the low-frequency hum of the very ships that, in the case of the Santa Barbara whale, killed it outright.

That's not incidental. In this particular whale's death year, 2007, NOAA's own records show that ship strikes on blue whales off the Channel Islands were frequent and severe enough that year for federal officials to declare it an "unusual mortality event." The Santa Barbara Channel is located where some of the busiest shipping lanes on the West Coast are located, and where whales feed. Today, that number of imports into Los Angeles and Long Beach has increased even more, more than 15 years later.

Why should this matter

The chemistry in that earplug, however, is the same chemistry that builds up fish, breast milk, your bloodstream, only on a different timeline and without the six-month accretions that allow scientists to “read” it back. We do not receive an earplug. We wait for years to get blood panels, and then it's too late. The blue whale's biography wasn't written by the whale. It was conceived by cargo lanes, pesticide runoff, and the flame-retardant industry, which was more concerned about furniture safety than ocean chemistry that lasts a lifetime.