North Atlantic orcas, also known as killer whales, a name reflective of their apex predator classification that puts them at the top of the marine food chain, have revealed just how polluted the ocean really is.
A new study led by Anaïs Remili, a marine biologist at McGill University in Montreal, Canada, has revealed an overwhelming accumulation of hazardous chemicals in blubber samples.
Remili and her team collected and analyzed samples from 162 North Atlantic killer whales (orcuinus orca) in various remote areas, including the Canadian Arctic, Greenland, and Norway, which according to the study, makes it "the most comprehensive assessment of legacy and emerging contaminant concentrations in killer whales across the North Atlantic."
The team discovered persistent organic pollutants, or POPs, in the orcas' blubber. POPs are often derived from household items such as paint, plastics, and coolants. A sub-category of pollutants found, known as polychlorinated biphenyls (PCBs) are human-made, hazardous chemicals that "do not degrade in the environment," Remili told conservation news outlet Mongabay.
The study reported that during gestation and lactation, adult female whales transfer these toxins to offspring. The toxins adhere strongly to orcas' body fat.
Killer whales can be found in all oceans, but each region's whales have different feeding habits, which can alter exposure to toxins. The study found that North Atlantic orcas feeding on marine mammals carry significantly higher levels of pollutants than those feeding primarily on fish.
Since marine mammals are higher up in the food chain, they are exposed to higher concentrations of pollutants that accumulate in their prey, and therefore whales who primarily feed on them ingest higher levels of toxins than whales consuming fish.
The study revealed about 100 parts per million of PCBs in the western North Atlantic population of orcas, which primarily feed on whales and pinnipeds like sea lions, as opposed to fish. These PCB levels "are 10 times higher than the threshold scientists have estimated as dangerous to the immune systems and fertility of orcas," reported Mongabay.
In contrast, the eastern North Atlantic orcas, which mostly feed on herring, showed PCB concentrations around 10 parts per million, significantly lower than their western counterparts.
This research highlights the persistent and pervasive nature of ocean pollutants. The United States banned PCBs in 1979 "because these chemicals harm human and environmental health" reported the National Oceanic and Atmospheric Administration, but PCBs continued presence in marine life is a stark reminder of their enduring impact.
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