A killer whale’s diet is the biggest factor in their exposure to hazardous pollution, according to new research.
The largest study to date of North Atlantic killer whales revealed the levels of pollutants in 162 individuals’ blubber.
The levels of one pollutant, a flame retardant, were the highest ever reported for any marine mammal – despite the fact that it was banned a decade ago.
Scientists say their worrying findings suggest that what the killer whales eat, rather than geographical location, most impacts the level of contaminants and potential health risks.
The information garnered could prove vital in saving the threatened species from extinction, according to the research team.
As the largest member of the dolphin family, killer whales – also known as orcas – are found in oceans around the world.
Marine vessel traffic can disturb their hunting and communication patterns.
But they face another type of human threat in the form of legacy and emerging persistent organic pollutants, or POPs, in their environments.
POPs include chlorinated hydrocarbons and flame retardants and can accumulate in orcas’ fat stores as the contaminants move up the food chain through a process called biomagnification.
Research co-author Dr. Anaïs Remili said: “Previous studies have shown that some Pacific orca populations can carry POP loads in their blubber that pose potential health risks, including reduced immunity, hormonal imbalances and reproductive issues.
“But information on orcas living in the North Atlantic are lacking.”
Dr. Remili, co-author Professor Melissa McKinney and their colleagues at McGill University in Canada wanted to assess the contaminants present in animals spanning from Eastern Canada to Norway.
The team collected skin and blubber biopsies from more than 100 free-ranging killer whales, across the North Atlantic Ocean from Canada, Greenland and Iceland to Norway.
They analyzed half of each tissue sample for five classes of POPs, including polychlorinated biphenyls (PCBs).
The other portion was used to evaluate the animals’ diets.
Dr. Remili said: “Specimens from orcas in the western North Atlantic contained substantially higher contaminant loads than ones from orcas on the eastern side — a pattern that contrasts with previously reported POP levels in other Arctic marine organisms.
“The pattern could be attributed to individuals’ diet rather than location.
“Specifically, killer whales foraging on fish had the lowest POP levels, and animals consuming marine mammals, such as seals or other whales, had the highest.
“PCB-associated health risks were highest for killer whales that ate primarily marine mammals, with most animals’ levels exceeding the threshold for a higher risk of female reproductive failure.”
She added: “The levels of one POP, known as α-HBCDD, were the highest reported for any marine mammal to date, despite the fact that this brominated flame retardant was banned a decade ago.”
The researchers say the findings support the need for proper waste disposal to prevent contaminants from entering the oceans’ food chains and reaching the top predators.
They explain that the study, published in the journal Environmental Science and Technology, underscores the need for action to protect North Atlantic killer whales and their ecosystems.
Produced in association with SWNS Talker
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