Researchers have known for decades that orcas (逆戟鲸) across the North Pacific have harmful pollutants in their system.
Now, a new study reveals orcas in the western North Atlantic, including those in the Arctic, are significantly more polluted than animals in the east — a finding that “shocked” study leader Anaïs Remili, a postdoctoral researcher at McGill University in Montreal. The research strongly points to their diet playing a major role in the level of pollutants, rather than their location.
The study looked at the presence of persistent organic pollutants, or toxic chemicals that degrade slowly and accumulate in the body, in the blubber (鲸脂) of orcas across the North Atlantic. These pollutants, relics of industrial and agricultural processes, “have a tendency to bind to fat,” says Remili, whose study was published in October in the journal Environmental Science & Technology. These chemicals weaken orcas’ immune systems, disrupt their endocrine (内分泌) function, prevent growth and brain development, and even interfere with reproduction.
Pollutants increase as they move up through the food chain, and the orcas that consume top predators — for example, those that primarily eat other marine mammals rather than fish—are most polluted. Thanks to their high body fat and position as apex (最高点) predators, orcas are some of “the most contaminated animals on the planet,” Remili says.
Her earlier research showed that eastern North Atlantic orcas primarily feed on herring (鲱鱼); mid-North Atlantic orcas feed on seals and mackerel (鲭鱼); and western North Atlantic orcas feed on baleen whales, porpoises (海豚) and seals.
It makes sense that western North Atlantic orcas would have higher pollutants, due to their diet, but “you would expect less contaminants overall in the Arctic compared to industrialized areas,” such as off the east coast of North America, Remili says.
“We’ve really come to learn that you are what you eat,” says Peter Ross, senior scientist and healthy waters program director at the Raincoast Conservation Foundation in British Columbia, who wasn’t involved in the study. “The top of the food chain, as illustrated by these long-lived killer whales, is extremely easy to hurt.”
12. What can we know according to Anaïs Remili’s study?
A.The polluted orcas in the Eastern Atlantic are in the lead. |
B.The orcas’ immune system is influenced negatively by chemicals. |
C.The blubber of orcas is easy to break down and accumulate in the body. |
D.Orcas’ location is more important than their diet in the level of pollutants. |
13. In paragraph 4, who is the most polluted animals on the Earth?
A.Those feeding on fish. | B.Those feeding on marine plants. |
C.Those feeding on predators. | D.Those feeding on marine mammals. |
14. What is the paragraph 5 mainly about?
A.Orcas’ tastes vary from place to place. | B.Orcas can be particular about food. |
C.Orcas are fond of fish and shrimps. | D.Orcas can only be found in the Atlantic. |
15. What can we infer from Paragraph 6—7?
A.Orcas’ diet resulted in more pollutants. | B.The marine food chain needs to be protected. |
C.Peter Ross participated in the study unwillingly. | D.Pollutants found in the Arctic orcas are not the most. |