The study by McGill University scientists, who examined levels of polychlorinated biphenyls, or PCBs, and pesticides in skin samples taken from six species of whales and dolphins, found that levels of toxins in orcas are twice the threshold that scientists say causes reproductive failure.
Samples taken from southern Newfoundland and Labrador between 2015 and 2022 showed that humpback, minke and fin whales, and dolphins had lower levels of persistent pollutants than orcas.
Lead researcher Anaïs Remili says the toxins attach to fats, like the blubber of whales and dolphins.
“These molecules … stick to grease and aquatic organisms that contain a lot of it,” she said in an interview Thursday, adding that the chemicals are transmitted from animal to animal during of their movement in the food chain. Orcas are particularly vulnerable to high levels of toxins because they are predators at the top of the food chain.
Increased toxins are just one of many environmental threats orcas face, including entanglements in nets, ship strikes, and difficulty finding food due to changes in sea temperature. ocean.
Ms Remili said it was difficult to establish a hierarchy of different threats to the orca in particular, adding that many other whale species face similar challenges.
Although there is no data available on toxin levels in orcas, Ms. Remili said there is still hope that contaminants in the species may decrease over time. His study cites data monitoring toxin levels in belugas over several decades, which indicated a downward trend in toxin concentration. This study, she explained, gives her some optimism for the future of orcas.
“We hypothesized in the study that because (toxin levels) have decreased in all of these cetacean species, they have probably decreased (in orcas) (…) but there is hope that these contaminants will decrease with additional efforts,” added Ms. Remili.
Although their use has long been banned in Canada, these chemicals persist in the environment and living tissues, as well as in aquatic ecosystems where carnivorous marine species are more likely to be exposed.
Ms Remili stressed the importance of strict regulations to prevent more toxins from entering the water.
