A new study from McGill University suggests that some Icelandic killer whales have very high concentrations of PCBs (polychlorinated biphenyls) in their fat. But it appears that other orcas in the same population have much lower levels of PCBs. It mainly depends on what they eat.
PCBs were industrial chemicals banned decades ago, after they were discovered to affect the health of humans and wildlife. But because they degrade very slowly after being released into the environment and still accumulate in the bodies of marine mammals.
After collecting skin and fat biopsies from 50 killer whales in Iceland, the researchers found considerable variation in the concentrations and profiles of contaminants in the population. Killer whales that ate a mixed diet consisting of both marine mammals (such as seals or other marine mammals such as porpoises) and fish (mainly herring) had PCB concentrations in their fat that were up to at 9 times higher on average than the killer. whales that eat mainly fish. This finding unexpectedly contradicts previous research that found relatively low levels of PCBs in Icelandic killer whales. Researchers argue that future assessments of the status of killer whales should take into account a factor that was previously overlooked: individual variations in food sources that can lead to high health risks from exposure to killer whales. PCBs for certain individuals within populations of the ultimate world. marine predator.
Exceeding known toxicity thresholds
“Killer whales are the ultimate marine predators and, being at the top of the food chain, they are among the most contaminated animals on the planet,” says Melissa McKinney, assistant professor in the Department of Natural Resource Sciences at McGill and Research on Canada. Chair on ecological change and environmental stressors. She is the lead author of the study, which was recently published in Environmental Science and Technology.
“The levels of PCBs we found in whales that ate a mixed diet exceeded all known toxicity thresholds and are likely to affect both their immune and reproductive systems, putting their health at risk.”
“The next step for us is to assess the proportion of marine mammals in the diet of these Icelandic killer whales and other killer whales in the North Atlantic,” adds Anaïs Remili, first author of the study and a doctoral student in the Department of Human Sciences. McGill Natural Resources. “We also plan to assemble a large dataset on contaminants in killer whales in the Atlantic Ocean to aid in their conservation efforts by quantifying potential health risks.”
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