A new study from McGill University suggests that some Icelandic killer whales have very high concentrations of PCBs (polychlorinated biphenyls) in their blubber.
A new study from McGill University suggests that some Icelandic killer whales have very high concentrations of PCBs (polychlorinated biphenyls) in their blubber. But it seems that other orcas from the same population have levels of PCBs that are much lower. It mainly depends on what they eat.
PCBs were industrial chemicals banned decades ago, after they were found to affect the health of both humans and wildlife. But because they degrade very slowly after being released in the environment and they still accumulate in the bodies of marine mammals.
After collecting skin and blubber biopsies from 50 orcas in Iceland, the researchers found considerable variation in contaminant concentrations and profiles across the population. The killer whales that ate a mixed diet of both sea mammals (such as seals, or other marine mammals such as porpoises) and fish (mainly herring) had concentrations of PCBs in their blubber that were up tp 9 times higher on average than the killer whales that eat mainly fish. This finding unexpectedly contradicts earlier research that had found relatively low levels of PCBs in Icelandic orcas. The researchers argue that future assessments of the state of killer whale populations should take into account a factor that has previously been overlooked: the individual variations in food sources that may lead to elevated health risks from PCB exposures for some individuals within populations of the world’s ultimate marine predator.
Read more at McGill University
Image: These killer whales may appear healthy, but a new study has found extremely high levels of PCB contamination in some of the whales. There was a 300-fold difference between the levels of PCBs among the most contaminated orcas compared to the least contaminated ones. The variation was mainly due to their eating habits. (Credit: Filipa Samarra - Icelandic Orca Project)