Last year, the body of a female orca was found on the shores of the Isle of Tiree, Scotland. Lulu, as the orca was called, was a member of the last orca pod living in the waters of the United Kingdom. She had died after becoming ensnared in fishing nets.
Recent tests of Lulu’s remains, however, have produced surprising results: as Rebecca Morelle reports for the BBC, the orca’s body was found to contain one of the highest concentrations of pollutants ever recorded in a marine mammal.
More specifically, Lulu’s blubber was contaminated with polychlorinated biphenyls, or PCBs, a man-made compound that is toxic to both humans and animals. According to Damian Carrington of The Guardian, PCBs are known to cause damage to marine mammals when they reach concentrations of nine milligrams per kilogram of lipids. The levels in Lulu’s blubber were more than 100 times that, at 950mg/kg.
“Given what is known about the toxic effects of PCBs, we have to consider that such a high-pollutant burden could have been affecting her health and reproductive fitness,” Andrew Brownlow, head of the Scottish Marine Animal Stranding Scheme, told Carrington.
Lulu was at least 20 years old when she died—far past the age of sexual maturity, which occurs between the ages of six and ten in orcas. But analysis of Lulu’s ovaries indicated that she had never given birth to a calf. Lulu may not have been the only member of her pod affected by infertility. Scientists have been monitoring the group for 23 years, but they have never spotted any babies. According to the World Wildlife Fund UK, the pod is likely “doomed to extinction.”
In an interview with Morelle at the BBC, Brownlow said that Lulu’s PCB contamination may have played a part in her death. "It is potentially plausible that there was some effect of the PCBs that was in some way debilitating her so she wasn't strong enough or even aware enough to deal with this entanglement [in the fishing lines],” he said.
PCBs are non-flammable, highly stable, and resistant to high temperatures, making them popular for a variety of uses. They were produced from the 1920s to the 1970s and used in a range of industrial applications, including as pigments in paint and dyes, plasticizers in plastics and rubber, and components in electrical equipment. But when mounting research demonstrated that the compounds not only cause cancer but compromise numerous systems in the body, PCBs were banned in Europe and the UK.
But that didn't mean they disappeared from the environment. PCBs break down slowly. So the PCBs released previously through industrial processes haven't gone anywhere in a hurry. And improper disposal of products containing PCBs add to the environmental load.
The compounds collect in animals lipids, so they are found in greatest concentration at the top of the food chain. Top predators like whales, dolphins and porpoises are particularly susceptible to PCB toxicity, according to the Whale and Dolphin Conservation. “[P]lankton absorb PCBs from their environment and pass these onto the small fish and squid, which in turn pass on the PCBs in their body tissues to the large fish and squid that eat them,” the group explains on its website. “Finally, the PCBs from all the large fish (and the small fish and the plankton) are absorbed by the whales, dolphins and porpoises that eat them.”
Dr. Paul Jepson of the Zoological Society of London told Morelle that Europe should be doing more to decontaminate remaining stockpiles of PCBs to make sure that the chemicals do not leech into waterways. Though it's too late for Lulu, taking action now could help save other marine mammals from the same fate.