UPDATE (May 03, 2017): When famed orca "Lulu" washed up dead on a beach in Scotland last year, a necropsy revealed that she likely drowned after becoming entangled in fishing gear. The death was a blow to the region's only resident pod of killer whales. Now, new test results have disclosed another disturbing piece of the puzzle.
According to Dr Andrew Brownlow, a veterinary pathologist at Scotland's Rural College, Lulu's tissues also contained a large amount of toxic pollutants. She harboured one of the highest levels of polychlorinated biphenyls (PCBs) ever recorded in a whale.
These industrial organic chemicals were most commonly used as insulating liquids in electronics, as well as in a wide range of products like copy paper and motor oil. Environmental concerns resulted in a ban on PCBs in the 1970s, but by that time an estimated 1.5 billion pounds (6.8 million kilograms) had gone into industry. Still today, ill-managed landfills (among other sources) leach PCB contamination into rivers and estuaries and eventually into the deepest reaches of the ocean.
"The levels of PCB contamination in Lulu ... were 20 times higher than the safe level that we would expect for cetaceans to be able to manage," Brownlow told BBC News. "That puts her as one of the most contaminated animals on the planet in terms of PCB burden, and does raise serious questions for the long-term survivability of this group (of UK killer whales)."
Like other contaminants, PCBs accumulate up the marine food web: microbes and plankton feed on contaminated material, fish then feed on contaminated plankton, whales feed on contaminated fish, and so on. This so-called "biomagnification" means that top-predators tend to have the highest levels of toxins in their tissues – often far higher than what entered the water to begin with.
Because chemicals like PCBs are fat-soluble, they pose an especially serious threat to whales. Once ingested, PCBs are stored in the blubber, and only leave the body during breast feeding – if the contaminated individual is female and bears young.
An examination of Lulu's ovaries showed that she never reproduced and Brownlow and his colleagues feel confident that contamination is to blame (previous research also backs up that hunch).
The high PCB readings do not necessarily indicate a spike in water contamination though. Lulu would have gradually gained more PCBs with every meal she ate throughout her life. However, the findings are still troubling for a region with just eight remaining killer whales.
Some evidence suggests that PCBs can also suppress killer whales' immune systems and inhibit cognitive functioning. Brownlow postulates there may be a hidden link between Lulu's contamination and her death, however there's no way to know with certainty.
"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 the entanglement," he said.
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Whale enthusiasts on Scotland's Isle of Tiree are mourning the loss of "Lulu", a 6.2-metre female orca found dead earlier this week. We don't yet know whether the large whale stranded before or after she died, but local scientists are working to unravel the mystery.
Lulu was identified by her scars, saddle patch (the white patch just below the dorsal fin) and eye patch, all of which are unique to individual orcas. "It is particularly sad to know that another one of these killer whales, unique to the British and Irish Isles, has died," said the Hebridean Whale and Dolphin Trust (HWDT).
Lulu belonged to the region's only resident pod of killer whales, one that had become well known in the waters off Scotland's west coast by visitors and residents alike. In more recent years, however, there have been mounting concerns about the future survival of the unique population.
Though scientists have been studying this small, isolated "West Coast Community" since the 1980s, not a single birth has been observed during that time. It's thought that there may be as few as eight individuals remaining in the pod – with just three females left since Lulu's death.
“It’s probably too late to save this group. I do believe that they will become extinct in our lifetime, which is very regrettable since not many people even know that such a distinctive group of killer whales exists just off our coast,” killer whale specialist Dr Andy Foote warned back in 2011. He believes contaminants in the water might be one of the reasons the group has failed to breed.
The HWDT team hadn't seen Lulu since July of 2014, but they explain this is nothing out of the ordinary. The whales patrol a huge area to the west of the British Isles, and are only sporadically seen. "The Scottish Marine Animal Strandings Scheme are hoping to conduct an examination which might shed light on the cause of death," they add.
We'll be updating you as more information comes in, so watch this space.
UPDATE: Since news of Lulu's death emerged earlier this week, experts from the Scottish Marine Animal Strandings Scheme have conducted a necropsy (animal autopsy) on the remains. The team posted some of their findings today, which indicate that the cause of death was likely drowning as a result of entanglement:
"There were deep, granulating wounds ... consistent with a rope wrapping around the tail and trailing behind the animal, probably still attached to something at the other end. This would have made normal swimming very difficult, and we suspect the animal had been entangled for several days. She hadn’t fed recently but had swallowed a large amount of seawater, most likely as she eventually succumbed to the entanglement and drowned."
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Top header image: Jon Attfield, Flickr
Whales and Dolphins
Whales and Dolphins
Predator vs Prey
