'Shocking' levels of PCB chemicals in UK killer whale Lulu
A member of the small West Coast of Scotland group of killer whales – found dead and stranded on the Isle of Tiree in the Hebrides, Scotland, last year – had one of the highest levels of polychlorinated biphenyl (PCB) pollution ever recorded in the species, said the Scottish Marine Animal Stranding Scheme today.
The adult killer whale – identified by the Hebridean Whale and Dolphin Trust as a well-known animal named ‘Lulu’ – died from becoming entangled in creel rope in January 2016, but subsequent analysis undertaken over the past year has shed further light on her case.
Analysis of Lulu’s blubber revealed PCB concentrations 80 times higher than the accepted PCB toxicity threshold for marine mammals. High PCB levels are linked to poor health, impaired immune function, increased susceptibility to cancers and infertility.
“Previous studies have shown that killer whale populations can have very high PCB burdens,
but the levels in this case are some of the highest we’ve ever seen”
Work, undertaken in collaboration with the University of Aberdeen, found that Lulu was at least 20 years old. Based on analysis of the ovaries, it appears that she never reproduced, despite being much older than the average age for maturity in killer whales.
These findings do not bode well for Lulu’s small pod. This small group is usually seen off the west coast of Scotland, and numbers only eight individuals. These individuals never interact with other groups of killer whale, nor has a calf been recorded within the group in the 23 years it has been monitored.
Commenting on these results, Dr Andrew Brownlow, head of the Scottish Marine Animal Stranding Scheme and veterinary pathologist at Scotland’s Rural College (SRUC) said: “Previous studies have shown that killer whale populations can have very high PCB burdens, but the levels in this case are some of the highest we’ve ever seen. We know ‘Lulu’ died from becoming entangled, but, given what is known about the toxic effects of PCBs, we have to consider that such a high contaminant burden could have been affecting her health and reproductive fitness. Lulu’s apparent infertility is an ominous finding for the long-term survivability of this group; with no new animals being born, it is now looking increasingly likely that this small group will eventually go extinct. One of the factors in this groups’ apparent failure to reproduce could be their high burden of organic pollutants.”
“Once PCBs get into the marine environment, they are difficult if not impossible to remove. They accumulate through food webs and persist over time. Killer whales, which can live for many decades and feed right at the top of the food chain, are particularly susceptible to their effects. Animals from groups such as Lulu’s, which are known to feed on marine mammals, would also probably have concentrations higher than those killer whales which are predominantly fish eaters."
"Following the ban on PCBs in the mid-1980s, levels in most marine mammals decreased. In some regions however, including Europe and the Arctic, this initial decline appears to have plateaued. There are still many PCB stockpiles in Europe, and it is absolutely essential that these toxic reserves do not reach the marine environment. PCBs are difficult pollutants to mitigate: they were produced in significant volume, used in a wide range of materials, exhibit long-term environmental persistence and toxicity and are remarkably difficult to render safe. Gaining a better understanding of the pathways by which these pollutants reach the marine environment is important, as is addressing other threats to these susceptible populations. This is particularly evident in the west coast population, which exhibit impacts from both chemical pollution and entanglement.”
There is a growing concern amongst many cetacean scientists that, unless a much more proactive approach is taken to assessing and decontaminating PCB-contaminated sites to stop these pollutants leaching into the marine environment, then the effects we’re seeing with this small group of killer whales on the west of Scotland could become evident in many more of our iconic marine mammal species.
Dr Lauren Hartny-Mills, the Hebridean Whale and Dolphin Trust’s Science Officer, said: “Monitoring the West Coast Community of killer whales is a concerted effort, with sightings reports and photographs from the public, wildlife operators and fishermen helping us better understand the group’s movements, range and social interactions. Anyone can help and if you are lucky enough to encounter a killer whale (or indeed any whale, dolphin or porpoise) please report it to us."
Other background information:
A total PCB concentration of 11 mg/kg lipid wt. has been reported as a threshold level above which there are health effects in mammals (Kannan et al. 2000). Work undertaken by Cefas as part of ongoing screening of samples from stranded cetaceans for persistent organic pollutants, including PCBs, found the total amount of PCB congeners in a sample of Lulu’s blubber exceeded 950 parts per million (mg/kg lipid). This is one of the highest levels ever recorded in a marine mammal and confirms that this species is especially vulnerable to these legacy pollutants. PCBs are very fat soluble so most of her contaminant burden would have been ‘locked away’ in her blubber, possibly explaining why cetaceans seem to survive carrying incredibly high levels of these pollutants. If the animal begins to mobilise blubber reserves, for example when food supplies are low, stored PCBs are released into the circulation where they can do much more physiological damage. These pollutants can also be passed from mother to calf, meaning the contaminant profile found in Lulu is a result of pollutant exposure not just over her lifetime, but also that of her maternal ancestors. Because Lulu had never been pregnant or lactated, this important “excretion” route would not apply, and concentrations in her blubber could progressively increase with time from dietary sources
Preliminary results from genetic analysis carried out by researchers at University College Cork support the hypothesis that Lulu belongs to a very small group comprising a limited number of individuals. These preliminary results, as well as historical observation of these killer whales dating back to the 1980's collated by the Hebridean Whale and Dolphin Trust, suggest it is unlikely that this iconic West Coast Population has a recent history of breeding with geographically proximate pods and is likely to be critically endangered (Beck et al. 2014). Genetic analysis of other samples from Lulu’s community could provide a more complete insight into the status of this population.
Recent pan-European collaborative research on persistent organic pollutants (POPs) - led by the UK cetacean strandings network - shows that Europe still has a major problem with persistent PCBs (Jepson et al. 2016) This study found that several cetacean species in Europe have very high mean blubber PCB concentrations likely to cause population declines and suppress population recovery. In a large pan-European meta-analysis of stranded (n=929) or biopsied (n=152) cetaceans, bottlenose dolphins, striped dolphins and killer whales, had mean PCB levels that markedly exceeded all known marine mammal PCB toxicity thresholds. Some locations (e.g. western Mediterranean Sea, south-west Iberian Peninsula) are global PCB “hotspots” for marine mammals. Blubber PCB concentrations have now plateaued in some cetaceans in the NE Atlantic where concentrations in harbour porpoise are below the estimated threshold for effects. However, some small or declining populations of bottlenose dolphins and killer whales in the NE Atlantic were associated with low recruitment, consistent with PCB-induced reproductive toxicity.
In a global review of marine apex predators, the killer whale remains one of the most PCB-contaminated mammalian species and is likely to be impacted throughout their entire global range (Jepson and Law 2016). Other species considered under potential or serious threat from PCBs include false killer whales; ringed seals in the Baltic Sea; all marine mammal species in the Mediterranean and Black Seas; belugas in the Saint Lawrence River, Canada and polar bears in the Arctic. Despite EU regulations and mitigation measures to reduce PCB pollution in Europe, their legacy in marine food webs continues to be of concern with, two of the remaining killer whale populations in the NE Atlantic – the Strait of Gibraltar population and the west of Scotland/Ireland population – being most acutely threatened.
All dead strandings in Scotland should be reported to the Scottish Marine Animal Stranding Scheme (www.strandings.org). The strandings project was set up in 1992, led by SRUC, funded by Marine Scotland and DEFRA. The project aims to collate, analyse and report data for all marine mammals (cetacean and seals), marine turtle and basking shark strandings.
Lulu’s skeleton is preserved at National Museums Scotland
Press release issued by Scottish Marine Animal Stranding Scheme
Image: © John Bowler, RSPB Scotland, Lulu, stranded on Tiree in January 2016