Split-view of a killer whale at sunrise off the coast of northern Norway. Photo: Audun Rikardsen / Science

By Damian Carrington
27 September 2018

(The Guardian) – At least half of the world’s killer whale populations are doomed to extinction due to toxic and persistent pollution of the oceans, according to a major new study.

Although the poisonous chemicals, PCBs, have been banned for decades, they are still leaking into the seas. They become concentrated up the food chain; as a result, killer whales, the top predators, are the most contaminated animals on the planet. Worse, their fat-rich milk passes on very high doses to their newborn calves.

PCB concentrations found in killer whales can be 100 times safe levels and severely damage reproductive organs, cause cancer, and damage the immune system. The new research analysed the prospects for killer whale populations over the next century and found those offshore from industrialised nations could vanish as soon as 30-50 years.

Among those most at risk are the UK’s last pod, where a recent death revealed one of the highest PCB levels ever recorded. Others off Gibraltar, Japan, and Brazil and in the north-east Pacific are also in great danger. Killer whales are one of the most widespread mammals on earth but have already been lost in the North Sea, around Spain and many other places.

“It is like a killer whale apocalypse,” said Paul Jepson at the Zoological Society of London, part of the international research team behind the new study. “Even in a pristine condition they are very slow to reproduce.” Healthy killer whales take 20 years to reach peak sexual maturity and 18 months to gestate a calf.

PCBs were used around the world since the 1930s in electrical components, plastics and paints but their toxicity has been known for 50 years. They were banned by nations in the 1970s and 1980s but 80% of the 1m tonnes produced have yet to be destroyed and are still leaking into the seas from landfills and other sources.

The international Stockholm Convention on Persistent Organic Pollutants came into force in 2004 to tackle the issue, but Jepson said the clean-up is way behind schedule. “I think the Stockholm Convention is failing,” he said. “The only area where I am optimistic is the US. They alone produced 50% of all PCBs, but they have been getting PCB levels down consistently for decades. All we have done in Europe is ban them and then hope they go away.”

The researchers said PCBs are just one pollutant found in killer whales, with “a long list of additional known and as yet unmeasured contaminants present”. Further problems for killer whales include the loss of key prey species such as tuna and sharks to overfishing and also growing underwater noise pollution.

The new research, published in the journal Science, examined PCB contamination in 351 killer whales, the largest analysis yet. The scientists then took existing data on how PCBs affect calf survival and immune systems in whales and used this to model how populations will fare in the future. “Populations of Japan, Brazil, Northeast Pacific, Strait of Gibraltar, and the United Kingdom are all tending toward complete collapse,” they concluded.

Lucy Babey, deputy director at conservation group Orca, said: “Our abysmal failures to control chemical pollution ending up in our oceans has caused a killer whale catastrophe on an epic scale. It is essential that requirements to dispose safely of PCBs under the Stockholm Convention are made legally binding at the next meeting in May 2019 to help stop this scandal.” Scientists have previously found “extraordinary” levels of toxic pollution even in the 10km-deep Mariana trench in the Pacific Ocean. [more]

Orca 'apocalypse': half of killer whales doomed to die from pollution

Simulated population trajectories of killer whales (Orcinus orca). A team of researchers from St Andrews and Aarhus University in Denmark found that the number of killer whales could rapidly decline in ten of the 19 killer whale populations due to PCB pollution. Killer whales are particularly threatened in heavily contaminated areas near Brazil, the Strait of Gibraltar, the west coast of the UK, and along the east coast of Greenland where they are affected due to high consumption of seals. Graphic: Desforges, et al., 2018 / Science

29 September 2018 (University of St Andrews) – Chemical pollutants in our seas could lead to the disappearance of half of the world’s killer whales in just decades.

Despite the first moves to ban polychlorinated biphenyls (PCBs) 40 years ago, the chemicals remain a deadly threat to the mammals at the top of the food chain.

A new study, involving researchers at the University of St Andrews, published in Science, shows that current concentrations could severely deplete populations of killer whales in the most heavily contaminated areas within 30 to 50 years.

Killer whales (Orcinus orca) are among the mammals with the highest level of PCBs in their fatty tissue (blubber), with values as high as 1300 milligrams per kilogram. Animals with PCB levels as low as 50 milligrams per kilogram can show signs of infertility and immunity problems.

A team of researchers from St Andrews and Aarhus University in Denmark found that the number of killer whales could rapidly decline in ten of the 19 killer whale populations. Killer whales are particularly threatened in heavily contaminated areas near Brazil, the Strait of Gibraltar, the west coast of the UK, and along the east coast of Greenland where they are affected due to high consumption of seals.

Professor Ailsa Hall, Director of the Sea Mammal Research Unit (SMRU) at the University of St Andrews, said: “In these contaminated areas, we rarely observe newborn killer whales.”

Models created by the researchers show that these threatened populations of killer whales may continue to decline or even collapse due to the persistence of PCBs.

Killer whales, whose diet includes seals and large fish such as tuna and sharks, showed high levels of PCBs which accumulate up through the food chain. While killer whales which primarily feed on small-sized fish, such as herring and mackerel, have a significantly lower PCB level and so are at a lower risk of effect.

PCBs have been used around the world since the 1930s. More than one million tonnes were produced and used in, among other things, electrical components and plastics, and have spread around the global oceans.

In the 1970s and 1980s, PCBs were banned in several countries and in 2004, through the Stockholm Convention, more than 90 countries committed themselves to phase out and dispose of the large stocks of the chemicals.

PCBs only slowly decompose in the environment and are passed down from the mother to its offspring through the mother’s fat-rich milk. This means that the hazardous substances remain in the bodies of the animals, instead of being released into the environment where they eventually deposit or very slowly degrade.

The research group, which includes participants from the United States, Canada, the UK, Greenland, Iceland, and Denmark, reviewed all the existing literature and compared all data with their own most recent results. This provided information about PCB levels in more than 350 individual killer whales around the globe – the largest number of killer whales ever studied.

Applying models, the researchers went on to predict the effects of PCBs on the number of surviving offspring as well as on the immune system and mortality of the killer whale over a period of 100 years.

A female killer whale may live for 60 to 70 years, and although the world took its first steps to phase out PCBs more than 40 years ago, killer whales still have high levels of PCBs in their bodies.

In the oceans around the Faroe Islands, Iceland, Norway, Alaska, and the Antarctic, the prospects are not so gloomy. Here, killer whale populations grow and the models predict that they will continue to do so throughout the next century.

Killer whale populations threatened by pollution

Diagram showing the PCB food web and how it contaminates killer whales (Orcinus orca). Graphic: Desforges, et al., 2018 / Science

ABSTRACT: Killer whales (Orcinus orca) are among the most highly polychlorinated biphenyl (PCB)–contaminated mammals in the world, raising concern about the health consequences of current PCB exposures. Using an individual-based model framework and globally available data on PCB concentrations in killer whale tissues, we show that PCB-mediated effects on reproduction and immune function threaten the long-term viability of >50% of the world’s killer whale populations. PCB-mediated effects over the coming 100 years predicted that killer whale populations near industrialized regions, and those feeding at high trophic levels regardless of location, are at high risk of population collapse. Despite a near-global ban of PCBs more than 30 years ago, the world’s killer whales illustrate the troubling persistence of this chemical class.

Predicting global killer whale population collapse from PCB pollution



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