Paris – According to a study released on Thursday in the journal Scientific Reports, killer whales in European waters face extinction due to toxic chemicals that have been harming the marine mammals and several species of dolphins for almost 30 years.
The new research analyzed levels of PCB, which is a persistent chemical used in electrical equipment and that were banned in 1987. PCB levels have been harming the mammal’s ability to reproduce and also threatening the immune systems in more than 1,000 dolphins and killer whales. But, despite regulations to reduce PCB pollution, their concentration in marine food webs continues to cause severe impacts among cetacean top predators in European seas.
The study results showed greatly exceed concentrations of the contaminant becoming more concentrated as they move up the food chain as PCB settle into the fatty tissue of top ocean predators.
“The levels are really high, probably the highest in the world right now,” said Paul Jepson, at the Zoological Society of London (ZSL), who led the new study. “These are global PCB hotspots.”
Scientist observed a community of 36 orcas off the coast of Portugal for decades and noticed that they have not produced any offspring in more than ten years. Jepson pointed out that just a few coastal orca populations remain in western European waters and that those in the Mediterranean and the North Sea have already disappeared.
PCB transfer
Europe produced around 300,000 tons of the toxic compound from 1954 to 1984, but even though 90% of it has been destroyed or safely stored away, PCB does not dissolve in water and it has been leaking from landfills into rivers and estuaries, and eventually into the marine environment.
The study by scientists in Spain, Ireland, Portugal, Slovenia and Britain, found that the pollutant has been transferring in the blubber of killer whales off Europe, as well as in striped dolphins and bottlenose dolphins through birth or food webs.
When female killer whales give birth, they transfer about 90% of the PCBs accumulated in their bodies to their calves.
PCBs also contaminate the seabed where they are eaten by creatures such as mussels or crabs that in turn get consumed by fish that are food for long-lived predators such as killer whales. From there, they gradually climb the food chain, becoming more toxic along the way.
PCB levels outside Europe
Near Iceland and northern Norway, orcas have ten times less PCB in their fatty tissue. The reason probably relies upon the fact that the Arctic orcas subsist almost exclusively on herring. As this fish basically eats plankton, they are outside the food chain along which PCBs climb.
In the United States, the levels of PCBs in killer whales are lower than in Europe. This is probably because Washington banned PCBs in 1979, 8 years before Europe.
Source: Nature