Europe's Orca Pods Under Threat from Banned Chemicals
Toxic PCBs are showing up at dangerously high levels in the blubber of killer whales and dolphins.
Long-banned chemicals threaten killer whales and dolphins in European waters, a new study by the Zoological Society of London (ZSL) suggests.
PCBs (polychlorinated biphenyls) were once used in the making of paints, electrical equipment and flame retardants. But the chemicals, found to be toxic, were banned in the United States in 1979 and in the United Kingdom in 1981. However, they linger in the environment, impact the marine food chain, and now may be harming Europe's cetaceans.
A team from ZSL studied more than 1,000 stranded or biopsied dolphins, whales, and porpoises. They found that killer whale, bottlenose dolphin and striped-nose dolphin blubber contained dangerously high levels of PCB.
When PCB levels are high enough, they can harm cetacean immune systems and make breeding more difficult for the animals, due to an increased rate of newborn calf mortality.
Top predators with good longevity, such as killer whales, tend to come by PCBs in their food-gathering travels.
"The long life expectancy and position as apex or top marine predators make species like killer whales and bottlenose dolphins particularly vulnerable to the accumulation of PCBs through marine food webs," said study lead Paul Jepson, of ZSL's Institute of Zoology, in a release.
"Our findings," said Jepson, "show that, despite the ban and initial decline in environmental contamination, PCBs still persist at dangerously high levels in European cetaceans."
The researchers paint a dim picture of current circumstances for the creatures.
"Few coastal orca populations remain in western European waters," said Jepson. "Those that do persist are very small and suffering low or zero rates of reproduction. The risk of extinction therefore appears high for these discrete and highly contaminated populations."
"Without further measures," he added, "these chemicals will continue to suppress populations of orcas and other dolphin species for many decades to come."
"Our research underlines the critical need for global policymakers to act quickly and decisively to tackle the lingering toxic legacy of PCBs," said study co-author Robin Law, "before it's too late for some of our most iconic and important marine predators. We also need to better understand the various pathways through which these iconic species are able to accumulate such high PCB concentrations through their diets."
The ZSL scientists' findings have just been published in the journal Scientific Reports.
Thanks to an effort by the Vancouver Aquarium and the National Oceanic and Atmospheric Administration's Fisheries department, scientists have used an unmanned aerial vehicle -- or a drone -- to monitor the health, movement and reproduction of killer whales. The team tracked northern resident killer whales off British Columbia, a group currently designated as threatened by the Species at Risk Act in Canada. Its custom-made hexacopter flew more than 100 feet above the whales -- far enough out of mind that the whales would not notice but still close enough to get tons of great detail. Killer whales travel in a family group for the better part of their lives. This family group includes a two-year-old calf (second from top), and a young-of-the-year (middle).
At issue for the team was a central question: Are the whales able to find enough food? These whales, like their British Columbia southern resident counterparts near Seattle, eat Chinook salmon, which are far smaller than they used to be. (Some of the salmon runs are also endangered, the NOAA says.) Here, two northern resident killer whales are photographed by the hexacopter. The whale on the left is in very poor condition and is thought by the researchers to have recently perished. The whale on the right, luckily, is considered healthy and in peak condition.
The drone photos can show scientists how fat or thin individual whales are, as well as which ones are pregnant and which calves are brought to term. In this photo, the female at top appears skinny and in poor condition. The female in the middle seems to be healthy and well fed. The whale at bottom is pregnant, the bulge in her body evident behind the rib cage.
A yearly census of mortality is not the most helpful of measures for how well a whale population is doing, the team says. That's because any problems the whales experience have already occurred and taken the whales' lives. The hexacopter "can give us a more sensitive measure that we might be able to respond to before whales die," said NOAA biologist John Durban in a release.
While the team's research permit allowed it to use a 100-foot limit above the whales for its studies, non-research permits restrict hexacopter approaches to, at closest, 1,000 feet above the creatures.
Here, a moment of playful behavior is caught between two killer whales, as they nuzzle each other, head-to-head.