Long-Living Greenland Sharks Accumulate High Concentrations of Contaminants
When it comes to pollutants such a PCBs contaminating the bodies of animals, the polar bear is often at the top of the list of most-polluted animals, but new research suggests that Greenland sharks harbor even more alarmingly high levels of pollutants than polar bears.
Greenland sharks are one of the largest living shark species. Growing up to 7 meters long and weighing up to a ton, their are dimensions comparable to a great white shark. Greenland sharks are also live farther north than any other shark species and can live as long as 100 years, the researchers said.
In an attempt to see how pollutants affect these large, long-lived sharks, a team of researchers from the Norwegian University of Science and Technology (NTNU), the Norwegian Polar Institute and Windsor University in Canada tagged 43 individual Greenland sharks in waters around Svalbard, Spitsbergen.
Liver samples taken from the sharks revealed high concentrations of PCB, brominated flame retardants and other pollutants, the researchers report.
"We think this is due to their diet, because Greenland sharks around Svalbard eat a lot of seals, which are high on the food chain, which leads to an accumulation of pollutants," Bjørn Munro Jenssen, an NTNU biologist who specialized in pollutants and arctic biology, said in a statement.
The researchers said this is also why polar bears, which also eat high on the food chain, tend to have high concentrations of pollutants in their livers as well.
Also, because the sharks live for so long, more and more pollutants accumulate in their bodies over time.
Previous researcher on Greenland sharks did not reveal such high containment levels, which prompted the researchers to suggest that the sharks' location has a lot to do with the pollutants they consume.
"The reason we found lower concentrations (in these areas) is because the sharks eat less seal. Around Svalbard, 43 percent of the individuals we studied had seal remains in their stomachs. In Canada, around Iceland and off Greenland, we found seal in only 14 percent of sharks. There the sharks prey lower down in the food chain, mostly on fish, which again results in less accumulation of pollutants," Jenssen said in a statement.
Jenssen and his collaborators believe the contaminants led to lower vitamin A and higher vitamin E concentrations in the Greenland sharks.
"These finds are very provocative. We are affected by pollutants, especially hormone inhibiting substances. Studies of wild animals give us information about effects that are also relevant for humans. The species highest up on the food chain are the most affected. We are among them," Jenssen said.