Great white sharks swimming off the SA coast have high concentrations of mercury, arsenic and lead in their blood.
The heavy metals are present in levels toxic to many animals but researchers found no apparent negative consequences on several health parameters measured in the sharks.
“The results suggest that sharks may have an inherent physiological protective mechanism that mitigates the harmful effects of heavy metal exposure,” said Liza Merly, lead author of a study published in the journal Marine Pollution Bulletin.
Co-author Neil Hammerschlag said: “As top predators, sharks bio-accumulate toxins in their tissues via the food web from the prey they eat.
“By measuring concentrations of toxins, such as mercury and arsenic, in the blood of white sharks, they can act as ‘ecosystem indicators’ for the health of the ecosystem, with implications for humans.
“Basically, if the sharks have high levels of toxins in their tissues, it is likely that species they eat below them will also have toxins, including fishes that humans eat.”..