A recent study by researchers from University of Miami Rosenstiel School of Marine and Atmospheric Science found that great white sharks were able to tolerate high levels of heavy metals that would be considered toxic to other marine animals.
Using blood samples taken from great whites off the coast of South Africa, the researchers found high concentrations of mercury, arsenic, and lead. Despite these high levels of heavy metal, they found “no adverse effects” to the sharks’ immune system based on the its body condition, total leukocytes, and granulocyte to lymphocyte ratios.
“The results suggest that sharks may have an inherent physiological protective mechanism that mitigates the harmful effects of heavy metal exposure,” study lead author Liza Merly said.
The 43 great white sharks that were analyzed were part of Ocearch’s 2012 expedition to the area. The shark’s blood was then screened for concentrations of trace elements and heavy metals. The results of this study was published in the most recent issue of the Marine Pollution Bulletin.
“As top predators, sharks bio-accumulate toxins in their tissues via the food web from the prey they eat,” co-author and research associate professor at UM’s Rosenstiel School Neil Hammerschlag said. “So 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.”