Scientists found high levels of mercury, lead, and arsenic in the blood of great white sharks at rates that would likely be considered toxic to other animals.
With their long lifespans, sharks, which are considered as top predators of the sea, may be especially vulnerable to exposure to toxic heavy metals.
Heavy Metal Concentrations
Researchers from the University of Miami Rosenstiel School of Marine and Atmospheric Science evaluated the plasma levels of 14 heavy metals and 12 trace elements found in great white sharks that were sampled for a study.
The scientists said that great white sharks can act as indicators for the health of the ecosystem based on the concentrations of toxins in their blood.
"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," said Neil Hammerschlag, study coauthor and research associate professor at UM's Rosenstiel School and Abess Center for Ecosystem Science and Policy.
The specimens were from a 2012 Ocearch expedition. For the study, 43 great white sharks were captured in South Africa. They were carefully raised on a specialized platform as biologists collected blood specimens and took body measurements. After the sampling, the animals were tagged and released.
It was found that heavy metal concentrations in great white sharks were not related to their sex and body size. With the exception of copper, high levels of toxic heavy metals did not affect the sharks' body condition.
Heavy metals also bear no negative effects on the immune system and health of great white sharks.
For Future Study Of Declining Shark Population
Overall, the study suggests that sharks may have protective mechanisms that can mitigate the harmful effects of heavy metal exposure.
This first published account of blood plasma of heavy metals and trace elements in great white sharks can provide novel opportunities for future research on the declining shark population.
Great white sharks often weigh 4,000 to 7,000 pounds, and measure as long as 16 to 20 feet. Their large size is comparable to a bus.
They are carnivores that commonly eat small fishes, seals, and dolphins. They look menacing with their serrated, triangular, sharp teeth, which they use to rip apart their prey.
Their torpedo-shaped body allows them to cruise in oceans for a long period, and then swiftly switch to high-speed bursts in pursuit of food.
Despite their status as large and powerful predators, great white sharks are considered as vulnerable species. They are often hunted for their fins and teeth, and as trophies in sport fishing. Scientists say that great white sharks population have been declining over the years due to overfishing and accidental catching.
The study is published on March 19 in the Marine Pollution Bulletin.
