Blood samples collected during our South Africa Expeditions show high levels of heavy metals
White sharks are among the oldest species on the planet and they never would’ve been able to survive for millions of years without a few tricks up their sleeve. As it turns out, two of our biggest expeditions of all time just helped to expose one of those important tricks. Data collected during our South Africa expedition reveals white sharks are incredibly tolerant to what would essentially be poison to other species.
During our South Africa expedition, we satellite-tagged 40 white sharks, but just like every expedition, we didn’t stop there. Our collaborating science team took a series of samples, including blood draws. Those blood samples helped researchers publish a new paper revealing alarmingly high levels of poisonous heavy metals, like arsenic and mercury, in sharks’ blood. The study goes on to discover that despite levels of heavy metals that would be toxic to most other species, white sharks seem to show no ill effects. The study suggests white sharks have protective mechanisms that limit the harmful effects of exposure to heavy metals.
“OCEARCH was instrumental in the field collection and sampling for this project, it could not have been done without them”
While that might be good news for the sharks, it’s not necessarily a good sign for ocean health.
“As top predators, sharks bio-accumulate toxins in their tissues via the food web from the prey they eat,” explains Neil Hammerschlag, study co-author and research associate professor at UM’s Rosenstiel School and Abess Center for Ecosystem Science & Policy. “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,” he said. “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.”
The study is the first published account of high heavy metal concentrations in white shark blood. As a result, it serves the important function of setting a baseline for future studies. Researchers can monitor the heavy metal levels and compare them back to this study to see if they are increasing or decreasing over time. This study also opens up new opportunities to research the mechanisms that might be helping these apex predators survive.
“OCEARCH was instrumental in the field collection and sampling for this project, it could not have been done without them,” said Liza Merly, study lead author and senior lecturer at the University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science. “It was a true team effort and I was very happy to be a part of it. This study yielded many new and interesting questions to explore further and we look forward to doing that in the future.”
Our research expeditions allow us to maximize the amount of learning on each animal we sample. This, in turn, allows scientists to publish research papers like this that form the foundation of responsible ocean management policies. That’s why a big piece of OCEARCH’s mission is to empower scientists to gather the essential data needed to publish their work.