By Leanne Yohemas
Scientists have uncovered a lot about the Earth’s greatest extinction event that took place 250 million years ago when rapid climate change wiped out nearly all marine species and a majority of those on land. Now, they have discovered a new culprit likely involved in the annihilation: an influx of mercury into the eco-system.
“No one had ever looked to see if mercury was a potential culprit. This was a time of the greatest volcanic activity in Earth’s history and we know today that the largest source of mercury comes from volcanic eruptions,” says Steve Grasby, adjunct professor, research scientist at Natural Resources Canada and co-author of a paper published in the journal Geology. “We estimate that the mercury released then could have been up to 30 times greater than today’s volcanic activity, making the event truly catastrophic.”
Benoit Beauchamp, co-author and professor of geology, says this is the first time mercury has been linked to the cause of the massive extinction that took place during the end of the Permian, about 250 million years ago.
“Geologists, including myself should be taking notes and taking another look at the other five big extinction events,” he says.
During the late Permian, the natural buffering system in the ocean became overloaded with mercury contributing to the loss of 95 per cent of life in the sea.
“Typically, algae acts like a scavenger and buries the mercury in the sediment, mitigating the effect in the oceans,” says lead-author Hamed Sanei, adjunct professor and research scientist at Natural Resources Canada. “But in this case, the load was just so huge that it could not stop the damage.”
The generally accepted idea is that volcanic eruptions burned though coal beds, releasing CO2 and other deadly toxins wiping out the majority of life in Earth’s biggest extinction event.
The mercury deposition rates could have been significantly higher in the late Permian when compared with today’s human-caused emissions. In some cases, levels of mercury in the late Permian ocean was similar to what is found near highly contaminated ponds near smelters, where the aquatic system is severely damaged, say researchers.
“The story is one of recovery as well,” says Sanei. “After the system was overloaded and most of life was destroyed, the oceans were still able to self clean and we were able to move on to the next phase of life.”