Mutated ferns shed light on ancient mass extincion
Most researchers believe that the mass extinction 201 million years ago was caused by release of CO2 by volcanism with global warming as a consequence. Now, new data from fern spores suggest there might have been more to it than that.
At the end of the Triassic around 201 million years ago, three out of four species on Earth disappeared. Up until now, scientists believed the cause of the catastrophe to be the onset of large-scale volcanism resulting in abrupt climate change. Now, new research suggest there might be several factors in play.
An international research team led by the Geological Survey of Denmark and Greenland (GEUS) have found a link between increased concentrations of the toxic element mercury in the environment. They recently published their finds in Science Advances.
”By looking at fern spores in sediments from the mass extinction, it was evident that these ferns were negatively affected by the mercury levels. Since mercury is accumulated in the food chain, it seems likely that other species have suffered as well,” says lead scientist Sofie Lindström.
“These results suggest that the end-Triassic mass extinction was not just caused by greenhouse gases from volcanoes causing global climate change, but that they also emitted toxins such as mercury wreaking havoc,” she says.
The mercury-volcano link
One of the co-authors of the study, Professor Hamed Sanei from Aarhus University, have previously demonstrated increased mercury levels from volcanism in a Large Igneous Province (LIP) during the most severe mass extinction known, the end-Permian crisis, where perhaps as much as 95% of life on Earth disappeared. Volcanic activity in LIPs is thought to be responsible for four of the five largest mass extinctions during the last 500 million years.
“Prior to industrialism, volcanic activity was the major release mechanism of large amounts of mercury from the Earth’s crust. That makes it possible to use mercury in sediments to trace major volcanic activity in the Earth’s past and in extent tie the extinctions of fossil organisms to LIP volcanism,” he explains.
Other previous studies have shown elevated mercury concentrations in Triassic-Jurassic boundary sediments over a very large area stretching from Argentina to Greenland and from Nevada to Austria and that made the team curious about the impact on the end-Triassic event.
“We decided to examine whether mercury could have played a role,” Hamed Sanei says.