Polysaccharides point to identity of Permian killer

The discovery of the chemical remains of polysaccharides supports a theory that the largest mass extinction in the Earth’s history was caused by massive volcanic eruptions.

Over 90 per cent of all marine species and 70 per cent of all terrestrial vertebrate species became extinct at the end of the Permian period, around 250 million years ago. Scientists have suggested a number of possible causes, including a meteorite or comet impact, the release of huge quantities of frozen methane hydrate beneath the oceans, or massive volcanic eruptions in present-day Siberia that lasted for hundreds of thousands of years.

To learn more, a team of US, Dutch and British researchers, led by Mark Sephton from Imperial College London, used pyrolysis-gas chromatography-mass spectrometry to study sedimentary rocks from the Dolomites in Italy that were laid down at the end of the Permian. Although these rocks were at the bottom of the sea during this time, the researchers discovered that they contained large quantities of organic molecules known as furans. Furans detected in fossilised organic material are usually interpreted as the remains of dehydrated polysaccharides, which are commonly found in soil.

The researchers propose that the volcanic eruptions in Siberia damaged the ozone layer and generated acid rain, which decimated terrestrial life and led to widespread soil erosion. Washing into the sea, this soil blocked out light and soaked up oxygen, leading to the extinction of the majority of marine species.

’The cause of the end-Permian extinction has been highly controversial,’ said Sephton. ’We show that the terrestrial ecosystem was the first to suffer [and] the continent-wide nature of the event implies that it was caused by something in the atmosphere.’

Michael Rampino, an associate professor in the Earth and Environmental Science Program at New York University, US, agrees with the researchers’ conclusions. ’There would have been massive erosion due to the plant extinction and braided river deposits everywhere,’ he told Chemistry World. ’Until the plants came back, there would have been a decrease in the burial of carbon on land and an increase in carbon burial in the ocean.’ Jon Evans