Hyper-saline: The likely pink colour of the Zechstein Sea would have been brought about by microbes with an extreme preference for salt, as is the case with salt lakes today.
Credit: Karsten Kotte/Universität Heidelberg
SYDNEY: Poisonous gases pumped out from massive salt lakes 250 million years ago could have caused the biggest mass extinction event ever recorded in the fossil record.
An international team of researchers report new evidence that microbes living in prehistoric salt lakes produced volatile halocarbon gases that clogged the atmosphere. The gases dramatically changed atmospheric composition during the Permian period (299 to 251 million years ago), causing climate change and wiping out over 90 per cent of life.
Likely culprits
The scientists warn that similar processes operating in modern salt lakes could speed up desertification and affect global climate today.
Previous research fingered emissions from volcanoes, asteroid impact or the release of methane hydrates from the sea for the Permian extinction event.
But the researchers, led by ecotoxicologist Ludwig Weissflog from the Helmholtz Centre for Environmental Research in Leipzig, Germany, say that volatile halocarbons released from a large inland sea would have had a "catastrophic effect" on vegetation. Volatile halocarbons are released naturally by microbes as well as by industrial processes. They are greenhouse gases and can also deplete the ozone layer.
To make the finding, the researchers studied the emissions of halocarbons – chloroform, trichloroethane and tetracholorethane – from present-day salt lakes in the Republic of Kalmykia, part of the Russian Federation.
"Using steppe plant species we were able to prove that halogenated gases contribute to speeding up desertification," said co-author and environmental geochemist Karsten Kotte from the University of Heidelberg in Germany.
"Catastrophic effects"
The researchers believe that similar processes were operating at the end of the Permian, when a 600,000 km2 inland sea (situated where Central Europe is today) was drying up. "Our calculations show that airborne pollutants from giant salt lakes like the Zechstein Sea must have had catastrophic effects at that time", said Weissflog.
But Australian geologist Rick Squire from Monash University in Melbourne questioned the result, published in the current issue of the Proceedings of the Russian Academy of Science.
Accelerated mutations
Accelerated mutations can and do coincide with stressed populations due to inbreeding.