The end-Permian extinction event is one of the biggest mysteries in paleontology. Scientists from Massachusetts Institute of Technology (MIT) have discovered that methane producing microbes may have been the primary cause of the event.
The new research was conducted by a team of researchers from the MIT have gathered enough evidence to back up the theory that an overabundance of methane may have caused the massive extinction.
The end-Permian extinction, also known as the Permian-Triassic (P-Tr) extinction event, happened approximately 252 million years ago. The P-Tr event is considered as the biggest extinction level event in the history of the Earth and over 90 percent of all species alive during the time perished.
The most popular theory to explain the extinction event usually involves meteor impacts. However, the new findings show that microscopic organisms may have been the largest contributors behind the P-Tr event. The team published its findings in the online journal the Proceedings of the National Academy of Sciences.
The methane producing microbes are prokaryotes from the Archaea domain known as Methanosarcina. The researchers found that these microbes suddenly and rapidly multiplied in the Earth's oceans producing massive amounts of methane into the Earth's atmosphere. This sudden influx of methane may have brought about rapid climate change while also adversely affecting the chemistry of the Earth's ancient oceans.
"A rapid initial injection of carbon dioxide from a volcano would be followed by a gradual decrease," said MIT postdoc Gregory Fournier. "Instead, we see the opposite: a rapid, continuing increase." Fournier is one of the authors of the study.
To complete the study, the researchers put together three distinct bodies of evidence to back up their theory. The scientists looked for geochemical evidence that proven a rapid increase in carbon dioxide in the Earth's oceans 252 million years ago. Due to the large amounts of organic carbon in the Earth's oceans at the time, scientists also looked for genetic evidence that indicated a change in Methanosarcina that allowed them to produce very large amounts of methane. Lastly, the scientists also looked for evidence in sediments that could provide them with more evidence to support the theory. They found that certain sediments dating from the P-Tr event also exhibited a sudden increase the concentrations of nickel.
"That suggests a microbial expansion," Fournier said. "The growth of microbial populations is among the few phenomena capable of increasing carbon production exponentially, or even faster."
The researchers say that their findings are very convincing. They also believe that the scale of the P-Tr extinction event was the result of the cumulative impact of many factors.
