Dan Rothman from MIT -
Roughly 252 million years ago, the end-Permian extinction resulted in the greatest loss of life in the fossil record. The cause remains mysterious, but decades of research indicate that a strong perturbation of the global carbon cycle occurs at the extinction's peak. This talk addresses three aspects of this disruption.
First, we show that geochemical signals indicate super-exponential growth of the marine inorganic carbon reservoir, coincident with the extinction and consistent with the expansion of a new microbial metabolic pathway. Second, we show that the efficient pathway via which members of the microbial genus Methanosarcina convert acetate to methane emerged at a time statistically indistinguishable from the extinction. Finally, we show that nickel concentrations in South China sediments increased sharply at the extinction, probably as a consequence of massive Siberian volcanism, enabling a methanogenic expansion by removal of nickel limitation. Collectively, these results are consistent with the instigation of Earth's greatest mass extinction by a specific microbial innovation.