Editing Permian–Triassic extinction event (section)

=== Methanogens ===
A hypothesis published in 2014 posits that a genus of [[Anaerobic respiration|anaerobic]] methanogenic [[archaea]] known as ''[[Methanosarcina]]'' was responsible for the event. Three lines of evidence suggest that these microbes acquired a new metabolic pathway via [[gene transfer]] at about that time, enabling them to efficiently metabolize acetate into methane. That would have led to their exponential reproduction, allowing them to rapidly consume vast deposits of organic carbon that had accumulated in marine sediment. The result would have been a sharp buildup of methane and carbon dioxide in the oceans and atmosphere, in a manner that may be consistent with the <sup>13</sup>C/<sup>12</sup>C isotopic record. Massive volcanism facilitated this process by releasing large amounts of [[nickel]], a scarce metal that is a cofactor for enzymes involved in producing methane.<ref name="Rothman2014">{{Cite journal | doi = 10.1073/pnas.1318106111| title = Methanogenic burst in the end-Permian carbon cycle| journal = [[Proceedings of the National Academy of Sciences of the United States of America]]| date = 31 March 2014 | last1 = Rothman | first1 = D.H.| last2 = Fournier | first2 = G.P.| last3 = French | first3 = K.L.| last4 = Alm | first4 = E.J.| last5 = Boyle | first5 = E.A.| last6 = Cao | first6 = C.| last7 = Summons | first7 = R.E.| pmid = 24706773 | pmc=3992638 | volume=111 | issue=15 | pages=5462–5467| bibcode = 2014PNAS..111.5462R| doi-access = free}} – Lay summary: {{cite web | url=https://www.sciencedaily.com/releases/2014/03/140331153608.htm | title=Ancient whodunit may be solved: Methane-producing microbes did it! | first=David L. | last=Chandler | website=Science Daily | date=March 31, 2014}}</ref> Chemostratigraphic analysis of Permian-Triassic boundary sediments in Chaotian demonstrates a methanogenic burst could be responsible for some percentage of the carbon isotopic fluctuations.<ref name="SaitohIsozaki2021">{{cite journal |last1=Saitoh |first1=Masafumi |last2=Isozaki |first2=Yukio |date=5 February 2021 |title=Carbon Isotope Chemostratigraphy Across the Permian-Triassic Boundary at Chaotian, China: Implications for the Global Methane Cycle in the Aftermath of the Extinction |journal=[[Frontiers in Earth Science]] |volume=8 |page=665 |doi=10.3389/feart.2020.596178 |bibcode=2021FrEaS...8..665S |doi-access=free }}</ref> On the other hand, in the canonical Meishan sections, the nickel concentration increases somewhat after the {{delta|13|C|}} concentrations have begun to fall.<ref>{{cite journal |doi=10.1093/nsr/nwu047 |title=The end-Permian mass extinction: A still unexplained catastrophe |journal=[[National Science Review]] |volume=1 |issue=4 |pages=492–495 |year=2014 |last1=Shen |first1=Shu-Zhong |last2=Bowring |first2=Samuel A. |doi-access=free}}</ref>