0
$\begingroup$

Science Daily reports that the mass extinction at the end of Permian period happened by the Methanosarcina archaea wiping out 90% of species:

Methane-producing microbes may be responsible for the largest mass extinction in Earth's history. Fossil remains show that sometime around 252 million years ago, about 90 percent of all species on Earth were suddenly wiped out […]. It turns out that Methanosarcina had acquired a particularly fast means of making methane, and the team's detailed mapping of the organism's history now shows that this transfer happened at about the time of the end-Permian extinction.

Is it possible by the global warming and all the spores of bacteria come out from melting glacier or anywhere else and mass extinction occur?

$\endgroup$
  • $\begingroup$ Worth considering that when reasons for a mass extinction are investigated the answer is often "All of the above", because anything that changes the environment contributes. we have for instance also found massive volcanics and a massive impact crater at the same time. $\endgroup$ – John Aug 7 at 15:03
  • $\begingroup$ The first problem here is that the theory that the P-T extinction was caused by bacteria (rather than bacteria being a possible effect/feedback) is contradicted by LOTS of evidence, primarily the Siberian Traps eruptions igniting large coal beds. $\endgroup$ – jamesqf Aug 7 at 16:29
5
$\begingroup$

First of all, let’s consider your Methanosarcina scenario in specific.

Methanosarcina with those properties are still around. So, there is no reason to expect that introducing some ancient Methanosarcina into a suitable environment today would do very much – as they should already be there. Any existing (large-scale) environment providing a niche for Methanosarcina should already be occupied by it as it only needs a single organism to get there by chance at some point.

Moreover, there must be some reason why our atmosphere stopped being filled with methane by Methanosarcina. For example some prerequisite resource could have been depleted, some other organism evolved that consumes this methane or controls the Methanosarcina population by feeding on it. Whatever this reason is, we should expect that it still applies: A required resource would still be gone and a second organism controlling this activity should still be around (or resurface together with the Methanosarcina in question). In fact, the hypothesis you mention maintains that the nickel required by Methanosarcina to produce methane was available in huge amounts due to specific volcanic activity at that time.

Finally, the current ice masses of the Earth are much younger and have not been around since the Permian period. In general, if geologically cryostoring microbes were relevant, climate change should be the least of our worries as drilling a hole into the ice or local geologic activity could suffice to bring back a few individuals – which is all that would be needed.

Now, what about unfreezing microbes in general? Due to lack of fossils, we have little knowledge about microbe extinction, except that it does happen. However, my ecological intuition is that microbes either lose their niche to a fitter alternative (which either be more apt at causing problems or avoid them resurfacing) or survive in small amounts (ready to occupy their niche if it should resurface). Microbes are considerably different from higher, sexually reproducing life forms here as it only needs a single individual to revive the species and individuals can survive for a long time in adverse conditions, not only by sporulation but also because they need little energy to maintain their state. Finally, if a niche for disastrous microbes exists, there is the constant risk that it will be filled by some ordinary microbes evolving, which brings us to the next point.

Something that is conceivable to happen is that some microbes spontaneously evolve to fill a big niche and have some disastrous by product leading to a mass extinction. It is hard to estimate this risk, but as far as I know, there is no historic precedent after the evolution of higher life forms. (As elaborated above, the Methanosarcina hypothesis for the Permian extinction features additional factors.) However, I consider it unlikely that climate change increases this risk. While climate change undoubtedly has disastrous ecological consequences, tilting individual ecosystems, I don’t see how it creates some fundamentally new environment (that wasn’t already there in similar form somewhere else on the planet) that would stimulate a spontaneous disastrous microbial evolution.

| improve this answer | |
$\endgroup$
  • $\begingroup$ "a fitter alternative (which would be even more apt at causing problems)" I think I've heard specialists mentioning that being fit, for a microbe, entails not causing too many problems. $\endgroup$ – bli Aug 7 at 8:56
  • $\begingroup$ @bli That is only true for microbes that live inside another organism and depend on it to stay alive. $\endgroup$ – jpa Aug 7 at 15:05
  • $\begingroup$ @jpa: Not necessarily. Consider for instance a microbe that produces oxygen as a waste product, but can't tolerate high concentrations of environmental oxygen. So as the Great Oxygenation Event gets under way, those microbes either mutate to tolerate oxygen (with the intolerant dying in large numbers), or they become extinct. Or consider yeast fermentation: at some point the yeast produces an ethanol concentration that's toxic to them. $\endgroup$ – jamesqf Aug 8 at 4:22
  • $\begingroup$ @jamesqf: Well, if we have something like the great oxygenation event, the oxygen producing microbes were fitter as far as the answer is concerned. More generally, my point is if microbes go extinct, it is because their niche is taken by some other species, which should either increase the problems (if the niche has gone too and then re-emerges) or voids them (because the dangerous microbes have no niche to go to). Also see my edit. $\endgroup$ – Wrzlprmft Aug 8 at 7:40

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.