Little oxygen hogs

Algae and bacteria hogged oxygen after ancient mass extinction, slowing recovery of marine life, say Stanford researchers

After the biggest mass extinction in Earth’s history – 250 million years ago – algae and bacteria in the ocean rebounded so fast that they consumed virtually all the oxygen in the sea, slowing the recovery of the rest of marine animals for several million years.

Katja Meyer A distant view of the field area in the Nanpanjiang Basin in south ChinaA distant view of the field area in the Nanpanjiang Basin in south China where limestone contained evidence of a slow recovery of marine animal populations after the mass extinction 250 million years ago. 

BY LOUIS BERGERON

A mass extinction is hard enough for Earth’s biosphere to handle, but when you chase it with prolonged oxygen deprivation, the biota ends up with a hangover that can last millions of years.

Such was the situation with the greatest mass extinction in Earth’s history 250 million years ago, when 90 percent of all marine animal species were wiped out, along with a huge proportion of plant, animal and insect species on land.

A massive amount of volcanism in Siberia is widely credited with driving the disaster, but even after the immense outpourings of lava and toxic gases tapered off, oxygen levels in the oceans, which had been depleted, remained low for about 5 million years, slowing life’s recovery there to an unusual degree.

The reason for the lingering low oxygen levels has puzzled scientists, but now Stanford researchers have figured out what probably happened. By analyzing the chemical composition of some then-underwater limestone beds deposited over the course of the recovery in what is now southern China, they have determined that while it took several million years for most ecosystems in the ocean to recover, tiny single-celled algae and bacteria bounced back much more quickly.

In fact, according to biogeochemist Katja Meyer, the tiny organisms rebounded to such an extent that the bigger life forms couldn’t catch a break – much less their breath – because the little ones were enjoying a sustained population explosion.

As the vast hordes of tiny dead organisms rotted, dissolved oxygen in the seawater was consumed by aerobic microbes involved in the decay process, leaving scant oxygen for larger organisms in what became an oxygen-depleted, or anoxic, environment.

The driver of the ongoing population boom appears to have been the massive amounts of carbon dioxide pumped into the atmosphere during the volcanism, Meyer said, which caused the world to warm.

“More warmth means an invigorated hydrological cycle, so you get more rain and this rain is also more acidic because there is more carbon dioxide dissolved in the rain,” Meyer said.

The increased amounts of more acidic rain increased weathering of the land surface, which sent more nutrients into the ocean, which fueled explosions of life such as algae blooms.

“It is kind of counterintuitive that high productivity on the part of algae and bacteria would likely be generating these toxic geochemical conditions that prevent most of animal life from recovering from mass extinction,” Meyer said.

But the process, she said, is basically the same as when excess runoff from fertilizers goes into a body of water, whether it’s a pond on a golf course or the infamous dead zone in the Gulf of Mexico created by farm runoff carried down the Mississippi River.

“You get this giant bloom of algae and then it starts to smell bad as that algae decays, pulling oxygen out of the water and causing fish die-offs,” Meyer said.

In spite of the almost inestimably high numbers of algae and bacteria living and dying during this time, there is little direct evidence of them in the fossil record because such tiny, soft-bodied creatures just don’t preserve well.

So Meyer and her colleagues had to work with indirect evidence of the microorganisms to determine their abundance during the years after the mass extinction. The population proxy they used was the carbon present in the limestone.

Carbon – like all elements – comes in different varieties, called isotopes, distinguished by the number of neutrons each has in its nucleus. The researchers worked with two carbon isotopes, carbon 12, which has six neutrons, and carbon 13, which has seven.

Both isotopes are present in ocean water, but living things on Earth have always shown a preference for incorporating the lighter isotope, carbon 12, into their structures. Thus, where life is abundant, the ratio of carbon 13 to carbon 12 in seawater is higher than it is where there is no life.

Limestone records the composition of the seawater in which it was deposited, including the relative amounts of light and heavy carbon isotopes, so by analyzing the isotope ratio in the rocks, Meyer could infer the abundance of life in the water where the limestone formed.

Comparable modern environments, such as the Bahama Banks in the Caribbean Sea, where carbonate platforms similar to the limestones are forming, are typically teeming with life at the range of depths in which Meyer’s limestones formed. In these environments, the ratio of carbon 13 to carbon 12 is generally constant from shallow to deep water.

But microorganisms are typically most abundant in shallow waters, so if marine life in the era after the mass extinction had been confined to algae and bacteria, then the shallower depths should show a markedly greater ratio of carbon 13 to carbon 12 than would be found at depth.

Meyer’s analysis showed there was a difference of about 4 parts per thousand in carbon isotope ratios from the shallow waters to depths, roughly twice what it is today.

“We only see this gradient in the interval after the mass extinction prior to the recovery of animal life,” said Meyer.

Meyer is the lead author of a research paper about the study published last month in Earth and Planetary Science Letters. The extinction 250 million years ago is known as the Permian-Triassic mass extinction, as it coincides with the end of the Permian period and the beginning of the Triassic period on the geologic time scale.

“It appears there was a huge amount of biological productivity in the shallow waters that was making the bottom waters uninhabitable for animals,” said Jonathan Payne, assistant professor of geological and environmental sciences, who is a coauthor of the paper and in whose lab Meyer has been working.

“It looks like the whole recovery was slowed by having too much food available, rather than too little,” Payne said. “Most of us think that if the biota isn’t doing well, maybe we should feed it more. This is clearly an example where feeding it less would have been much better.”

Funding for the research was provided by the National Science Foundation, Agouron Institute, American Chemical Society and National Geographic Society.

Editor’s Note

Research paper in Earth and Planetary Science Letters (DOI: 10.1016/j.epsl.2010.12.033)

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36 thoughts on “Little oxygen hogs

  1. UR messing with my head. If life prefers C12, why is the ratio of C13 in sediments and limestones etc. HIGHER when life is more abundant?

  2. OK, sorry. Now I follow the steps. Limestone is formed from whatever is present, with no preferences. So if C12 is being “withdrawn” (or held in-process by the algae, etc.) then it is somewhat depleted in the water used by the corals, so the C13/C12 ratio is higher.

    Sorry, late-nite slow-brain problem.
    ;)

  3. I guess I wonder why the blooms flourished in an oxygen deprived world (they caused it so obviously need oxygen) but other life forms did not.

    It seems obvious in a fluid biosphere that when the oxygen is gone, the biota that took it away need also to go away. And turbidity and natural ocean mixing would clear away these dead zones. This is the fox and rabbit population game. Too many foxes? Quickly there are no rabbits? No foxes? Rabbit population outgrows the food supply, so no rabbits. The best chance is for the two populations to maintain a healthy relationship.

  4. This mass extinction could have been caused by a mass anoxic event. This can happen when there is a sudden influx of methane into the atmosphere, clathrates breaking down perhaps. When methane breaks down it uses oxygen and forms CO2 and water. This could have used a good amount of atmospheric oxygen and increasing atmospheric CO2 by a large amount. There would have been a long period of time required to break down the CO2 to produce the required volume of oxygen for life of the non plant variety to resume. Remember it is only plants that can produce oxygen from CO2 and all life needs oxygen for respiration. (Except some bacteria of course)

  5. “More warmth means an invigorated hydrological cycle, so you get more rain …” Meyer said.

    That is SO last week – can’t these guys keep up!

  6. “so you get more rain and this rain is also more acidic because there is more carbon dioxide dissolved in the rain”

    So it’s “carbonic acid” that got created from the sulphur spewing volcano in Siberia?

  7. Population biology is ruled by simple differential equations; the growth rate of any species’ population depends on the hysteresis period (the time between the ‘birth’ of an organism and the moment is becomes able to reproduce) and the availability of resources. Right now we are struggling to get people to understand the ‘availability’ question with regard to CO2, but the hysteresis period will dominate after any ‘mass extinction’ as those species that are quickest to reproduce are first ‘in line’ for the available resources.

  8. From above, “The driver of the ongoing population boom appears to have been the massive amounts of carbon dioxide pumped into the atmosphere during the volcanism, Meyer said, which caused the world to warm.”

    So there it is, WUWT finally admits increased CO2 increases Global temperature.

  9. Correct me if I’m wrong but weren’t algae blooms at one point supposed to be the bestest carbon sink ever?

  10. jcrabb,

    They also say:

    “It looks like the whole recovery was slowed by having too much food available, rather than too little,” Payne said. “Most of us think that if the biota isn’t doing well, maybe we should feed it more. This is clearly an example where feeding it less would have been much better.”

    So starvation causes increased populations? I’ll have to think about that one.

    Also, no one disputes that CO2 doesn’t cause any warming, so your assertion that WUWT “finally admits” it does is just spin. The warming caused by CO2 is insignificant. Most of the warming is due to the planet’s natural emergence from the LIA. The small fraction due to CO2 can be disregared as inconsquential, as it is too minuscule to even measure.

  11. Smokey says

    “So starvation causes increased populations? I’ll have to think about that one.”

    I think it might be more like decreased predation — the algae eaters being mostly dead — allows increased populations.

    In any case, I think some healthy scepticism might be in order. Paleo anything tends to be mostly a best current guess and to change quite a lot over time as new evidence comes in and old evidence is reinterpreted.

    I’d be more sold on this theory if there were widespread, organic rich, marine black shale deposits just above the Permian-Triassic boundary. But I don’t think there are.

  12. The location these samples come from, South China, 252 million years ago was a much different place at the time as can be seen in this map from Christopher Scotese.

    Note that 251 Mya, the entire block labeled as Siberia in the map was one big volcano that lasted for a million years and built up a volcanic rock plateau that was 4 kms high, enough to cover the entire Earth 6 metres high in magma. If you don’t think that made for a bad million years on Earth, then nothing will.

    Secondly, one has to look at the Paleo-Tethys Sea (which eventually turned into the Mediterranean, the Black Sea and the Caspian Seas) would have been an extremely hot ocean. Located on the west side of the Panthalassic Sea (Pacific) at the equator, it would be like the Pacific Warm Pool today at 32C.

    Except the planet was 8C warmer then and the Pacific was twice as big as it is now and the Paleo-Tethys was a relatively enclosed shallow Sea at the equator. All the warm surface ocean water in the Pacific would have be blown/dragged into the Sea by the Trade Winds (which have always existed on our rotating spherical planet).

    The sea surface temperatures in the Paleo-Tethys Sea, at South China, would have been as much as 45C for long periods of time which is too hot for most complex life-forms. It would have been bacteria only. The Geography explains why there would have been million of years at a time, when no complex life existed in this Sea. If they go back to 230 Mya or 240 Mya, they will also find similar periods.

  13. Open question: is there a scenario with a large projected increase in CO2 where the biosphere could become a positive feedback?

    IOW, would there be enough CO2 to establish a giant worldwide (albeit tropical) algae bloom, followed by a synchronous die-off, killiung the other plant-life, thereby removing that sink of CO2?

  14. This is interesting, but for these scientists to say that the evidence they have found in one little area of the Earth makes their scenario a fact for the entire planet is one hell of a big WAG.

  15. A piece of the Permian-Triassic climate puzzle that is missing from the discussion here (and most places) is that the P-T was also coincident with one of those grand galactic cosmic ray flux minima that occur when our solar system is between galactic spiral arms, every 135 million years or so.

    http://www.juniata.edu/projects/oceans/GL111/celestialdriverofclimate.pdf

    The Great Dying wasn’t only because of GCR, but it’s clear from SV03 that GCR have a major impact on the world’s climate that is unmistakable when averaged over geologic time.

    Dick Alley, in his oft-cited AGU meeting talk (Dec ’09?), makes it clear that CO2 was responsible for the P-T extinction ‘because there isn’t anything else’ that could explain it. Not true.

  16. db:“I guess I wonder why the blooms flourished in an oxygen deprived world (they caused it so obviously need oxygen) but other life forms did not. ”

    Ok, algae and cyanobacteria are photosynthetic, they produce net oxygen. However, the decay of dead matter (including algae) consumes oxygen, so an algae bloom can create a hypoxic environment. The algae are not wiped out because they produce their own oxygen. This is actually an all too common result of algae blooms.

  17. Wouldn’t you know people have already been lining up to demonstrate that a little knowledge is a bad thing.

    CO2 bad – algae good.

    http://www.sciencedaily.com/videos/2007/0407-possible_fix_for_global_warming.htm

    The new Godzilla – man-made algae blooms. Oh – wait! Here come scientists to defeat the algae monster!

    http://www.sciencedaily.com/releases/2008/08/080818184434.htm

    Ruh roh – more scientists smack down previous scientists – no consensus nonsense here…

    http://www.sciencedaily.com/releases/2010/01/100121135856.htm

    Oh – more science! Like watching tennis from net line!

    http://www.sciencedaily.com/releases/2011/02/110217151443.htm

  18. @LarryD says:
    March 28, 2011 at 8:12 am

    db:“I guess I wonder why the blooms flourished in an oxygen deprived world (they caused it so obviously need oxygen) but other life forms did not. ”

    Ok, algae and cyanobacteria are photosynthetic, they produce net oxygen. However, the decay of dead matter (including algae) consumes oxygen, so an algae bloom can create a hypoxic environment. The algae are not wiped out because they produce their own oxygen. This is actually an all too common result of algae blooms.

    The algae (greens & blue-greens) can switch between autotrophic (photosynthetic) and heterotrophic (using organic carbon as an energy source) growth, so the authors are saying that the oceans became a massive population of heterotrophs gone wild.

    Possible, but I’d think there would be enough photosynthesis to provide some balance. This story rather reeks of sensationalism to me.

  19. Please, look at the abundant life on the planet today. Somehow this chemical mixture settled out and created the conditions for life to thrive, for now, maybe not for tomorrow, then again for tomorrow, maybe not forever-truly be thankful for today for it hinges on decimals.

  20. John Marshall says:
    March 28, 2011 at 1:43 am
    Remember it is only plants that can produce oxygen from CO2….
    ____________________

    Cyanobacteria were the first oxygen producers, and still exist.

    It is unlikely that CO2 would be limiting. N or P would be more likely. That’s why you get anoxic events with fertilizer runoff. These nutrients can be produced by volcanic events. If nitrates and phosphates wash into the oceans in large enough quantities, the hypothesis could be supported that way. Otherwise, it wouldn’t matter that vast quantities of CO2 were available. You can’t build DNA, for example, without N and P.

    There is some debate about the cause of the extinction, but nutrient transport and volcanism seems to be involved. Some suggest ash clouds blocking sunlight as the immediate cause.

    See:
    http://geology.gsapubs.org/content/38/5/447.abstract (2009)
    “The well-known Siberian volcanism is proposed herein, on the basis of the current compilation of dating data, to protract the Early Triassic faunal recovery rather than to cause the end-Permian extinction.”

    http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V61-4VW4VCT-2&_user=10&_coverDate=05%2F15%2F2009&_rdoc=1&_fmt=high&_orig=gateway&_origin=gateway&_sort=d&_docanchor=&view=c&_searchStrId=1696822810&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=74147a676f3e46edec0641aa3c16d40f&searchtype=a (2009)
    “The induction of marine euxinic conditions, worldwide, at the end of the Permian was likely a consequence of the aggregation of Pangea and the uplift, weathering and transport of nutrients to the ocean well in advance of the PTB.”

  21. UMMMMM, but, all those little green things absorbing the CO2 release OXYGEN!!!!!!

    WTFUWT?!?!?!?!?!?!?!?!

  22. The CAGW crowd may soon realize they are on the losing side of the science plus actual climate behavior, so that crisis over, the new tipping point will surely morph into the mantra- that burning up all the fossil fuel will soon deplete the available oxygen and we will all surely suffocate. Gasp! Much worse than slowly burning to death which is our current fate. Of course it will be worse than we thought. /sarc.

  23. So let’s see… giant million year volcanism creating a CO2 concentration measured in percent instead of parts per million… and no runaway greenhouse boiling the oceans and creating a second Venus.

    Somehow my concern over catastrophic AGW drops to zero…

  24. ====

    Correct me if I’m wrong, but it sounds like a couple of scientists went on a (likely government funded) junket to China, and now are fishing for their next big grant — having noticed only some slight variances in Carbon 13 in a rock sample….

    I can hear them now…

    “Hey Louis, that rock sample that we got from the campsite where you outdrank that sherpa in China… It’s got 0.2 percent more carbon 13 in it from around 200 million years ago than usual, so I’m thinking here… Now if we cut off the ends of the data at 199 and 201 million years, it looks like me might be able to make a real hockey stick outta this thing.. Ya think we should give it a whirl, Louis? Maybe the NSF or some other biased, partisan front organization would spring a few million on a grant for another government bender — to go collect a rock!”

    ====

  25. “…The driver of the ongoing population boom appears to have been the massive amounts of carbon dioxide pumped into the atmosphere during the volcanism, Meyer said…”

    This acknowledges that volcanoes are a major source of CO2. There are currently estimated to be 3 million subsea volcanoes.

    http://iceagenow.com/Three_Million_Underwater_Volcanoes.htm

    If these subsea volcanoes emit CO2 at rates similar to the Lake Nyos vent, then there are 111 Gigatonnes of volcanic CO2, not counting releases from land based volcanoes, put into the atmosphere per year, compared to the mere 130 to 230 million tonnes estimated in Wankapedia.

  26. If their theory is mostly true, then the Triassic ought to be known for rich source rocks all around the world because it is anoxic. I don’t think it is. In fact, Trassic Red Beds

    \\ Several independent studies have demonstrated that rich source rocks are largely concentrated in several stratigraphic intervals during the Phanerozoic (the past 542 million years).

    (6) The Oligocene-Miocene (34-5 Ma)
    (5) The Middle Cretaceous (125-89 Ma)
    (4) The Late Jurassic (165-145)
    [-- Triassic, not listed as a source interval here --]
    (3) The Pennsylvanian-Late Permian (318-270)
    (2) The Late Devonian (385-360 Ma)
    (1) The Silurian (444-416 Ma) //

    http://www.geoexpro.com/geoscience/rich-petro/

    My guess is that they are looking at a restricted basin artifact, not a world-wide event.

    One thing I have never figured out is why an asteroid impact isn’t included in the list of possibilities for extinction AND the the creation of the flood basalts of Siberian Traps.

  27. @ kuhnkat

    Yes the algae and phytoplanton while alive absorb CO2; the problem that leads to oxygen deprivation arises when these organisms exhaust the available nutrients and then die, and are oxidated (taking up oxygen) or eaten by anoxic bacteria, or at night-time when photosynthesis ceases and respiration takes over. The loss of free dissolved oxygen occurs during algal blooms sparked by excess nutrients in a body of water and is a well documented phenomenon called eutrophication, discovered during the mid-20th century (earlier scientists scorned the idea that overloading a system with nutrients would cause such problems). The relevant passage on this from Wikipedia states:

    Under eutrophic conditions, dissolved oxygen greatly increases during the day, but is greatly reduced after dark by the respiring algae and by microorganisms that feed on the increasing mass of dead algae. When dissolved oxygen levels decline to hypoxic levels, fish and other marine animals suffocate. As a result, creatures such as fish, shrimp, and especially immobile bottom dwellers die off.[16] In extreme cases, anaerobic conditions ensue, promoting growth of bacteria such as Clostridium botulinum that produces toxins deadly to birds and mammals. Zones where this occurs are known as dead zones.

  28. Wait, wait, wait…

    The spread of ‘diablo rojo’ squid is because of anoxic water. Anoxic water caused by human behavior. Supposedly. But have the waters where the diablo rojo have spread been checked for abundance of bacterial life? I cannot find a conclusive “Yeah, we ruled out bacteria.” So, if there is an uptick in oceanic bacterium, that could really explain quite a bit of the change in biodiversity there, couldn’t it? Any takers on providing the silver bullet to my hypothesis?

  29. Hang on a mini. These algae didn’t suck the Oxygen out of the oceans overnight. These processes take hundreds if not thousands of years.
    As algae numbers increased, their predators, the algae eaters, would also have increased in numbers keeping up with the available food supply.
    Afterall, we’re not talking about life spans of elephants here.

    There had to have been a shortage of oxygen in the atmosphere for a long long time leading to the non-replenishment in the oceans via mixing.
    I would suggest a mass die off of photosynthesising life forms, possibly from an extended period of lack of sunshine possibly due to volcanism.
    Lack of sunshine can also lead to the reduction of temperature gradients leading to less wave mixing. Algae grows in still waters.

    I’m hope someone more knowledgable can comment.

  30. “The extinction 250 million years ago is known as the Permian-Triassic mass extinction, as it coincides with the end of the Permian period and the beginning of the Triassic period on the geologic time scale.”

    Why is that sentence near the bottom? Are you writing a mystery novel?

  31. While this observation quoted above is valid:

    “there is little direct evidence of them in the fossil record because such tiny, soft-bodied creatures just don’t preserve well”

    it does not mean that we can build a hypothesis of abundant microbial life in an anoxic environment that leaves no physical remains. Anoxia in the marine environment typically leads to sapropel production.
    A search using the following keywords “sapropel permian triassic” finds the following paper:-
    Palaeogeography, Palaeoclimatology, Palaeoecology
    Volume 252, Issues 1-2, 20 August 2007, Pages 304-327
    The Permian-Triassic Boundary Crisis and Early Triassic Biotic Recovery

    Abstract
    The Permian–Triassic boundary at Nhi Tao, Cao Bang Province, Vietnam was sampled in a 7.5-m-thick outcrop section at high resolution (~ 5 cm intervals) for chemostratigraphic and magnetic susceptibility analysis. The section consists entirely of slightly argillaceous limestone representing shallow-marine facies of the Jinxi Platform, one of several large carbonate platforms within the Nanpanjiang Basin, located on the southern margin of the South China Craton.
    Upper Permian strata (Beds 1–7) are mainly dark-gray, cherty fossiliferous wackestones and packstones containing a diverse open-marine fauna, whereas uppermost Permian and Lower Triassic strata (Beds 9 and higher) are medium-gray calcimicrobial framestones containing rare macrofossils.
    These facies are separated by a 12-cm-thick oolitic–pisolitic grainstone (Bed 8) that coincides with the disappearance of most Late Permian faunal elements as well as with the first appearance of various geochemical anomalies that continue into the Lower Triassic part of the section. This “Late Permian event horizon” is characterized by
    (1) an abrupt decline in total organic carbon to near-zero values,
    (2) the onset of a sustained decline in carbonate δ13C, and
    (3) the first of eight concentration peaks in pyrite sulfur.
    Significantly, each sulfide peak is associated with lower pyrite δ34S values as well as with the onset of a negative carbonate δ13C excursion (or the acceleration of an excursion already in progress).
    These chemostratigraphic relationships are consistent with multiple episodes of upwelling of sulfidic, 34S- and 13C-depleted deep-ocean waters onto the Jinxi Platform. The first upwelling event was the most intense and caused a drastic reduction in primary productivity and the demise of the Late Permian fauna; subsequent episodes were less intense but may have contributed to a delay in recovery of Early Triassic marine ecosystems.
    A ten-fold increase in magnetic susceptibility in Bed 9 may record the influx of fine detrital particles following destruction of terrestrial ecosystems and massive soil erosion. The terrestrial signal of the end-Permian catastrophe thus follows the marine signal with a 12-cm lag, which may reflect the time-of-transit of soil-derived particles across the Nanpanjiang Basin, suggesting that the marine and terrestrial crises in the Nhi Tao region occurred more-or-less synchronously.
    These observations suggest a model in which renewal of global-ocean overturn followed a prolonged interval of deep-ocean stagnation during the Late Permian, with upwelling intensity modulated by short-term (~ 20 kyr) climate cyclicity.

  32. Just noting as well, that there is a distinct drop in the do18 isotope data centred right on 251.4 Mya, the time of the peak number of extinctions during the event.

    The do18 isotope data indicates that temperature fell by as much 7C for half a million years or so (consistent with a really big volcano or a series of large volcanic events which is more likely). I don’t think this has been noticed before because everyone uses a really long smoothing parametre on the isotope data while I have tightened that up as much as seems reasonable.

    Last 570 Mys showing the Permian Extinction as one of the features.

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