Oxygen depletion in ancient oceans caused major mass extinction

Oxygen depletion in ancient oceans caused major mass extinction
For years, scientists struggled to connect a mechanism to this mass extinction, one of the 10 most dramatic ever recorded in Earth's history. Now, researchers from Florida State University have confirmed that this event, referred to by scientists as the Lau/Kozlowskii extinction, was triggered by an all-too-familiar culprit: rapid and widespread depletion of oxygen in the global oceans. Credit: Stephen Bilenky

Late in the prehistoric Silurian Period, around 420 million years ago, a devastating mass extinction event wiped 23 percent of all marine animals from the face of the planet.

For years, scientists struggled to connect a mechanism to this , one of the 10 most dramatic ever recorded in Earth's history. Now, researchers from Florida State University have confirmed that this event, referred to by scientists as the Lau/Kozlowskii extinction, was triggered by an all-too-familiar culprit: rapid and widespread depletion of oxygen in the global oceans.

Their study, published today in the journal Geology, resolves a longstanding paleoclimate mystery, and raises urgent concerns about the ruinous fate that could befall our modern oceans if well-established trends of deoxygenation persist and accelerate.

Unlike other famous mass extinctions that can be tidily linked to discrete, apocalyptic calamities like meteor impacts or volcanic eruptions, there was no known, spectacularly destructive event responsible for the Lau/Kozlowskii extinction.

"This makes it one of the few extinction events that is comparable to the large-scale declines in biodiversity currently happening today, and a valuable window into future climate scenarios," said study co-author Seth Young, an assistant professor in the Department of Earth, Ocean and Atmospheric Science.

Scientists have long been aware of the Lau/Kozlowskii extinction, as well as a related disruption in Earth's carbon cycle during which the burial of enormous amounts of organic matter caused significant climate and environmental changes. But the link and timing between these two associated events—the extinction preceded the carbon cycle disruption by more than a hundred thousand years—remained stubbornly opaque.

"It's never been clearly understood how this timing of events could be linked to a climate perturbation, or whether there was direct evidence linking widespread low-oxygen conditions to the extinction," said FSU doctoral student Chelsie Bowman, who led the study.

To crack this difficult case, the team employed a pioneering research strategy.

Using advanced geochemical methods including thallium isotope, manganese concentration, and sulfur isotope measurements from important sites in Latvia and Sweden, the FSU scientists were able to reconstruct a timeline of deoxygenation with relation to the Lau/Kozlowskii extinction and subsequent changes to the .

The team's new and surprising findings confirmed their original hypothesis that the extinction record might be driven by a decline of ocean oxygenation. Their multiproxy measurements established a clear connection between the steady creep of deoxygenated waters and the step-wise nature of the extinction event—its start in communities of deep-water organisms and eventual spread to shallow-water organisms.

Their investigations also revealed that the extinction was likely driven in part by the proliferation of sulfidic ocean conditions.

"For the first time, this research provides a mechanism to drive the observed step-wise extinction event, which first coincided with ocean deoxygenation and was followed by more severe and toxic ocean conditions with sulfide in the water column," Bowman said.

With the oxygen-starved oceans of the Lau/Kozlowskii extinction serving as an unnerving precursor to the increasingly deoxygenated waters observed around the world today, study co-author Jeremy Owens, an assistant professor in the Department of Earth, Ocean and Atmospheric Science, said that there are still important lessons to be learned from ecological crises of the distant past.

"This work provides another line of evidence that initial deoxygenation in ancient oceans coincides with the start of extinction events," he said. "This is important as our observations of the modern ocean suggest there is significant widespread deoxygenation which may cause greater stresses on organisms that require oxygen, and may be the initial steps towards another marine mass ."


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In ancient oceans that resembled our own, oxygen loss triggered mass extinction

More information: Chelsie N. Bowman et al, Linking the progressive expansion of reducing conditions to a stepwise mass extinction event in the late Silurian oceans, Geology (2019). DOI: 10.1130/G46571.1
Journal information: Geology

Citation: Oxygen depletion in ancient oceans caused major mass extinction (2019, August 30) retrieved 17 September 2019 from https://phys.org/news/2019-08-oxygen-depletion-ancient-oceans-major.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
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Aug 30, 2019
Since it can't be AGW, what was it and why can't it be the same natural forces again?

Aug 30, 2019
I hypothesize that the prevailing motive (yes, there is a sociology involved here) isn't curiosity, as it was in older science. It is fear.

Therefore "scientific" research tends to be aborted before asking that kind of question.

Even the scientific pursuit itself is, I posit, challenged by a negative zeitgeist. Puzzle that one, Einstein.

Aug 30, 2019
And I can't help but wisecrack that we have signs of a loss of science-supporting "oxygen" in the zeitgeist.

This old globe has been through some rough stuff (scientifically speaking :-) before becoming what it is today. Cataclysmic volcanic or meteoric strike activity seems to be the scientific cause of its "brown" eras. The feeble fires of Homo sapiens in a year aren't even close in earth browning effect to what a good volcano can do. In fact one might theorize that relatively clean CO2 sources could give us a greener globe with more oxygen -- thanks to photosynthesis. Whatever one's theory, this globe certainly has been time tested, and fears are not rational at least on the time scale of scientifically documented human history.

Aug 30, 2019
But as a side note -- the earth we know kept coming back from these blows to its "greenness" and even managed to incorporate the results of the "browning" agents as it did so. Our Sun is located so as to help this along. Science could easily be unearthing (pun intended) many such salutary coincidences if it weren't so shackled by fear. Even if one is not theistic about this, even if the globe and its surroundings rolled out of some celestial bingo machine -- it did so with enough good stuff to survive with gusto.

Aug 30, 2019
Mass extinction event on earth are normal. There is evidence of five such events and currently we are heading towards the sixth. Why mass extinction occurs is beyond human comprehension at this time. More research is needed. But, humans can destruct anything.

Aug 30, 2019
So, the question here is, is this a bunch of Brazilians lying and denying, or a bunch of Russians stirring up more shit, or a combination of both?

That's the only question that remains to be answered.

Aug 31, 2019
Some people just can't get their mind wrapped around the fact that the impact of billions of human beings spewing billions of tons of waste each year into the atmosphere could have the same kind of impact as a major volcano or other natural events.

But the measurements are quite clear. Pre-industrial carbon dioxide levels were on the order of 200 ppm, while current levels are over 400 ppm. In addition, measurement of carbon isotope ratios clearly indicates most of the CO2 is from biological sources (i.e. burning dead dinosaurs).

These are just the facts. There aren't Republican measurements or Democratic measurements, they just are.

Further, while it's true that mass extinctions are normal, the time frame between most of them are tens of millions of years, and the effects on the planet when they occur are catastrophic. They have different causes, but generally speaking, they are either external (massive meteor strikes/human activity), or quite rare (global volcanic eruptions).


Aug 31, 2019
So, what would we be talking about (assuming that volcanoes can't also roast up some dead dinosaurs as they go off, a question that I am curious whether has been addressed). Two drops in a bucket vs. one?

The problem is too little science, not too much. The field has been controlled by fear and not hope.

Aug 31, 2019
Also, are supposedly official global readings of CO2 happening in the back yard of a volcano? The devil is in the details, and they too are "neither Democrat nor Republican." This looks more like R&D in pursuit of one hypothesis. Trump himself suggested the return of "Red Team/Blue Team" public research. Let's look down both alleys. As it stands, public research and "eeeeeeeevil corporations" are being pitted against one another. The grant recipients seem to be getting the benefits here, if they can promise the one alley. That's not even science anymore.

Aug 31, 2019
Ah, one day we may have a "science of scientists" recognized as such. We actually do have the roots for such a thing, and it's called things like sociology and psychology and anthropology. But somehow it has hardly ever turned its own lens back on academia.

The reasons for the directions that the "hard sciences" look are very much potentially visible to the "soft sciences." And earth sciences aren't even hard like physics. They are, at best, mushy. We cannot command enough data to do otherwise.

I suppose this will garner about a hundred thumbs down. And so what. Science needs to be about truth as best we can get at it -- including truth about ourselves.

Aug 31, 2019
so DS as much as i used to envy brazilians
& loathe russians?

am i imagining a tiny hint of rancor on your part?
i'm sure you have good reasons...

Carnival in Rio wasn't as much fun as you expected?
u can assure you none if them around the world are
you just have to be phlegmatic about it
& only carry a decoy wallet
& lots of quality condoms

as for russiam's? they're assholes, 'nuff said

but,specifically to this article
does that sign over your desk read "NIH"?

Aug 31, 2019

Anonym357924
what "scientifically documented human history"?

what we have right now are millions & millions of mixed puzzle pieces in a titan-sized pile of chaos
many illegible, defaced or other wise damaged

all we can be assured of?
is that billions more obscured clues remain undiscovered, unrealized, destroyed
or just plain missing for a wide variety of natural & unnatural reasons

if you have ever worked large scale industrial construction & public works?

without a shred of doubt in my mind...
from my years of running heavy machinery on big projects
that a constant refrain from your job boss was
"We got a fucking schedule to keep!
Plow that crap under before that damned faggot college-boy sees it."

Aug 31, 2019
"The feeble fires of Homo sapiens in a year aren't even close in earth browning effect to what a good volcano can do."

Wrong, by two orders of decimal magnitude, when comparing the total CO2 output of volcanoes and the total CO2 of the fires of humanity, for a single year. In any year, humans produce more than 100 times the CO2 that volcanoes do.

https://www.scien...-humans/

Aug 31, 2019
As it stands, public research and "eeeeeeeevil corporations" are being pitted against one another.

As it turns out, the "evil" corporations agree with public research. They just didn't like what that said about their profits, so they funded the disinformation campaign that you fell for (or are part of?).

Sep 01, 2019
@rrwillsj, do I need any better reasons than stealing the election in the US and burning the Amazon?

Sep 01, 2019
Since it can't be AGW, what was it and why can't it be the same natural forces again?


Haven't you read the paper? And what do you mean "again"? The article describes how the result of anoxia is catastrophic regardless of mechanism. Anoxia is among other known factors driven by warming climate - like in AGW [ https://en.wikipe...ic_event ].


Sep 01, 2019
I hypothesize that the prevailing motive (yes, there is a sociology involved here) isn't curiosity, as it was in older science. It is fear.


Fact finding simply cannot be driven by fear, you have to use curiosity - else you are looking for confirmation of your beliefs. Like you evidently are, you did not discuss the science *at all*.

But never mind any of that, you have larger problem: what is claimed without evidence can be rejected without evidence. So: climate science 1 - fact resistance 0.

Sep 01, 2019
volcanoes can't also roast up some dead dinosaurs as they go off, a question that I am curious whether has been addressed


I would like to answer straight questions., Please reformulate to something that others can understand! What do you men by "roast up some dead dinosaurs"? They are fossils soon after death, little organic matter remains. Or did you mean right after the Chixculub impactor hit? Mostly the mass extinction derived from the impact effects.

Sep 01, 2019
are supposedly official global readings of CO2 happening in the back yard of a volcano?


Are you referring to the Mauna Loa Observatory [ https://en.wikipe...ervatory ]? It is a complex (5 observation sites) but long standing above inversion layer reference, i.e. it is mostly unaffected by local changes. "The contamination from local volcanic sources is sometimes detected at the observatory, and is then removed from the background data.[6]"

It is a reference; CO2 is measured all over the world and from satellites these days.

Sep 01, 2019
And there the science questions came to an end of a bit of a Gish Gallop - the troll was just eager to cast uncertainty where none exist, we know AGW happens even though earth sciences are a bit "fuzzy". And fast downhill to politics, in US climate is politicized instead of researched and acted on:

"Trump himself suggested the return of "Red Team/Blue Team" public research. Let's look down both alleys."

Trump is a stable idiot, science is the process of red/blue (and more) sides - been there, done that, many more than two alleys looked down in. Time to act; or is US feeble and weak, has it forgotten how to protect itself? Hurricane Dorian is the strongest hurricane in modern times, why do you think that is? Do you *want* Bahamas drowned?

Sep 01, 2019
@Anonym357924.

Mate, just because nature can start wildfires with lightning doesn't mean we should also start even more with matches, does it? Have some common sense and realise that suddenly burning the vast quantities of coal/oil, which nature sequestered over millions of years, is reversing too rapidly what nature did when she sequestered those vast quantities of coal/oil. Those who believe that burning all that previously naturally sequestered carbon won't affect the planet's temp/climate equilibrium/patterns is a danger not only to themselves and their family/descendants, but to the whole of humanity. Please stop being a sophist and contrarian just for the sake of it, and wake up to the fact that science/logic/reality are not your playthings. They are there for intelligent humans to use as tools to survive and prosper without 'fouling our nest' like we have been doing for too long now. Nature demonstrates that animals that foul their own nests/dens/environments are the losers.

Sep 02, 2019
No matter what, it's always AGW isn't it? Regardless of what is "discovered" by "science" it's always caused by humanity, never ever by by natural forces. Fine then. Let's start eliminating the problem one true believer and their families at a time. *scribbles believable-looking graph on napkin* I have proof here that if every liberal and their entire family volunteers to off themselves then we can just make the Paris Climate Accords. So, who's first? Saving Mother Earth is most important, right? The line forms right here. Don't worry, there's plenty of room in the boxcars for all of you. The rest of us won't already be in there like you wanted and planned for.

Sep 02, 2019
rhugh
Regardless of what is "discovered" by "science" it's always caused by humanity, never ever by by natural forces
rhugh - like all the science deniers that soil the internet - you obviously don't read much science. On Physorg - and any other science site - there is article after article talking about the natural world. One single example for you - https://scied.uca...-climate

As to the rest of your right wing crap - you are saying that if we feel there is a problem - we should not want to address the problem - but just line up and kill ourselves. No. That is the point of science. Study things - evolve our understanding of them - make smart decisions.
Idiot...

Sep 02, 2019
Go ahead, believe the Nancy Pelosies of this world, hand over your wallet then then your guns then your children and for what? A pile of lies designed to make gullible fools like you enrich the Marxist tyrants running your party while impoverishing the rest of humanity? You can preen and rave all you want from your mom's basement and it'll change nothing. Try to carry out your Antifa schemes and you'll find out what the word reality truly means. You obviously have no clue of its definition at present.

Sep 02, 2019
rhugh
Go ahead, believe the Nancy Pelosies of this world
Who is Nancy Polosie? What branch of science is she in? You do know this is a science site - right? And we talk about things like the current research on the climate - and other sciency shit like that.
Reality is an interesting word. It seems to me that science is our best way of understanding the complexities of our universe (could call that reality). Science is a complex topic - millions of highly trained experts - working in a complex collaborative world - trying to unlock the workings of our universe. I think maybe you took a wrong turn somewhere - maybe getting directions from Alex Jones....

Sep 02, 2019
@rhugh1066.

The username, @rhugh1066, has all the hallmarks of yet another 'weaponised stupid' and/or 'bot' let loose by the Russian/GOP/Fossil/Nuclear interests-funded troll-factory gang. It's patently obvious political/ignorant rant doesn't just deserve ridicule, but also pity; since it is so tragically stupid; and so totally irrelevant to the reality we are all living every day now around the globe (the latest example being the unprecedented fourth year in a row that a Cat-5 Hurricane has formed in the Atlantic). Good luck to all those experiencing the evolving reality there; and to us all.

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