Science Articles

Can Our Oceans Survive the Acid Attack?

Thu, 27th Jan 2011

...and what will rising carbon dioxide do to the world's seas?

Natalie Roberts

Atmospheric carbon dioxide levels are rising fast, global temperatures are increasing, sea levels are encroaching and now the oceans are becoming more acidic. But is it really all such doom and gloom?Foram Dissolution

As a scientist researching climate change, I am interested in putting everything into perspective, and lucky for us, there is so much work taking place in all fields of climate science at the moment that our knowledge is expanding faster than ever.

One of the most interesting and hotly debated questions at the moment is: how acidic will the oceans become and what effect will this have on the creatures that live within them?

The oceans began acidifying around the same time as the Industrial Revolution. As carbon dioxide was pumped into the atmosphere owing to the burning of fossil fuels, some of it diffused into the oceans.

Since most of the surface ocean has a lower concentration of carbon dioxide than the atmosphere, it acts like a sponge, dissolving the carbon from the air. Over two hundred years, the ocean as a whole has only lowered in pH by 0.1 of a unit. This seems small but the pH scale is logarithmic, which means that sea water is now actually 30 per cent more acidic than before the Industrial Revolution began.

Acidifying the ocean is a very similar chemical process to producing carbonated drinks – except the ocean does not become fizzy… I have a very vivid memory of my parents dropping one of my baby teeth into a glass of fizzy drink and watching it dissolve; though I cannot say it put me off drinking carbonated drinks, it certainly demonstrated their acidic nature.

The chemistry behind this process is fairly simple; when CO2 dissolves it reacts with a water molecule to produce carbonic acid (H2CO3). This dissociates into a bicarbonate ion (HCO3-), and an acidic hydrogen ion (H+) which causes the water’s acidity level to rise. Fortunately, the ocean happens to be loaded with plenty of other negative ions, which can help mop up any excess hydrogen ions - but only up to a point.

Just like teeth, shells are made of readily-dissolvable material, most often calcite or in a few cases, aragonite, which are both forms of calcium carbonate. So animals that live within shells are vulnerable to any change in acidity. But how vulnerable they are also depends on where they live.

We can divide the oceans into three main environments; shallow coastal habitats, polar oceans and the rest, simply called "open ocean", where the majority of life-forms are microscopic and inhabit only the very top layer of sea water.

The shallow shelf areas are hugely productive. Here we find most of the large calcifying organisms; corals, brittle stars, star fish, molluscs and sea urchins. They can be quite vulnerable to changes in their habitat as they do not have much space to adapt; they require lots of light and a narrow range in temperature, so sudden changes can really stress certain species.

Corals, in particular, are thought to be at risk because they make their structure out of aragonite, which is even easier to dissolve than calcite. A group from Columbia University, in Arizona, have predicted that some coral species will almost halve the amount they can calcify by the time CO2 concentrations reach twice the pre-industrial revolution level; according to the Intergovernmental Panel on Climate Change (IPCC), this could be as early as 2045. Sea urchins and brittle starts are also at risk because the acidity affects the larval stage of their life cycle, although studies so far have found that some species are more at risk from rising temperatures than acidification.

However, there is a flip side to living near the coast. The natural acidity of these habitats varies quite a lot depending on the location. Species near estuaries and river mouths live happily in more acidic (lower pH) conditions than normal seawater, so these species are less likely to be affected by rising CO2 levels. This could give them a competitive advantage and they may even thrive in the future.

Polar species are predicted to be hit first. This is because CO2 dissolves most readily in cold water. You can observe this with fizzy drinks – less gas is released when you open a can that’s been the fridge compared with one left out in the warm. So the polar oceans will become more acidic more quickly.

MesocosmsThere are teams of scientists funded by a European initiative called EPOCA, who are currently doing experiments with whole ecosystems in the Arctic. They envelop a parcel of sea water, along with all its inhabitants, in a giant 17m long tube called a mesocosm. They can then change the CO2 concentration, simulating higher atmospheric levels, while otherwise keeping the environment similar to the surrounding Arctic water. These experiments are still in their infancy, but will hopefully yield useful results and providing a more well-rounded view by virtue of assessing the responses of multiple species simultaneously.

The open ocean covers by far the largest area, but the inhabitants are mostly microscopic plants and animals. Many laboratories have been involved in culturing these tiny creatures under differing CO2 conditions and, so far, the results are contrasting. First, because plants take up carbon dioxide and use it to photosynthesise, these species tend to flourish in elevated CO2 conditions. But their hard-shelled animal counterparts, however, a group known as the coccolithophorids, may fare less well.

Recent experiments growing coccolithophorids demonstrate the need for such studies to replicate the natural world as closely as possible. For example, in one study seawater was acidified with dilute hydrochloric acid but plants reportedly failed to thrive. But another study used carbonic acid in place of hydrochloric, thereby simulating CO2-driven acidification, and the plants grew even better than under normal conditions.

So the jury is still very much out as to how much open ocean calcifying plants will suffer from increasing atmospheric CO2, and as with all habitats the effects will be species specific. One argument for coccolithophorid adaptation is they have a high degree of genetic diversity within each species, this may allow them to evolve quickly to changing environments.

A really important question is not just how each individual species will be affected, but whether ecosystems will be able to adapt? But this is a difficult question to answer when we still do not know that much at a species level. There are several groups using computer models to assess impacts on ecosystems. Their aim is not just to include environmental pressures like temperature and CO2 change, but also human interaction, such as fishing. So far, these models have not been very good at assessing shelf areas, mainly because they vary so much, and have the highest biodiversity. But since these models rely on actual scientific data, the more experiments are conducted, the better the models become.

In summary, ocean acidification is a daunting problem we will have to face. It has occurred several times before in Earth’s history, so not only can we use experiments to predict the outcome of the ocean, we can also learn from geological records which preserve past environmental conditions and species response.

It is extremely important that laboratory experiments replicate real environments, not only testing CO2 changes, but also temperature rises, competition for nutrients and sea level change – and this is no small task. We are only now learning that some areas of the ocean and different species will be affected more than others, and with ongoing world wide science collaborations and experiments, we will hopefully be able to tackle this problem head on.


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This certainly is an issue worth looking into.

However, keep in mind relative vs absolute acidity.

The current pH shift in the oceans has been from about 8.2 to 8.1, still strongly basic, although it could still affect the carbonate weathering and bicarbonate equilibrium.

Ca2+CO32‾(s) + H2CO3 (aq) <==> Ca2+(HCO3‾ )2 (aq)

This process, of course, would be indiscriminate between living and dead carbonates, but would have the net effect of increasing the bioavailability of both calcium and carbon dioxide.  Living organisms might be able to compensate with more shell/exoskeleton growth (in a calcium rich environment).

It will also do silicate weathering in a similar process which will also buffer the carbonates.

My question would be if the oceans are thought to have been a primary CO2 sink during the previous glacial period where the atmospheric CO2 levels had dropped from about 300ppm down to about 180ppm.  How did that affect the ocean pH balance? CliffordK, Fri, 28th Jan 2011

This could be a far greater, and more immediate problem, than rising sea levels. A small pH change could result in the total collapse of the ocean's food chain.

Some oyster farmers in the Pacific Northwest now have to alter the pH of seawater to allow their oysters to reproduce. I'll try to dig up the article in question again. Geezer, Sat, 29th Jan 2011

The carbonate equilibrium in sea water actually made up a large portion of my last midterm. We used acid-base equilibrium, the solubility of CaCO3, and various other information to determine the change in pH necessary to force the equilibrium far enough so that CaCO3 shells could no longer form. We assumed that all increase in pH was entirely from CO2 (which is inaccurate because chemical fertilizers also can have an effect). I think CliffordK is right. We used this article: Bill.D.Katt., Sun, 27th Feb 2011

Here's a link to the story about oyster farms in the Pacific NW. Geezer, Sun, 27th Feb 2011

We will see. Some points I would like to make.

"Scientists estimate that surface ocean pH has fallen by about 0.1 pH unit from preindustrial times to today. Because pH is a measure of hydrogen ion concentration and the the pH scale is logarithmic — for every drop of 1 pH unit, hydrogen ion levels increase by a factor of 10 — a 0.1-unit pH drop is equivalent to about a 26% increase in the ocean hydrogen ion concentration.

If we continue on the expected trajectory for fossil-fuel use and rising atmospheric CO2, pH is likely to drop by 0.3-0.4 units by the end of the 21st century and increase ocean hydrogen ion concentration (or acidity) by 100-150% above what it was in preindustrial times." — Scott Doney, Senior Scientist, Woods Hole Oceanographic Institution, USA

And addressing Clifford's Question.

"When ice sheets build up into glaciers, air bubbles become trapped in the freezing ice. Scientists have analyzed the CO2 concentration of air in these bubbles and have developed a record of the atmospheric CO2 concentration in the recent past. Because large parts of the surface ocean CO2 concentration remains roughly in equilibrium with the atmospheric CO2 concentration, the ocean CO2 content can be calculated from these air bubbles, and ocean pH can also be calculated. In fact, the ice core record shows that the atmospheric CO2 concentration has never been higher than about 280 ppm during the last 800,000 years, creating conditions leading to an average preindustrial surface ocean pH of ca. 8.2." — Jelle Bijma, Biogeochemist, Alfred Wegener Institute for Polar and Marine Research, Germany.

"The photosynthesis of some, but not all, algae increases when CO2 rises to levels projected for the end of this century (700-800 ppm). The single-celled algae called zooxanthellae that live within coral animals’ cells are some of the algae whose photosynthesis does not significantly increase at projected future CO2 levels.  Normally, zooxanthellae and corals maintain a delicately balanced symbiosis, in which the zooxanthellae transfer photosynthetically formed carbon-based nutrition to the coral host and provide an important source of carbon for the coral and for coral calcification (skeleton building). 

If the algae within the corals’ cells do too well and their numbers greatly increase, the transfer of nutrition to the coral host can be disrupted. So even if zooxanthellae photosynthesis were to increase under high CO2, this does not necessarily benefit the corals.  In the great majority of experiments, coral calcification rate decreases when the CO2 level increases, so it is clear that the rise in CO2 is decreasing the corals’ ability to build their skeletons rather than protecting them by altering zooxanthellae photosynthesis. — Chris Langdon, Associate Professor, University of Miami, USA; Anne Cohen, Research Specialist, Woods Hole Oceanographic Institution, USA

And "Communities of organisms found near shallow near-shore volcanic CO2 vents demonstrate that certain microalgae, seaweeds and seagrasses grow very well in areas that experience long-term exposure to elevated CO2. However, this work also shows that coastal ecosystems are degraded due to the long-term effects of ocean acidification. Biodiversity is lost: groups of organisms such as coralline algae gradually disappear as pH falls, and they are replaced by thriving stands of invasive algae. This raises concerns that ocean acidification will allow alien algae to proliferate and disrupt coastal habitats." — Jason Hall-Spencer, Lecturer, University of Plymouth, UK

"Evidence for the ecological effects of ocean acidification today can be found at “champagne sites,” locations where volcanic CO2 vents naturally acidify the water and small CO2 bubbles rise through the water column.  At one of these sites around the Island of Ischia (Italy), for example, biodiversity is reduced by 30% at the acidity level that matches the level expected globally in 2100."

And we're not discussing overfishing at all.


Atmospheric CO2 is already at 390 ppm and is increasing at about 2 ppm per year. Without dramatic reductions in CO2 emissions, atmospheric CO2 will continue to rise, and most emission forecasts for the near future indicate a likely increase (rather than decrease) in atmospheric CO2 growth rate. The first step in addressing ocean acidification, therefore, is to stabilize and eventually reduce CO2 emissions. Atmospheric CO2 almost certainly will peak well above 400 ppm, because we will not stop increasing emissions in the next 5 years...  Even if we stabilized CO2 emissions, atmospheric fossil fuel CO2 will continue to penetrate into the deep ocean for the next several centuries, which may impact deep water organisms such as cold-water corals. — Scott Doney, Senior Scientist, Woods Hole Oceanographic Institution, USA

What that refers to is the CO2 cycle, expected to take anything between 50-100 years for ?? percent, up to several thousand years, for all of the CO2 to be recycled from the atmosphere. And with the CO2 building up in our 'sinks' like oceans, those will stop taking them in, leaving us with a increased warming per volume produced man-made CO2. And that we already see in the Arctic and to a lesser degree in Antarctic, where we have our best sinks. One of them soon to be gone.

"The Atlantic Ocean as a whole, which has 23.5% of the global ocean area, is the region with the strongest net CO2 uptake (41%). The high-latitude northern North Atlantic, including the Greenland, Iceland and Norwegian seas, is responsible for a substantial amount of this CO2 uptake while representing only 5% of the global ocean in area. This reflects a combination of two factors: the intense summertime primary production and the low CO2 concentrations in subsurface waters associated with recent ventilation of North Atlantic subsurface waters. The Pacific Ocean as a whole takes up the smallest amount of CO2 (18% of the total) in spite of its size (49% of the total ocean area)."

Also "The solubility pump is driven by two interrelated factors. First, CO2 is more than twice as soluble in cold polar waters than in warm equatorial waters. As western surface boundary currents transport water from the tropics to the poles, the waters are cooled and absorb more CO2 from the atmosphere. Second, the high-latitude zones are also regions where intermediate and bottom waters are formed. As these waters cool, they become denser and sink into the ocean interior, taking with them the CO2 accumulated at the surface.

The primary production of marine phytoplankton transforms CO2 and nutrients from seawater into organic material. Although most of the CO2 taken up by phytoplankton is recycled near the surface, a substantial fraction, perhaps 30%, sinks into the deeper waters before being converted back into CO2 by marine bacteria. Only about 0.1% reaches the seafloor to be buried in the sediments. The CO2 that is recycled at depth is slowly transported over long distances by the largescale thermohaline circulation."

And for what happens then? Take a look here Read and ponder.. Carefully. "Basically, oceanographers lower the white disk on a rope and note how deep it is when it disappears from view. Oceanographers have taken half a million measurements like this throughout the world's oceans, so Worm and his colleagues collected piles of that data and looked for trends. "What we found was that phytoplankton was declining in 8 out of 10 large ocean regions," he says. And the trend was pretty dramatic, averaging 1 percent per year, year after year, according to their study in this week's Nature."

I'm not saying life is threatened here. But I sure expect us to be.. You have to be very optimistic, as well as equipped with exquisitely discerning 'blinkers' to  miss all the warning-signs, flashing as mad :)

And I'm not even squinting at overfishing here. But I should, and so should you. yor_on, Sun, 27th Feb 2011

"Phytoplankton use sunlight to convert carbon dioxide into carbon-based food. As small fish eat the plankton and bigger fish eat the smaller fish, an entire ecosystem develops. The Bering Sea is highly productive thanks mainly to diatoms, a large type of phytoplankton. "Because they're large, diatoms are eaten by large zooplankton, which are then eaten by large fish," Hutchins explained.

The scientists found that greenhouse conditions favored smaller types of phytoplankton over diatoms. Such a shift would ripple up the food chain: as diatoms become scarce, animals that eat diatoms would become scarce, and so forth. "The food chain seems to be changing in a way that is not supporting these top predators, of which, of course, we're the biggest," Hutchins said.

A shift away from diatoms towards smaller phytoplankton could also undermine a key climate regulator called the "biological pump." When diatoms die, their heavier carbon-based remains sink to the seafloor. This creates a "pump" whereby diatoms transport carbon from the atmosphere into deep-sea storage, where it remains for at least 1,000 years.

"While smaller species often fix more carbon, they end up re-releasing CO2 in the surface ocean rather than storing it for long periods as the diatom-based community can do," Hutchins explained. This scenario could make the ocean less able to soak up atmospheric carbon dioxide. "Right now, the ocean biology is sort of on our side," Hutchins said. "About 50 percent of fossil fuel emissions since the industrial revolution is in the ocean, so if we didn't have the ocean, atmospheric CO2 would be roughly twice what it is now.""

yor_on, Mon, 28th Feb 2011

Yes, but what about the oysters? Geezer, Mon, 28th Feb 2011

Yeah, I read you Geezer. If I get it right its not the already grown oysters that are the problem, it's the oys­ter lar­vae that can't make their shells? I think that's another of the, rather simple, causality chains in nature that we haven't considered fully. We look on grown specimens forgetting that they all start weak. A worrying story that one. yor_on, Mon, 28th Feb 2011

Yes, it's the larvae that can't form their shells. It certainly got my attention when I heard about it. I hate to think what would happen if it had a similar effect on a lot of other sea creatures. Would the entire ocean food chain suddenly collapse? Geezer, Mon, 28th Feb 2011

... some are saying we have about 2 more generations... then Earth will no longer habitable for us... thanks to AGW denial...  and now unstoppable 

Phytoplankton :: Produce about 70% of the Oxygen on Earth...
Building Block #1 in the Food Chain and Oxygen Cycle for Life on Earth...

What do you think is killing the phytoplankton?...

maybe it's the PCBs...

... The trees on Earth are often called the 'lungs' of the biosphere.... yet we are cutting and selling our 'lungs' for a profit... that goes to the richest corporations... and special favors to the most disloyal of all politicians in American history...

... and the biggest 'gardens' on Earth are in the Oceans... yet industrial mavericks save money by using the Oceans for their toxic toilet... killing the phytoplankton that freely provided 70% of the Oxygen on Earth for millions of years.... freely generated from the Light of the Sun.... soon we will be buying oxygen from the same industrial mavericks that are destroying the phytoplankton...

in the profound lyrics of Joni Mitchell :
We are stardust... we are golden...
We are caught in the devils bargain...
And we got to get ourselves back to the Garden...

We are already loosing the Coral Reefs on Earth caused by Ocean Acidification

… and the Climate Change unfolding today is clearly anthropogenic…

… can we get the 'voters' and our governments to recognize that the industrial ‘revolution’ is driving up the CO2 that is causing Ocean Acidification… potentially harming the health of phytoplankton… Earth’s #1 source of Oxygen for us to breathe in the air.

..:: ” A recent study by Dalhousie University oceanographer Boris Worm and his team found that phytoplankton populations in the ocean are declining at an alarming rate because of human activity and climate change.

..:: ” Why should you care?

..:: ” PHYTO - PLANKTON removes CO2 from our AIR and produce more than half the OXYGEN we breathe.

..:: ” The report, published in the July 29 edition of Nature, states that PHYTO - PLANKTON have already declined by about 40 per cent since 1950.

..:: ” We can’t BREATHE without them…

..:: ” While governments stall and deniers spread confusion, it gets more and more difficult to achieve the kind of emissions reductions that scientists say are necessary to prevent the Earth from reaching a cataclysmic period.

..:: ” It was once possible… and “MAY” still be…

Mod edit - links removed
Larry, Tue, 1st Mar 2011

"some are saying we have about 2 more generations... then Earth will no longer habitable for us... thanks to AGW denial."

No, that I don't believe. First of all, the AGW denial as you call it is just the normal way we humans react to anything threatening us. We will discuss and argue about it :) It's just the way we are. If you expect us to throw that time honored tradition to the winds you're sadly mistaken :) But there are interests not wanting us to change, involving a lot of money and they have their own agenda of course. I'm pretty sure we will be here for the next ten generations, and more hopefully :)

It's not that the world is 'ending' for us, it's more that we need to live up to those ideas we have of us being 'caretakers' of our Earth. We're no longer adapting to Earth, instead we are forcing the Earth to adapt to us. That means that we need to start accepting the responsibility instead of blaming it on every/one/thing else, another time honored way of taking care of a problem btw :)

Hopefully we will. yor_on, Wed, 2nd Mar 2011

Yes, it's the larvae that can't form their shells. It certainly got my attention when I heard about it. I hate to think what would happen if it had a similar effect on a lot of other sea creatures. Would the entire ocean food chain suddenly collapse?

Maybe, at least the chain from where we get our food fish would hurt immensely. And the way we're overfishing and killing of our food fish and other species doesn't help there. But humans can be marvelously stubborn when it comes to their own income, only seeing the things that will make them make their living. But it goes both ways, getting enough information they can surprise you too, it's all about how serious it is. I don't know Geezer, I just hope that people will try to look at what is happening and wake up from the dream of everyone getting 'f*ng rich and happy'. Greed is what lead us to this place, common sense and information will hopefully lead us back to a sustainable world.

Then again, it hangs on the governments too. If they want their ingenious  population understanding or not. We all love our 'experts' don't we, or else we love to hate them. I put great hope in Internet, the most important invention since the wheel. yor_on, Wed, 2nd Mar 2011

But you're right 'guest Larry' we do have a very serious issue in the Phytoplankton population shrinking. " "A measure of productivity is the net amount of carbon dioxide taken up by phytoplankton," said Jorge Sarmiento, a professor of atmospheric and ocean sciences at Princeton University in New Jersey. The one-celled plants use energy from the sun to convert carbon dioxide and nutrients into complex organic compounds, which form new plant material. This process, known as photosynthesis, is how phytoplankton grow.

Herbivorous marine creatures eat the phytoplankton. Carnivores, in turn, eat the herbivores, and so on up the food chain to the top predators like killer whales and sharks... Phytoplankton need two things for photosynthesis and thus their survival: energy from the sun and nutrients from the water. Phytoplankton absorb both across their cell walls.

In the process of photosynthesis, phytoplankton release oxygen into the water. Half of the world's oxygen is produced via phytoplankton photosynthesis. The other half is produced via photosynthesis on land by trees, shrubs, grasses, and other plants."

As for it producing 70%? of the oxygen. as above I trust in fifty percent myself. Another thing we can't really say we know though, but 50% seems a comfortably conservative number :) Here's a article about  'PLANKTON LEVELS IN THE OCEAN' from 2002.. So, that was then, how about now? A simple way of checking that statement, although not proving that it is only the Phytoplankton, is to look at the atmosphere, do you agree?

So is the oxygen concentration in our atmosphere shrinking? Well, yes, unfortunately it is. A Scientist, His Work and a Climate Reckoning. The overshadowing problem being if it is the CO2 raising, or if it is a combination of both the oxygen-levels shrinking as well as our man-made CO2 raising. I would put my guess on a combination myself.

If the oxygen lever really shrunk 50% it should mean your babies born into a world, constantly of short breath, and, just guessing here, it should also mean that species not needing that much oxygen should flourish, taking a larger part of the world than those needing oxygen. It would become a harsh world for us humans to adapt too, as you can forget most of what your wilderness programs shows you on the telly. Jelly fish seems to flourish under such conditions though, as well as some species of octopuses, cockroaches too I presume, but as for the rest of the animal kingdom? I don't really expect them to survive.. Some idiots envision a depleted Earth with us as the sole inhabitants, and that, that is more than stupidity. It's Egos screaming 'MEEE !!' and believing in it too. Don't become one of those please.

And if someone have read this far you should try to read this link too :)
What Goes Around Comes Around.  It's actually good for you :)

Believe it or not. yor_on, Wed, 2nd Mar 2011

Yoron - there's a good article in yesterday's nature on ocean acidification that you might be interested in.  it's recent enough to still be open access on the nature website.  if you cannot get hold of the article let me know by pm imatfaal, Fri, 11th Mar 2011

Geezer, you might like this one? Well, not like exactly, but it's interesting. On wild oysters, the headlines that came 100 years too late, and turning poop-water into salty Evian.   

And, This one Imatfaal? Environment: Earth's acid test.

And maybe this one, no immediate problem maybe. CO2 is the real culprit to worry about in the near future, but still. This may be the darkest horse of them all? Arctic methane leak, its official. Nature..

yor_on, Wed, 16th Mar 2011

That is what a lot of Marathon runners and athletes do.
They head off to Colorado for high mountain training.

It is the only legal method of blood doping.

The body reacts to low oxygen by producing more hemoglobin.  Likewise, most animals would react similarly.  How this would affect birth?  I don't know.  Perhaps the infant would also develop a greater concentration of hemoglobin reacting to conditions in the mother.

Certainly in the wild... natural selection would favor those that adapted better.

Atmospheric levels of CO2 up to a couple of percent are also not toxic to humans.  And, presumably our bodies could adapt to very high CO2 levels.

That isn't to say that a change of atmospheric CO2 levels of say 0.1% couldn't affect aquatic species while being insignificant to land species.

CliffordK, Thu, 17th Mar 2011

Not 50 % Clifford.

There is roughly 21% oxygen mixed in the volume of air.

21% normal
17% anoxia
10-14% dizzy
6-8% collapse
3-6 % death by asphyxiation within 6-8 min
<3 % death in 45 sec

navy marine corps and occupational safety health rules said that a person should wear a breathing apparatus when oxygen is 19.5 %, a pilot should put on the mask at 12,000 ft and 16% is the minimum we breath in in fire fighting apparatus in the military."

Et tu, O2? yor_on, Fri, 25th Mar 2011

Yoron - I think Clifford is talking about a situation where the amount of oxygen is reduced by 50%. Geezer, Sat, 26th Mar 2011

A reduction of 50% from 21% would leave 10.5%, that's well into the range of "dizzy" according to that table and it would make it impossible to do anything. Even walking across the room would be impossible.

However, there's no sensible way we could see the oxygen levels drop by 50% so I don't understand why anyone is talking about it.

If we burned enough oil to use up 1 percentage point of the atmosphere (ie to go from about 21% to about 20%) then we would add about 1% of CO2 to the air.
2% CO2 in air is toxic to people.
That would certainly have serious effects on other organisms, and also on ourselves.
Very roughly, it would mean an increase in the CO2 by a factor of 25.
That, in turn would drop the pH of the oceans by about  log(25) i.e. about 1.4 pH units so the pH would shift from slightly alkaline to slightly acid.

Some things might cope with that, but the change, if it wasn't incredibly slow, would cause a lot of trouble. Bored chemist, Sat, 26th Mar 2011

I think there are many different calculations.

I was thinking of Mt. Everest which is supposed to have an atmospheric pressure of about 1/3 ATM, or the equivalent of 1/3 the oxygen.  People can tolerate the pressure as long as the changes aren't sudden.  The oxygen is too low for westerners, although the natives can get pretty high up without oxygen supplements.

I had read that CO2 toxicity started at about 5% which is extremely high.  I have no doubt we will run out of coal, oil, and natural gas long before we reach that level.

What got us into this mess?
Is it the people?
"Big Oil"?

Perhaps that is the core of humanity.  We've never been content with living within our means.

When hunting became burdensome, we domesticated animals.
When grazing became burdensome, we started growing crops.
We've done what no other animal has done, growing our food, and selectively breading for yield and quality.

But... finally we've found ourselves using more energy than we can sustain.

It isn't cars or windmills or solar panels...  we just have too many people all requiring too much energy.  CliffordK, Sun, 27th Mar 2011 Thought you might find this interesting. I read somewhere that there has been a 40% decline in Phytoplankton since 1950. When I read this article after the above to learn more I became quite concerned considering the amount of marine deaths of late around the globe. Just wondered what your thoughts were? raven, Thu, 5th May 2011

Yep, there are some serious stuff going on. And you can backtrack it to the way we live and pollute. And then we have 'saviors' that reminds me more of fanatics than using common sense, wanting to fill the seas with tailored genes for cleaning it up. man-made organisms designed to pump out fuel and clean up waste. It's painfully obvious that some still believe Jules Verne to be fine and hearty. Also that 'Big Business' hope that this will let them make some real dough. All put together, with politicians that never hesitated to cut the Gordian knot, I'm sure we will see something like this soon enough. And when it backfire, as I expect it to do, those that did it will look at you and ask 'And what did you do ? Sat on your ass, didn't you. At least we tried.."

Well, fanatics has never won the day, of any kind. yor_on, Sun, 10th Jul 2011

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