From the British Antarctic Survey and the University of East Anglia comes one of those press releases where I just have to wonder if this won’t eventually go the way of the “global warming causes mutated frogs” claim that turned out to be a parasite and not global warming. After all, it is well known that ships ballast can transport invasive species to places they normally would not migrate to, so with eco-tourism in Antarctica being all the rage now, I wonder if the issue isn’t somehow related to the snails being more susceptible due to some such influence? After all, how did they survive climate shifts (with changes to ocean pH) for millions of years if nature so poorly equipped them? I’m just not convinced that a slight shift (-0.11) to the ocean pH being more neutral than basic is the cause of this. The oceans are still basic at ~8.069, not acidic. To be acidic they’d have to be less than 7.0 See table.
On the plus side, they avoided that ridiculous “canary in the coal mine” meme in this PR.
First evidence of ocean acidification affecting live marine creatures in the Southern Ocean
The shells of marine snails – known as pteropods – living in the seas around Antarctica are being dissolved by ocean acidification according to a new study published this week in the journal Nature Geoscience. These tiny animals are a valuable food source for fish and birds and play an important role in the oceanic carbon cycle*.
During a science cruise in 2008, researchers from British Antarctic Survey (BAS) and the University of East Anglia (UEA), in collaboration with colleagues from the US Woods Hole Oceanographic Institution and the National Oceanic and Atmospheric Administration (NOAA), discovered severe dissolution of the shells of living pteropods in Southern Ocean waters.
The team examined an area of upwelling, where winds cause cold water to be pushed upwards from the deep to the surface of the ocean. Upwelled water is usually more corrosive to a particular type of calcium carbonate (aragonite) that pteropods use to build their shells. The team found that as a result of the additional influence of ocean acidification, this corrosive water severely dissolved the shells of pteropods.
Above: before and after images.
Ocean acidification is caused by the uptake of carbon dioxide from the atmosphere emitted as a result of fossil fuel burning. A number of laboratory experiments have demonstrated the potential effect of ocean acidification on marine organisms. However, to date, there has been little evidence of such impacts occurring to live specimens in their natural environment. The finding supports predictions that the impact of ocean acidification on marine ecosystems and food webs may be significant.
Lead author, Dr Nina Bednaršek, formerly of BAS and UEA, and now of the National Oceanic and Atmospheric Administration (NOAA) says:
“We know that the seawater becomes more corrosive to aragonite shells below a certain depth – called the ‘saturation horizon’ – which occurs at around 1000m depth. However, at one of our sampling sites, we discovered that this point was reached at 200m depth, through a combination of natural upwelling and ocean acidification. Marine snails – pteropods – live in this top layer of the ocean. The corrosive properties of the water caused shells of live animals to be severely dissolved and this demonstrates how vulnerable pteropods are. Ocean acidification, resulting from the addition of human-induced carbon dioxide, contributed to this dissolution. ”
Co-author and science cruise leader, Dr Geraint Tarling from BAS, says:
“Although the upwelling sites are natural phenomena that occur throughout the Southern Ocean, instances where they bring the ‘saturation horizon’ above 200m will become more frequent as ocean acidification intensifies in the coming years. As one of only a few oceanic creatures that build their shells out of aragonite in the polar regions, pteropods are an important food source for fish and birds as well as a good indicator of ecosystem health. The tiny snails do not necessarily die as a result of their shells dissolving, however it may increase their vulnerability to predation and infection consequently having an impact to other parts of the food web.”
Co-author, Dr Dorothee Bakker from the University of East Anglia, says:
“Climate models project a continued intensification in Southern Ocean winds throughout the 21st century if atmospheric carbon dioxide continues to increase. In turn, this will increase wind-driven upwelling and potentially make instances of deep water – which is under-saturated in aragonite – penetrating into the upper ocean more frequent. Current predictions are for the ‘saturation horizon’ for aragonite to reach the upper surface layers of the Southern Ocean by 2050 in winter and by 2100 year round. ”
This research was funded by the UK Natural Environment Research Council (NERC) and the European Union Marie Curie Early Stage Training Network.
Extensive dissolution of live pteropods in the Southern Ocean by N. Bednaršek, G. A. Tarling, D. C. E. Bakker, S. Fielding, E. M. Jones, H. J. Venables, P. Ward, A.Kuzirian, B. Lézé, R. A. Feely, and E. H. Murphy is published in the journal Nature Geoscience.
Abstract:
The carbonate chemistry of the surface ocean is rapidly changing with ocean acidification, a result of human activities1. In the upper layers of the Southern Ocean, aragonite—a
metastable form of calcium carbonate with rapid dissolution kinetics—may become undersaturated by 2050 (ref. 2). Aragonite undersaturation is likely to affect aragonite-shelled organisms, which can dominate surface water communities in polar regions3. Here we present analyses of specimens of the pteropod Limacina helicina antarctica that were extracted live from the Southern Ocean early in 2008. We sampled from the top 200m of the water column, where aragonite saturation levels are around 1 as upwelled deep water is mixed with surface water containing anthropogenic CO2. Comparing the shell structure with samples from aragonite-supersaturated regions elsewhere under a scanning electron microscope, we found severe levels of shell dissolution in the undersaturated region but not elsewhere. According to laboratory incubations of intact samples with a range of aragonite saturation levels, eight days of incubation in aragonite saturation levels of 0.94–1.12 produced equivalent levels of dissolution. As deep-water upwelling and CO2 absorption by surface waters is likely to increase as a result of human activities2,4, we conclude that upper ocean regions where aragonite-shelled organisms are affected by dissolution are likely to expand.
The paper is available here: ftp://ftp.nerc-bas.ac.uk/pub/photo/PR-2012-13-Tarling/ngeo1635_GT%20edits.pdf
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Some clarification about marine carbonate chemistry:
Stability of solid carbonates in seawater depends on a property called the “saturation state”, of in the case of pteropods, the aragonite saturation state. This is simply the ratio of calcium and carbonate ions in water to aragonite. So if the ratio is greater than 1, the there are more calcium and carbonate ions in sea water and aragonite won’t dissolve. If the ratio is less than 1, aragonite will not dissolve. In most parts of the surface ocean, aragonite saturation states are on average between 3-5.
How does this relate to pH?
Dissolved carbon in the ocean comes in three flavors: aqueous CO2, bicarbonate ion, and carbonate ion. The relative concentrations of each species, or the “equilibrium” is very sensitive to pH. Thus, a small change in pH (e.g 0.1) can significantly decrease the carbonate ion concentration in seawater. Less carbonate ions means the aragonite saturation state decreases, and as such aragonite starts to dissolve. Seawater doesn’t need to become “acidic” on the pH scale in order for this to happen.
A decrease in pH of 0.1 does have significant ramifications …
From anon298 on November 27, 2012 at 2:16 pm (bold added):
So if the ratio is greater than 1, the there are more calcium and carbonate ions in sea water and aragonite won’t dissolve. If the ratio is less than 1, aragonite will not dissolve.
Which leaves the magical case of the ratio being perfectly equal to 1 as where aragonite might dissolve, but it seems unlikely.
@kadaka
I should have proof read that. When the saturation state is above 1, aragonite is stable. When the saturation state is equal to or below 1, aragonite will start dissolving as observed in the article.
anon298 says:
November 27, 2012 at 2:16 pm
Some clarification about marine carbonate chemistry:
“The relative concentrations of each species, or the “equilibrium” is very sensitive to pH. Thus, a small change in pH (e.g 0.1) can significantly decrease the carbonate ion concentration in seawater.”
I am led to believe the PH scale is logarithmic so a change of PH0.1 should have differing significance depending on how far from PH7 that change is. The closer to PH7 the less the significance. Is my understanding wrong?
Stephen Skinner wrote: “If substances can be indifferent to alkaline conditions then when they are within the Alkaline part of the PH scale, even at 10 C, they cannot be affected by acidity …”
This is not quite right for two reasons, Firstly, at a pH = 8.0, for example, the [H3O^1+] = 10^-8, and the [OH^1-] = 10^-6 (at 25-deg C). So strictly speaking, there are acidic species in aqueous solution albeit now in lower proportion to the alkaline hydroxide anion compared to neutral conditions (where both concentrations are 10^-7). Also, as I pointed out in part 1 of my post (not quoted) the solubility of a species such as Fe(OH)2 is 100x greater at, say, pH = 8 than at pH = 9: the solubility is most certainly affected by the “shift to a more acidic pH” and, in fact, the relative change in solubility is the same for pH = 7 to pH = 6. So the real issue is this: at what pH does the solubility of the material under consideration become appreciable or significant? It might be that a change in pH from 9 -> 8 makes the solubility change from 10^-8 molar to 10^-6 molar which might be effectively insignificant. But a change from 10^-4 molar to 10^-2 molar might lead to significant degradation (these values are not specific to my earlier Fe(OH)2 example, I’m just using some convenient ranges for illustrative purposes). Another example is in chelation therapy: chelates might bind their metals to a very high degree, yet not so much as to reduce the metal below its LD50 value in vivo. One of the most important things I teach my students is to appreciate when a given number is “big” or when it is “small” based on the context.
You also wrote: “But considering the scale is only 14 units long.” This is a common misconception. It SEEMS that way given Kw = 1.0E-14 for water at 25-deg C, but consider this: 10M (ten molar) HCl => 10.0 M H3O^1+ whose pH would then be -1.0 (yes, negative pH’s are possible). Ditto 10.0 M NaOH has a pH =15. Of course, solutions become increasingly non-ideal at these higher concentrations, so just to keep things simple I’m ignoring such matters for discussion here.
Hope this clarifies some of your points or questions, Stephen.
Here’s a very interesting comment on the New Scientist write-up:
So they overdosed the snails and de-strapolated? Gude Gad!
Poor Yorek, thank you for that explanation. I can see that as long as the chemists know to what the reference pertains, all is fine.
@Stephen Fisher Skinner
Yes, the pH change is small. BUT, the resulting change in carbonate ion concentration is significant. That is key. Dissolution of pteropod shells is not occurring because the pH of the ocean is dropping below neutral, but rather because that small decrease in pH is driving a large change in the aragonite saturation state. The saturation state is what determines the stability of a carbonate in seawater.
Here is graph that illustrates how carbonate ion concentration changes with pH: http://bit.ly/WY0Rl6. Notice how steep the carbonate ion slope is around surface ocean pH? Small change in pH = substantial change in carbonate ion concentration. Enough to cause dissolution.
Source of graph and more information on marine carbonate chemistry: http://bit.ly/TpCsPN
trafamadore says:
November 27, 2012 at 4:28 am
Two points from your “researching”:
1. Most creatures can not adapt to major changes in the environment when they are sudden.
2. Rapid cooling changes would be expected to affect life just as severely as rapid heating.
======================================================
Ants have twice the biomass of humans on this planet. While I applaud the inclusion of rapid cooling, creatures that have been around awhile have passed many tests. Humans are toddlers of the Pleistocene. While I believe in our potential, Neandertals had larger brains and they are extinct. Let’s not join them by failing to recognize that there are far greater forces at play than carbon dioxide.
Thanks Pooor Yorek and anon298. I understand most of your explanations but not the more technical. The graph is very useful and I need to understand further.
“The expedition ship: The RRS James Clark Ross underway in Antarctica”.
Ha ! I have been onboard that vessel !
Poor Yorek,
I calculate that if all 1.1 trillion tonnes of aggregate human CO2 were dissolved in a volume of distilled water representing the mixed layer of the ocean (350m km^3) the resulting molar solution would be 2.35×10^-9 and the resulting pH would drop from 7 to 6.95. The arm waving media consistently claims that humans have caused a .1 decrease in ocean pH, twice what I see as an absolute upper limit to human liability.
The water currently upwelling around Antarctica likely comes from well below the mixed layer from water equilibraded with CO2 in downwelling zones in about AD 1012. Blame the Vikings.The water endured a millenium of carbonate raining from above at enormous pressure.
Certainly there parts of distrubution curves of many ocean chemicals that are highly leveraged by pH. The clades in question have seen it all before.
^
Gymnosperm,
Not quite sure why I am the specific addressee of your post: my purpose in commenting above was to clarify some “loose language” and establish some general chemistry concepts that underlay much of the discussion. I thought I made it clear that I was not commenting at all, in defense or attack, on the paper itself: I do not presume to be sufficiently well read on the presumably complex mechanisms affecting equilibrium and non-equilibrium pH in ocean waters. That being said, I am reasonably expert in general acid-base and solubility-product type matters (e.g. the carbonate buffer system) and so I kept my comments pointed towards more general chemical matters.
anon298 says: ”A decrease in pH of 0.1 does have significant ramifications” CON!!!
Fellas, you are playing too much with your little water-pistols – to prevent you of getting blind; here are some real facts / important facts”::::::
pH in the sea varies between 7-pH9 / average 8,3pH. Therefore 0,1 changes on different places, every day, and much more!!!
2] carbonic acid is not even acidic – your darker colour blood in your vines is darker, because is saturated with CO2 – carrying it to your lungs, to let it out.
3]Eno, Dexal, Ural medications are BI-CARBONS – used as ”ANTACIDS”!!!
4]Amazon river, Mekong, Congo river drain every year from the ”rainforests” billions of tons of strong / real acidity as sulfuric acid, nitric acids +++ you don’t like acidity in the sea… sharpen your chainsaws!
5] increase in human population -> lots of chlorine, bleach and products with bleach in it ends up into the sea every day. bleach is pH13!!!
6] Lots of magnesium, potassium, salts, ash is getting washed into the sea from the hills, every day; they are all highly alkaline = needs some acidity, to counteract the real alkaline substances, forget CO2, IDIOTS!!!
7] higher alkalinity than normal, does bigger damages, than lower
8] all the CO2 from fossil fuel from 17 planets equal to earth; will not make the sea acidic!
9] from 8,3pH, going down to 7,1pH, is NOT becoming acidic!!! same as: going from Florida to New York = you are NOT gone into Canada!!!
10] what nobody takes into account is: pH7, as neutral – is NOT harming anything, BUT: at pH7, lots of primitive nusties start to grow in the water!!! When in the distant past; water was pH7 + oxygen depleted -they evolved, they like it that way. Water with pH7, after short time becomes sick water for all the modern critter – rainwater is pH7, leave it in the yard for few weeks = will see lots of primitive goodies growing in, that would make every modern fish sick / dead. Water in the sea is alkaline – most of the rivers are acidic; and should be that way. b] some soils in Canada, Australia are very alkaline = washes lots of extra alkalinity into the sea.
11] this supposed to be a Skeptic’s blog – debating that CO2 making the sea acidic = you are dignifying the Warmist lies = therefore: you are a Fake Skeptics; Warmist in-bedded as ”Fake Skeptics”!!! Stop playing with your little water pistols, it may fall-off!!! :::, Seawater is getting too alkaline, thanks to human overpopulation and artificial fire started bushfires. get some real truth:: http://globalwarmingdenier.wordpress.com/seawater-is-getting-too-alkaline/
Gail Combs says:November 27, 2012 at 6:17 am
”stefanthedenier You make absolutely no sense.”
When the truth doesn’t make sense for you; tells a lot about you: here is more truth:1: you burn your eyes twice as fast from telescope, than when looking direct at the sun. 2: you can get from the leading Warmist and the media: ”the date and company that made the filter in 2005-6, to see sunspots. 3: if you look 7-8 seconds at the sun – you will not see the sunspots there; but will see sunspots even in a dark room, for a day – and will never see anything else, for the rest of your life.
People that forged / falsified ”sun’s activity” to feet the mountains of phony past GLOBAL warmings -> pressed against those phony GLOBAL temp charts (which look as seismographs) will be the first to be jailed. Not one of you sods want to demonstrate how they were collecting data from sun’s activity for the past 1000years. It takes to look 7-8 minutes at the sun; to get permanent blindness. The CON who did it; will have to demonstrate, under oath – or three jail therms, minimum