Ocean Acidification... It's All About pH

Wow - you really don't look like yourself in this picture! Had a rough night?

Sorry, could not help myself with the joke. Anyway, I'll go and read your post on Correlations now....

Howdy Sheril,

As a marine scientist I'm sure you are aware that atmospheric CO2 concentrations, and therefore ocean concentrations, were much higher during past geologic ages. In fact our current epoch, the Holocene, has a relatively CO2 depleted atmosphere compared to the time periods when calcium carbonate bodied creatures, like corals, evolved and thrived.

Fauna of the Ordovician period included a large diversity of corals, bryozoans, bivalves and gastropods as evidenced by their abundant fossil remains. The atmosphere was an order of magnitude higher than present levels, or even high end predictions of future atmospheric CO2. So I imagine the crusty critters will be just fine.

And are you serious about "the last 250 years of evolution" making these organisms unable to adapt to slight changes in pH? How much genetic difference do you suppose could have happened over that time in evolutionary processes that takes millennia to detect any measurable difference?

Oh, of course you also know that while it may be correct to say that becoming slightly less alkaline may be called "acidification" no one expects the oceans to change pH enough to actually become acidic.

It makes for nice scary headlines though doesn't it?

Hi Sheril...

I'm posting here 'cause I'm not sure if you'd want it at Correlations. Feel free to cut and paste if you think it'll add to the discussion over there.

I'm a big proponent of GeoEngineering with proper study and care, and I've been playing around with a couple ideas for reversing this trend (or stalling it). I brought them up at Michael Tobis's blog, so I won't spam you by cross-posting, but I'm wondering if you see any immediate reasons why they wouldn't work, or would damage the biota.

Obviously, if there aren't any immediate reasons, that doesn't mean we should go ahead and do it, but it might be worth some deeper study, as well as perhaps some small trials.

I would assume distributing light amounts of finely ground basalt would fertilize as well as raising the pH and absorbing CO2. In fact, I'm not sure it would raise the pH, but I'm pretty sure it would increase the supersaturation.

Lance:

The critters in the oceans of the Ordovician had millions of years to evolve to thrive in the conditions of the Ordovician oceans -- and geologic terminations indicate to us that when things change rapidly, extinctions happen.

The pH of the oceans is changing rapidly now, and with more CO2 in the atmosphere and then into the oceans, it will change even more rapidly. Ergo...

Nice try, though. Classic misapplication of time-scale in consideration of climate processes. I recommend reading some science articles about this subject, such as:

Orr et al. Nature, 2005, Vol. 437, 681-685, "Anthropogenic ocean acidification over the twenty-first century and its impact on calcifying organisms".

If you have any questions after you read this, feel free to ask.

Jimbo,

Sheril waxes eulogistically about the fate of organisms that have "evolved" over the last 250 years and I'm misapplying times scales?

BTW read Orr et al. a while back, not so impressed. I don't want to get into a long list of papers but let's just say that their dire warnings are not shared by a majority of scientists in the field. Also, as I have already pointed out, organisms that rely on the formation of calcium carbonate skeletons have thrived in much higher CO2 conditions in the past, hence Sheril's appeal to the 'evolution" of the last 250 years being the issue.

Jimbo and others,

Lance is a regular troll and there's no reason to address him. He comments (poorly) on every post involving climate change imeediately and I half bet works for some group for profit to counter good science on excellent blogs such as this one. I have heard there are many partisan groups doing this now to push their agendas. I've noticed although he always claims he's a "scientist" - and admittedly is a decent writer, all of his arguments are immediately full of holes to anyone with real credentials in our profession.

Sheril,
Great post here and especially at Correlations. This is an issue coming up now in policy and there is a good deal of confusion. You did a terrific job explaining a complex topic. Ocean acidification is a critical issue and will continue to be for a very long time.

Lance, It happens I AM a climate scientist. A very good one too.

I just read a very interesting article: Origin and Evolution of Coccolithophores: From Coastal Hunters to Oceanic Farmers chapter 12 of a new book regarding one of the major groups of plankton. One small sample quote:

Obviously, extant coccolithophores are
facing a fast-changing ocean imposing
strong pressures on their calcification. However,
recent culture and mesocosm studies
mimicking predicted pCO2 conditions
(e.g., Delille et al. 2005; Riebesell et al. 2000a,
2000b) have major limitations. In these studies,
the carbonate chemistry was modified
abruptly in short-term experiments involving
a single clone of a single species. This is
basically testing the physiological response
(or acclimation potential) of an individual
to abnormal change, ignoring the ongoing
evolutionary adaptation of species and
communities. In fact, natural populations of
pelagic species are immense, occupying circum-
global biogeographic ranges, and thus
genetically highly polymorphic (Medlin
et al. 1996). Pelagic genomes are dividing on
daily time scales, thus adapting (i.e., slightly
modifying their fitness and ecological range)
at exceptionally high pace through the
constant and rapid reset of the worldwide
population. The intense genetic turnover
characterizing pelagic biodiversity may be
a key evolutionary strategy for survival in
this unstable and climatically responsive
environment, which is obviously difficult
to test in laboratory conditions.

To sum up, we have shown in this chapter
that there is not a singular coccolithophore
(and certainly not Emiliania!) but
several, widely divergent groups of potentially
calcifying haptophytes, the Calcihaptophycidae.
Our journey through their fossil
record and molecular evolution has shown
that their biomineralization was originally
selected in a high CO2, low pH, aragonite
ocean (Figure 5), whose conditions may
actually resemble the future Anthropogenic
world after 2100. They radiated into
an astounding morphological diversity of
highly productive species in the Cretaceous
Calcite II Ocean, which was relatively acidic
under a high CO2 atmosphere (Figure 5).
And they were bigger than ever, producing
thicker and large coccoliths across the Paleocene-
Eocene Thermal Maximum (probably
the best geologic analogue for future
global change), when a massive increase in
atmospheric CO2 over a 10,000-year period
caused rapid CaCO3 dissolution at the seafloor
and shoaling of the CCD by at least
2 km (Zachos et al. 2005). Thus, representing
the ultimate haptophyte adaptation to
the pelagic realm, the Calcihaptophycidae
may in fact be strongly equipped against
extinction, capable of multiplying in both
haploid and diploid, calcifying or noncalcifying
phases of their life cycle and having
the potential to reinvent biomineralization
at any time from coastal pools of noncalcifying
taxa. Future palaeontogenomic
approaches (De Vargas and Probert 2004b)
will certainly help unveil the biological and
functional complexity of the calcareous
flowers of the oceans.

Of course, a 10,000-year response doesn't say much about a 10-year (or 20-year) change, but the whole chapter was interesting reading.

Thanks to Hank Roberts for the link.

Climate Scientist,

So you are a scientist eh? And my posts are "full of holes" yet your answer to my points is to call me names? My training as a physicist has taught me to inspect scientific claims for falsifiable hypotheses and then test those claims against verifiable evidence. Your training as a "very good" "climate scientist" seems to prompt you to hurl paranoid invective. Our curricula apparently differed somewhat.

I am quick to respond to alarmist unfounded posts on climate change, but your paranoya is showing when you infer I am part of some nefarious

ooops

... right wing conspiracy.

(Apologies, I hit the "post" button instead of the "preview" button. Maybe I need some mouse dexterity training.)

Don't mean to annoy ya about your paranoya, Lance, but there's a paper in press in Science by a whole gaggle of the world's top coral reef biologists who are now very distressed about the acidification thing for corals. I'm afraid you've got an increasingly large group of experts to disagree with on this issue. Good luck discrediting them all.

Randy,

I guess I can't refute an entire "gaggle". BTW as a scientist I don't try to "discredit" people, just their invalid theories. That's how science advances. Anyone that's ever submitted a paper for peer review or faced a thesis defense should know that.

Lance:

I invite your comment on the following:

"If the response of other high-latitude pteropod species to aragonite undersaturation is similar to that of C. pyramidata, we hypothesize that these pteropods will not be able to adapt quickly enough to live in the undersaturate conditions that will occur over much of the high-latitude surface ocean during the twenty-first century."

Please discuss whether or not you feel the hypothesis stated above is adequately supported by the research findings in the paper. If not, please indicate why not and where further information is needed. Also discuss the potential downstream effects on higher trophic levels in the north Pacific.

I'm rarely impressed by people who say that they are not impressed by something unless they are able to specifically indicate why they aren't impressed.

Note to AK; calcite is the safest pseudomorph. Aragonitic and high-Mg organisms (the latter being corals) are more susceptible. However, biocalcification rate and ease will be affected equally by altered saturation state.

Thanks, Jimbo.

I was more concerned about whether my proposed plan of seeding "artificially eroded" basalt in warm low-latitude oceans would be dangerous to calcifying haptophytes. I actually posted the link because I found it interesting and thought others might.

I note in the paper you referenced that sub-arctic waters are currently supersaturated with respect to aragonite, even in winter. Does this mean that seeding "artificially eroded" limestone in sub-arctic water would be pointless? Would the same be true of calcium silicate minerals?

Jimbo,

The study was predicated on the results of "13 models" to assess the calcium carbonate saturation level "scenarios" that "might" result from "business as usual" emissions of future anthropogenic carbon dioxide.

There's enough uncertainty woven into those presumptions to render the rest of the experiment useless.

Then they proceeded to dunk some terapods in a tank for "two days" and observed "notable dissolution" of their argonite shells.

So they set up a tank with some adverse conditions, based on models of course, and then observed adverse effects.

As I said, not very impressive stuff.

AK:

Since the waters are supersaturated there won't be much of an effect at the surface, but in the far northern Pacific the saturation horizons are very close to the surface for aragonite: 150-175 meters. So dissolution would commence, especially for very fine stuff, below that depth (slowly just below the depth, faster with increasing depth).

But the sheer magnitude of how much would be needed to have an effect is unfathomable, to coin a phrase. Much, much, much, MUCH more than the amount of iron to seed phytoplankton blooms, because iron is a limiting micro-nutrient.

Lance: thanks for your comments. I would seek clarification of the questionable "presumptions". If so inclined, discuss the Uncertainties section of the paper. Figure 5 shows a very tight prediction range for the undersaturation of Southern Ocean waters, despite postulated uncertainties in "presumptions".

By the way, the correct spelling is "pteropods". If you re-read Orr et al., you will note this particular zooplankton group name occurs in the Abstract. They are quite beautiful and amazing creatures.

Jimbo,

Uncertainties of the "models" are not quantified, nor could they be. Predictions based on systems of coupled non-linear differential equations are like that.

Yes, I hastily typed out my reply and misspelled pterapods. How kind of you to point it out. I've had trouble spelling pterodactyl and pneumonia as well.

I agree they can be quite beautiful creatures but some are extraordinarily grotesque in appearance. Beauty is in the light receptor array of the beholder I suppose. I don't want even the uglier ones to disappear. Of course if they failed to adapt as well as other creatures to a changing environment I suppose we might call that evolution. It happens all the time apparently.

I wouldn't worry though, the little critters, and somewhat larger ones, did quite well when the atmosphere was much, much higher in CO2. Why didn't they have "dissolution" issues in past geologic ages?

Lance:

Two things: one, put simply, the rate of surface ocean pH changes is going to be a function of atmospheric CO2 concentration. Climate effects are far more uncertain than this effect. What is happening is equilibrium chemistry. The only way to affect it is to change the rate of increase of atmospheric CO2, as the "Uncertainties" section of Orr et al. clearly states. This is why I put "presumptions" in quotes. Air-sea CO2 exchange rates will not vary much except as a function of atmospheric CO2 concentration. The basics of carbonate equilibria are standard chemical relationships.

Speaking of that, point two. The chemistry of the oceans, however, in past geologic ages was clearly different than the chemistry of the oceans now. A classic demonstration of this with respect to carbonates is the mineral dolomite. If you've ever been to northern Italy, you might know that there is a lot of dolomite there. Very pretty mountains made of it. All of this formed in the ancient oceans. Dolomite does not form in modern oceans, and attempts to get it to form in the laboratory at all have been difficult.

So, to answer your terminating question blithely and quickly, one of the reasons that calcifying organisms didn't have dissolution issues in a high CO2 world is because the chemistry of the oceans in past geologic ages was considerably different. (There are papers about this: Garrels, Berner, Kump, Archer, Mackenzie, Lerman are some likely authors to search on for those papers, off the top of my head.) Furthermore, it can easily be postulated (though impossible to prove) that the physiology of calcification of organisms in past geologic ages was different than that of modern calcifiers. By the way, it appears in the specific case of the Italian Dolomites that they are calcite depositions altered to dolomite diagenetically -- and this is a process only rarely observed in unique aquatic environments today, underscoring my point about differences between ancient and modern oceans.

As an example, related to my points above, read this abstract:

http://gsa.confex.com/gsa/2003AM/finalprogram/abstract_60959.htm

Jimbo,

Thanks for the wealth of information. You obviously know a lot more about this topic than I do. Also thanks for not ripping into me with sarcastic remarks, which your superior knowledge of the subject could have easily provided.

To be honest it has given me pause. I will have to invest more time and effort on the subject before I spout off again.

One comment, while Henry's law can easily be used to give the relative concentrations of CO2 in the atmosphere and ocean it is not a trivial matter to predict future amounts of CO2 in the atmosphere. That is where I take issue with the models used in the study.

Lance:

I wish a lot more people would "give pause" to consider carefully what scientists who understand these issues are saying about these issues. And there are many who understand them much better than I do.

Quick comment: I looked back at your first post here and you characterized what's happening as "slight changes in pH". Well, 0.1 pH unit doesn't seem like a lot at first.

Then you realize pH is a logarithmic scale. So 0.1 is more than first impressions indicate. Then you consider that seawater is a buffered chemical system (mainly by the carbonate ionic species). A measurable shift of 0.1 pH units in a buffered system as big as the Pacific is a major change. And it indicates considerably larger changes in the concentrations of the active chemical species.

And it's important in the context of potential geoengineering, because using emplaced stratospheric sulfur aerosols to reduce incoming solar radiation wouldn't do a thing about ocean acidification. If someone could devise a way to improve the efficiency of the carbon pump, then iron fertilization might possibly offer some potential. But current research indicates that as the oceans work in general, it's a useless idea for long-term transfer of carbon from atmosphere to deep ocean.

Jimbo...

It's my guess that the only way to increase the carbon pump is to inject more calcium (++) into the surface waters. As you showed above, that's less a "silver bullet" than a "lead pipe", although the numbers aren't really unfathomable. My rough estimate is that to balance (and hopefully remove) the excess CO2 in the air would require on the order of 500-1000 gigatons of CaCO3, perhaps twice that of CaSiO3. Given typical available proportions in available minerals, perhaps the same number of cubic kilometers, the size of a few good-sized mountains. I don't suppose that would count as "improv[ing] the efficiency of the carbon pump", but with the typical exponential growth of technology it's probably reachable within 2-3 decades.

And, of course, while it might prevent acidification and greenhouse warming, it probably would have it's own (hopefully) longer term prices that would have to be met. Perhaps we should think of such things as loans from nature rather than gifts (or robberies).