[Note: some understanding of chemistry (approximately A-Level) is necessary to understand this post, and it will be helpful to read the background in the previous post Ocean Acidification Scam.]
The theory behind the ‘toxic ocean acidification’ scam proceeds like this: as the concentration of CO2 in the atmosphere increases, the concentration in the oceans also increases due to dissolution [true – all other things being equal]. CO2 dissolved in water reacts with water to form carbonic acid, making the seas acidic [a half truth – they become very slightly less basic]. This acidity dissolves the shells of marine life causing mass extinction [an utter falsehood].
As a matter of fact, seawater is alkaline and basic. Dissolving the carbon dioxide from all the world’s known fossil fuel reserves would never make the sea acidic. The climate alarmists coined the phrase “ocean acidification” to make it sound alarming, whereas the process is actually what is known as neutralization. The term ‘acidification’ of course sounds more scary than talking about the oceans becoming slightly less basic or a little more neutral.
To put this into perspective, the pH of seawater is, on average, around pH 8.2. Pure water is pH 7.0, and clean rainwater is pH 5.6. What is more, seawater is a highly buffered solution – it can take up a huge amount of dissolved inorganic carbon without significant effect on pH. There is not the slightest possibility that the oceans could approach the neutral pH of pure water even if all the fossil fuel reserves in the world were burned, so all talk of ‘acid’ oceans is utter nonsense. What sort of change are we talking about? Possibly a change of pH of 0.2 units this century, say from 8.2 to 8.0. That would mean by definition that the concentration of the ‘acidic’ H+ ions would still be no more than 10% of their concentration in pure water.
The so-called science behind this ‘acid ocean’ scare is highly questionable. Firstly, an increasing concentration of CO2 in the water improves the efficiency of photosynthesis in the oceans (as it does on the land), and so increases the growth of plant life in the ocean, including phytoplankton, upon which ‘graze’ zooplankton, which is food for a vast range of sea animals, including whales.
Secondly, it’s not possible through lifeless inorganic chemistry to predict what is happening with living processes. Fish pump huge quantities (hundreds of millions of tonnes annually) of available carbonate in the oceans as a byproduct of the systems that enable them to survive in high salinity. This is using the energy of life processes to buck the normal dissolved inorganic carbon equilibria. The calcium carbonate of dead calcifying organisms dissolves naturally in seawater. What stops a sea creature’s shell from dissolving away is the living creature’s continually producing more calcium carbonate, just like a land animal continually produces skin cells to replace those that are lost to the environment.
Thirdly, an increasing concentration of dissolved inorganic carbon (e.g. dissolved carbon dioxide, bicarbonate ions, carbonate ions) makes the process of laying down calcium carbonate in shells efficient. This is because there is a far greater supply of calcium ions (441ppm) in seawater than dissolved inorganic carbon (90ppm) and any increase in dissolved carbon dioxide simply pushes the reactions towards the production of more bicarbonate and carbonate ions. The reactions are reversible and in equilibria:
CO2 + H2O <=> H2CO3 <=> H+ + HCO3- <=> H+ + H+ + CO32-
Add more CO2 at the left and the reaction proceeds to a greater or lesser extent to the right. Most of the additional carbon ends up as bicarbonate. Note that as the reaction is driven to the right by the dissolution of additional CO2 there is increased production of H+ ions, so acidity is increasing (= decreasing pH).
Fourthly, the situation is completely different from the case where pH is artificially lowered by adding, say, hydrochloric acid, where there would be no addition of dissolved inorganic carbon. Unfortunately, many scientists have failed to understand this basic chemistry and have conducted crude experiments on shellfish by adding mineral acids to seawater. Whilst this duly lowers the pH, it drives the equilibrium reactions in the opposite direction, so is completely invalid as an experimental model. In the equilibrium equation above, introducing mineral acid (which introduces no additional dissolved inorganic carbon) adds H+ ions on the right of the equilibrium equation, which drives the reaction to the left. The increase in H+ ions (equivalent to lower pH), arises because the experimenter is tipping in mineral acid and is thereby forcing the reaction drastically to reduce carbonate and to increase dissolved carbon dioxide, which will come out of solution into the atmosphere as bubbles, decarbonizing the seawater. But if increasing atmospheric CO2 is the driver, the reaction is forced the other way; if mineral acid is the driver, the pH goes down and carbonates and possibly bicarbonates also go down. Looking at pH alone tells us absolutely nothing about the concentrations of carbonates, bicarbonates, dissolved CO2, equilibria, reaction rates or reaction directions. At the very least we also need to know the amount of dissolved inorganic carbon. Moreover, calcium carbonate dissolves in alkaline seawater (pH 8.2) 15 times faster than in pure water (pH 7.0), so it is silly, meaningless nonsense to focus on pH.
At pH 8, seawater is supersaturated with carbonate. Why does this excess carbonate not precipitate out as calcium carbonate, since there are so many free calcium ions in the water? This seldom happens because of the presence of magnesium ions in seawater that preferentially ion pair with the carbonate in solution. With ion pairing, the reaction moves further to the right than would be the case without magnesium ions, yet without precipitation of magnesium and calcium carbonate salts, and this ensures there is an abundance of dissolved carbonate ions available for living organisms in spite of the low alkalinity. Moreover, phosphorus and dissolved organic compounds permit high levels of carbonate to exist without precipitation. Seawater is a truly marvelous and complex chemical system, which includes non-volatile borate, phosphate and silicate buffers.
Increasing CO2 partial pressure in a CO2/carbonate equilibrium will always drive the reaction towards the production of more dissolved inorganic carbon, irrespective of any associated reduction in pH arising from the shift in equilibrium itself. So if atmospheric CO2 increases, leading to increased dissolution of CO2, we can be sure that there will be a higher concentration of available carbon – the complete opposite of what the scare mongers are telling us. It seems that those creating the ‘ocean acidification’ scare would like us to believe that a reduction in pH is analogous to tipping mineral acid in the oceans, which would indeed be damaging, and would liberate CO2 from the oceans and decarbonize it, whereas the effect of increasing dissolution of CO2 is beneficial both to marine plants and animals.
To see what muddled thinking and ignorance of chemistry there is, it is sufficient to examine the report by the Royal Society, Ocean acidification due to increasing atmospheric carbon dioxide. They state
Carbonic acid is an acid because it can split up into its constituents, releasing an excess of H+ to solution and so driving pH to lower values. Carbonic acid splits up by adding one H+ ion to solution along with HCO3- (a bicarbonate ion)…This increase in H+ causes some CO32- (called carbonate ions) to react with H+ to become HCO3-…Thus the net effect of the dissolution of CO2 in seawater is to increase concentrations of H+, H2CO3 and HCO3- , while decreasing concentrations of CO32-
The reasoning in the Royal Society’s paper (and many others) is that because addition of carbon dioxide causes more acidity, the increasing H+ ions will eventually force the reaction to the left. But where are the H+ ions coming from in the first place? As a result of the reaction moving to the right! The reasoning of this Society is that as the reaction proceeds to the right and liberates H+ ions it must subsequently swing back to the left (which would create higher CO2 in the water as well). Equilibrium processes don’t work in unstable, oscillatory ways, and can’t pull themselves up by their own bootstraps: the H+ ions that are generated from addition of carbon dioxide become a significant brake on the reaction proceeding to the right, and a new equilibrium point is reached with lower pH.
Of course, the above equation showing the chain of reversible reactions doesn’t specify absolute concentrations. Seawater is a complex system, and whether carbonates increase or decrease in concentration with increasing dissolution of carbon dioxide requires careful analysis, the solution of many simultaneous equations, and knowledge of other systems such as magnesium and borates, as well as ion pairing.
Whilst the relative concentration of CO32- (carbonate) with respect to the increasing concentration of HCO3- (bicarbonate) can reduce with increasing dissolved inorganic carbon, it is not obvious what happens to the absolute concentration of carbonate as more CO2 dissolves. For example, consider a beaker of pure water, pH 7.0. The beaker contains nothing but H2O molecules and its dissociated ions H+ and OH-. If carbon dioxide is bubbled through the water for some hours and the system left to rest and establish equilibrium the pH will go down, perhaps to pH 5. There will be now be some dissolved CO2, some bicarbonate ions and some carbonate ions in solution and many more H+ ions than there were before. Carbonate ions have thus increased because there were literally none before, yet pH has gone down and the absolute quantity of H+ ions has increased considerably. So, in absolute terms, carbonate ion concentration can increase as dissolved CO2 increases even though pH has reduced. Notwithstanding, many studies modeling seawater in its usual composition, salinity, temperature and pressure, show some decline in carbonate with increasing dissolved inorganic carbon. But we are inclined to say ‘so what?’ Of the various dissolved carbon species, bicarbonate is typically dominant as the form in which the carbon exists, and since it is bicarbonate ions (not carbonate ions) that are used to form calcium carbonate shells, then we would expect biological pumps to find increased bicarbonate concentration very advantageous. Why should we care what happens to carbonate concentration?
However, the Royal Society’s paper also has this to say:
From our understanding of ocean chemistry and available evidence, it is clear that increasing the acidity of the oceans will reduce the concentration and therefore the availability of carbonate ions. It is expected that calcifying organisms will find it more difficult to produce and maintain their shells and hard structures.
Here also is a classic trick of the illogical argument, the non sequitur. We are being led to believe from these two sentences that the availability of carbonate ions is important to the production and maintenance of shells. As a matter of fact, nearly all the literature teaches (as was found by measuring carbon isotopes) that the biological process of calcification proceeds from the reaction between calcium ions and bicarbonate ions, and there’s no shortage of either of those – in fact bicarbonate strongly increases as more carbon dioxide is introduced. Thus Kleypas et al:
…HCO3- is the preferred substrate for coral photosynthesis (Al-Moghrabi et al., 1996; Goiran et al., 1996; Allemand et al., 1998), coral calcification uses both HCO3- from seawater and metabolic CO2 as sources of carbon (Erez, 1978; Furla et al., 2000)…Biochemical studies fail to provide any evidence that CO32- plays a direct role in coral calcification…Results from several studies indicate that the substrate for calcification in E. huxleyi is HCO3- (cf., Paasche, 2001), which increases under elevated pCO2 conditions…
Even the Royal Society report says as much 12 pages earlier, but you are expected to have forgotten that by now:
two ions of bicarbonate (HCO3-) react with one ion of doubly charged calcium (Ca2+) to form one molecule of CaCO3
This makes the “availability of carbonate ions” a moot point, but you are not supposed to pick up on this false logic. Of course, by removing some dissolved inorganic carbon to form shells, calcifiers are reducing the total alkalinity of the oceans, depositing more carbon dioxide in the oceans, and reducing the pH of the oceans. So what would be evidence that calcifiers were thriving? Reducing pH in the oceans and either a slower uptake from or even an outgassing of CO2 into the atmosphere, i.e. “ocean acidification”!
The reaction mentioned by the Royal Society is written variously, but commonly as follows:
Ca2+ + 2HCO3- <=> CaCO3 + CO2 + H2O
Calcifiers use biological pumps to drive the reaction to the right to build calcified shells using the superabundant calcium ions and the abundant bicarbonate ions, liberating dissolved carbon dioxide and water, and thus reducing ocean pH. It is widely assumed that if dissolved CO2 increases in the ocean due to increased atmospheric concentration, it makes it increasingly more difficult for life processes to move the reaction to the right because the equilibrium is shifting adversely. And as dissolved CO2 increases then it must push the reaction to the left, dissolving calcium carbonate along the way. So we are allegedly faced with the spectre of a greater difficulty for organisms in laying down calcium carbonate, coupled with a greater propensity for dissolution of the carbonate they have already produced as shells – a ‘double whammy’.
Yet for the purposes of laying down shell we can pretty much forget about standard reaction kinetics and equilibria because the whole thing is driven by a biological process. Moreover, since CO2 is liberated as part of the calcification process, then the local CO2 concentration at the site of calcification is determined by the calcification process itself practically independent of the very low concentration of dissolved CO2 generally available. Thus Kleypas et al
Most models assume that the calcifying fluid is isolated from external seawater. This is supported by microelectrode observations that show that the pH of the calcifying space is elevated relative to external waters (as high as 9.3) (Al-Horani et al., 2003) and by the well-known fractionation of oxygen and carbon isotopes in the calcifying fluid.
We could also observe that as DIC increases and the concentration of bicarbonate increases, which is the precursor used in the calcification process as above, then biological pumps have an easier time of it. Thus as shown in the quoted articles below, many calcifiers including corals benefit from higher atmospheric concentration of CO2 dissolving in the oceans. Metabolically, they also benefit from increased [H+]. As far as dissolution of shells is concerned, this is a pretty slow process. In living organisms there does not seem to be any detrimental effect because calcium is continually deposited. The main changes that seem to have been measured are slightly faster dissolution of shells after the death of the organism. And who cares about that?
Just as the availability of CO2 on land and in the oceans constrains plant growth, and plants flourish when the concentration is increased, so calcifiers benefit from increased dissolved inorganic carbon, especially in the bicarbonate form, which is the form in which most of the DIC ends up. Thus, Marubini and Thake noted in 1999:
…the present dissolved inorganic carbon (DIC) content of the ocean limits coral growth…adding DIC increases coral calcification rates and confers protection…
And Herford et al noted in 2008 that a large projected increase in atmospheric CO2 “will result in about a 15% increase in oceanic HCO3-” which “could stimulate photosynthesis and calcification in a wide variety of hermatypic corals.”
And here comes the classic from the Royal Society:
…the lack of a clear understanding of the mechanisms of calcification and its metabolic or structural function means that it is difficult, at present, to reliably predict the full consequences of CO2-induced ocean acidification on the physiological and ecological fitness of calcifying organisms.
So, let’s consign this report to the waste bin, please, and look at papers by authors who do know what they are talking about. But in this regard, the following assertion given in the Royal Society paper is an outright lie, as inspection of the sources below shows:
Published data on corals, coccolithophores and foraminifera all suggest a reduction in calcification by 5–25% in response to a doubling of atmospheric CO2 from pre-industrial values (from 280 to 560 ppm CO2)
So, what’s the effect of increasing carbon dioxide in seawater on calcifying organisms? Here are some reported findings:
Wood, Spicer, and Widdicombe (2008) found that increasing dissolved CO2 increases calcification rates and improves the rate of regeneration of damaged body parts [Proc Biol Sci. 2008 August 7]. The following extracts are given at length because of the importance of these findings, which overturn ‘assumptions’ (read, false reasoning and bad science):
…we have investigated the effect of CO2-induced acidification on the ability of a calcifying organism (the ophiuroid brittlestar Amphiura filiformis) to regenerate calcium carbonate structures (arms).
Amphiura filiformis collected from Plymouth Sound, UK, were maintained in sediment cores (five individuals per core) supplied with filtered seawater of the allocated pH (pH modified using CO2). Each pH treatment (8.0, 7.7, 7.3 and 6.8) had four cores (20 individuals per pH)…
One of the most surprising results is that there was no decrease in the total amount of calcium carbonate in individuals exposed to acidified water. Indeed, individuals from lowered pH treatments had a greater percentage of calcium in their regenerated arms than individuals from control treatments, indicating a greater amount of calcium carbonate…In regenerated arms, calcium levels were greater in those organisms exposed to acidified seawater than in those held in untreated seawater. This was true for all three levels of acidified seawater…there was actually an increasing rate of calcification with lowered pH. Calcium carbonate in established arms was also affected by lowered pH. At pH 6.8, calcium levels increased and at pH 7.7 and pH 7.3, calcium levels were equal to the control indicating that A. filiformis actively replaced calcium carbonate lost by dissolution.
Rates of oxygen (O2) uptake (as a measure of metabolic rate), or MO2, were significantly greater at reduced pHs (7.7, 7.3 and 6.8) than in controls (pH 8); However, MO2 was not significantly different between the three lowered pH treatments. Increased rates of physiological processes that require energy are paralleled by an increase in metabolism; this relationship is seen with growth and metabolism here in our results.
Seawater acidification stimulated arm regeneration. After the 40-day exposure, the length of the regenerated arm was greater in acidified treatments than in the controls…This increased rate of growth coincided with increased metabolism. Regeneration was not affected by the number of arms removed, nor was there a significant difference in any of the physiological parameters measured as a result of having two arms regenerating instead of one. The ability to regenerate lost arms faster meant a reduction in the length of time animal function (e.g. burrow ventilation and feeding) was compromised by reduced arm length.
Interestingly, even at high levels of hypercapnia (the 6.8 pH treatment crosses the threshold into acidic water, i.e. pH<7.0) investigated here, no mortality was observed.
These results change the face of predictions for future marine assemblages with respect to ocean acidification. Whereas it was previously assumed that all calcifiers would be unable to construct shells or skeletons, and inevitably succumb to dissolution as carbonate became undersaturated, we now know that this is not the case for every species.
Marubini and Thake (1999)
The addition of 2 mM bicarbonate to aquaria containing tropical ocean water and branches of Porites porites caused a doubling of the skeletal growth rate of the coral. Nitrate or ammonium addition (20 μM) to oligotrophic sea-water caused a significant reduction in coral growth, but when seawater containing the extra bicarbonate was supplemented with combined nitrogen, no depression of the higher growth rate was evident. We infer that (1) the present dissolved inorganic carbon (DIC) content of the ocean limits coral growth, (2) this limitation is exacerbated by nitrate and ammonium, and (3) adding DIC increases coral calcification rates and confers protection against nutrient enrichment.
coccolithophores may benefit from the present increase in atmospheric CO2 and related changes in seawater carbonate chemistry…increasing CO2 availability may improve the overall resource utilization of E. huxleyi and possibly of other fast-growing coccolithophore species…if this provides an ecological advantage for coccolithophores, rising atmospheric CO2 could potentially increase the contribution of calcifying phytoplankton to overall primary production…a moderate increase in CO2 facilitates photosynthetic carbon fixation of some phytoplankton groups…CO2-sensitive taxa, such as the calcifying coccolithophorids, should therefore benefit more from the present increase in atmospheric CO2…
Iglesias-Rodriguez et al (2008) confirmed Riebesell findings experimentally, concluding that coccolithophores, which account for a third of all marine calcium carbonate production, flourish and calcify much better at higher levels of CO2:
Here, we present laboratory evidence that calcification and net primary production in the coccolithophore species Emiliania huxleyi are significantly increased by high CO2 partial pressures. Field evidence from the deep ocean is consistent with these laboratory conclusions, indicating that over the past 220 years there has been a 40% increase in average coccolith mass. Our findings show that coccolithophores are already responding and will probably continue to respond to rising atmospheric CO2 partial pressures, which has important implications for biogeochemical modeling of future oceans and climate.
Richardson and Gibbons (2008):
…no observed declines in the abundance of calcifiers with lowering pH have yet been reported…the role of pH in structuring zooplankton communities in the North Sea and further afield at present is tenuous.
Vogt et al (2008), experimenting with atmospheric concentrations up to three times current levels,
…the ecosystem composition, bacterial and phytoplankton abundances and productivity, grazing rates and total grazer abundance and reproduction were not significantly affected by CO2 induced effects.
Gutowska (2008) subjected cuttlefish larvae to CO2 concentrations of 6000 ppm (sixteen times current CO2 concentration), at pH 7.1. Results:
No differences in soft tissue growth performance were measured between cuttlefish incubated at ~4000 and ~6000 ppm CO2 and controls…Standard metabolic rates of cuttlefish exposed acutely to ~6000 ppm CO2 showed no significant increase or decrease over time…there were no significant differences between the mantle lengths of control cuttlefish and those incubated at 6000 ppm CO2…Interestingly, in the ~6000 ppm CO2 growth trial, the CO2 incubated animals incorporated significantly more CaCO3 [calcium carbonate] into their cuttlebones than did the control group…Functional control of the cuttlebones (i.e. buoyancy regulation) did not appear to be negatively affected by low pH conditions.
Herford et al (2008):
A wide range of bicarbonate concentrations was used to monitor the kinetics of bicarbonate (HCO3-) use in both photosynthesis and calcification in two reef-building corals, Porites porites and Acropora sp…additions of NaHCO 3 [bicarbonate is added as the sodium salt because additional sodium ions are ‘lost’ in the sodium ions already present in seawater] to synthetic seawater proportionally increased the calcification rate of this coral until the concentration exceeded three times that of seawater (6 mM). Photosynthetic rates were also stimulated by HCO3- addition…Similar experiments on aquarium-acclimated colonies of Indo-Pacific Acropora sp. showed that calcification and photosynthesis in this coral were enhanced to an even greater extent than P. porites, with calcification continuing to increase above 8 mM HCO3-. Calcification rates of Acropora sp. were also monitored in the dark, and, although these were lower than in the light for a given HCO3- concentration, they still increased dramatically with HCO3- addition…
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Herford et al., Bicarbonate stimulation of calcification and photosynthesis in two hermatypic corals, Journal of Phycology, Vol 44 Issue 1, pp. 91 -98 (2008)
Kleypas, J.A., R.A. Feely, V.J. Fabry, C. Langdon, C.L. Sabine, and L.L. Robbins, 2006. Impacts of Ocean Acidification on Coral Reefs and Other Marine Calcifiers: A Guide for Future Research, report of a workshop held 18–20 April 2005, St. Petersburg, FL
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Wood, H.L., Spicer, J.I., and Widdicombe, S., Ocean acidification may increase calcification rates, but at a cost. Proc Biol Sci. 2008 August 7; 275 (1644): 1767–1773.
The Royal Society, Ocean acidification due to increasing atmospheric carbon dioxide, 2005