• what is the carbon situation? Where is all carbon stored and how much of it is circulating?
• is the level of carbon dioxide rising? What evidence exists that CO2 in air is rising?
• where is the CO2 in the oceans? the oceans and the sea soil form a massive store of CO2.
• is carbondioxide absorbed by the sea? CO2 takes part in the normal exchange but is it being sequestered?
• how acidic are the oceans? what is the normal acidity of the oceans and by how much does it vary?
• are oceans becoming more acidic? what evidence exists that the oceans are becoming more acidic?
• the Bjerrum plot of the carbonate system: much value is attached to classical carbonate theory but does it stick?
• so why is acidification a problem? the main fear is that increased acidity would erode shells and coral reefs.
• is CO2 a potent fertiliser? Land plants are seriously limited by a dearth of CO2, but what is the situation in the sea?
• natural CO2 vents  A recent study found that biodiversity decreased near natural CO2 vents. What does it mean?
• phytoplankton calcification  A recent study finds that CO2 improves calcification in coccolithophores, as we predicted.
• crustose coralline agae affected by raised levels of CO2? A much-hailed study with severe deficiencies.

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-- Seafriends home --Global problems index-- Rev:20070820,20080629,

What is the carbon situation? Over the past two decades scientists gained a fair understanding of where all carbon is found and how much of it circulates between atmosphere, land and sea, although significant differences can be found among authors. As one can see, the human contribution is about 8Pg carbon per year (8Gt, billions of tons) against a global respiration rate of about 100-250Pg/y (fossil fuel alone: 2%, some say 3%). It is though that this contribution is the cause of the observed increase in the concentration of CO2 in the atmosphere from a supposed 180ppm pre-industrial to a pesent-day 400ppm. So there is good certainty that the amount of CO2 in the air is rising. The critical question remains why? Many scientists believe it is caused by the burning of fossil fuels and other human activities, but considering the presence of a huge reservoir of carbondioxide in the ocean, one should ask whether the tail is wagging the dog. [for more about where the carbon is locked up on land, look at soil54.gif ]

This diagram shows the latest figures (after Holmen, 2000) with residence times and today's atmospheric carbon at 700Gt.  The land has been split in two compartments and the oceans in three. Apparently plants assimilate 122Gt/y in photosynthesis, with leaves dying after 5 years, and their stems and decaying wood estimated at 1100Gt, decaying in 20 years while returning 60Gt back to the air. Of the total, only 2Gt is sequestered. From this less than 0.1Gt is sequestered for 1000y in fossil fuels and shales. The oceans have been split into three compartments, with mainly the surface ocean interacting with the atmosphere, photosynthesising and respiring/decaying 100GtC/y while sequestering 2 GtC/y. Only 0.3 GtC/y rains down in the form of carbonate oozes of marine sediments of which a massive 30 million GtC exists, to be circulated to the surface through ocean floor spreading, subduction and volcanic activity, which takes 100 million years.

I have some reservations about this diagram:

• of the plants, their soils have been neglected
• a cycle of 122 Gt on a living biomass of 70Gt living plant matter cannot result in residency time of 5y
• fossil oil and shales come from the sea, not the land but peat and coal do.
• the figures differ too much from previously published ones.
• values for sequestration are guessed at, being the small difference between two large figures.
• residence times for deep ocean water have been measured to be in the order of a few thousand years, not 100,000.
• carbon exchange with sea soil is not shown.
• river deposits into the sea are not shown
• forest burning and habitat change are not shown.
• deep carbon clathrate deposits are not taken account of.

"Eighty percent of inputs from land to sea are deposited here [in coastal margins], and 85% of organic carbon and 45% of inorganic carbon are buried in the ocean margin sediments (Gattuso et al., 1998a; Wollast, 1998; Chen et al., 2003)". This suggests that carbon from the terrestrial biosphere finds its way to the sea, carried by rain water and rivers,  not shown in the diagram.

"Carbonate accumulation in coral reef environments alone accounts for an estimated 20–30% of the global ocean accumulation (Milliman and Droxler, 1996)".

"Ocean margins are also heavily impacted by human activities, as nearly 40% of the global population lives within 100 km of the coastline (Cohen et al., 1997). Since the onset of the Industrial Revolution, burning of fossil fuels and land-use changes have caused substantial increases in both atmospheric CO2 concentration and in the delivery of organic matter and nutrients to ocean margins (Mackenzie, 2003). Such changes could alter the role of this system and considerably affect important processes such as air-sea CO2 exchange".

Is the level of carbon dioxide in air rising? The diagram shows the growth in population and our use of resources. The vertical scale is logarithmic, which shows exponential growth best. In the top left one sees three lines for a 5,10 and 100 times growth rate per century. It brings the shocking reality that population (p) still grows at the rate of 10x per century, all energy use (e) at close to 100x per century. Ironically, the top brown curve for CO2 (h) does not keep up with these trends, and by comparison, appears to be levelling off. In other words, the relationship between increased CO2 levels in air, and the growing use of energy, is rather weak. Then again, a doubling in 30 years would imply an underlying growth rate of close to ten times per century, still far removed from the actual rate of increase in fossil burning. Note also that the world is still doing relatively well, as measured by GDP per person (gp), and even the use of water per person is still climbing, but not for long (wp). An interesting fact is that the total energy (e) until 1800 consisted of burning biomass (sustainable). In 1800 the use of coal took off, later flattening off (b) because by 1870 oil replaced it and later still, gas.

There is a lot of panic about CO2 levels rising to 400ppm and above, but in the history of the planet, CO2 has often been much higher, and the present low levels of CO2 could be considered an anomaly. At the time of the great dinosaurs, carbon dioxide levels were five times higher still (2000ppm) and life as we know, was prolific back then. Evolution towards diversity also thrived. The work of Budyko has been replicated and refined, and essentially been confirmed, see diagram and further below. To understand ancient epochs, read our Geologic Timetable.

The general consensus is that the concentration of CO2 in the atmosphere is increasing. Very accurate measurements at mount Mauna Loa and independently at Baring Head in New Zealand, show a steadily growing CO2 concentration. But the data before 1960 remains sketchy. The IPCC attaches high value to CO2 measurements from air bubbles trapped in ice which indicated that the pre-industrial concentration was about 270ppm. Knowing the age of each point by the year rings in the ice, the brown curve resulted from the Siple Dome in West Antarctica (drilling 1996-2005, 990m deep). However, this curve did not join up with that of Mauna Loa, so it was arbitrarily shifted right by 83 years, and also down a little. The reason for doing so is that the first part of the core, containing compressed snow or firn, is still 'open' to atmospheric influences, see dotted brown curve with question marks, and the box below. Russian scientists mention that the method is flawed, since CO2 does dissolve into ice and it even escapes. For instance, the starting pressure at the top of the curve is already 5 bar, but increases to 15 bar at the bottom. Already since about 1750, chemistry scientists have done CO2 measurements in a more classical way, and the tens of thousands of data points join up quite well, even though many measurements were taken in industrial cities. The green curve shows that perhaps the CO2 concentration was not all that ideal both inside the industrial age and before.

CO2 glaciology depends on the following unproved assumptions:

• No liquid phase occurs in the ice at mean annual temperatures below -24ºC
• The way air is entrapped in ice is a mechanical process and does not differentiate between gas components (fractionation)
• The air inclusions represent the original atmospheric air composition
• High pressure of the ice does not influence the makeup of entrapped gases and does not dissolve CO2 into ice in the form of clathrates.
• The age of gases in the air bubbles is much younger than the age of the ice in which they are entrapped, ranging from decades to millennia.
• Drilling the ice core does not pollute it
• Relaxation of the ice core after its pressure drops from hundreds of bar to one, does not influence its content. (one bar per 12 metre)

Measurements of gases, temperature and volcanic activity are done by measuring proxies, such as the amount of dust in a core for volcanic activity, and the ratios of radioactive elements for temperature and carbon dioxide. In all cases, a consistent record is obtained for the distant past, but this never seems to join up with the situation of today and the past two centuries. An inconvenient discontinuity remains. So we can't be sure whether the proxies are right. The fact that the past does not join up with the present, is in fact proof that there is something wrong. If only the top of the ice core or sediment core would agree with today, the methods would gain more credibility. So far, they don't. The graph shown here illustrates the point: scientists have abutted three different proxies to the reliable measurements of Mauna Loa, without expressing doubt about the scientific validity of it. For instance, has anyone tried to grow plants and seedlings at 180ppm? It suggests that life on Earth during the ice ages was much less than half of what we have today and very much less productive too.

Where is the CO2 in the oceans? There is a difference between CO2 from burning wood and that from fossil fuels in the amount of radioactive carbon. Weak cosmic rays are capable of changing a normal nitrogen atom into radioactive carbon. So a very small percentage of the air we breathe is radioactive. When plants incorporate this CO2 into their woody tissues, it is locked in place while its radioactivity slowly decays to zero. On the basis of this, scientists are able to measure the date of anything that has been made by life. However, in the course of millions of years, the remaining radioactivity can no longer be determined, as in fossil coal and oil. CO2 from burning coal is thus entirely non-radioactive.

With great difficulty the amount of fossil CO2 can be calculated from the total CO2 encountered:

• the amount of non-radioactive CO2 is large, and that of the radioactive part is small.
• only a very small amount of non-radioactive CO2 originated from fossil fuel.
• one cannot tell from the reduced radioactivity whether this was caused by age or by dispersion into the rest of the ocean which is also rather old, or by the amount of human-made CO2.

The question now remains whether this CO2 caused the oceans to become more acidic. But first we need to know how acidic the oceans normally are.

How much CO2 is absorbed by the oceans? We have rough estimates of how much carbon dioxide is recycled by the oceans (40-100GtC/y), but no hard data as to how much is permanently absorbed by it. The whole question about whether CO2 causes global warming or global warming causing CO2 has not been solved either. With nearly 40,000 GtC in the oceans, of which about half would escape for 10 degrees warming, means that a very small warming of 0.1 degree would still release 200 GtC to the air, or 25 years of human consumption. Global warming protagonists insist that more warming has happened than that, since the industrial revolution.

From sediment cores, scientists were able to obtain a record of past carbon dioxide levels, and these were very high for about 200 million years, with some 50 million years of low levels, and earlier still, very high indeed. So where did all that carbon come from and where did it go to?
From the blue line one can see clearly two sequestration periods, one in the Carbon/Devonian 350-400 million years ago, and this was when coal was laid down in the freshwater marshes (a vast quantity). During the dip at the end of the Cretacious (K), all oil was laid down in the middle seas while Gondwana was breaking up. Presumably all this CO2 came from volcanic activity.

It is important to remember that in order for the oceans to permanently fix CO2 (which is true also for plants on land), the level of CO2 in the air needs to be higher than it was before the industrial revolution (the hockey stick for global temperatures). Sequestration at previous CO2 levels is not possible.

To understand ancient epochs, read our Geologic Timetable.

How acidic are the oceans? As this map suggests, ocean pH measurements have been done all over the world and in the most unlikely places. The false colour scale on the right suggests a range from 7.9 to 8.2 (personally I have measured a wider range from 7.8 to 8.3). The lowest pH occurs in upwelling areas whereas highest pH occurs in the centres of ocean gyres. From this extensive mix it would be difficult to state what the 'average' pH is for the oceans, let alone whether the oceans have become more or less acidic. Note that upwelling areas are more acidic because high-CO2 bottom water surfaces, warms up and makes CO2 more readily available, a bonus for photosynthesis by marine plankton.

My own measurements (see DDA) showed that the resulting pH is a tug-of-war between photosynthesisers that scavenge hydrogen ions to such extent that some lakes in summer and rock pools can go as high as 9.0, and decomposers that decompose living and nonliving biomatter to unlikely levels of 5.0 in putrid mud. pH is relatively low in eutrophied (overnourished) seas that can only be called sick. This implies that the degrading state of our coastal seas must have been accompanied by a decrease in pH. However, none of the scientific papers I read even mentioned this.

The Bermuda Atlantic Time-series Study (BATS) There exist very few time series of ocean measurements. The longest are HOTS (Hawaii Ocean Time Series, since 1990, does not measure pH) and BATS (Bermuda Atlantic Time-series Study, since 1984). Shown here is BATS for twenty years, with total dissolved inorganic carbon (DIC, mmol/kg), TA (Total Alkalinity), CO2 concentration (ppmv) and pH. One can see that there is quite a high degree of variability, with total carbon varying by 50mmol/kg (1.4%), CO2 all over the place, varying 100ppmv (25%) and the pH by 0.12 (32% hydrogen ions). With some difficulty a slanting line can be drawn for -0.03 pH (7%H) and +20ppm CO2 (5.9%) in 20 years. In the same period Mauna Loa measured an increase from 345 to 375ppm (8.6%). Before one can say that the decline in pH was caused by carbondioxide, one needs to prove that it was not caused by other acid gases, land-based effluent and eutrophication/degradation were not the cause. This has not been attempted. Note that the time series does not show any cyclic effect from El Niño (temperature variation) or any other cycle and is therefore too short to draw any certain conclusions from. Note that the pH makes large excursions that must have been caused by life. Note also that the pH makes large excursions downward but not upward, as if it reaches a maximum. This agrees with our observations that a high pH is limiting plankton growth: as plankton blooms, it scavenges hydrogen ions (and CO2 which is practically a mirror image), which causes the pH to rise until a dearth of (lack of) hydrogen ions becomes limiting, while there is still plenty of CO2 for photosynthesis (300-320ppm)! It also shows that measuring pH without first disabling all life in the sample, does not make much sense.

Those familiar with science know that a single experiment cannot be hailed as conclusive, as it needs to be replicated by others, and also shown to be true over a representative extent of ocean. But the situation becomes worse, if one knows that an increase in hydrogen ions of pH=-0.1also makes the sea 20% more productive, leading to 20% more biomass if nutrients were sufficiently available. Such is the case in all coastal seas above continental shelves and far beyond due to rampant soil erosion.

In 2003 a paper appeared by Caldeira & Wickett which is based on computer simulations. They claim that already the oceans have acidified by 0.1 pH units. No actual measurements to back this up, and no mention of the calcium ion and carbonate buffering of sediments and no mention of eutrophication either. The 0.1pH amounts to 21% more hydrogen ions. This paper is interested in the possibility of injecting CO2 into the deep sea, a technological 'solution' to reducing emissions.

In 2005 a paper by Jacobson appeared, who calculated pH from dissociation constants, assuming that the ocean is in equilibrium with the air.  In his paper he includes dissociation constants of over 50 possible ion species in seawater, a truly complex system with enough scope for error. He claims that in 1751 ocean pH was 8.25 and now 8.14, a difference of 0.11 pH units or 22% more hydrogen ions. We wonder why the measurements in 1751 were so accurate and reliable. He goes further by claiming that when CO2 reaches 750ppm, the ocean will eventually settle at a pH=7.88, or a drop of 0.37 or an increase in hydrogen ions of nearly 60%.

Reader please note that around 1750 electricity was about to be invented by Benjamin Franklin (see our timetable of human inventions), and pH could be determined only by the method of titration (litmus test?), and it is not possible to get more accurate than 0.2pH unit with this, regardless of the amount of sampling and averaging. Even today it is difficult to guarantee this kind of absolute exactness, considering the state of pH sensors and calibration buffers. In addition, the pH of the sea changes night to day, from day to day and winter to summer and from place to place. In fact, after our discoveries (DDA), natural alkalinity of the water can be established only after first disabling all life in the sample, and this has never before been considered. For Jacobson to claim an average ocean pH of 8.25 in 1751 is rather naive. His paper builds further on this by extrapolating:
 

Did he verify this with tests? No. The interacting chemistry of seawater is just too complicated to fully understand and even the carbonate part of it is not fully understood.
Although time series are still too short, other stations report increases of 0.4 to 2.2 µmol/y, equating to a decrease in pH of around 0.0012 per year. Note that because pH is a logarithmic scale, this annual decrease cannot be extended far into the future by multiplying it with the number of years.

The Bjerrum plot of the carbonate system Much ado is being made of the Bjerrum Plot, named after N Bjerrum (1914) who invented the diagram for visually representing the equilibrium between the three carbonate species CO2, HCO3 and CO3. With very precise equations, corrected for temperature, this system is well defined for the ideal situation (distilled water). What the plot says, is that for instance at a pH of 8.1 for the ocean, the three carbonate species are given by the intersection of the dashed vertical with each of the curves, giving 0.02, 2.05 and 0.12 mmol/kg for each (note that the drawing above is not accurate). By making the sample more acidic, hydrogen ions out-compete the hydroxyl ions, which results in more CO2 in solution, less CO3 and an inconsequential change in HCO3 (the FAT arrows). No problems here, but scientists now claim that an increase in CO2 is the same, and this cannot be true as an increase in CO2 simply lifts all three curves a little higher.

Le Chatelier's Principle: Adding CO2 to a CO2/carbonate equilibrium will drive the reaction towards the formation of MORE carbonates, not less.

But there is more wrong:

• the plot doesn't explain the difference in pH between rain water and sea water. Neither does it explain the wide range in the pH of lakes.
• the plot does not take account of other mineral ions, of which calcium is the most important. These ions compete for hydrogen or hydroxyl ions and even for ions of the carbonate system.
• the plot does not include stabilising carbonate deposits.
• the plot has never been proved experimentally for the complex sea water system.
• what the Bjerrum plot DOES show is that if the sea becomes acidic for other reasons than CO2 (acid rain, runoff, eutrophication, warming), CO2 levels WILL increase even if atmospheric CO2 does not increase.

So why is acidification considered a problem? This brings us to some questionable science that was looking for an excuse (Victoria Fabry in James C Orr et al. 2005). By examining certain shell forming plankton species like pteropods (wing-foots, pelagic snails that swim with their foot), it was found that some had minor damage to their shells. Apart from being inconclusive, these results were then hailed as proof that higher acidity in the sea would dissolve shells faster and that eventually the snails would not be able to make their shells fast enough, and that this would lead to extensive ecosystem changes and extinction of species. Also coral reefs would dissolve and weaken and combined with global warming, disappear from the face of the ocean. Oops. Correct me from being wrong, but there is something very fishy here. It is known that CO2 dissolved in rain water, makes it more acidic (pH=5.5-6), thus capable of dissolving limestone at a very slow rate, which takes a dripstone stalagmite thousands of years to grow a few kg.  CO2 + CaCO3 + H2O => 2(HCO3)- + 2Ca2+ (note the one way reaction => because water is transported away) So it is thought that more CO2 in ocean water would do the same. Apart from the fact that a pH=6 has 100 times more hydrogen ions than a pH=8, and does not seem to worry freshwater snails in lakes, sea water is almost saturated with calcium (Ca).

Remember the CO2 equilibrium equations that end in carbonate CO3^2- of 0.12 mmol/kg compared to that of Ca²⁺ of 10.4 mmol/kg? This means that there is not enough carbonate in the water to combine with the free calcium, and any increase in CO2 would mean that laying down a limestone skeleton becomes easier rather than more difficult. An increase in carbonate leads to calcification of CaCO3, just the opposite of what is being claimed! In other words, the vast store of calcium in the oceans has a buffering effect. Notice in this respect also the way salts precipitate when making table salt from sea water (/oceano/seawater.htm), with CaCO3 the first to settle out, followed by gypsum CaSO4.

Sarma et al. (1971) reported an increase in alkalinity of about 11 µmol/kg when DIC (CO2 species) increased by about 20µmol/kg, which should create some inconvenient doubt.

There is a vast discussion going on and many experiments focusing on 'aragonite saturation', meaning that normal sea water should be in balance with the limestone in sea shells, oversaturated even. However, in practice all sea shells dissolve back into sea water, which means that the concept of aragonite saturation and calcite saturation may live only in our minds. Here is what's behind this idea:
 
 

On the surface of the ocean all dissolved gases are in balance with those in air. But in the water, with the help of sunlight, plants produce oxygen while consuming CO2. So oxygen concentrations are higher and carbon dioxide concentrations lower than in air. As one goes deeper, the beneficial effect of photosynthesis decreases, and CO2 increases due to breathing and decomposition. In theory at least, the water becomes more acidic with depth, to the point that the thin skeletons of plankton critters (coccolithophores, pteropods, foraminifers, etc) could begin to dissolve. This is called the aragonite saturation horizon (0.5-2.5km). Below it, the shells dissolve, whereas above it, they supposedly don't. As we have shown above, this is a dubious concept (Sarma et al, 1971). There is likewise also a calcite saturation horizon (1.5-5km). The concept explains why clay deposits without limestone occur deeper than those with limestone as carbonate ooze. The diagram shows actually measured values for the carbonate ion CO32-  versus depth (red line). Below 2km the concentration is rather static although it decreases further with pressure. Where it crosses the (hypothetical) aragonite saturation horizon, sea shells will be dissolved gradually, and below where it crosses the calcite horizon, calcite will dissolve as well. It is thought that increased CO2, and thus acidity is the cause of this. Sadly actual pH is missing from this graph (why was it not measured?).

These hypothetical horizons are very dependent on temperature and pressure: the higher the pressure, the more readily calcite dissolves. Lower temperatures also increase the solubility of the water, and temperature decreases with depth. Hence it is not clear whether acidity or pressure or temperature are the main drivers. For this reasons the cold oceans like the Southern ocean are most likely to become under-saturated, one of the main scares.

What must also be remembered that the act of dissolving CaCO3 (limestone) into seawater also increases the pH. Thus the huge amount of ocean sediment will neutralise any acidification. It is estimated that ocean sediments amount to 30,000,000Gt carbon, a massive reservoir. But since most of it is in the deepest parts of the oceans, it may take a millennium to become effective.
 
 

0708135: a smooth tiger shell (Maurea tigris) has almost completely dissolved back into seawater, showing its spire made from  more dissolution-resistant nacre. It took just over a year from live animal to this stage.

f012810: after about 6 months the fragile shell of a paper nautilus becomes too brittle to handle. In 12 months it has dissolved completely in clear seawater. Aluminium cans dissolve in 5-10 years!

Our own discoveries (DDA) show that the sea does not at all work as expected, and that marine plants (and corals) depend more or less on symbiotic decomposition. We have shown that a lowering of the pH is beneficial to overall productivity and biomass.

As far as measuring the effect of raised CO2 levels on marine animals, the situation is complicated because CO2 rapidly becomes toxic, with symptoms of depression of physiological functions, depressed metabolic rate + activity + growth, followed by a collapse in circulation. Remember that free CO2 amounts to only 1% of the total CO2 'bonded' to the water and that it takes some time for equilibrium with the other CO2 species to happen. It is thus too easy to overdose the free CO2 by increasing the CO2 in the air above. In other words, it is nearly impossible to mimic the natural situation truthfully in an experiment.

In the BBC report (http://news.bbc.co.uk/2/hi/science/nature/7437862.stm), the following quote appears: "I can't count the number of times that scientific talks end with 'responses have not yet been documented in the field'," said Elliott Norse, president of the Marine Conservation Biology Institute (MCBI), "This paper puts that to rest for several ecologically important marine groups."
"The reason that the oceans are becoming more acidic is because of the CO2 emissions that we are producing from burning fossil fuels," observed Dr Turley, "Add CO2 to seawater and you get carbonic acid; it's simple chemistry, and therefore certain. This means that the only way of reducing the future impact of ocean acidification is the urgent, substantial reduction in CO2 emissions."  - Oops, what about the sea's buffering capacity?

However, we have some reservations about this work, since science is not only about measuring a correlation between supposed effect and cause, but also about proving that the correlation is not caused by anything else, which is what these scientists omitted. The CO2 vents were found towards the main coast and the coastal gradient extended outward from this coast (co-inciding with an increase in pH). Along such a gradient one also finds a change in water clarity, sediment deposition, shelter from waves (exposure), and human influences like sewage and run-off. It was telling that the measurements done at the northern side of the islet were not reported. Loss of biodiversity accompanied with a loss of coralline algae, urchins, limpets and others, can also be observed anywhere in the world in a gradient from an estuary to an outlying promontory, which is essentially the situation at the location of study. However, the fact that most changes happened within 25 metres, suggests that they were indeed caused by CO2.
More important, down to a pH of 7.6 (4x more acidic), no measurable effect was found and minor loss of biodiversity. Thus a doubling (pH=7.9) or quadrupling (pH=7.6) of CO2 concentrations in the atmosphere is not going to have any measurable effect on marine life. This was not mentioned in the article. In fact, the conclusion above is somewhat at odds with it.

Our main criticism with the study concerns the fact that water with a pH of 6.0 contains over 100 times the natural amount of CO2, and this is poisonous enough to kill almost all water-breathing organisms. The fact that animals went from perfectly healthy to completely dead within 25 metres, means that the study can in no way be assumed to have any relationship to the real-world situation. Researchers claimed to have calculated 'tipping points' for various organisms, but in this case one cannot meaningfully calculate 'average' CO2 concentrations. To understand this, study the results in the box below.
 
 

The graph shows the essence of the study. From left to right the transect distance along the rocky shore, moving landward towards the field of CO2 bubblers on right. In this field the pH varies considerably between 6.0 and 7.5 (30-fold). Note that the gas was nearly pure CO2, capable of acidifying the water locally 1000-fold to a pH of 5. However, mixing through turbulence, currents and waves soon dilutes the acid, even though an area of over 50m remains consistently highly acidic. Within a distance of a mere 25m, average acidity changes from 6.5 to 7.7, accompanied by a critical change in the environment, affecting in particular grazing sea urchins, snails and limpets. In their absence while fed by higher CO2 levels, non-calcareous (edible) algae multiply. The early decline of calcareous algae may not be entirely due to CO2 but also to competition with the edible algae and normal coastal degradation. The problem with this study is that it does not reflect a real-world situation where CO2 levels rise slowly, evenly spread over all oceans. This study looks more like a local CO2 Chernobyl with fatal fall-out wafting unpredictably here and there, such that it becomes meaningless to talk of average pH. Note that humans die at a 50-fold increase in CO2, and the situation here comes pretty close to this, if not far worse. For instance, what is the average between 1 and 100? Is it 50? 10? 90? It depends on what the numbers mean (weighted). If the numbers mean food, then the average lies close to one, because hunger kills. If the numbers mean threat, then the average lies close to 100, because threats kill.  It is also important to note that nature is affected more by bad times than by good times, because during bad times, one is more likely to die. Thus a killer cloud of pH 6.2 wafting over, can be quite decisive, even though it may happen sporadically, not affecting the average. Particularly affected are the young (recruits) of all species. But the long-lived creatures are disadvantaged more than the short-lived ones. It so happens that many of the long-lived ones live in limestone houses.  See also our chapter on the principles of degradation.

[1] http://www.nature.com/nature/journal/vaop/ncurrent/full/nature07051.html Volcanic carbon dioxide vents show ecosystem effects of ocean acidification by Jason M. Hall-Spencer, Riccardo Rodolfo-Metalpa, Sophie Martin, Emma Ransome1, Maoz Fine, Suzanne M. Turner, Sonia J. Rowley, Dario Tedesco & Maria-Cristina Buia. Unfortunatelly this publication is not free and sets you back by US$32.

• a doubling of particulate organic carbon, a doubling of size and calcite shell
• slightly slower growth rates but photosynthetic health unaffected
• near-constant C:N ratio (6.8-8.3), an indication of food value for grazers
• the deep cores showed an increase in coccolith mass of about 40% in the past 220 years, which roughly agrees with experiments. The curve has a hockey-stick appearance, climbing more steeply in the past 25 years (~25%).

The graph shown here illustrates how coccolith mass was derived from deep sea core RAPID 21-12-B, dating back to before 1800. Also shown is the IPCC curve for CO2 concentrations in the atmosphere. The past 25 years of coccolith growth suggests that it follows the rapid increase in CO2 concentration in air. For a 20% increase in CO2, size increased about 30%. In laboratory experiments, however, coccolith size and calcification increased mainly betwen 400 and 600 ppm CO2, which has not happened in the sea yet. Could temperature be a driving factor?

[1] Phytoplankton Calcification in a High-CO2 World: M. Debora Iglesias-Rodriguez, Paul R. Halloran, Rosalind E. M. Rickaby, Ian R. Hall, Elena Colmenero-Hidalgo, John R. Gittins, Darryl R. H. Green, Toby Tyrrell, Samantha J. Gibbs, Peter von Dassow, Eric Rehm, E. Virginia Armbrust, Karin P. Boessenkool. Science 230, 336-340, 18 Apr 2008. Available for US$10 from Sciencemag.com, but freely downloadable from http://www.sb-roscoff.fr/Phyto/index.php?option=com_docman&task=doc_details&gid=418&Itemid=112

Owing to anthropogenic emissions, atmospheric concentrations of carbon dioxide could almost double between 2006 and 2100 according to business-as-usual carbon dioxide emission scenarios. Because the ocean absorbs carbon dioxide from the atmosphere, increasing atmospheric carbon dioxide concentrations will lead to increasing dissolved inorganic carbon and carbon dioxide in surface ocean waters, and hence acidification and lower carbonate saturation states. As a consequence, it has been suggested that marine calcifying organisms, for example corals, coralline algae, molluscs and foraminifera, will have difficulties producing their skeletons and shells at current rates, with potentially severe implications for marine ecosystems, including coral reefs. Here we report a seven-week experiment exploring the effects of ocean acidification on crustose coralline algae, a cosmopolitan group of calcifying algae that is ecologically important in most shallow-water habitats Six outdoor mesocosms were continuously supplied with sea water from the adjacent reef and manipulated to simulate conditions of either ambient or elevated seawater carbon dioxide concentrations. The recruitment rate and growth of crustose coralline algae were severely inhibited in the elevated carbon dioxide mesocosms. Our findings suggest that ocean acidification due to human activities could cause significant change to benthic community structure in shallow-warm-water carbonate ecosystems.

...Although previous work examined the effects of calcium carbonate saturation state on calcification rates of corals and coral communities in realistic mesocosm studies, none has examined how community structure may change under increasing degree of ocean acidification. ....
... Under high conditions, CCA recruitment rate and percentage cover decreased by 78% and 92%, respectively, whereas non-calcifying algae increased by 52% (Fig. 2) relative to controls. ....
... we did not attempt to replicate the natural compliment of herbivores found on Hawaiian reef flats, and thus only microherbivores (for example sea hares and amphipods) were in abundance. ...
... Under all proposed scenarios, continuous anthropogenic emissions of CO2 to the atmosphere will result in a continuous decline in the pH and calcium carbonate saturation state of ocean waters, with all the ecological implications of such a change in a major Earth-surface-system carbon reservoir. The only way to slow or prevent the continuing acidification of surface ocean waters is to reduce the emissions of CO2 from human activities to the atmosphere; however, because of the slow mixing rate of the oceans, they will continue to be a major sink of anthropogenic CO2 emissions well into the future, and ocean acidification will continue to intensify. ... [sigh]

These scientists placed two times three plastic cages (mesocosms) of 1x1x0.5m under water at shallow depth. The advantage of this method is that the study mimics as closely as possible the natural situation, including day-night light rhythm. In one set of three they manipulated acidity to reflect a doubling of CO2 to 800ppm. Then they placed perspex cylinders in each to see what would happen. In the control set they were encrusted by coralline algae (CCA), whereas in the CO2-rich set they were encrusted by fleshy green algae. The differences between the two sets were quite dramatic as shown by the photograph and graphic. The conclusion is that man-made CO2 is bad, and that major ecosystem changes can be expected. A final blow to the acid ocean skeptics. End of debate. Period. ... Unless we examine the fine print and do some detective work.

Crustose calcareous algae or pink paint as divers call it, is a group of the most astounding organisms on our planet. If you were told about stones that grew and replicated, you would disbelieve. Yet it is true. CCA is living limestone, physically a red seaweed but without any flesh or vessels. It grows in the shallows, exposed to ultraviolet and low tide, yet forming extensive rocky platforms with caves and tunnels in a mere 6000 years. On coral reefs it is the glue between corals, forever scraped and nibbled at by urchins and fish, yet surviving and growing. When algae peter out at the end of the photic zone, there is still CCA and at twice that depth too. A boulder in a rock pool may be turned by a storm, leaving its CCA cover buried in darkness. Yet turned back upright after two months, the bleached CCA soon turns pink again, resuming business as usual. When going from healthy waters to extremely degraded environments, CCA is one of the last to give up. So come-on, why can this sturdy creature not handle a little extra CO2? What is wrong we must ask? We have some serious misgivings about this work for a variety of reasons.

• Whenever a scientific article begins with 'anthropogenic emissions' and 'IPCC', it raises the hairs on my back because these people show to have a bias. Real science is about curiosity in about how things work; not about 'proving' an idea. The experiment took only seven (!) weeks (a student's summer holiday), immediately after which the results were published - and accepted! The experiment was not replicated; the cylinders were not swapped; mature CCA was not investigated and so on. Instead these people focused on replicating their publication: dial any of the authors (Kuffner or Jokiel will do) on Google and see how many references and duplications come up. Other publications were quick to refer to this shoddy work which is on a par with school science.
• For instance, it is equally interesting to see what halving CO2 levels does, because the claim of 250ppm pre-industrial level may be a myth. Why did the scientists not include a set of enclosures for testing this? Note that this is a general criticism of ALL studies of the effect of raised CO2. Just show me one that does.
• The raised level of CO2 was not achieved by adding CO2 to the water but a highly concentrated solution of hydrochloric acid (HCl) that was trickled into the treatment enclosures. This releases CO2 from the HCO3 species as discussed in the Bjerrum Plot above, but this is not like the real world as it also diminishes the shell-building CO3 ion. It also assumes various densities before diluting completely. And even if this happens in the water above the cylinders, it will still influence the plankton and spores and their settlement.
• The experiment was not about death or slow growth but about settlement. Algae have a two-phase birth: the mature plant makes asexual spores that hatch into male and female plants, too small to see, but these reproduce sexually, and their 'seeds' grow into the colonies observed on the perspex cores, after first some time in the plankton. Thus settlement is about the minute or hour that a 'seed' decides to attach or not; a flash in a CCA's life. And that is all this experiment was about.
• Settlement is an extremely fickle (not constant, uncertain) process. Put your plastic cores out, together with concrete tiles, and you will see different creatures settle on each type. Put them out today and it may be CCA that dominate. Next week could give barnacles. Next month green algae and limpets, and so on. Settlement experiments are almost impossible to replicate. Which means that they also have little relevance. In the bar chart above, you can see some of that unpredictability.
• Let me take you to the laboratory where these experiments were done, at Kaneohe, Hawaii (photo below). The water here is not blue as one would expect, but green. It is indicative of degradation from eutrophication. Now look at the pH curves in the graph next to it. The green curve shows the daily pH rhythm for the environment there. For starters, average pH is well below 8.2, a sure sign of degradation. The water here is already 50% more acidic than average ocean water. Now look at how pH changes from mid day to mid night -0.3 units or 2x more acidic, another sure sign of degradation. This is caused mainly by decomposing planktonic bacteria, who never sleep. The bacterial activity follows from the down slope of the curve in darkness, amounting to an RoA (bacterial Rate of Attack) of 20-40 hion (see our DDA method), an indication that the environment here is under significant stress. The point here is that all stresses add up, such that the extra stress caused by high CO2, is only part of the whole and cannot be singled out (see our principles of degradation chapter).

Summarising it all: a naive study in a highly stressed already acidic environment, using hydrochloric acid, not replicated and perhaps not reproducible, with the low relevance of a settlement experiment. Their far-reaching conclusions are not warranted by the experiment.

[1]  Ocean acidification impacts on coral reefs: changes in community structure, Ilsa Kuffner, Andreas Andersson, Paul Jokiel, Ku’ulei Rodgers & Fred Mackenzie  http://www.whoi.edu/cms/files/Kuffner_OA_Scripps_34825.pdf [free] a slide show with more information about the work done.