| Ocean acidification has become a major scare in the scientific literature and the media. This chapter shows what is known about carbon dioxide in the oceans in order to understand how ocean acidification works and what effects it could cause. |
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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:
| Does the tail wag the
dog?
Present-day thinking goes as follows: human-made CO2 is extra to the normal carbon cycle. It therefore accumulates in the atmosphere, which makes the sea more acidic. Thus human CO2 => atmosphere => ocean => oceans more acidic => oceans store C But the ocean is vast and CO2 has an uncanny affinity with water. Thus oceans stabilise the CO2 fluctuations from the seasons and the differences between ocean and land. The oceans contain far more CO2 than air 38,000Gt versus 700 Gt. A slight warming of the ocean expels CO2 while becoming more acidic. Thus ocean warming => acidic water => releases CO2 to air => higher CO2 levels in air. Only very little warming is required. From the latter follows:
ice
ages => cool seas => absorb more CO2 => low CO2 in air => poor world =>
loses stored carbon
Which of the two scenarios is most likely? |
"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".
![]() 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. |
| Is the 83 year shift
scientifically acceptable?
In the Siple Dome ice core the age of each point in the core was accurately known from the core's 'year rings'. At the top of the core, snow is gradually being compressed until it becomes ice. During all that time, the air in the core is thought to stay in contact with the air above, which causes CO2 to escape. But why would CO2 escape from a lower concentration to a higher one? If there still exists an air path to the open air, should CO2 not escape from the air to a lower concentration, thereby lifting the resulting curve upward? Clearly there remain too many unanswered questions about whether the measured CO2 in trapped air bubbles indeed represents the CO2 concentrations of the past. |
CO2 glaciology depends on the following unproved assumptions:
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. |
With great difficulty the amount of fossil CO2 can be calculated from the total CO2 encountered:
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.
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.
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.
Reader please note that these are the ONLY experimental smoking guns for ocean acidification!
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:
| Year | 1751 | 2000 | 2100? |
| CO2 ppmv | 275 | 375 (1.36x) | 750 (2.73x) |
| pH of ocean | 8.24691 | 8.13647 (1.29x H+) | 7.87615 (2.35x H+) |
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.
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:
| Fraudulent CO2 science,
scientific CO2 fraud
Doing experiments in the ocean that truly reflect the real-world situation is difficult if not impossible. So scientists take shortcuts, essentially in two ways:
|
Remember the CO2 equilibrium equations that end in carbonate CO32- 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.
| An ilustration of the
problem in understanding ocean chemistry with models
The Royal Society UK (2005) report gives a good example of reasoning gone wrong: "Marine organisms that construct CaCO3 structures, such as shells, are dependent on the presence of bicarbonate and carbonate forms of dissolved inorganic carbon. Once formed, CaCO3 will dissolve back into the water unless the surrounding seawater contains sufficiently high concentrations of carbonate ions (CO32-). . . .The formation of CaCO3 leads to an increased CO2 concentration in the water. This apparently counterintuitive behaviour arises because two ions of bicarbonate (HCO3-) react with one ion of doubly charged (Ca2+) to form one molecule of CaCO3, which leads to the release of one molecule of CO2. . . . Under current conditions, for each molecule of CO2 produced during calcification, about 0.6 molecules are released . . . A decrease in calcification resulting from increased acidity would . . decease the total emission [of CO2] from the oceans . . (Zondervan et al. 2001)" "To make these calcareous structures, seawater has to be supersaturated with calcium and carbonate ions to ensure that once formed, the CaCO3 does not dissolve." "For example if the deep oceans start to become more acidic, some carbonate will be dissolved from sediments. This process tends to buffer the chemistry of the seawater so that pH changes are lessened." The report adds: "Essentially this is an area of great uncertainty. This example is provided, in part to highlight the complexity of the interactions between the chemical and biological processes in the oceans." Reader, figure it out: The more carbon dioxide is absorbed by the oceans, the more it produces ??? The three equilibrium equations: an increase in CO2 on left decreases CO3 on right??? What's wrong with experimenting? Water needs to be saturated with CaCO3 in order to make shells? |
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| How much carbonate in
sediments interacts with the sea water?
I haven't found a useful figure for this, apart from 30 million Gt in marine sediments. But what we know is that the surface of the ocean is about 360 million km2 (360E12 m2). Thus the sea bottom is similar in size. If only 20cm of the sea soil is perturbed (dug over) by benthic organisms, this would amount to 0.2m3 per m2. If only one fifth of this is limestone, then a cautious estimate would yield 0.01 tC/m2 and the whole active ocean floor 3.6E12 tC or about 4000 GtC. The coastal regions, estimated at 10% of the ocean surface, would have at least 400 GtC in active contact with the sea water. In all, this is a formidable factor to consider, particularly for the CO3 ion. |
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 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. |
| Will the environment
adapt?
As far as organisms are capable of learning to avoid a killer cloud by migrating away, closing up, burrowing and so, they are capable of adapting somewhat. But adaptation by natural selection of the fittest is not possible because the vents are not isolated like an island where the offspring are born near their surviving parents. In the sea where everything is connected, and larvae drift vast distances, the young of others are born near the vents whereas the offspring of the survivors is born far away in normal conditions. Survivor genes disappear or are diluted. |
[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.
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.


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.
.