Study: CO2 causes Starfish to Dissolve

Guest essay by Eric Worrall

Dr. Heidi Burdett has published a study which claims intense CO2 shocks cause starfish and coraline algae to dissolve. The study has implications for siting carbon capture and storage facilities.

Carbon dioxide ‘pulses’ threaten Scotland’s coralline algal reefs

Scotland’s marine ecosystems may be more sensitive to carbon dioxide than previously thought, and could be damaged irreparably by the CO2 ‘pulses’ created by industrial activities, land run off or natural tidal processes.

Dr Heidi Burdett, a research fellow at Heriot-Watt University’s Lyell Centre for Earth and Marine Science and Technology, said: “Coralline algal ecosystems can be found in all the world’s coastal oceans and are particularly common along the west coast of Scotland. Since coralline algae are highly calcified, we knew they would probably be quite sensitive to CO2.

“These beds have significant ecological and economical value: in Scotland, they act as nurseries for important catches like scallops, cod and pollock.

“We found that there was a rapid, community-level shift to net dissolution, meaning that within that community, the skeletons of calcifying organisms like star fish and coralline algae were dissolving.

“If you think of pulses of carbon dioxide being carried on the tide to a particular site, it’s like a flash flood of CO2.

“Our continued monitoring of the site directly after the CO2 exposure found recovery was comparably slow, which raises concern about the ability of these systems to ‘bounce back’ after repeated acute CO2 events.”

“If a local authority or government agency is deciding the location of a new fish farm, forestry or carbon capture site, we should be looking at what marine ecosystems are nearby, and the potential for those ecosystems to be impacted by the new activities as a whole, rather than focusing on the impact on individual organisms.

Read more:

The abstract of the study;

Community-level sensitivity of a calcifying ecosystem to acute in situ CO2 enrichment

Heidi L. Burdett, Gabriela Perna, Lucy McKay, Gemma Broomhead, Nicholas A. Kamenos

ABSTRACT: The rate of change in ocean carbonate chemistry is a vital determinant in the magnitude of effects observed. Benthic marine ecosystems are facing an increasing risk of acute CO2 exposure that may be natural or anthropogenically derived (e.g. engineering and industrial activities). However, our understanding of how acute CO2 events impact marine life is restricted to individual organisms, with little understanding for how this manifests at the community level. Here, we investigated in situ the effect of acute CO2 enrichment on the coralline algal ecosystem—a globally ubiquitous, ecologically and economically important habitat, but one which is likely to be sensitive to CO2 enrichment due to its highly calcified reef-like structures engineered by coralline algae. Most notably, we observed a rapid community-level shift to favour net dissolution rather than net calcification. Smaller changes from net respiration to net photosynthesis were also observed. There was no effect on the net flux of DMS/DMSP (algal secondary metabolites), nor on the nutrients nitrate and phosphate. Following return to ambient CO2 levels, only a partial recovery was seen within the monitoring timeframe. This study highlights the sensitivity of biogenic carbonate marine communities to acute CO2 enrichment and raises concerns over the capacity for the system to ‘bounce back’ if subjected to repeated acute high-CO2 events.

Read more (Paywalled):

Sadly the study is paywalled, so we don’t get to learn how CO2 enriched the test water was. If Heidi was attempting to simulate an industrial release or maybe a volcanic eruption, the answer is likely “quite a lot”.

There are studies which suggest many calciferous organisms are highly resistant to elevated CO2. Some calciferous species have demonstrated the ability to control the acidity of their immediate environment, regardless of external influences – particularly corals which live in highly variable coastal environments.

It is interesting Heidi mentioned carbon capture sites as a possible risk to coastal ecosystems.

I’m not a fan of carbon capture. An abrupt volcanic CO2 release from Lake Nyos in 1986 killed people up to sixteen miles from the source of the release. Thankfully Lake Nyos was a sparsely inhabited region.

The amount of CO2 released in the Lake Nyos disaster was comparable to the amount of CO2 produced by a medium size coal plant in a month. There are thousands of medium size coal plants in the world, and some very big coal plants. Concentrating CO2 on a large scale is dangerous – the scale of CO2 concentration required for a serious global carbon capture effort would in my opinion ensure someone, somewhere would cut one corner too many. A Lake Nyos scale release near a major city could kill millions of people.

74 thoughts on “Study: CO2 causes Starfish to Dissolve

    • Bingo. The first three sentences don’t even belong in an abstract, they belong in a grant proposal. Then they continue to waste valuable abstract space and can’t even hint at any methodology.
      They do hint at results, however, but they are very confusing — “Most notably, we observed a rapid community-level shift to favour net dissolution rather than net calcification.” They observed community level shift to favour net dissolution rather than net calcification. Observed favouring net dissolution? Did they ask the red algae what was favored or did they actually observe the dissolution of living organisms?
      Strange, that an algae class that is often important in bioerosion of reefs using acids to bore into other calcifiers is sensitive to acute natural CO2 changes. Given that marine calcifiers utilize biomineralization and have several different processes of protecting their shells from pH changes, the calcite sediment without anything to protect it must have vanished into solution before their very eyes /s.

  1. I liked the part best where they said that the ecosystem “could be damaged irreparably by the CO2 ‘pulses’ created by … natural tidal processes.”
    Right. The ecosystem could be damaged irreparably by natural tidal processes … do these folks not have Editors? Never mind, I don’t want to know …

  2. The world-view that sees man and his activities as entirely unnatural is amusing, to say the least.
    I wonder how long an ecological ‘green’ beaver would last.

    • Leo,
      On a related theme, you may be amused to hear the old nickname of Herriot-Watt University is “Hairy Tw*t*. Quite a coincidence it seems.
      Yes, Willis, Eric and co, I agree that we shouldn’t drag this site into the gutter with such comments. In my defence, however, this paper belongs in the gutter. I’d have liked to see some real life examples of how anthropogenic CO2 had caused such devastating effects. I suspect, however, that they don’t exist and never will.

    • from reading the paper they bubbled co2 into the water and measured caco3 precipitation over a day or two to determine that the organisms were losing shell.
      this seems flawed to me because they did not appear to run a control to see if adding co2 would causes caco3 to precipitate without any. marine organisms present.
      additionally the experiment only ran for 80 hours total. this is hardly sufficient to judge how the organisms will adapt to environmental changes. many organisms adapt via changes to the next. generation which means testing over months and years.

      • What they did was jack the pH around for four days….add CO2 to lower pH, and do it fast enough the buffers can’t keep up…..everytime they stopped, the pH would bounce right back to normal almost immediately

      • Oh my, it’s worse than we thought:

        Net calcification/dissolution (carbonate chemistry)
        Samples for AT and CT were stored in borosilicate
        glass vials (Labco) and poisoned with mercuric chloride,
        following Dickson et al. (2007). AT was measured
        on a Metrohm 848 Titrino Plus using the 2-stage
        open-cell potentiometric titration method on 10 ml
        sample volumes with 0.01 M HCl (Dickson et al.
        2007). All AT samples were analysed at 25 ± 0.1°C
        with temperature regulation using a water bath
        (Julabo 19). CT was determined by infra-red detection
        of CO2 from acidified samples on a dissolved
        Mar Ecol Prog Ser 587: 73–80, 2018
        inorganic carbon analyser (Marianda Airica). Additional
        carbonate chemistry parameters (pHNBS, pCO2,
        −], [CO3
        2−], aragonite saturation state [ΩArg])
        were calculated from AT and CT using CO2SYS (Pierrot
        et al. 2006) with dissociation constants from
        Mehr bach et al. (1973) refit by Dickson & Millero
        (1987) and [KSO4] using Dickson (1990). In situ water
        temperature (°C), salinity and pH were measured
        hourly throughout the experimental period using an
        Exo2 multiparameter sonde (YSI). Nitrate and phosphate
        concentrations were calculated throughout the
        experimental period (see below) and included in carbonate
        chemistry calculations. Net community calcification
        rates were calculated
        using the alkalinity
        anomaly technique (Chisholm & Gattuso 1991) based
        on the change in seawater AT during the incubation
        period. For each mole of CaCO3 precipitated (i.e. calcification),
        AT is lowered by 2 molar equivalents.
        Therefore, the change in alkalinity can be converted
        to the mass of CaCO3 precipitated. Certified sea –
        water reference materials for oceanic CO2 (Scripps
        Institution of Oceanography, University of California,
        San Diego) were used as AT and CT standards, following
        Dickson et al. (2007).

        In summary, they took water samples during the “experiment” and performed some simple carbonate chemistry analyses on them, and they discovered that lowering the pH of water will reduce precipitation rates of inorganic CaCO3 precipitation. Then in true climastrology fashion, they pretended that this reduced CaCO3 saturation states translates into reduced organic CaCO3 biomineralization.
        100% pure unadulterated junk science.

  3. I saw this nonsense on BBC this morning and almost cracked up! I was minded to lodge yet another complaint about their single-minded pursuit of alarmist drivel but I’ve found from repeated attempts that it’s a waste of time and effort!
    On another note, though, ion the spirit of technical accuracy, it’s worth pointing out that the deaths caused by the Lake Nyos event involved not just CO2 but also H2S, another gas associated with volcanic activity and an altogether more dangerous material than CO2. The deaths would probably have still occurred by asphyxiation as the gases poured from the crater lake but H2S (which has a toxicity akin to hydrogen cyanide) certainly contributed to the horrendous outcome. Anyway, just a comment….

    • Hello Phil.
      Your comment about H2S at Lake Nyos is of interest. Can you provide any more information or references?
      H2S is heavier than air and is instantly lethal to humans in concentrations of 0.1% or even less.
      Thank you, Allan

    • Not only that, Phil, but the statement that a CO2 spill near a major city could result in millions of deaths is highly exaggerated. Lake Nyos is a crater lake in a volcano. It is very deep & highly stratified. There was a de-stratification event, in which the lake waters burped out huge quantities of gas. This occurred in the dead of night, & the gases flowed down the mountain, like water pouring out of a jug, killing people as they slept. This could only have happened on a still night, which kept the gases from being diluted by turbulence. The fact it happened in rural Africa, where people probably sleep closer to the ground than we westerners do, would have increased the death toll. See the article on WUWT about the Gates of Hell in Turkey.

  4. “only a partial recovery was seen within the monitoring timeframe”
    Aye, we watches the poor wee thingies all day, but they had’ne recovered much at all when we had to go in for our tea.

    • It was also only a four day experiment, with the abstract not specifying how long each phase lasted.
      A classic ruse in many fields is to either cut the experiment short in order to avoid reporting unwanted data, or extending it almost without limit until some ‘random’ event produces the data you want.
      They also note a change from “net respiration to net photosynthesis” during the experiment, but consider this to only be a minor change!

      • Like the experiment that Griff pointed out last year that determined elevated CO2 levels were actually bad for tapioca plants? That’s true, if you put them in a container nowhere big enough to grow a tapioca plant, they reach the stage of determining that the sight that they are growing is unsuitable faster.

  5. It seems ‘climate scientists’ are back to their previous similar level of dumping creatures in concentrated acid and going OMG CO2 will kill them all.
    If carbon capture ever does go wrong, it’ll probably be 1000’s of people that get suffocated, never mind the starfish.

  6. Give me a few squirts of CO2 over a prolonged period and I will probably “cark it” also.
    Same applies for nitrogen, argon and any other gas or vapour you may wish to conjure up.

  7. 4 x 28L benthic chambers imbedded @ 6m. Seawater circulated @ 120 l/h via the surface where it was enriched with CO2. 3 phases 15h ambient. 28h enrichment. 37h post enrichment. Sampled at intervals + continuous measurement. Seems good enough but no control chamber as a baseline.

      • Worse, they did the inorganic chemistry calculations and then applied that to the living organisms as if they were literally dissolving and had actually observed this, but there is no indication that they literally observed any dissolution of any organism but plenty of weasel words to make it sound like they did.

        At the level of CO2 enrichment
        used in this study, the skeleton and epithelial cell
        surface of Lithothamnion glaciale is compromised
        (Burdett et al. 2012, Kamenos et al. 2013), allowing
        for skeletal dissolution (Langdon et al. 2000) — supporting
        the observed shift towards net community
        dissolution. This may have also been facilitated by
        dissolution of carbonate sediment and dead sections
        of coralline algae, which cannot exert biological
        control and buffering against changes in carbonate
        chemistry (Kamenos et al. 2013). Like other reefbased
        marine ecosystems, this coralline algal community
        is highly diverse across multiple trophic levels
        (BIOMAERL Team 1999, Barbera et al. 2003,
        Kamenos 2004). Calcifying invertebrates are especially
        abundant (e.g. Ophiocomina nigra, which can
        make up 47% of total faunal biomass;
        BIOMAERL Team 1999), and CO2
        enrichment is known to lead to a
        reduction in calcification rate/ increase
        in dissolution rate of these organisms
        (Kroeker et al. 2010). Thus, these
        organisms are likely to have also contributed
        to the observed shift towards
        net dissolution

        I don’t have the time to follow the junk science trail –especially when they are citing themselves– but citing other studies and then assuming those results apply to your observations (that you didn’t actually make) isn’t even a stretch in claiming reproducing science, it’s fraud.
        Here are the calculations that they based their “observations” on.
        Ambient CO2 / enrichment period / Recovery conditions
        Temperature (°C) 15.3±0.32 15.3±0.32 15.3±0.32
        Salinity 33.0±0.38 33.0±0.38 33.0±0.38
        Max PAR (µmol 158 158 158
        photons m–2 s–1)
        AT (µmol kg–1) 2190.7±87.2 2202.0±123.28 2210.8±68.2
        CT (µmol kg–1) 2084.8±12.8 2168.9±31.20 2066.2±23.2
        pHNBS 7.9±0.2 7.7±0.39 8.0±0.2
        pCO2 (µatm) 821.6±343.4 1747.7±1403.33 646.7±320.6
        – (µmol kg–1) 1961.1±27.5 2033.5±20.35 1927.6±49.2
        2– (µmol kg–1) 92.0±45.9 67.8±50.77 113.5±45.5
        ΩArg 1.4±0.7 1.0±0.78 1.7±0.7
        How about that precision on their enriched CO2, 300 ppm-6,000 ppm. What condition are they testing for, volcanic eruption?

    • David, how in this world does CO2 affect aragonite?….CO2 might effect the pH if buffers run out….but there’s no danger buffers like aragonite will ever run out

      • how in this world does CO2 affect aragonite?…
        adding co2 to the oceans causes caco3 to. precipitate as limestone. this limestone is carried by plate tectonics into the earth where it is reduced by iron to produce natural gas.
        this natural gas bubbles up into the oceans and atmosphere where it is oxidized by living organisms as a source. of energy. this process. has been ongoing for hundreds. of millions of years.

      • It affects the saturation state of both aragonite and calcite. Although aragonite is far more sensitive.
        Increasing atmospheric CO2 also causes the carbonate compensation depth (lysocline) to become somewhat shallower. This is the depth below which carbonates won’t precipitate.

      • David, the study you linked “assumed”….CO2 can only do that by affecting pH…CO2 by itself can not displace anything
        CO2 with magnesium, you get aragonite
        CO2 without magnesium, you get calcite

      • Aragonite and calcite are two crystalline forms of calcium carbonate. Once they dissolve, there is no way of telling whether it was an aragonite or a calcite that had dissolved.

      • CO2 and a lot of other factors affect pH…
        pH decreases with depth. The depth at which carbonates will no longer precipitate is called the carbonate compensation depth. Below this depth carbonates will dissolve.

        Calcite compensation depth (CCD) is the depth in the oceans below which the rate of supply of calcite (calcium carbonate) lags behind the rate of solvation, such that no calcite is preserved. Aragonite compensation depth (hence ACD) describes the same behaviour in reference to aragonitic carbonates. Aragonite is more soluble than calcite, so the aragonite compensation depth is generally shallower than the calcite compensation depth.
        Calcium carbonate is essentially insoluble in sea surface waters today. Shells of dead calcareous plankton sinking to deeper waters are practically unaltered until reaching the lysocline where the solubility increases dramatically. By the time the CCD is reached all calcium carbonate has dissolved according to this equation:
        {\displaystyle \mathrm {CaCO_{3}+CO_{2}+H_{2}O\ \rightleftharpoons \ Ca^{2+}(aq)+2\ HCO_{3}^{-}(aq)} } {\mathrm {CaCO_{3}+CO_{2}+H_{2}O\ \rightleftharpoons \ Ca^{{2+}}(aq)+2\ HCO_{3}^{-}(aq)}}
        Calcareous plankton and sediment particles can be found in the water column above the CCD. If the sea bed is above the CCD, bottom sediments can consist of calcareous sediments called calcareous ooze, which is essentially a type of limestone or chalk. If the exposed sea bed is below the CCD tiny shells of CaCO3 will dissolve before reaching this level, preventing deposition of carbonate sediment. As the sea floor spreads, thermal subsidence of the plate, which has the effect of increasing depth, may bring the carbonate layer below the CCD; the carbonate layer may be prevented from chemically interacting with the sea water by overlying sediments such as a layer of siliceous ooze or abyssal clay deposited on top of the carbonate layer.[1]
        Increases in atmospheric CO2 cause the carbonate compensation depth to become shallower (shoaling of the lysocline).

        Ocean Chemistry:
        Lysocline: the depth at which a rapid increase in dissolution occurs; it separates the well preserved (above) from the poorly preserved (below) calcareous microfossil assemblages . The typical depth of the lysocline is between 3700-4500m and varies are a result of the carbonate ion concentration in the deep and intermediate water masses. It is shallowest when the CO2 concentration of the water is highest because those waters are the most corrosive to the calcareous microfossils.
        Compensation Depth (of aragonite or calcite): the depth at which the amount of calcium carbonate delivered to the seafloor is equal to the amount removed by dissolution. The average depth of the calcite compensation depth (CCD) is 4500 m in the Pacific and 5500 m in the Atlantic and shallows when there is a greater supply of carbonate material to the seafloor. Only above the CCD can carbonate materials be deposited (below the CCD they dissolve and do not reach the sea floor). The deep depth of the CCD results only in dissolution on the lower parts of the slope.
        Factors that affect the depth of the lysocline and the compensation depth include:
        Water temperature
        CO2 concentration
        pH (high pH values aid in carbonate preservation)
        Amount of carbonate sediment supply
        Amount of terrigenous sediment supply
        Calcium carbonate solubility increases with increasing carbon dioxide content, lower temperatures, and increasing pressure. Other factors that can influence the dissolution of calcium carbonate: organic coatings on the grains, size of the grain (smaller grains dissolve faster).
        One of the geologic markers of the PETM is clear evidence of a shoaling of the lysocline.
        During periods of very high CO2 levels, the seas have been calcitic. During periods of low CO2, like the Pennsylvanian-Permian and Oligocene-Holocene, the seas have been aragonitic.
        Marine calcifers adjust. Some adjust better than others. Coralline algae adjust very well.

      • correct…but the only effect CO2 has is pH…
        Like you just said….coralline adjusts fairly easily to fluctuating calcium and carbonates… does not adjust well to rapidly fluctuating pH…and that’s exactly what they did in this study at the top of this post…they jerked the pH around for 4 days

    • Question for D. Middleton re the top graph MLO CO2 vs Aragonite Saturation: Is that blue blot in the upper left corner an ink blot, or the data points from which the nonlinear regression line was extrapolated? If the latter, there are statisticians who should be weighing in. My stats profs warned me to never try that at home, or anywhere else. There are limited exceptions (hydrology), but this does not appear to be one of them.

      • Those are the measured aragonite saturation data from Station Aloha (Hawaii Ocean Time Series). The the red curve is the relationship between CO2 and aragonite saturation from Ries et al., 2009. I just applied the same type of trend line function to the real data that Ries modeled.
        Aragonite and calcite saturation is a function of DIC CO3 2-, HCO3 – and atmospheric CO2.
        My point was to demonstrate that the measured reduction in aragonite saturation at Station Aloha was much less than indicated in Ries.

  8. The problem at Lake Nyos purportedly wasn’t CO2 toxicity — which is unclear, but is thought to be quite low — but the fact that the CO2 displaced a large percentage of the oxygenated air in the enclosed basin. That may have been exacerbated by the presence of strongly toxic gases like HS and H2S in the gas cloud.
    Assuming Wikipedia is correct, and it likely is, Lake Nyos would seem to have little relevance to marine algae.

      • The deaths at Lake Nyos were likely caused by a downhill flow of gases replacing the breathable air. It also occurred at night when most were sleeping, probably on low pallets. Many may have survived if standing, which could have put their heads above the flow. A gas flow, while not being obvious, will not knock you about like a water flow does.

      • This event makes me think of the Permian Extinction — an H2S signature all over the planet and more marine organisms going extinct than land organisms.

  9. “If a local authority or government agency is deciding the location of a new fish farm, forestry or carbon capture site, we should be looking at what marine ecosystems are nearby, and the potential for those ecosystems to be impacted by the new activities as a whole, rather than focusing on the impact on individual organisms.”
    I would think that is a prudent thing to do any time an agency is deciding on the location of a project, but especially if it is a government project.

  10. A PhD study gives a ‘still’ picture of an ecology that changes ever so slowly. These industrial cities had a heck of a lot of coal burning plus sulphuric acid rain for two centuries. The fact the reefs are still operating and providing a nest for fish and shellfish tells us that these systems are “…robustly resistant to the lesser damaging reagents they are exposed to these days” (quote from crotchety geologist/mining engineer who rants here quite frequently).
    For ‘climate’ the best qualification is to have lived for a heck of a long time (It doesn’t work for all, e.g. The Shipper of Fools types). Axel Morner is the guy I go to for sea level insights, for example.

  11. The standard practice among researchers is not to bother with CO2, but add hydrochloric acid to water instead.

  12. ‘the scale of CO2 concentration required for a serious global carbon capture effort would in my opinion ensure someone, somewhere would cut one corner too many. A Lake Nyos scale release near a major city could kill millions of people.”
    Carbon dioxide kills in a manner similar to water. A major release would be little different from a major dam break. I suspect the incidences would be at least as rare and would cause much less property damage or death from reasons other than asphyxiation.
    That said I cannot escape the absurdity of storing large amounts of CO2 to keep an infinitely small amount of the gas out of the atmosphere. Storage only restricts access to natural mechanisms that remove it quite rapidly.

  13. This is a study described as “Here, we investigated in situ the effect of acute CO2 enrichment on the coralline algal ecosystem” — the key is the word acute.
    In situ means that they put an enclosure of some kind over an area in the sea. “Acute CO2 enrichment” means that pumped in some amount of CO2 never expected to occur naturally in that environment.
    I have written to the author and requested a copy of the paper and SI — if she responds favorably, I’ll write it up for publication here.

  14. Global warming is SO 1990’s. Even global weirding is old. The new term should be Intense CO2 shocks. That’ll scare ’em.

  15. According to the article, the experiment consisted of three phases: “(1) before CO2 enrichment at ambient (control) conditions (15 h), (2) during CO2 enrichment (28 h), and (3) post-enrichment recovery (37 h).
    The unperturbed in situ pH was 7.9±0.2; the pH during CO2 enrichment was 7.7±0.39, and during recovery was 8.0±0.2. These pH values are identical within one standard deviation.
    The major change was in the carbonate equilibrium system, and those changes are not particularly large. Here are the data:
    p CO2 (μatm)____________821.6±343.4___1747.7±1403.33__646.7±320.6
    Bicarbonate (μmol kg^-1)__1961.1±27.5___2033.5±20.35___1927.6±49.2
    Carbonate (μmol kg^-1)_____92.0±45.9____67.8±50.77_____113.5±45.5
    Calcification (μmol m^2 hr^-1)_0.055±0.03___-0.01±0.02_____0.02±0.04
    Calcification was read off Figure 1.
    Dissolved CO2 approximately doubled (no surprise there). Bicarbonate increased modestly, and carbonate decreased.
    But pH didn’t move materially.
    So, whatever caused the coral dissolution, it was not caused by a decrease in alkalinity following dissolved [CO2] increase.

  16. It’s truly amazing that the starfish survived during the time a lot of atmospheric CO2 was in the ocean.
    More junk science

  17. In view of the evolution of all calcified phyla – corals, molluscs, echinoderms etc. during the Cambrian era when CO2 levels were 10-30,000 ppm: how do they expect anyone with an IQ larger than their show size to believe this infantile nonsense about stress to marine calcified organisms during a glacial period with low CO2 – only a few hundred ppm? Sorry – this just baffles me.

  18. Some truth re organisms that live in the extremes in nature, they are the organisms that most often have the least tolerance to changes because their niche at an extreme, in ocean water context, the high end of the pH and kDH\hardness scale.
    Also you won’t find studies on organisms that benefit from some acidity, like many Amazon species of fish, some of which cannot reproduce if their reproductive organs get calcified.

    • Extremes? Like all those volcanic hydrothermal vents around the coast of Scotland 🏴󠁧󠁢󠁳󠁣󠁴󠁿 , you mean? Please elaborate.

  19. Anyone any idea of the total sulfur\sulfide inputs into the oceans, seem this study’s author didn’t bother to wonder about it

  20. Thanks to MarkMcD, I’ve read the full text of the article by H.Burdett et al. They bubbled CO2 in a mixing chamber and measured the concentrations of dissolved CO2, bicarbonate, and carbonate ions under ambient, CO2-enrichment, and recovery phase conditions. The fact that carbon dioxide addition favors “net dissolution rather the net calcification” is obvious for anyone familiar with school chemistry:
    CaCO3 + CO2 + H2O –> Ca(HCO3)2 (soluble).
    The authors found also that in recovery period p CO2 is even less, and pH and carbonate ion concentration are slightly larger than under ambient conditions. In this regard, it’s generally unclear what is a danger from CO2 to marine organisms and does it relate to real conditions in seawater.

    • Aleks, calcification is an energy-driven biological process. Organismal CaCO3 does not directly respond to pH in an equilibrium chemistry sense.
      Also, the calcareous surfaces are typically coated with protein, so the CaCO3 doesn’t directly contact the water in any case.

    • Yes, and no.
      Many calcifying organisms (probably not all) don’t actually rely on the supersaturation of calcite or aragonite (crystal forms of Calcium carbonate) to create solid carbonate from solution. They actually cause precipitation of carbonate in localised micro-environments where the living organism itself controls the acidity and salt concentrations, plus specialized proteins that catalyze the precipitation process. This makes sense when you consider that many calcifying life-forms live in environments where the conditions do not favour precipitation of carbonates, but they still do it.
      The ‘dissolving coral reef’ stories are usually based solely on a high school understanding of carbonate chemistry which is not relevant to the real world.

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