Dying Coral Reefs



Global warming has been causing the "bleaching" of coral reefs. A bleached coral reef has lost its photosynthesizing symbiotic organisms, called zooxanthellae. It may look white as a ghost — as in the picture above — but it is not yet dead. If the zooxanthellae come back, the reef can recover.

With this year’s record high temperatures, many coral reefs are actually dying:

• Dan Charles, Massive coral die-off reported in Indonesia, Morning Edition, August 17, 2010.

DAN CHARLES: This past spring and early summer, the Andaman Sea, off the coast of Sumatra, was three, five, even seven degrees [Fahrenheit] warmer than normal. That can be dangerous to coral, so scientists from the Wildlife Conservation Society went out to the reefs to take a look. At that time, about 60 percent of the coral had turned white – it was under extreme stress but still alive.

Caleb McClennen from the Wildlife Conservation Society says they just went out to take a look again.

DR. CALEB MCCLENNEN: The shocking situation, now, is that about 80 percent of those that were bleached have now died.

CHARLES: That’s just in the area McClennen’s colleagues were able to survey. They’re asking other scientists to check on coral in other areas of the Andaman Sea.

Similar mass bleaching events have been observed this year in Sri Lanka, Thailand, Malaysia, and other parts of Indonesia.

For more, see:

• Environmental news service, Corals bleached and dying in overheated south Asian waters, August 16, 2010.

It’s interesting to look back back at the history of corals — click for a bigger view:



Corals have been around for a long time. But the corals we see now are completely different from those that ruled the seas before the Permian-Triassic extinction event 250 million years ago. Those earlier corals, in turn, are completely different from those that dominated before the Ordovician began around 490 million years ago. A major group of corals called the Heliolitida died out in the Late Devonian extinction. And so on.

Why? Corals live near the surface of the ocean and are thus particularly sensitive not only to temperature changes but also changes in sea levels and changes in the amount of dissolved CO2, which makes seawater more acid.

We are now starting to see what the Holocene extinction will do to corals. Not only the warming but also the acidification of oceans are hurting them. Indeed, seawater is reaching the point where aragonite, the mineral from which corals are made, becomes more soluble in water.

This paper reviews the issue:

• O. Hoegh-Guldberg, P. J. Mumby, A. J. Hooten, R. S. Steneck, P. Greenfield, E. Gomez, C. D. Harvell, P. F. Sale, A. J. Edwards, K. Caldeira, N. Knowlton, C. M. Eakin, R. Iglesias-Prieto, N. Muthiga, R. H. Bradbury, A. Dubi and M. E. Hatziolos, Coral reefs under rapid climate change and ocean acidification, Science 318 (14 December 2007), 1737-1742.

Chris Colose has a nice summary of what this paper predicts under three scenarios:

1) If CO2 is stablilized today, at 380 ppm-like conditions, corals will change a bit but areas will remain coral dominated. Hoegh-Guldberg et al. emphasize the importance of solving regional problems such as fishing pressure, and air/water quality which are human-induced but not directly linked to climate change/ocean acidification.

2) Increases of CO2 at 450 to 500 ppmv at current >1 ppmv/yr scenario will cause significant declines in coral populations. Natural adaptive shifts to symbionts with a +2°C resistance may delay the demise of some reefs, and this will differ by area. Carbonate-ion concentrations will drop below the 200 µmol kg-1 threshold and coral erosion will outweigh calcification, with significant impacts on marine biodiversity.

3) In the words of the study, a scenario of >500 ppmv and +2°C sea surface temperatures “will reduce coral reef ecosystems to crumbling frameworks with few calcareous corals”. Due to latitudinally decreasing aragonite concentrations and projected atmospheric CO2 increases adaptation to higher latitudes with areas of more thermal tolerance is unlikely. Coral reefs exist within a narrow band of temperature, light, and aragonite saturation states, and expected rises in SST’s will produce many changes on timescales of decades to centuries (Hoegh-Guldberg 2005). Rising sea levels may also harm reefs which necessitate shallow water conditions. Under business-as-usual to higher range scenarios used by the IPCC, corals will become rare in the tropics, and have huge impacts on biodiversity and the ecosystem services they provide.

The chemistry of coral is actually quite subtle. Here’s a nice introduction, at least for people who aren’t scared by section headings like “Why don’t corals simply pump more protons?”:

• Anne L. Cohen and Michael Holcomb, Why corals care about ocean acidification: uncovering the mechanism, Oceanography 22 (2009), 118-127.

54 Responses to Dying Coral Reefs

  1. Uncle Al says:

    Sunblock, especially high SPF versions abundantly slathered upon pale dermis, could easily devastate photosynthetic marine organisms.

    1) Heavily touristed and studied coral reefs would suffer anomalous bleaching, plus down-current plumes of bleaching, and

    2) Enviro-whiners screaching “proximity is not causality” in the manner that Global Warmists decry the saturated spectral lines of CO2 while ignoring “ecological alternative” hydrochlorofluorocarbon refrigarant crappy working fluids with 10,000+ times the IR-trapping intensity of CO2 and operating in formerly transparent atmospheric spectral windows.

    To “do something about it,” gene-gineer high temp coral symbionts and seed bleached regions. That solves the Official problem. A social advocate makes virtue of failure. The worse the cure the better the treatment – and the more that is required.

    Female hormone pharma (contraception and menopausal hormone replacement) survives sewage treatment. SSRI anti-depression pharma (e.g., Prozac) ditto. Recreational pharma ditto. The first two empirically exert massive deleterious impacts upon aquatic life downstream: male fish are feminized, shellfish are reproductively disordered, considerable collected observations “remain to be published.”

    This is neither the first warm interglacial period nor the warmest interglacial period. 300 ppm CO2 levels are not even interesting. The difference is anthropogenic sewage – especially the imposed Enviro-whiner trinity of expensive, shoddy, deadly pruning the tree of knowledge by displacing proven technologies with Tinker Bell’s butt dust.

    • John Baez says:

      Hi, Uncle Al! Interesting suggestions.

      I know there are lots of bad consequences to the massive release of hormones into the environment, including feminization of male fish in rivers that get a lot of waste water effluent. Are you suggesting that this is what’s killing coral? I haven’t heard of hormonal effects in oceans.

      Or are you saying that sunblock is the cause?

      As far as I can tell, while small outbreaks of coral bleaching can be attributed to many causes, the mass coral bleaching events, and the current dieoff, are correlated to ocean temperatures. For example, a really big coral bleaching event occurred during the 1998 El Niño, and this is another El Niño. But there’s a lot more evidence than that. Try reading this:

      • Paul Marshall and Heidi Schuttenberg, A reef manager’s guide to coral bleaching.

      A little taste:

      At a local scale, many stressors may cause corals to bleach, including storms, disease, sedimentation, cyanide fishing, herbicides, heavy metals, and changes in salinity and temperature [18]. The primary cause of regional, or mass, bleaching events is increased sea temperatures [8, 9, 13, 18-20]. Sea temperature increases of 1-2ºC above the long term average maximum are all that are required to trigger mass bleaching [9, 23]. Both the intensity and duration of temperature anomalies are important in determining the timing and severity of bleaching responses. Higher temperatures can cause bleaching over a shorter exposure time, while lower temperatures require longer exposure times. While temperature is the trigger for bleaching, light also influences the severity of bleaching impacts [24]. The types of conditions that cause the rapid warming of waters characteristic of spatially extensive bleaching events often coincide with calm, clear conditions that increase light penetration. For this reason, shaded corals are likely to bleach less severely than corals exposed to normal light levels during heat stress.

      You write:

      This is neither the first warm interglacial period nor the warmest interglacial period.

      The last interglacial this hot occurred about 400,000 years ago. With just 1°C more warming it’ll be the hottest it’s been in the last 1,350,000 years. Weather isn’t climate, and they didn’t have weather stations back in the Pleistocene, but as far as I can tell, this summer could easily be one of the hottest summers in the last 1,350,000 years.

      300 ppm CO2 levels are not even interesting.

      So sayeth thou.

      By the way: Calling people rude names like ‘whiner’ isn’t allowed on this blog. I’ve made an exception this once for you because I know this is your typical tone of voice and I value your expertise in chemistry — but I won’t allow it in the future. For one thing, it’ll piss people off and make my job as moderator harder.

      People who are tempted to take Al’s bait and flame back: your posts won’t show up, so don’t bother.

      • Uncle Al says:

        rude names like ‘whiner’ Point taken for local rules of engagement.

        An engineer’s first task in solving a problem is to determine its real world cause. Consonant warming of Mars, Jupiter, and Saturn falsify a purely anthropogenic sourcing of terrestrial “warming,” itself suffering manipulated data.

        “We must do something” is not “we must do something pertinent.” Politics is a stomach: it has no brain; it knows it is hungry, and the inevitable results are somebody else’s problem. Hunger is due to weather, famine is due to politics.

        The Earth is pushing 7 billion people when family size is trivially restrained. The vast majority is atechnological, even within the First World, but it has its votes. Earth is stripped of all easily obtainable resources. Its food productivities are flensed to the bone. Its wastes are planetary. The planet is dying. Best case we are increasingly screwed. Current case we are imploded.

        Technology has always found ways to make way more from much less, teosinte to Intel. Luddite recidivism is common: Dark Ages, Cambodian Khmer Rouge, Cuba until it switched from snit to productivity. Sacrifice only engenders more sacrifice. Conservation is a crock – do the maths. March or die.

        The ongoing Harvard ethics scandal is emblematic of social engineering. Reality is not a peer vote. We are not passengers on Spaceship Earth, we are crew. Anybody who will not swab the decks is out the airlock – or we all are.

        Finally… Is there a loophole in physics? Can we satisfy what is but find a way out, as whale oil became petroleum? 2000 years of Euclid were not dinged by triangles on the Earth’s surface always containing more than 180 degrees. Physics cannot imagine mass distribution chirality, for no fundamental symmetry can be emergent. That is why I call for one modest experiment that cannot possibly work – unless it does. Do opposite shoes vacuum free fall identically?

        http://www.mazepath.com/uncleal/erotor1.jpg
        The worst it can do is succeed.

        Physics is not stupid, nor is chemistry. The only way to know is to look. Discovery is always insubordinate. Mediocrity is a vice of the doomed. Somebody should look. We are well and truly screwed if what we have is all there is.

    • John Baez says:

      I wrote:

      The last interglacial this hot occurred about 400,000 years ago. With just 1°C more warming it’ll be the hottest it’s been in the last 1,350,000 years.

      Hoegh-Guldberg et al, in the abstract of their paper “Coral reefs under rapid climate change and ocean acidification”, put it a bit more conservatively:

      Atmospheric carbon dioxide concentration is expected to exceed 500 parts per million and global temperatures to rise by at least 2°C by 2050 to 2100, values that significantly exceed those of at least the past 420,000 years during which most extant marine organisms evolved.

      But we’re not disagreeing much. The point is that the temperature record for the last 1.35 million years shows a peak around 420,000 years ago. We’re getting close to overtaking that peak. Once we pass that peak, it seems like it’ll be the hottest it’s been for 1.35 million years — or more, I’m not sure how much more.

  2. Max Eskin says:

    Err, I meant http://www.tos.org/oceanography/issues/issue_archive/issue_pdfs/22_4/22-4_cohen.pdf . . . should really be more right when correcting people :)

  3. Steve Bloom says:

    Just to note that there are extensive populations of (relatively) deep-water corals that are also vulnerable.

  4. John Baez says:

    Uncle Al reminded me: I shouldn’t just bemoan the death of coral reefs, I should say a bit about how to “do something about it”, and solicit suggestions from all of you.

    Here’s what Hoegh-Guldberg has to say:

    The situation is not hopeless – there is much we can do individually and as a society to help coral reefs survive. First, we can address the rise in greenhouse gases. Your everyday actions affect the total amount of carbon going into the atmosphere, so taking steps to reduce your carbon footprint, e.g., switching to CFL (compact fluorescent light bulbs) and using energy efficient appliances and vehicles does matter. Because it takes time for the climate system to stabilize once we reduce emissions, we also suggest three important actions to help protect reefs unrelated to climate change:

    1. Manage Coral Grazers – One of the most practical solutions is to increase the number of herbivores on coral reef systems to graze on the algae that grow there. Improving sea urchin populations and limiting fishing of important grazers like parrotfish is a simple, but powerful step that gives corals a
    fighting chance at surviving bleaching events.

    2. Coral Restoration Projects – Coral reef restoration is not yet practical on the huge scale demanded by climate change. However, new technologies for “farming” corals may make this a better option in the future. Growing those corals best able to tolerate high temperatures improves corals’ chances for survival.

    3. Manage Major Local Stressors – Any actions we can take to reduce the effects of overfishing, improve water quality by reducing pollution, deforestation and sediment and nutrient runoff from land helps. For instance, a healthy reef environment may still bleach, but more corals will survive and regrow faster than a reef that is subjected to ongoing and
    severe local stresses.

    The bottom line is there is still time to act, but we must act quickly. The longer we wait, the harder it is to effect positive change. Learn more about reducing your carbon footprint in your everyday actions. Support local actions to reduce major stressors on coral reefs. Most important, share your knowledge with your nondiver friends, telling them about the importance of healthy coral reefs and the actions they can take to safeguard their future.

    The big problem is global warming. This will not be stopped by small individual actions like replacing our light bulbs and the like — though it’s good to do all that stuff as part of an overall movement towards greater intelligence in energy usage. So, I think Hoegh-Guldberg is doing us a disservice in acting as if these small actions are significant steps towards solving that problem. As far as I can tell, only something like a carbon tax or cap-and-trade system can fix the big gaping externality of CO2 pollution.

    However, he knows about coral reefs, so his points 1)-3) are very useful. In particular: it’s not instantly obvious that algae-eating herbivores like sea urchins and parrotfish can help coral reefs survive! But it goes like this, apparently: after a reef gets bleached, it has a lot more trouble bouncing back to good health if it gets covered with algae.

    Farming corals sounds cool, especially if people can figure out how make money off it somehow, so they do it without anyone forcing them. Ideas?

    I also wonder if some types of coral that may otherwise go extinct can be saved in artificial environments — big aquaria, basically.

    Genetically engineering or breeding corals that can survive higher temperatures is also fine with me, if we can do it!

    • Tim van Beek says:

      I think Hoegh-Guldberg is doing us a disservice in acting like these small actions are significant steps towards solving that problem.

      More important is the political message that everyone (or at least a vast majority) acknowledges that there are global effects of local resource consumption and the responsibility to do something about it, even if that is inconvenient. In Germany there was a long debate amongst politicians if waste separation had a chance to become accepted, with counter arguments like “people won’t accept to have three different trash cans in their kitchen”.

      But it worked, smoothly, and now similar policies are installed without much fuss, see:

      EU to switch off traditional light bulbs by 2012.

      IMHO these small steps – with more symbolic significance than effects – are necessary before anyone has the courage to suggest more drastic measures (“anyone” is addressing people who are at risk to lose a significant amount of power, wealth and reputation if they publicly voice opinions that are unanimously repudiated by the mainstream, like MoP :-).

      • John Baez says:

        Tim wrote:

        More important is the political message that everyone (or at least a vast majority) acknowledges that there are global effects of local resource consumption and the responsibility to do something about it, even if that is inconvenient.

        I agree that this is an important message. Back home in Riverside I have replaced my lightbulbs with compact fluorescents, I recycle trash religiously, and I have set up a composting bin. Only the last would be considered weird.

        Here in Singapore there is no obvious way to recycle trash, and I think that’s shockingly backward. The lightbulbs are all fluorescent, but people blast the air conditioning at ridiculously cold temperatures — and indeed a repair man in our apartment complex suggested that leaving the air conditioner set at a temperature as high as 28°C (as we do) could damage the unit. Is that true??? I got the feeling he was just offended by the idea of someone living at such a high temperature. It’s a bit hard to have a personal compost pile when you live in an apartment, but I might try one on the balcony. (It might attract a bunch of scary tropical insects, and then lizards.)

        In Shanghai people just set their trash in plastic bags by the entrance to the apartments, and workers take these bags to a large building in the apartment complex and sort it out by hand! — they have more poor people there. Semi-feral cats control the rodents that tend to accumulate in these trash heaps.

        All these things matter.

        What I meant was that if someone asks “what can we as a society to help coral reefs survive?”, and your main answer regarding carbon emissions is “switch to compact fluorescent light bulbs and use energy efficient appliances and vehicles”, that could lull people into thinking that’s enough action to solve the problem. And that would be a dangerous illusion: it’s nowhere near enough. The problem is orders of magnitude bigger than that.

        As someone put it: if everybody does just a little to help prevent global warming… just a little will get done. And as someone else put it: we need to change our leaders, not just our lightbulbs.

        IMHO these small steps – with more symbolic significance than effects – are necessary before anyone has the courage to suggest more drastic measures…

        That’s probably true. However, in the United States there are well-respected people in Congress who have been working hard to pass cap-and-trade legislation for CO2. Their efforts fell through this year, but it is important to keep thinking and talking about such ideas: they have a lot of support, just not enough yet.

    • Tim van Beek says:

      Is the link behind “Hoegh-Guldberg” broken?

  5. Tim van Beek says:

    You may be interested in an international research project called FORCE (Future of Reefs in a Changing Environment), one of their projects is about conserving and re-breeding corals, as you can see here.

  6. Nullius in Verba says:

    I’m glad this topic has come up. I’ve got a few questions.

    The equilibrium in question is

    CO2+H2O ⇌ H2CO3 ⇌ HCO3- + H+ ⇌ CO32- + 2H+

    If you take a carbonate solution and add another acid, like hydrochloric acid, it adds hydrogen ions to the right hand side of the equation, which by Le Chatelier’s principle, pushes the equilibrium to the left. CO3 is converted to bicarbonate and CO2.

    What if you add CO2 on the left hand side? Why does this not push the equilibrium rightwards? (Please be careful not to use diagrams that assume constant DIC.) I’d be very interested in a proper explanation of this. (I suspect it’s true, but I don’t understand it.) And I’m not afraid of explanations involving rate constants.

    If you take pure water and dissolve CO2 in it, the pH goes down. Which has more carbonate ions in it? Does lower pH always mean lower CO3?

    Second question: the Earth’s history goes back more than a million years. What was the atmospheric CO2 level at the time corals first evolved?

    The solubility of CO2 varies significantly with temperature. How far does pH vary, from freshwater to seawater, tropics to poles, surface to the deeps? How much from day to day, with turbulent mixing? How much does the shallow water temperature of the sea vary over the year? (Note, I mean the temperature, not the temperature anomaly.)

    Fourth, Charles Darwin reported on the mechanism of the formation of coral atolls – something else he did on his travels. He said that atolls were at sea level or in shallow waters because the islands grew from coral and coral growth was limited by the surface, not the other way round. Given that coral species have already survived meltwater pulse 1a, can you say what the maximum growth rate of coral is, and what rate of sea level rise would exceed it? Is this rate less than what the IPCC projects?

    Thanks.

    • John Baez says:

      I can’t answer your questions, at least not instantly — but they’re very interesting, so I hope some chemists and biologists jump in and help out. This is precisely the sort of thing I want to do here at Azimuth: join forces to figure things out.

      All I can do instantly is quote some mildly relevant passages from the paper I cited:

      • Anne L. Cohen and Michael Holcomb, Why corals care about ocean acidification: uncovering the mechanism, Oceanography 22 (2009), 118-127.

      These passages don’t exactly answer your chemistry question, but they provide some clues that are worth pondering:

      Stony corals build hard skeletons of calcium carbonate (CaCO3) by combining calcium with carbonate ions derived, ultimately, from seawater. The concentration of carbonate ions relative to other carbonate species in seawater is rather low, so corals expend energy to raise the pH of seawater sequestered in an isolated, extracellular compartment where crystal growth occurs. This action converts plentiful bicarbonate ions to the carbonate ions required for calcification, allowing corals to produce CaCO3 [calcium carbonate] about 100 times faster than it could otherwise form. It is this rapid and efficient production of CaCO3 crystals that enables corals to build coral reefs. Ocean acidification reduces the pH and thus the abundance of carbonate ions in seawater. Corals living in acidified seawater continue to produce CaCO3 and expend as much energy as their counterparts in normal seawater to raise the pH of the calcifying fluid. However, in acidified seawater, corals are unable to elevate the concentration of carbonate ions to the level required for normal skeletal growth. In several experiments, we found that boosting the energetic status of corals by enhanced heterotrophic feeding or moderate increases in inorganic nutrients helped to offset the negative impact of ocean acidification. However, this built-in defense is unlikely to benefit corals as levels of CO2 in the atmosphere continue to rise. Most climate models predict that the availability of inorganic nutrients and plankton in the surface waters where corals live will decrease as a consequence of global warming. Thus, corals and coral reefs may be significantly more vulnerable to ocean acidification than previously thought.

      And then:

      Biomineralization Basics

      Understanding the fundamentals of coral calcification (i.e., the processes involved in the nucleation and growth of aragonite crystals) is a crucial first step in predicting the response of corals and coral reef ecosystems to future climate change, including ocean acidification. A useful place to start thinking about calcification strategies in the marine environment is to recognize that all marine calcifiers, including the reef-building or “stony” corals, have to overcome the kinetic barriers to CaCO3 precipitation that exist naturally in seawater.

      Today, the surface ocean is supersaturated with respect to CaCO3, which means that there are more than enough calcium and carbonate ions in solution to enable CaCO3 to precipitate out. The saturation state of seawater with respect to aragonite, the form of calcium carbonate that corals produce, is denoted by the symbol Ωar. It is defined as the product of the actual measured concentrations of calcium and carbonate ions dissolved in seawater divided by the product of the concentrations of calcium and carbonate ions when they are saturated (at equilibrium) in seawater, as follows:

      Ωar = [Ca2+] × [CO32–] / ([Ca2+] × [CO32–])sat

      Because the calcium ion concentration [Ca2+] in seawater is very high and relatively constant, variations in Ωar are determined mainly by the carbonate ion concentration [CO32–]. Today, the [CO32–] of seawater in the low-latitude surface ocean is about 250 μmol kg-1. Aragonite saturation is reached at a [CO32–] of about 60 μmol kg-1. Thus, the tropical surface ocean is, in general, but with notable exceptions such as the eastern tropical Pacific, about four times supersaturated with respect to aragonite.

      When Ωar > 1 (i.e., [CO32–] > 60 μmol kg-1), aragonite should, theoretically, precipitate from seawater. Conversely, when Ωar < 1, aragonite should dissolve in seawater. The warm tropical ocean where most coral reefs are found is highly supersaturated with respect to aragonite, in other words, Ωar can be significantly greater than 1. Nevertheless, neither calcite nor aragonite will form spontaneously because there are kinetic barriers that prevent nucleation and/or crystal growth. These kinetic barriers include the high hydration energy of the calcium ions (e.g., Lippmann, 1973), the low concentration and activity of the carbonate ions (e.g., Garrels and Thompson, 1962; Lippmann, 1973), and the presence of high concentrations of sulfate and magnesium (e.g., Usdowski, 1968; Kastner, 1984).

      Most marine calcifiers, therefore, must nucleate and grow CaCO3 crystals within compartments that are isolated or semi-isolated from the external seawater, and within which they can modify, regulate, and control conditions, including in some cases the carbonate chemistry of the calcifying fluid, to enable CaCO3 precipitation to occur. Coccolithophores and gorgonians, for example, produce calcite and high-magnesium calcite intracellularly, the marine alga Halimeda accretes aggregations of acicular aragonite needles extracellularly within spaces created between cell membranes, and corals and mollusks accrete their CaCO3 crystals within compartments created between the tissue and the existing skeleton or shell. In addition, there is substantial evidence for the involvement of organic molecules in the biomineralization processes of many marine calcifiers. Organic molecules may play a role in reducing the surface free energy required for nucleation (e.g., Teng et al., 1998), in guiding site-specific nucleation that results in species-specific skeletal architectures, or in buffering the pH of the calcifying fluid against large fluctuations in internal CO2 concentrations caused by cycles in photosynthesis and respiration (Holcomb et al., 2009).

      And this is where things get complicated… read the paper for more.

      But returning to your chemistry question, which is much more basic — pardon the pun — I guess the most relevant passage was Ocean acidification reduces the pH and thus the abundance of carbonate ions in seawater. But what you’re asking is: why?

    • John Baez says:

      Nullius wrote:

      Second question: the Earth’s history goes back more than a million years.

      Some scholars claim it was created on the night before October 23rd, 4004 BC — but I’m inclined to agree with you here.

      What was the atmospheric CO2 level at the time corals first evolved?

      Good question! Yes, whenever I mention how temperatures and CO2 levels may soon soar above those we’re used to in late-Pleistocene interglacials, I think about how these conditions are still cold compared to earlier times. I’m no expert — indeed, the only reason I’m trying to answer your question is to learn stuff — but I believe the danger to corals has a lot to do with the suddenness with which conditions are changing. If conditions changed slowly enough, the corals could migrate to temperatures they liked, or even evolve to adjust. But we are seeing CO2 levels, and I believe temperatures as well, rise at spectacular rates.

      (These rates may not be unprecedented: witness for example the Paleocene-Eocene Thermal Maximum. But a lot of stuff died during that episode.)

      A bit more on coral’s adaptive abilities before I actually come around to your question. From:

      • CRC Reef Research Centre, Coral bleaching and global climate change.

      Can corals adapt to warmer temperatures?

      For corals to survive the increases in seawater temperatures predicted for this century, they would need to adjust to the higher temperatures. There are several ways that they might do this.

      Firstly, corals could alter their physiology in a process known as acclimatisation. Corals have several internal mechanisms to cope with stresses such as increased temperature and sunlight. However, these mechanisms are usually only effective for short periods and up to defined limits. They are unlikely to prepare corals for a future bleaching event. There is evidence that many corals have bleached two or three times during successive bleaching events, suggesting that acclimatisation may not be a reliable way for corals to adjust to climate change. If global temperatures rise in the predicted way, water temperatures in 100 years will be much greater than those that trigger bleaching now, so corals would need to acclimatise continually to survive. Most research indicates that acclimatisation is limited and unlikely to allow corals to adapt to the predicted water temperatures.

      A second process by which coral populations could adapt to new conditions is by natural selection. This results in a gradual change in the temperature-tolerance of the population through the elimination of the coral colonies that cannot tolerate higher temperatures. Different colonies of the same coral species may respond to thermal stress differently. If only the most temperature-tolerant corals survive a bleaching episode, the offspring from those corals might be on average more temperature-tolerant than the previous generation. Again, there might be limits in how high the temperature can rise before corals reach the limits of adaptation. Such adaptations are thought to occur slowly, over several generations (with most corals having generation times of at least 5-10 years), but potential rates of adaptation have never been estimated.

      A third process is one in which larvae from warm-adapted coral populations may disperse to cooler areas as they warm, thereby changing the distribution of species. However, this is likely to be a slow process.

      Corals can have several types of zooxanthellae in their tissues. Some scientists have suggested that corals may adapt to warmer conditions by changing the dominant type of zooxanthellae within their tissues. Corals with a certain type of zooxanthellae can tolerate temperatures of 1-1.5°C higher than corals of the same species without that type. Scientists do not yet know how many of the 400 or so species of hard corals can change the type of dominant zooxanthellae or, indeed, what stimulates the change. Increased temperature tolerance may also come at a cost. For example, juvenile corals with heat-tolerant zooxanthellae grow up to three times slower than those with a different zooxanthellae type. The type of zooxanthellae that occur in the corals may also affect other aspects of coral fitness.

      It is possible that a combination of natural selection and switching of zooxanthellae may help corals cope with climate change over the next few decades. Faster rates of change are possible for zooxanthellae than for the coral animal because the algae have shorter generation times. However, adaptation of corals and zooxanthellae to high temperatures has not yet been studied. Research is underway to investigate these different adaptation possibilities.

      Okay, now back to your actual question: “What was the atmospheric CO2 level at the time corals first evolved?”

      As I explained, corals of significantly different kinds have evolved several times in the Earth’s history, so the first corals were quite different from those we see today. I know practically nothing about those early corals, so I’ll stick to the corals we see today.

      The kind we see today are the Scleractinia, or stony corals. They showed up about 220 million years ago, in the Middle Triassic. They filled a niche that was left open when the two main previous types of coral died out in the Permian-Triassic Extinction Event — along with 90% of all marine species.

      So, you are asking me about the atmospheric CO2 concentration in the Middle Triassic (and later).

      Of course my instant reaction is that there must be considerable uncertainty when it comes to questions like this. But I can browse the web with the best of them, and pull up a chart like this:

      And indeed, there’s quite a spread of opinion (click for more info) — but we see that CO2 levels in the late Triassic and late Cretaceous may have hit a whopping 2000 ppm.

      In case anyone out there hasn’t been keeping score, it’s only about 390 ppm today. So, clearly corals have survived much higher CO2 levels. It was also much warmer back then: for parts of the the Cretaceous, tropical sea surface temperatures may have commonly reached 35 C!

      Did corals live in the tropics then, or did they prefer cooler locations? I don’t know.

      Anyway: since the end of the Cretaceous around 65 million years ago, when the dinosaurs went extinct, it’s generally been getting colder, and CO2 levels have been dropping. So, to repeat myself: I’m not sure that what corals once tolerated long ago has much to do with what they can tolerate suddenly today.

      • Steve Bloom says:

        Just to note that given sufficient time the ocean will buffer the acidity, meaning that pH wouldn’t have been much different from current even with much higher atmospheric CO2. A fast rise in CO2 will be accompanied by an increase in acidity, as we are seeing.

        • John Baez says:

          Do you know any place one can read a simple description of the chemistry involved? You’re making it sound like Nullius in Verba’s comment:

          And I’m not afraid of explanations involving rate constants.

          is exactly on target: namely, that the acidification is not an equilibrium effect, so understanding it requires thinking about reaction rates.

        • Steve Bloom says:

          I’m certainly no expert, but I think one can speak in terms of a short-term equilibrium since the buffering process takes such a long time.

          As for a comprehensive chemistry discussion, I’m not sure. Jean-Pierre Gattuso (who runs the EPOCA blog) should be able to give you a pointer.

        • John Baez says:

          Steve wrote:

          I’m certainly no expert, but I think one can speak in terms of a short-term equilibrium…

          Okay, I’ve changed my mind. I now think you’re right here: equilibrium chemistry should be enough to answer this question:

          Why does adding CO2 to seawater make it more acid and reduce the level of CO3- (“carbonate”)?

          An outline of the answer can be found in Kleypas and Langdon and the Royal Society report. But, it’s subtle.

      • Steve Bloom says:

        See this discussion of a new paper on the Aptian acidification event (~121 mya). Of interest is the length of time it took for pH to return to normal. There’s nothing about corals, although at least some survived.

        Also, EPOCA (the European Project on Ocean Acidification) has a very active blog. They don’t seem to miss much.

    • John Baez says:

      For anyone out there who is feeling really confused, it might help to start with this cheat sheet. Plain old water actually does fancy stuff like split into protons and hydroxide:

      H2O = water

      H+ = proton

      OH- = hydroxide

      But in fact a lone proton is very aggressive, so it usually latches onto a water molecule to form hydronium:

      H3O+ = hydronium

      There’s a lot more to this story… water is incredibly complex… but there’s no time for that now.

      When you add carbon dioxide even more things form:

      CO2 = carbon dioxide

      H2CO3 = carbonic acid

      HCO3- = bicarbonate

      CO32- = carbonate

      Carbonate looks like this:

      Stick a proton on one of the oxygens here and you get bicarbonate (an illogical name; the chemistry nomenclature gurus prefer ‘hydrogen carbonate’). Stick on another proton and you get carbonic acid.

      Okay, now read what Nullius wrote:

      The equilibrium in question is

      CO2 + H2O ⇌ H2CO3 ⇌ HCO3- + H+ ⇌ CO32- + 2H+

      If you take a carbonate solution and add another acid, like hydrochloric acid, it adds hydrogen ions to the right hand side of the equation, which by Le Chatelier’s principle, pushes the equilibrium to the left. CO3 is converted to bicarbonate and CO2.

      What if you add CO2 on the left hand side? Why does this not push the equilibrium rightwards?

      You’re making me feel I need a refresher course on chemistry! The Wikipedia writes the reaction a bit differently and seems to sidestep your paradox by bringing calcium carbonate into the game:

      The Earth’s oceans contain a huge amount of carbon dioxide in the form of bicarbonate and carbonate ions — much more than the amount in the atmosphere. The bicarbonate is produced in reactions between rock, water, and carbon dioxide. One example is the dissolution of calcium carbonate:

      CaCO3 + CO2 + H2O ⇌ Ca2+ + 2 HCO3-

      Reactions like this tend to buffer changes in atmospheric CO2. Since the right-hand side of the reaction produces an acidic compound, adding CO2 on the left-hand side decreases the pH of sea water, a process which has been termed ocean acidification.

      • Nullius in Verba says:

        Thank you!

        All of that is enormously helpful. Even if they don’t quite answer all the questions, they do move things forward. And I applaud your approach.

        You’re absolutely right about the biological complexities. Life exists in a wide range of pH’s, each type of organism adapted to its own niche. Freshwater shellfish tolerate a far lower pH than found in salt water, for example. The tolerance of any particular species has more to do with its own individual biochemistry than any fundamentals of inorganic chemistry.

        But I was already struggling to follow the basic chemistry without diving into the biology just yet.

        The thing is, I strongly suspect that there is a good explanation, but every time somebody gives an explanation of ocean acidification for the general public, the real explanation is seen as too complicated and a simplified version substituted in its place. This makes it very difficult for a sceptic to approach the subject. You want to understand and check the science, not taking some Authority’s word for it. But the explanation on offer seems to have big holes in it. What are you supposed to do?

        Adding CO2 does of course reduce pH. CO2 added on the left hand side shifts the balance to the right, increasing H(+) concentration. But there is an essential difference between adding carbonic acid and adding any other acid, and this point constantly gets glossed over. Adding any other acid reduces both pH and CO3 concentration, no argument. But that particular argument doesn’t extend (without modification) to adding CO2.

        Introducing calcium ions may indeed have something to do with it, but at first glance it appears to be an equivalent way of writing the reaction we’ve already discussed; the steps all lumped together. The equation also doesn’t show the production of any hydrogen ions required to lower pH. And if you write in the next step implied by that statement “the right-hand side of the reaction produces an acidic compound” and show it acting as an acid, what do you get?

        • John Baez says:

          Nullius wrote:

          But I was already struggling to follow the basic chemistry without diving into the biology just yet.

          I understand — but alas, my knowledge of chemistry seems approximately equal to yours, so I’m able to see why you’re confused, and be equally confused myself, but I’m not instantly able to help you. (I could probably figure it out with a bit of reading, but I’m kinda hoping that someone reading this knows some chemistry.)

          And if you write in the next step implied by that statement “the right-hand side of the reaction produces an acidic compound” and show it acting as an acid, what do you get?

          I understand most of your worries but I don’t understand this sentence. What do you mean by “what do you get?” Do you mean “what acidic compound do you get?” or “what conclusion do you draw?”

          Hmm, I guess you mean “what acidic compound do you get?”

        • Nullius in Verba says:

          What I meant was that for HCO3(-) to act as an acid, it means:
          HCO3(-) = H(+) + CO3(2-)

          i.e. it only acts as an acid by producing more carbonate ions.

          In a sense, the calcium carbonate reaction is precisely the opposite of acidification. It is actually a case of the alkaline CaCO3 partially neutralising the (relatively) strong acid CO2 (or H2CO3 as it is in solution) to form a weaker acid HCO3(-). Instead of being able to donate two protons, like CO2, HCO3 can donate only one.

          I suspect Wikipedia’s version is related to the IPCC’s AR4 Chapter 7 box 7.3 on page 529. Eqn 7.2 with the addition of Ca(2+) ions on either side would give it. But the IPCC’s version is even more obviously a rearrangement of the same equilibrium. The first step is the same as the first step of Eqn 7.1, and the second step is the second step of 7.1 written backwards.

          I honestly wasn’t really expecting you to know the answer. But I thought you might be better placed to find one. A lot of places I ask the question, I’m dismissed as a ‘denier’ and ignored. “Scientists say…” and that’s good enough for them. Whereas you demonstrate the true spirit of scientific enquiry far better by wanting to know the answer yourself, and are less likely to be dismissed.

          It may even be relevant to the solution. If it turns out that it is a matter of biology rather than chemistry, maybe we can do something about it by that means. Genetically engineering pH-tolerant corals, for instance?

          In any case, I am grateful that you are even asking the question. I’m sure the answers will come in time.

        • Nullius in Verba says:

          Hmm, I guess you mean “what acidic compound do you get?””

          ‘Guess’? Well, I assume you don’t require an answer to that, now.

          My apologies. I didn’t intend to start any trouble. I’m still grateful that you are asking the question.

        • John Baez says:

          No need for apologies!

          I’m tracing back the literature, and some papers point to these for information on the underlying chemistry:

          Coral reefs and changing seawater carbonate chemistry, Royal Society Policy Document, 2005.

          • J. A. Kleypas and C. Langdon, Coral reefs and changing seawater carbonate chemistry, in: Coral Reefs and Climate Change: Science and Management, edited by: Phinney, J. T., Hoegh-Guldberg, O., Kleypas, J., Skirving, W., Strong, A., American Geophysical Union, Washington, DC, 2006, pp. 73-110.

          • S. Doney, V. Fabry, R. Feely, and J. Kleypas, Ocean acidification: the other CO2 problem, Annual Review of Marine Science 1 (2009), 169-192. Available here with subscription.

          • K. Caldeira and M. E. Wickett, Anthropogenic carbon and ocean pH, Nature 425 (2003), 365-365. Available here with subscription.

          Annex 1 of the first reference and the first few pages of the second one promise to be quite helpful. Reading a good chemistry book might also be good for me.

          Anyone want to join in and figure this out?

        • John Baez says:

          Nullius: I think you want to understand the section beginning here in Kleypas and Langdon’s paper:

          A common inference from Equations (2-5) is that the addition of CO2 to the water column will ultimately lead to an increase in the carbonate ion content, and given the following equation, one intuitively would consider that this would also lead to an increase in the formation of calcium carbonate (CaCO3):

          Ca2+ + CO32– ⇌ CaCO3

          This inference is incorrect, however,…

          The explanation that follows is not easy.

    • John Baez says:

      The discussion here may be getting a bit hard to follow, but I’ve become fascinated by a question Nullius raised, so let me summarize it as follows:

      Why does adding CO2 to water decrease the level of carbonate (CO32-)?

      Some ideas from chemistry make this seem paradoxical at first glance. But let me show you this graph from the Royal Society report, which shows this effect at work:

      I don’t think there’s a really a paradox. Extra CO2 in the water creates carbonic acid (H2CO3) which, being acidic, splits into bicarbonate (HCO3-) and free protons (H+):

      CO2 + H2O ⇌ H2CO3 ⇌ HCO3- + H+

      The free protons then react with existing carbonate to form bicarbonate:

      CO32- + H+ ⇌ HCO3-

      So, carbonate levels drop and bicarbonate levels increase.

      However, it’s a tricky business, and it would really take some detailed calculations to understand the curves in the graph above!

      • Nullius in Verba says:

        Thanks for the links.

        The Royal Society appendix just appears to repeat the same argument as in the IPCC or Wikipedia. It uses eqn 3 to increase concentrations of H(+) and HCO3(-), which appear on both sides of eqn 4, but only seems to consider the forward effect of the H(+) while failing to discuss the backwards influence of the extra HCO3(-). It doesn’t explain it at all.

        However, after struggling to understand both papers, I think I can now see a way to salvage this. The rate equation for eqn 4 would be
        [H(+)][CO3(2-)]/[HCO3(-)] = K
        where K is a constant for the current temperature, pressure, etc.

        If we simplify notation to get hc/b=K, rearrange K/c=h/b, and increase h and b by the same amount d, we get K/c’ = (h+d)/(b+d) = h/b + (b-h)d/(b(b+d)).

        Now, if eqn 3 was all that was going on, then b=h and nothing happens. But we know from your second link that this isn’t the whole story. There’s this ‘total alkalinity’ that is also involved.

        The Kleypas and Langdon paper also has some confusing aspects, and fails to really explain what is going on. For example, just after eqn 10 it discusses the effect of CaCO3 precipitation which obviously removes both Ca and CO3 ions – but where they only mention the removal of Ca ions and then state that Ca reduces by the conversion of carbonate to bicarbonate. Why does the direct removal of carbonate by precipitation not count?

        I think they’re probably right that it does, but I don’t see how their explanation can be the right one.

        Similarly, they make an approximation by dropping the Borate alkalinity (which they discuss, and is fair enough) and the hydrogen ion concentration, which they do almost entirely without discussion. With two terms dropped, they then use the remainder as an equality to say that as bicarbonate increases the carbonate must decrease. As explanations go, it’s somewhat lacking.

        But again, with the insertion of a few assumptions and missing steps, I can see how to make progress. Eqn 7 seems to be based on the idea that the dissolved ions of the strong acids/bases are fixed, and those of the weak acids/bases adjust to fit. So the top line of eqn 7 may be considered a constant, and the bottom line says that a weighted sum of bicarbonate, carbonate, and hydrogen must be constant. This isn’t telling us anything new, of course. Just that for every hydrogen ion formed, a bicarbonate must turn into a carbonate, or carbon must enter externally from some uncharged species.

        But I believe the reason that they neglect the hydrogen ions in TA to consider only Ca instead is that the salts of the strong acids and bases are balanced by carbonate/bicarbonate far in excess of what dissolved CO2 would create. The bicarbonate concentration is a huge number compared to the hydrogen ion concentration. Which brings us back to the end point we reached after considering the Royal Society paper.

        With b much greater than h, (b-h)d/(b(b+d)) is positive, and so on adding CO2 the carbonate concentration c decreases. It happens because there’s proportionately a lot more bicarbonate (from other sources) than hydrogen, so the addition of CO2 has proportionately less effect on the bicarbonate, which is why they can just consider the forwards influence of the H(+) and ignore the backwards influence of the HCO3(-).

        Fundamental to this argument are the rate equation given above, and the observation that most of the carbonate/bicarbonate is there to balance the strong acid/base salts. (Although there is a logical gap here – why carbonate and not anything else?) Only one paper alludes indirectly to the latter. Neither paper mentions the former. I don’t see how they could have derived the result without them.

        I get the distinct impression with both papers that the authors didn’t fully understand why, only that it was so, and they tried to generate an ad hoc explanation that would pass. The reasoning is muddled and imprecise.

        Which is concerning.

        (I may of course be doing them an injustice – maybe they simply thought the real explanation was too complex. What do you think?)

        But I think I can declare myself satisfied. Although there are still gaps and uncertainties in my understanding, I do at least have a plausible explanation now. My thanks!

        • Nullius in Verba says:

          I forgot to note – their equation for TA also neglects OH(-), which given that the sea is alkaline, is perhaps a significant omission.

          However, it doesn’t affect the overall argument.

        • John F says:

          Balancing equations involving single weak acids and bases can be tricky. It is important to keep in mind that not only are are there multiple species, only *variable* fractions of them are ionized as indicated in the “intuitive” equations, and reality does not follow the “intuitive” stoichiometry.

          Correctly balancing equations of multi-buffered systems like seawater (borate is very important, other not so much) is indeed complex. Worse, it’s not even a closed system and there are exchanges with gaseous and solid components!

        • Graham says:

          I tried submitting this before, but it didn’t seem to work.

          The Wikipedia page on calcium carbonate is the best thing on this issue that I have found so far. See especially the section on solubility with varying CO2 pressure.

          http://en.wikipedia.org/wiki/Calcium_carbonate#With_varying_CO2_pressure

          Increasing CO2 pressure causes more calcium carbonate to dissolve in pure water, so I don’t think there is any need to bring in concepts like total alkalinity in order to understand the basic mechanism.

        • John Baez says:

          Sorry, Graham, this comment of yours — and perhaps your previous try? — went into my spam box. I don’t know why.

          Anyway, thanks for the comment.

  7. Hybrid Moiety says:

    Yes, as the pH level of the ocean drops, corals are on the way out. They are among the “walking dead” species, much like the Polar Bears.

  8. John F says:

    John B,
    Because of misinformation trumpeted by a few, you may not know that it is U.S. federal policy that climate change is happening, and that federal response is both required and happening e.g. plans to move docks to adapt to changing sea levels. One example is the interagency Climate Change Adaptation Task Force:
    http://www.whitehouse.gov/administration/eop/ceq/initiatives/adaptation

    Apropos of combining geometry, dynamics, wave-particle duality, phase transitions, and quantum information transmission (but not environmental, alas), it is interesting to me that Moire patterns from interfering holograms have been experimentally useful for decades. But where are the quantum gravity category theorists on this?

    • John Baez says:

      John F. wrote:

      Because of misinformation trumpeted by a few, you may not know that it is U.S. federal policy that climate change is happening, and that federal response is both required and happening e.g. plans to move docks to adapt to changing sea levels.

      Thanks for the reminder!

      I cheered on the Supreme Court decision that forced the EPA to address the threats due to CO2.

      But I didn’t pay enough attention to the subsequent decision by the EPA that:


      the current and projected concentrations of the six key well-mixed greenhouse gases — carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6) — in the atmosphere threaten the public health and welfare of current and future generations

      and


      the combined emissions of these well-mixed greenhouse gases from new motor vehicles and new motor vehicle engines contribute to the greenhouse gas pollution which threatens public health and welfare.

      As for what category-theoretic physics says about Moire patterns, this isn’t the right blog entry for discussing that.

      • Steve Bloom says:

        In case you don’t know the EPA is mid-process (IIRC they’ve received initial comments and are now writing the rule) for a parallel rule for ocean acidification per the Clean Water Act. This will create an entirely independent legal basis for regulating CO2 since the existing rule is under the authority of the Clean Air Act. It will be interesting to see how all of this unfolds, but an obvious key point is that with a CWA-based rule in place it would be difficult for Congress to gut independent CO2 regulation by the EPA since the only plausible way to do so is by way of a poison pill in a bill adding climate provisions to the CAA. Obama has promised to veto any direct attempt to take away the EPA’s authority.

        But with the failure of Congress to act on a climate bill in this session and poor prospects for next session, the question becomes one of what the EPA is willing to do with its considerable authority. Sufficiently strong action would force Congress into trying to cut a deal, but we have yet to see much evidence for a willingness by the administration to engage in that sort of power politics, or indeed to take strong regulatory action absent legislative considerations.

        On the plus side, for the first time we have scientists who understand the problem (Chu, Holdren and Lubchenco) in key policy-making positions, and I’m pretty sure they’ll insist on seeing something real in place during Obama’s first term (in part because there’s no guarantee of a second one).

  9. Steve Bloom says:

    This new paper (press release) on possible rates of acidification during the next century looks interesting, although not good news.

  10. [...] reefs are also having trouble due to warming oceans. For example, there was a mass dieoff of corals this summer off the coast of [...]

  11. [...] reefs are also having trouble due to warming oceans. For example, this summer there was a mass dieoff of corals off the coast of [...]

  12. Steve Bloom says:

    This press release describes a new paper finding that an ocean area of naturally low pH (due to volcanic CO2 emissions) points to major biodiversity trouble ahead.

  13. [...] and produce hydrogen ions, leading to ocean acidification. You have already discussed this on your blog. In addition to acidification, the chemical buffering effect is lessened (the Revelle factor [...]

  14. Eric says:

    This popped up on my radar this morning.

    The heat kills Caribbean Coral

    Southern Caribbean Sea could be experiencing the beginning of a mass mortality of corals, scientists suggest

    http://translate.google.com/translate?js=n&prev=_t&hl=en&ie=UTF-8&layout=2&eotf=1&sl=es&tl=en&u=http%3A%2F%2Fwww.hoy.com.do%2Fel-pais%2F2010%2F9%2F12%2F341637%2FTierramericaEl-calor-mata-a-corales-caribenos

  15. Zoran Škoda says:

    Yesterday on Croatian TV there was a woman from Dalmatia who does artistic jewelry out of sea shells. She was very concerned about the polution in the oceans. One of the striking details she was claiming is that even the structure of a shell is clearly falling down with the polution in oceans.
    For example the shells from around Indonesia, while they look externally equally nice like the shells from somewhere around New Guinea where the polution is smaller, in fact are much easier to break during working on it (for jewelry purposes); there are more natural fractures and the material is less hard. It would be interesting to know what aspect of polution makes the shells “softer”. I consider the places where such beautiful shells live, relatively clean, so it is interesting that the mechanical properties fall down with relatively low polution.

    • bane says:

      This page

      http://www.whoi.edu/OCB-OA/FAQs/

      under

      Why does increasing the dissolved CO2 concentration in seawater affect shell building in marine organisms?

      says that what sound like small increases in ocean acidity (especially on the logarithmic pH scale) can have significant effects. I guess the question becomes why there’s significant acidity differences at various points around the globe.

  16. John Baez says:

    There are a bunch of potentially useful links here, though the article itself is not very informative: what, for example, does it mean to say that oysters are ‘functionally extinct’? I still see them for sale.

    State of the ocean: ‘shocking’ report warns of mass extinction from current rate of marine distress, Huffington Post, 20 June 2011.

    The preliminary report from the International Programme on the State of the Ocean (IPSO) is the result of the first-ever interdisciplinary international workshop examining the combined impact of all of the stressors currently affecting the oceans, including pollution, warming, acidification, overfishing and hypoxia.

    “The findings are shocking,” Dr. Alex Rogers, IPSO’s scientific director, said in a statement released by the group. “This is a very serious situation demanding unequivocal action at every level. We are looking at consequences for humankind that will impact in our lifetime, and worse, our children’s and generations beyond that.”

    The scientific panel concluded that degeneration in the oceans is happening much faster than has been predicted, and that the combination of factors currently distressing the marine environment is contributing to the precise conditions that have been associated with all major extinctions in the Earth’s history.

    According to the report, three major factors have been present in the handful of mass extinctions that have occurred in the past: an increase of both hypoxia (low oxygen) and anoxia (lack of oxygen that creates “dead zones”) in the oceans, warming and acidification. The panel warns that the combination of these factors will inevitably cause a mass marine extinction if swift action isn’t taken to improve conditions.

    The report is the latest of several published in recent months examining the dire conditions of the oceans. A recent World Resources Institute report suggests that all coral reefs could be gone by 2050 if no action is taken to protect them, while a study published earlier this year in BioScience declares oysters as “functionally extinct”, their populations decimated by over-harvesting and disease. Just last week scientists forecasted that this year’s Gulf “dead zone” will be the largest in history due to increased runoff from the Mississippi River dragging in high levels of nitrates and phosphates from fertilizers.

    A recent study in the journal Nature, meanwhile, suggests that not only will the next mass extinction be man-made, but that it could already be underway. Unless humans make significant changes to their behavior, that is.

    The IPSO report calls for such changes, recommending actions in key areas: immediate reduction of CO2 emissions, coordinated efforts to restore marine ecosystems, and universal implementation of the precautionary principle so “activities proceed only if they are shown not to harm the ocean singly or in combination with other activities.” The panel also calls for the UN to swiftly introduce an “effective governance of the High Seas.”

    “The challenges for the future of the ocean are vast, but unlike previous generations we know what now needs to happen,” Dan Laffoley of the International Union for Conservation of Nature and Natural Resources (IUCN) and co-author of the report said in a press release for the new report. “The time to protect the blue heart of our planet is now, today and urgent.”

    • Tim van Beek says:

      John wrote:

      what, for example, does it mean to say that oysters are ‘functionally extinct’? I still see them for sale.

      There is one – and only one – German oyster farm in the north sea at the coast of the island Sylt. The tides have a very strong effect in the north sea; the water line moves several kilometers, so that the oysters are under water half of the time, which is a kind of body building (open shell, close shell, open shell, close shell).
      Those oysters are really expensive, but you’ll see them on sale, if you go to the really good chefs, for quite some time after there are no oysters left in the wild.

  17. [...] and produce hydrogen ions, leading to ocean acidification. You have already discussed this on your blog. In addition to acidification, the chemical buffering effect is lessened (the Revelle factor [...]

  18. [...] and produce hydrogen ions, leading to ocean acidification. You have already discussed this on your blog. In addition to acidification, the chemical buffering effect is lessened (the Revelle factor [...]

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