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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

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Ocean acidification: global warming's evil twin

What the science says...

Select a level... Basic Intermediate

Ocean acidification threatens entire marine food chains.

Climate Myth...

Ocean acidification isn't serious

'Our harmless emissions of trifling quantities of carbon dioxide cannot possibly acidify the oceans. Paper after paper after learned paper in the peer-reviewed literature makes that quite plain. Idso cites some 150 scientific sources, nearly all of them providing hard evidence, by measurement and experiment, that there is no basis for imagining that we can acidify the oceans to any extent large enough to be measured even by the most sensitive instruments.' (Christopher Monckton)

At-a-glance

Have you heard of ocean acidification? Does it mean that if you go swimming in the sea, you are liable to dissolve? No. You'll be OK because you are not a calcifying organism, such as a mollusc, a coral or a sea-urchin.

So why is ocean acidification serious? Because it can potentially lead to massive collapse of marine food-chains. Let's take a look at what the term means.

The pH scale, which measures acidity and alkalinity of water-based chemical solutions, runs from 0 (highly acidic) to 14 (highly alkaline), with pH 7 being the neutral halfway point. Importantly, the scale is logarithmic, meaning that a jump of one point towards zero means a tenfold increase in acidity.

Acidification simply means lowering the pH value from any point on the pH scale towards zero. It's similar to the way we talk about temperatures. If the pH of a solution shifts from 9 to 8, that is acidification, even though the pH is still on the alkaline side of neutral. Likewise, if the temperature rises from -40°C to -15°C, it has noticeably warmed, even though it's still darned cold.

Now, typical seawater is slightly alkaline at around pH 8.1. Rainwater, which always contains dissolved carbon dioxide (the old name for which was 'carbonic acid gas'), has a more acidic pH of around 5.6. You have likely visited or watched footage of spectacular caves, have you not? All carved out by carbonic acid, dissolving solid limestone over many thousands of years.

Carbonic acid is not only present dissolved in raindrops. It also forms by the dissolving of carbon dioxide at the air-water interface of our oceans. The more carbon dioxide in the air, the more goes into the oceans, driving their pH from 8.1 downwards. Now, the huge problem this creates, well before we get anywhere near the neutral value, is as follows.

Many marine organisms build and maintain their protective shells or skeletons from 'biogenic' calcium carbonate. The word biogenic means made by living things. These creatures extract the calcium and carbonate ions dissolved in seawater and combine them together. Under normal conditions, such calcium carbonate is stable in shallow waters. That's because dissolved carbonate ions are present in such high concentrations that the waters are said to be saturated with them.

But if seawater pH falls, even by a small amount, the concentration of dissolved carbonate ions falls. When that happens, biogenic calcium carbonate becomes more soluble and can start to dissolve. Depletion in dissolved carbonate ions thus makes it harder for such organisms to maintain their protective or skeletal structures. In the worst case scenario, the rate of calcium carbonate dissolution is faster than its formation. When that happens, mass-mortality of calcifying organisms can occur.

We're talking about critters that underpin entire marine food-chains here. Things from near-microscopic calcifying plankton to shellfish, lobsters and crabs the seafood we eat in other words. That's why ocean acidification is deadly serious.

Please use this form to provide feedback about this new "At a glance" section. Read a more technical version below or dig deeper via the tabs above!


Further details

Not all of the CO2 emitted by human industrial activities remains in the atmosphere. Between 25% and 50% of these emissions over the industrial period have been absorbed by the world’s oceans, preventing atmospheric CO2 buildup from being much, much worse. But this atmospheric benefit comes at a cost.

As ocean waters absorb CO2 they become more acidic. This does not mean the oceans will become like the acids one encounters in a chemistry lab. However, marine life can be highly sensitive to slight changes in pH levels and any drop in pH is an increase in acidity, even in an alkaline environment. Worse, the pH scale is logarithmic, meaning that for each single-digit decline in pH, acidity (defined as hydrogen ion activity) rises tenfold.

Surface seawater pH has been relatively stable over recent geological time, fluctuating between cold glacial periods (pH 8.3) and warmer interglacials (pH 8.2). But since the Industrial Revolution, average seawater pH has dropped towards a recent figure of less than 8.06, an approximately 30% increase in acidity (fig. 1). This is a faster change than any over the past 50 million years (Rhein et al, 2013, available from IPCC here).

Decline in ocean pH

Fig. 1: Decline in ocean pH measured at the Aloha station (in the Pacific Ocean off Hawaii) and yearly mean surface seawater pH reported on a global scale Source: European Environment Agency (Copernicus Marine Service).

Because of its inextricable link with CO2 emissions, this rate of acidification is projected to accelerate even further through the 21st century under a business-as-usual scenario with potentially catastrophic impacts to marine ecosystems (Bindoff et al. 2019 (PDF from IPCC)). These trends are becoming clearer globally.

According to the IPCC's Sixth Assessment Report (AR6), there is, " a very likely rate of decrease in pH in the ocean surface layer of 0.016 to 0.020 per decade in the subtropics and 0.002 to 0.026 per decade in subpolar and polar zones since the 1980s. Ocean acidification has spread deeper in the ocean, surpassing 2000 m depth in the northern North Atlantic and in the Southern Ocean (fig. 2)."

 Spread of ocean acidification from the surface into the depths

Fig. 2: Spread of ocean acidification from the surface into the depths since pre-industrial times. (a) Map showing the three transects used to create the cross sections shown in (b), showing the vertical sections of the changes in pH between 1800–2002 due to anthropogenic CO2 emissions; the darker the colours the greater the change. Contour lines are their contemporary values in 2002. Graphic sourced from IPCC AR6. (Lauvset et al. 2020).

Such changes in ocean chemistry, if allowed to occur, will be irreversible for many thousands of years. The biological consequences could last much longer.

How do we know that? Through the geological record. When mass-extinctions have occurred, most of them are tied-into unimaginably severe episodes of volcanism, at a scale never witnessed by humans. But the carbon footprint of such cataclysms has in fact been similar to our own. And what do we see as a consequence of such events? The fossil record shrinks in terms of its biodiversity and there are what we call 'reef-gaps', periods of several million years during which coral reefs - large highly diverse colonies of corals and myriad other species - were to all intents and purposes absent.

The reason why reef-gaps occur at such times is because as surface waters become more acidic, it becomes more difficult for corals, shellfish and other calcifying organisms to form and maintain the hard calcium carbonate skeletons or shells necessary for their survival. When things start getting really bad, that calcium carbonate dissolves away as fast as it can be deposited - that means curtains for such critters.

 Life-forms at deadly risk from the acidification of near-surface ocean waters.

Fig. 3: just some of the life-forms at deadly risk from the acidification of near-surface ocean waters.

Coral reefs provide a home for more than 25% of all oceanic species, so you can see why this matters so much. Some calcifying organisms, such as the tiny pteropods (fig. 3), underpin many oceanic food chains: take them out of the system and down those food-chains come crashing. Many communities around the world, constituting millions of people, are at the apex of such food-chains, relying on seafood as part of a healthy diet. You should now be able to see the problem. Like a thief in the night, ocean acidification is creeping up on us, while we sleep on in blissful unawareness.

Last updated on 25 June 2023 by John Mason. View Archives

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Denial101x videos

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Fact brief

Click the thumbnail for the concise fact brief version created in collaboration with Gigafact:

Question: Is the ocean acidifying?

fact brief

Comments

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Comments 1 to 25 out of 100:

  1. John Abraham has dissected Moncktons presentation on climate science here: http://www.stthomas.edu/engineering/jpabraham/ It's well worth listening from beginning to end!
  2. "Past history shows us that when CO2 rose sharply, this corresponded with mass extinctions of coral reefs." The mass extinction events you refer to- End Permian, PTEM, End Triassic- occured over tens of thousands to millions of years, at a rate not relevant to human time frames. Corals went extinct, and ocean acidity rose, but it did not rise 'sharply'. We should equally start worrying about continental drift rates and extinction. Past history also shows us that when continents collided, numerous species went extinct, but at a rate not relevant to humans. "The change in seawater pH over the 21st Century is projected to be faster than anytime over the last 800,000 years and will create conditions not seen on Earth for at least 40 million years." This is entirely based on model projections, which are themselves based on dubious assumptions. Past pH in industrial times has been modelled, not measured, therefore the current rate of change in oceanic pH is itself doubtful. A recent paper which measured pH in the last 15 years in the north pacific shows it has experienced an average change of 0.03pH in the last 15 years. I'm not sure this is a rate to which there is concern. The geological record indicates that oceans appear to be strongly buffered, and do not change pH easily. They have apparently not changed pH more than 0.6 in the last 300 M years, presumably because of negative feedbacks/buffering to any rise in C02/other factors. Hundreds of thousands of years of widespread explosive volcanism is generally required to lead to a modest rise in oceanic acidity. I would suggest that most of the research papers on potential ocean acidification are written by biologists and chemists who do not take into account processes outside their own, specialist fields. An illustrative example is, for eg, the question of where all the water in the oceans themselves originally comes from. If you ask some NASA scientists, it comes from comets. These scientists have, incidentally, never studied effects of large cooling magmas in the earth's crust. When granitic magmas cool, they expel water; the Earth's cooling crust in its early history is more than enough to account for all the world's ocean water, a process that still goes on today in eg mountain ranges, although the net water balance of the planet is more or less constant due to water saturated crust also being subducted into subduction zones. The point is, the comets, which are the NASA scientists special field, have nothing to do with the origin of the vastly greater portion of the world's water. The subsurface, and its processes, as usual, are presumed to be stable and unchanging, and therefore ignored. Another illustrative example is when geologists first reported the presence of numerous species of microrganisms feeding on 'dead' rock masses thousands of metres below the surface-these findings were initially totally ignored-how could deep subsurface 'rocks' be relevant to Earth's Biological processes? Now some scientists think that life itself may have originated deep within the earth, from/in association with these deep-dwelling micro-organisms (eg Paul Davies). Also of note, is that these micro-organisms are believed to account for by far the greater mass by weight of biota on earth, they extend well into the earth's crust, and are ore or less everywhere/abundant. Much the same sort of ignorance goes for various ocean acidification theories/projections; buffering procesess in the subsurface, for eg the >100,000km of Mid Oceanic Rifts, which extend down several kilometres of heated, carbonate-enriched rock, where large amounts of carbonic acid are produced/exchanged/ precipitated in the subsurface, are generally totally ignored by biologists and chemists, who think all you have to do to prove ocean acidification is carry out an experiment in a controlled lab with some H20, gases and no real-world earth subsurface processes, ie if you add c02 to the atmosphere, then oceans will experience runaway acidification. Their field and their models do not take into account rates of chemical precipitation /dissolution of eg c02 in the world's subsurface,rates of oceanic mixing, microbiological feedbacks, or any other potential buffering/negative feedback effects, nor the long geological record which indicates that the oceans only change pH significantly on geological timescales, not human timescales. The idea that oceans will acidify markedly over the next century is a result of inaccurate and incomplete modelling, nothing more.
  3. @thingadonta: you seem to contradict yourself in your post. First, you write: "A recent paper which measured pH in the last 15 years in the north pacific shows it has experienced an average change of 0.03pH in the last 15 years. I'm not sure this is a rate to which there is concern." You then go on to write: "The geological record indicates that oceans appear to be strongly buffered, and do not change pH easily. They have apparently not changed pH more than 0.6 in the last 300 M years" Minus 0.003 pH per year would yield an decrease of 0.6 pH in a mere 300 years, not 300 million - to me, this rate of change really is matter for concern. Now, to be fair you didn't claim pH dropped by 0.6 over 300My, but rather that this was the extent of the variation (which in itself is meaningless when talking about the rate of change). Fortunately, we can take a look at the CO2 vs. pH graph above to have an idea of the rate at which acidification can take place outside of human intervention. Looking at the last drop of 0.2 in the pH, we can see it took place quite rapidly, but not any quicker than about 2,000 years (there is 20ky per tick on that graph). This is a rate of 0.0001 pH per year, or about 50x slower than the current decrease in pH. That figure is actually quite conservative, as research has shown the current acidification is occuring about 100x faster than what the geological record reveals. Your skepticism is natural, but in this case I think it's clear you're off-mark by two orders of magnitude...
  4. Is there a way to read Pelejero 2010 w/o buying a membership with Science Direct? If not, this page would be improved by a summary of the proxies used and how they were validated.
  5. The first deep basin observations of Aragonite undersaturation in surface waters have already been observed in 2008 in the Arctic (Yamamoto-Kawai 2009), and in 2009 the extent of surface waters with undersaturated aragonite increased, although this is not yet region-wide. This means that these waters crossed the threshold where they are beginning to be corrosive to certain types of calcifying organisms. The trends in the Arctic regions have been a cause for concern for some time (Bates 2009), as the Arctic waters are subjected to the dual effects of decreasing alkalinity due to increasing pCO2 (directly due to uptake of the increasing atmospheric CO2 due to anthropogenic emissions), and increased sea ice meltwater due to increases in regional temperatures which are greater than the average global temperature rise. Models also predicted Aragonite undersaturation in these regions would occur in the near future, but the recent increased rate of ice melt has accelerated the process (eg Steinacher 2009). As both atmospheric CO2 and Arctic sea ice melt rates are on accelerating trends this will have a negative effect on populations of both planktonic and benthic calcifying organisms in the Canada Basin, and potentially over wider areas within a relatively short time span.
  6. I got to wondering if anyone had estimated the numeric relationship between atmospheric CO2 concentration change vs. ocean pH change. The dots in the graph you show suggest the glacial-interglacial difference of 100 ppm corresponded to a pH variation of 0.2 units of pH, so about 50 ppm / (0.1 pH) A bit of searching in Google Scholar yielded: K Caldeira, ME Wickett - Nature, 2003 "Anthropogenic carbon and Ocean pH", cited by 499 http://crecherche.ulb.ac.be/facs/sciences/biol/biol/CaldeiraWickett2003.pdf A key finding of theirs is that large but slow pCO2 changes led to somewhat smaller final ocean pH response, thanks to geologic-scale "buffering" effects (top 1/4 of their figure 1(b)). However, over shorter time spans, "[w]hen a CO2 change occurs over a short time interval (that is, less than about 104 yr), ocean pH is relatively sensitive to added CO2" So, just how sensitive, I wondered? I tried to glean from their graph whether ocean pH response to changes in pCO2(atm) is basically linear or logarithmic (they don't state either way). The X axis of figure 1(b) is log (or semi-log?) while the vertical bands for each pH level are spaced about equally, suggesting a logarithmic relationship. If so, the response for a doubling of CO2 along the bottom of fig. 1(b) (i.e. over short, human-scale time spans relevant to ACC) looks like roughly 0.3 pH units per doubling of pCO2. I'd appreciate if others would review the article and see if my takeoffs make sense of what's there.
  7. Also, lately I'm seeing frequent repetitions of the argument that ocean pH is still > 7 and so it is not "acidic", and that somehow precludes or invalidates use of the term 'Acidification' for lowering pH (even though this is perfectly valid and common scientific usage). Do we need to define this as a new "skeptic argument", or at least include a direct refutation of that move under this "it isn't serious" topic?
  8. Jim Prall #7, you think the hysterics over 'acidification' are bad? I just had a 'skeptic' (who was cited in the Cuccinelli vs Mann case) very determinedly telling me that the oceans are NOT becoming more acidic. Rather, they are becoming less alkaline. I suppose I should just be thankful that they have some grasp on reality... even if they refuse to allow words to hold their traditional meanings.
  9. They seem to be relying on a simplistic reading of the terminology, where "only pH below 7 is 'acidic'" to support a serious fallacy--that by implication, any pH over 7 must be fine, even if it is falling fast The problem is that any significant change in pH affects biological systems and the solubility of the basic building blocks like CaCO3. There is no magic threshold at pH = 7.0 other than a semantic one; for a biochemist, nothing special happens crossing that line. Changing pH from, e.g. 8.3 to 8.2 has a real, tangible effect on the solubility of CaC03, and on the equilibria between CO2(aq), H2CO3, and HCO3[-1]. These changes alter the "saturation horizon"--the depth at which CaCO3 is saturated, and that has a vital effect on organisms that form hard carbonate shells. There are ecological impacts to any substantial change in pH, whether the starting point is 8.3, 7.9, or 7.001. Arguing that lowering pH substantially "isn't acicification" is just debating semantics, and certainly walks and quacks like a diversion tactic. If we need some evidence that working oceanographers don't have a problem with calling current changes from 8.3 to 8.2 "acidification," we need look no further than the Monaco Declaration on Ocean *Acidification* signed by 155 experts in the field: http://www.ocean-acidification.net
  10. Jim, they probably aren't gardeners. Gardeners fully understand more and less acidic/alkaline in relation to soils. Though I think it would be pushing it to propose an analogy based on blue and pink hydrangea blooms.
  11. Some new data revealing the results of ocean acidification on marine corals: New Ocean Acidification Study Shows Added Danger to Already Struggling Coral Reefs Source study here. And yes. Acidification is the term used in the study. Like it, or not. The Yooper
  12. This paper leads one to believe that it is not as simple as the AGW believers want us to believe. Increased CO2 does seem to decrease CO3 in the lab, which is considered a limiting factor for coral growth. But, it also increases photosynthesis output, and actual coral growth in terms of biomass does not seem to suffer, and actually increases in some studies http://www.isse.ucar.edu/staff/kleypas/docs/PUBS/kleypas_langdon_icrs_2000.pdf More information http://scienceandpublicpolicy.org/images/stories/papers/originals/coral_co2_warming.pdf Are they trying to measure coral growth the wrong way when they concentrate on calcium carbonate measurements? Would we not expect the ocean equivalents of plants to also grow more as the CO2 increases as well, providing more food for sea life? Yes, plankton growth will be stimulated by increased CO2 levels, as long as other limiting factors do not come into play http://epic.awi.de/Publications/Tor2008b.pdf Another paper I scanned said that parts of the ocean are deficient in iron, which limits plankton growth http://www.nature.com/nature/journal/v331/n6154/abs/331341a0.html Plankton and algae will increase productivity as CO2 levels increase in seawater, they die, raining down on the sea floor, sinking more CO2. Chris Shaker
  13. This paper leads one to believe that it is not as simple as the AGW believers want us to believe You're arguing a strawman there. Changes in seawater chemistry are anything but simple. Would we not expect the ocean equivalents of plants to also grow more as the CO2 increases as well, providing more food for sea life? No. Decreased carbonate concentrations in seawater, combined with acidification and ocean stratification affect the long-term viability of phytoplankton populations. For example: Global phytoplankton decline over the past century "Here we combine available ocean transparency measurements and in situ chlorophyll observations to estimate the time dependence of phytoplankton biomass at local, regional and global scales since 1899. We observe declines in eight out of ten ocean regions, and estimate a global rate of decline of ~1% of the global median per year. Our analyses further reveal interannual to decadal phytoplankton fluctuations superimposed on long-term trends.
  14. Rob Painting: Did you read the paper I referenced, showing increased biomass in coral with increased CO2? Did you read the paper I referenced, showing increased plankton growth with increased CO2? Are you offering me any peer reviewed papers proving the opposite? No. Chris Shaker
  15. Your link to a nature article does not appear to work http://www.nature.com/nature/journal/v466/n7306/abs/nature09268.html%3Cbr%20/%3E Did you notice the paper I referenced, showing plankton growth limited by iron? Chris Shaker
  16. The paper I referenced, showing plankton growth limited by iron was from Nature "We conclude that Fe deficiency is limiting phytoplankton growth in these major-nutrient-rich waters." http://www.nature.com/nature/journal/v331/n6154/abs/331341a0.html Chris Shaker
  17. Please search for 'Iron Fertilization' in this paper to see that iron is well recognized as a limiting factor in plankton growth. They are talking about using Iron to cause plankton blooms to sequester CO2 and drop it down to the ocean floor http://www.cephbase.org/refdb/pdf/8122.pdf That paper also seems to show that mortality rates for some sea creatures, such as mollusks, increase with CO2. Chris Shaker
  18. There is also a Wiki on Iron Fertilization of the Ocean http://en.wikipedia.org/wiki/Iron_fertilization "Perhaps the most dramatic support for Martin's hypothesis was seen in the aftermath of the 1991 eruption of Mount Pinatubo in the Philippines.[citation needed] Environmental scientist Andrew Watson analyzed global data from that eruption and calculated that it deposited approximately 40,000 tons of iron dust into the oceans worldwide. This single fertilization event generated an easily observed global decline in atmospheric CO2 and a parallel pulsed increase in oxygen levels.[7]" Chris Shaker
  19. Chris Shaker, You have so many misconceptions about the topic, it's difficult to know where to start. The advanced version of Ocean Acidification should be out by years end and hopefully that clears up some of your confusion. Coral reefs - long term monitoring is showing a rise in bleaching events and coral death. Both acidification and ocean warming negatively impact coral reefs. Again, this is a topic for a later post but some reading: Caribbean Corals in Crisis: Record Thermal Stress, Bleaching, and Mortality in 2005 Worst coral death strikes at SE Asia - 19 October 2010 "Many reefs are dead or dying across the Indian Ocean and into the Coral Triangle following a bleaching event that extends from the Seychelles in the west to Sulawesi and the Philippines in the east and include reefs in Sri Lanka, Burma, Thailand, Malaysia, Singapore, and many sites in western and eastern Indonesia. “It is certainly the worst coral die-off we have seen since 1998. It may prove to be the worst such event known to science,” says Dr Andrew Baird of the ARC Centre of Excellence for Coral Reef Studies and James Cook Universities. “So far around 80 percent of Acropora colonies and 50 per cent of colonies from other species have died since the outbreak began in May this year.”
  20. Chris Shaker @17 Please search for 'Iron Fertilization' in this paper to see that iron is well recognized as a limiting factor in plankton growth Well aware of that thanks. Sorry, but "iron fertilization" is one of those ill-considered "engineering" ideas: Can ocean iron fertilization mitigate ocean acidification? " Here, using a global ocean carbon cycle model, we performed idealized ocean iron fertilization simulations to place an upper bound on the effect of iron fertilization on atmospheric CO2 and ocean acidification. Under the IPCC A2 CO2 emission scenario, at year 2100 the model simulates an atmospheric CO2 concentration of 965 ppm with the mean surface ocean pH 0.44 units less than its pre-industrial value of 8.18. A globally sustained ocean iron fertilization could not diminish CO2 concentrations below 833 ppm or reduce the mean surface ocean pH change to less than 0.38 units. This maximum of 0.06 unit mitigation in surface pH change by the end of this century is achieved at the cost of storing more anthropogenic CO2 in the ocean interior, furthering acidifying the deepocean. If the amount of net carbon storage in the deep ocean by iron fertilization produces an equivalent amount of emission credits, ocean iron fertilization further acidifies the deep ocean without conferring any chemical benefit to the surface ocean"
  21. The bleaching of coral reefs seems to actually be caused by fungus, which is transported across oceans by dust in the wind as the climate naturally warms and dries. http://imars.usf.edu/~cmoses/PDF_Library/Shinn%20et%20al%202000.pdf It looks like fungi have been attacking coral reefs for a long time http://www.biolbull.org/cgi/reprint/198/2/254.pdf Chris Shaker
  22. Chris , I find it insightful to actually read the studies linked to. The authors are proposing a hypothesis (back in 2000). They claim that two bleaching events in the Caribbean (1983/1987) coincide with increases in dust transport into the region. They lay the foundations for their hypothesis, that's the extent of it. In those two years (1983/1987) anomalously warm waters occurred too. Furthermore 1988 was a year of Caribbean coral bleaching and according the graph in Shinn 2000, this was a year of very low dust import into the region. In the meantime, coral reefs the world over have begun to bleach, as sea surface temperatures rise (see links at @ 19 for instance). I would certainly be interested to see how the authors of that study explain that away on African dust. I don't doubt that the transport of dust into the caribbean region has an influence of the marine life, however the evidence for warming waters as the cause of coral bleaching has strengthened to such a level that scientists are now able to accurately forecast bleaching events: Coral bleaching forecast - Coral Bleaching Likely in Caribbean This Year - Sept 22 2010 And reality: Caribbean Coral Die-Off Could Be Worst Ever - 14 Oct 2010 And yes, coral diseases are a major problem, often after bleaching events have occurred.
  23. Rob: I searched for, found, and read that paper after watching an educational TV program that covered the fungus, possibly a Nova? Chris Shaker
  24. Most references I see on coral bleaching list increased temperature as the main stress likely to cause it. Reading the wiki on Coral bleaching seems to offer a contradiction http://en.wikipedia.org/wiki/Coral_bleaching It says, "Bleaching occurs when the conditions necessary to sustain the coral's zooxanthellae cannot be maintained.[4] Any environmental trigger that affects the coral's ability to supply the zooxanthellae with nutrients for photosynthesis (carbon dioxide, ammonium) will lead to the zooxanthellae's expulsion.". That seems to say that CO2 is required for photosynthesis. Yet, they also state, "Coral bleaching is a vivid sign of corals responding to stress, which can be induced by any of: increased (most commonly), or reduced water temperatures[5][6] increased solar irradiance (photosynthetically active radiation and ultraviolet band light)[7] changes in water chemistry (in particular acidification)[8][9] starvation caused by a decline in zooplankton[10] increased sedimentation (due to silt runoff) pathogen infections changes in salinity wind[6] low tide air exposure[6] cyanide fishing" How much stock am I supposed to put in the 'acidification' mention when CO2 appears to be essential for coral photosynthesis? Chris Shaker
  25. f Found some more current research on wind born problems for coral reefs, from a Government source http://www.usgs.gov/newsroom/article.asp?ID=1970&from=news_side "African Dust Poses Threat to Coral Reefs and Human Health:  Contaminants carried with African dust to the Caribbean and the Americas may be a threat to marine organisms and humans, according to preliminary results of a new study by researchers with the U.S. Geological Survey, Oregon State University, and the University of the West Indies. The scientists compared contaminant levels in sources of African dust and downwind regions. Of the more than 100 persistent organic pollutants screened for in the samples, including banned and common-use pesticides, six pesticides (chlorpyrifos, dacthal, endosulfans, hexachlorobenzene, chlordane, and trifluralin) were detected in samples from all sites. Concentrations were significantly higher in Mali. DDE (a breakdown product of DDT) was also identified in Mali, U.S. Virgin Islands, and Trinidad samples. To date, DDT and carcinogenic dioxins and furans have been detected only in samples from Mali. Many of the identified contaminants are thought to be toxic to corals and other marine organisms and can interfere with reproduction, fertilization, or immune function. For more information, contact Virginia Garrison at 727-803-8747, ext. 3061 or ginger_garrison@usgs.gov." "The Origin of Aspergillus Sydowii, a Common Disease of Caribbean Corals:  Coral reefs are increasingly suffering outbreaks of disease, causing dramatic declines in population abundance and diversity. One of the best-characterized coral diseases is aspergillosis, caused by the fungus Aspergillus sydowii. A. sydowii is a globally distributed fungus commonly found in soil, so its presence in marine systems raises questions about its origin. By using microsatellite markers, researchers analyzed the population structure of A. sydowii from diseased sea fans, diseased humans and environmental sources worldwide. The results indicate that A. sydowii forms a single global population, with low to moderate genetic differences between the disease found in sea fans and the same fungus from environmental sources. Past researchers have suggested that A. sydowii originates from African dust blown into the Caribbean, and have identified Aspergillus from dust samples, although often only to the genus level. To test this, researchers isolated fungi from dust samples collected in Mali and St. Croix. Although a diversity of fungi was documented from African dust, including seven species of Aspergillus, none of the samples contained A. sydowii. Taken in conjunction with recent molecular evidence suggesting lack of a single point source of the fungus, this research suggests  that there are likely multiple sources and introductions of this pathogen into marine systems. For more information contact Krystal Rypien at 858-534-3196, krypien@ucsd.edu or  Virginia Garrison at 727-803-8747, ext. 3061 or ginger_garrison@usgs.gov." "The Emperor Has No Coral? Results of research on coral reefs in the Florida Keys reef challenge the highly popular notion that present declines in reefs in Florida and elsewhere are related to human activities. High-resolution sub-bottom profiling, reef drilling, and mapping of benthic habitats along the reef tract present a paradox in coral growth patterns: reefs that are dead or dying -- and therefore not building -- outnumber live and building reefs about 100 to 1. Yet growth rates of all common coral reef species should have kept pace with the well-documented rise in sea level over the past 6,000 years. Why did so few reefs keep pace or build up with the rise in the present sea level? Geological history may provide an answer: two 500-year periods of non-growth of coral reefs occurred in the region 4.5 thousand years ago and 3,000 years ago. These periods of non-growth indicate times of environmental crises that predated modern human presence in the Florida Keys. The present period of rapid coral demise has spanned only about 30 years. For more information, contact Eugene Shinn at 727-533-1158, eshinn@marine.usf.edu or Barbara Lidz at 727-803-8747, ext. 3031, blidz@usgs.gov." Chris Shaker

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