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Ocean acidification threatens entire marine food chains

Posted on 28 August 2010 by Michael Searcy

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 considerable price.

As ocean waters absorb CO2 they become more acidic.  This does not mean the oceans will become acid.  Ocean life can be sensitive to slight changes in pH levels, and any drop in pH is an increase in acidity, even in an alkaline environment.

The acidity of global surface waters has increased by 30% in just the last 200 years.  This rate of acidification is projected through the end of the century to accelerate even further with potentially catastrophic impacts to marine ecosystems.

Endorsed by seventy academies of science from around the world, a June 2009 statement from the InterAcademy Panel on International Issues (IAP) stated the following.

"The current rate of change is much more rapid than during any event over the last 65 million years. These changes in ocean chemistry are irreversible for many thousands of years, and the biological consequences could last much longer."
- The InterAcademy Panel, June 1, 2009

As surface waters become more acidic, it becomes more difficult for marine life like corals and shellfish to form the hard shells necessary for their survival, and coral reefs provide a home for more than 25% of all oceanic species.  Tiny creatures called pteropods located at the base of many oceanic food chains can also be seriously impacted.  The degradation of these species at the foundation of marine ecosystems could lead to the collapse of these environments with devastating implications to millions of people in the human populations that rely on them.

The IAP also stated that, if atmospheric CO2 were to reach 550 parts per million (ppm) along its current rapid ascent from its pre-industrial level of 280 ppm, coral reefs around the globe could be dissolving.

Oceanic species threatened by acidification

This post is the Basic version (written by Michael Searcy) of the skeptic argument "Ocean acidification isn't serious". We're currently writing plain English versions of all the skeptic rebuttals. If you're interested in helping with this effort, please contact me.

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Comments 1 to 36:

  1. Might be worth adding that there are not simply species "at risk" but there are already changes occurring which have been observed. I have forgotten the details, but it is among the planktonic species of the Antarctic.
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  2. Michael - One of the great metaphors for how small changes do great things is the alligator. At one temperature range, all the offspring become females, but just a few degrees away they all become male. " The gender of alligators is determined by the temperature of the eggs. Temperatures between 90 and 93 degrees Fahrenheit will produce males. Temperatures between 82 and 86 degrees Fahrenheit will produce females. " http://www.ehow.com/facts_5972765_difference-between-male-female-alligator.html
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  3. As this deary nightmare has unfolded , some winners have begun to show themselves. Just off the top of my head I can think of the following : Kudzu Poison Ivy Pine Bark Beetles Spruce Bud Worms No doubt the oceans will turn up winners in a more acidic world. I got 5 bucks sez , they aren't things we'll enjoy.
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  4. Jellyfish
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  5. Bacteria that eat hydrocarbons.
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  6. Not certain if it's heat or acidification, but we recently had the news about phytoplankton: http://www.nature.com/nature/journal/v466/n7306/full/nature09268.html
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  7. @dsleaton Looks like heat. This hypothessis has been supported by correlation between local temperature and phytoplancton abundance.
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  8. "The acidity of global surface waters has increased by 30% in just the last 200 years. " As I understand, 200 year old data on ocean pH is modelled, not measured, so we don't know for certain how much ocean pH has changed in the last 200 years. "These changes in ocean chemistry are irreversible for many thousands of years," This also is uncertain. From Wiki: "Leaving aside direct biological effects, it is expected that ocean acidification in the future will lead to a significant decrease in the burial of carbonate sediments for several centuries, and even the dissolution of existing carbonate sediments.[50] This will cause an elevation of ocean alkalinity, leading to the enhancement of the ocean as a reservoir for CO2 with moderate (and potentially beneficial) implications for climate change as more CO2 leaves the atmosphere for the ocean.[51]" The ocean subsurface is by far greater in area than all the worlds coral reefs. Sedimentation/dissolution processes could create a strong buffer to changes in ocean pH. This has never been factored into any IPCC or other models of ocean pH projections. We dont know what kind/magnitude of negative feedbacks occur in the ocean subsurface, and therfore there is no way we can make any meanigful statment regarding ocean pH projections. Past geological events indicate that it takes a long time for oceans to acidify (of the order of thousands of years++); this implies that negative feedbacks to changes in C02 in the atmosphere are likely to be strong, and current prjections far too simplistic and overstated.
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  9. Dsleaton @ 6 - yup, a real double whammy for phytoplankton, which are the basis for the ocean food web & recycle much of the Earth's oxygen. The warming oceans are becoming more stratified, thereby reducing nutrient upwelling and therefore leading to declines in phytoplankton abundance. Press release here: Marine Phytoplankton Declining: Striking Global Changes at the Base of the Marine Food Web Linked to Rising Ocean Temperatures Then there this bad news: Acidifying Oceans Spell Bleak Marine Biological Future 'by End of Century', Mediterranean Research Finds ,
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  10. Thingadonta @ 8 "Past geological events indicate that it takes a long time for oceans to acidify" Yes, exactly, past geological events (volcanic activity) released CO2 much more slowly than the rate at which humans are currently adding it to the atmosphere. That's why the current acidification is progressing much faster. Obvious really.
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  11. #Dappeldwater: Volcanic events can be rapid, medium term or long term. C02 has been released faster than humans are currently adding c02 to the atmosphere, and yet oceans didnt acidify. As usual coral researchers take no account of the geological record. Obvious really.
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  12. 9.Dappledwater I think some old denier pointed this out on WUWT. As you say phytoplankton are virtually the sole source of energy for the whole of the marine environment. Without them there is no food chain, nothing. If phytoplankton halved since 1950 that would have to mean the whole marine ecosystem would have to also have havled. I think a total biomass drop in the ocean of 50% would a) be easy to see and b) have people screaming. I don't think we've lost 50% of the living biomass of the oceans unless you know otherwise.
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  13. Humanity Rules - I take your overall point that we would notice a 50% drop. However I googled food supply from the ocean and came up with 5% (5% of all food humans eat comes from the ocean). Way out of my depth (tiny pun intended) on this issue - but maybe we wouldn't notice for a few years. And marine biologists tell us the oceans and transitions zones are in a WORLD of hurt. So maybe we have, in fact noticed.
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  14. Something that would be worth making reference to is the impact of the Well Mixed Layer at the top of the ocean and its impact on Total CO2 uptake by the oceans (and thus Ph) vs uptake just by the WML. Although this may not be appropriate for the Basic version, perhaps an update to the Intermediate version. The WML is the top of the ocean where wind and wave action, tidal movements and even movements of living things ensure that it is fairly well mixed - hence the name. The rest of the ocean below it, around 97% of it is extremely NOT well mixed, with the main mixing force for the bulk of the oceans appearing to be upwelling and downwelling currents at certain points. The result of this is that both overall CO2 Uptake rates by the ocean, and Ph changes, in the short timescale of decades is driven predominantly by what happens to the WML - the bulk of the ocean volume isn't particularly in play on this timescale The oft cited sceptic argument that the ocean contains 50 times as much CO2 as the atmosphere and therefore CO2 in the atmosphere can't be from us - the oceans soaked it all up - and Ph consequently can't change that much is based on the fallacy that on short time scales the whole ocean is in play. It isn't. Over centuries and millenia, yes and this is relevant to Thingadonta's comments about short geological timescale evidence, what might happens due to the geochemistry of the depths etc. However we probably can't read very much into what this signifies for our modern experience since the rate at which change is occuring swamps past rates and substantially removes whole-of-ocean measures from consideration. Perhaps Ocean Acidification should actually be called Well Mixed Layer Acidification. And this is bad enough since most of the marine lfe we are concerned about lives in or survives from the WML. An interesting Back-of-the-envelope calculation. If the oceans hold 50 times as much CO2 as the atmosphere, and the average depth of the oceans is around 3800m, and the WML at the top is on average about 100m deep, then the WML holds 1.32 times as much as the atmosphere (ignoring temperature, salinity,etc, this is a BOTE calc) 43% in the Atmosphere and 57% in the WML. Rather in the ballpark for the usual figures for percentage uptake by Oceans vs Atmosphere. The following text from Spencer Wearts 'The Discovery of Global Warming', http://www.aip.org/history/climate/Revelle.htm is fascinating reading. Particularly the discovery of just how much an atomic bomb exploded at depth DIDN'T disrupt ocean stratification. Also the not spelled out link between CO2 uptake in the oceans and Boron! This sort of puts simplistic arguments by sceptics that it is just about Henry's Law in the shade
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  15. thingadonta @8 "The ocean subsurface is by far greater in area than all the worlds coral reefs. Sedimentation/dissolution processes could create a strong buffer to changes in ocean pH. This has never been factored into any IPCC or other models of ocean pH projections." Why do you exclude all of the work that has been done on this topic, for example, by David Archer of the University of Chicago (also contributor to REALCLIMATE)? David has been modeling sedimentation and dissolution of calcium carbonate for two decades, and then incorporating those results into global models of ocean buffering and its impact on pH and CO2. Is there something about this work that you find unsatisfactory so that you discount it in making the statement quoted above? Of course, as worrisome as ocean acidification is, corals face a greater danger from bleaching due to ocean warming, as described in a news item in yesterday's issue of SCIENCE.
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  16. Thingadonta @ 9 -"C02 has been released faster than humans are currently adding c02 to the atmosphere" When, for instance?. Some supporting evidence for your assertion would help. "and yet oceans didnt acidify." Well actually they did, mostly the deep ocean though. See the intermediate version of this rebuttal. And Ocean Acidification in Deep Time And note some comments from the study: "Nevertheless, observations and modeling clearly show that during the PETM the deep ocean, at least, became highly corrosive to CaCO3. These same models applied to modern fossil fuel release project a substantial decline in surface water saturation state in the next century. So, there may be no precedent in Earth history for the type of disruption we might expect from the phenomenally rapid rate of carbon addition associated with fossil fuel burning." And: It is the rate of CO2 release that makes the current great experiment so geologically unusual, and quite probably unprecedented in Earth history. Indeed, much of industrialization and economic activity revolves around energy generated from fossil fuels. In other words, much of humanity is, in efect, engaged in a collective and deliberate efort to transfer carbon from geological reservoirs to the atmosphere as CO2. The resulting rate of environmental change very likely far exceeds that associated with past greenhouse transient events, and will have been exceeded in the geological record only by bolide impacts of the sort that caused the K/T extinction 66 million years ago".
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  17. Colorado Bob writes: The gender of alligators is determined by the temperature of the eggs. Temperatures between 90 and 93 degrees Fahrenheit will produce males. Temperatures between 82 and 86 degrees Fahrenheit will produce females. Huh. So I guess another danger of AGW is that we'll be overrun by mobs of angry male alligators, all frustrated at their inability to find a mate ...
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  18. #16: dappledwater "...rate of CO2 release that makes the current great experiment so geologically unusual, and quite probably unprecedented in Earth history. " I dont think so. A volcanic event such as a flood basalt event associated with a emerging hotspot or Siberian Traps event exceeds rate and magnitude of human C02. Volcanic events such as the Siberian Traps emitted more c02 than humans ever will. Oceans did not acidify for tens of thousnds of years from this kind of output, in both rate nor magnitude greaer than human c02 emissions, so they wont acidify from human emissions of c02 on short time scales. The geological record indicates that these sort of amounts of c02 are buffered in the oceans-which is why oceans take a long time to acidify. Some researches acknowledge this but twist this around and say such and such rates of acifidication haven't happened in such and such million years; this actually provides good evidence that the oceans are buffered. #15 Boba10960 There is a vast and dynamic interplay between c02/c03 and the ocean subsurface. Most limestone in the world is in fact formed as a result of precipitation of c03 from ocean waters, and not from coral reefs. How his actually occurs/rate has been a matter of debate for decades. An example is the dolomites in Italy, which is the type area for dolomite rock. Tese formed from ocean precipitation. Currently I am engaged (along with other work) in analysing/reviewing thousands of metres of carbonate-enriched sediments formed close to the ocean/subsurface interface. These sort of carbonate- saturated sediments are everywhere. The interface of c03/c02 in eg volcanic realms extends thousands of metres beneath the sea floor, eg along much of the Mid Ocean Ridge system. One question: has David Archer and the IPCC, along with coral reef researchers, factored in the thousands of metres of c03/c02 interaction/interface along all the world's ocean ridges? I bet the answer is, they haven't. (Note: some NASA sceintists think the world's ocean water comes from comets-they know nothing about crustal geology and how granites expel water when they cool-which is how the world's oceans formed when the earths crust first cooled; the point is they are ignorant of what goes on in the subsurface. Couldn't coral reef researchers be making the same sort of mistake?)
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  19. HR @ 12 - one of those logical fallacies I suspect - personal incredulity. Much of the food chain higher up, things like fish, squid, shrimps etc have had their populations devastated on a global scale by overfishing, sediment and nutrient run off. How many people notice that decline?. Anyone remember the North Atlantic cod fisheries?. If you spend as much time under the sea, as I do, you do tend to notice the changes to the marine environment. It's not pretty I assure you.
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  20. Thingadonta @ 18 - " I dont think so. A volcanic event such as a flood basalt event associated with a emerging hotspot or Siberian Traps event exceeds rate and magnitude of human C02." That's simply your non expert opinion, not supporting evidence. Read the study I linked, it actually addresses such issues.
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  21. thingadonta writes: A volcanic event such as a flood basalt event associated with a emerging hotspot or Siberian Traps event exceeds rate and magnitude of human C02. From Saunders 2009:
    However, if we consider the province as a whole, the eruption of between 2×10^6 and 3×10^6 km3 of basalt could release 12000 to 18000 Gt of C, enough to significantly change the carbon content of even a Permian atmosphere. Note that the eruption of 18000 Gt of C over 1 million years equates to only 0.018 Gt per year, a fraction of the current output from burning of fossil fuels (~ 7 Gt C/a).
    There's lots of other useful information in Saunders 2009, if you're interested in flood basalt episodes.
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  22. #8 Thingadonta, Yes, the historical composition of the ocean's carbonate system and pH is modeled, but it's done with the same models used to measure modern values since the constituents cannot be easily measured directly even today. The models are empirically derived and have very small uncertainty ranges for the modern era when seawater B11 and C12/13/14 isotope concentrations are known. #11 thingadonta Actually, we DO take into account the geologic record and the effects that changing carbonate chemistry in the ocean has affected calcifiers in the the past, which is precisely why we're worried about them now. The oceans DID acidify multiple times in the geologic record with major associated diverstiy changes and in at least a few cases, major extinction events. Reefs in particular have been wiped out, with the dominant reef-builders at the time being driven completely or ecologically extinct, 4 or 5 times at least. In the most recent major event, reef building ceased entirely for 12-18 million years and skeleton-building corals virtually disappeared. The re-emergence of calcifying coral diversity and reef building only began again after the seas switched back from calcitic to aragonitic.
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  23. 12 Humanity rules, You're making several huge errors here. First, primary producers are bottom of the food chain. While phytoplankton are included in that, they are far from the only constituents. In coastal waters there the highest concentration of biomass is, there is also high productivity of autotrophic bacterioplankton, vascular plants, and benthic micro/macroalgae in addition to the phytoplankton. There are complete food chains that don't include phytoplankton at all. Second, most phytoplankton dies and sinks without being eaten- i.e. it is in excess. A 50% drop in phytoplankton would only equate to a 50% drop in heterotroph biomass if all of the phytoplankton was being eaten. That's not to say that a 50% loss of phytoplankton has no effect, because it does- particularly on C/N/P cycling, but that it does not translate linearly to changes in heterotroph biomass Third, the majority of the world's fish stocks have declined over the historical period. Traditionally we have viewed this as a top-down process (i.e. we're removing them faster than they reproduce), but that doesn't mean that bottom-up processes (lack of food) isn't also behind the decline. Until very recently we just haven't been looking for evidence from that perspective and you tend not to find things you don't look for.
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  24. 18 Thingadonta Yes, we're well aware that the ocean is well-buffered. That is absolutely no comfort to us because it is well-buffered due to the carbonate/bicarbonate buffer system. When you add CO2 to seawater you convert bicarbonate to carbonate. That conversion is what buffers the pH change, but in the process it lowers the bicarbonate concentration in the water. That is bad news for corals and most other extracellular calcifiers which rely on a high ambient bicarbonate concentration to lay down CaCO3. While the change in pH is easier for most people to understand than a change in the CaCO3 saturation state and it does allow us to calculate changes in HCO3/CO3 concentrations, the actual concern over acidification is the change in bicarbonate ions moreso than the change in pH. Also, while most limestone isn't laid down by corals, virtually all CaCO3 production in the ocean is biotically driven or facilitated. There is very little precipitation of CaCO3 in the ocean that's still considered abiotic. As for whether coral reef researchers have factored in the effects of carbonates near the Atlantic ridges- no, because on the timescale we're concerned with they are irrelevant. If we were interested in what would happen in 1000 years or so they would be important. However, they're interfacing with bottom water, not the mixed layer and any changes they induced would take ca. 800 years to be telecommunicated to the mixed layer where most calcifiers, including corals, live. Whether those carbonates are relevant to or have been factored into Archer's or the IPCC's models, I don't know.
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  25. #24 Mike G "virtually all CaCO3 production in the ocean is biotically driven or facilitated." A question I have is this: in the ocean subsurface, volcanic rocks around mid ocean ridges (not just in the Atlantic-the 100,000km+ of volcanic ridges around the world), where seawater circulates down several thousand metres, carbonate dissolution/precipiation is driven by volcanic procesess, including heat, not biotic processes. This domain is far larger than areas of limestone/biotic procesess. Carbonate-enriched rocks from volcanic processes are widespread. This carbonate isnt biotic related, and it isnt factored into the models. The volcanic domains which produce/effect carbonate levels extend from ocean floors right through to shallow-subaerial environments (eg mId Ocean Ridges-through to areas like NZ North Island). Surely this must have a large effect on ocean pH/carbonate levels?
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  26. thingadonta @18: (Note: some NASA sceintists think the world's ocean water comes from comets-they know nothing about crustal geology and how granites expel water when they cool-which is how the world's oceans formed when the earths crust first cooled; the point is they are ignorant of what goes on in the subsurface. My guess is that they know more about it than you. I've known any number of geologists and geophysicists that worked for NASA--they're not all aeronautical engineers. Where do you think the water that granite expels when it cools comes from in the first place? The bulk of granite is emplaced above subduction zones where water-saturated sediments and rock are subducted and heated, resulting in partial melting in the upper mantle/lower crust. When those melts cool and crystallize (into granite), the water that facilitated the melting is released.
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  27. Glenn Tamblyn at 19:12 PM, whilst your reference to the WML focused on CO2, the same conditions will also apply to any heat circulation relating to absorption and release as well as changes in volume due to temperature changes.
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  28. I see people are trying the "ocean water is well buffered" argument again. But wait a minute: we have managed to lower the pH _despite_ that buffering. What do you think that means will happen as we continue to pour yet MORE CO2 into the ocean? Soon, we will have only jellyfish to eat from the sea. Unless we wise up and do it FAST.
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  29. johnd @27 Agreed John. I once had a sceptic show me an analysis he had done, looking at the change in energy distribution around the planet over the course of a year and ocean temperature changes over the same period as an argument for why the oceans don't have a big thermal lag. All he had actually done was make a rough calculation of the size of the WML. Somehow he just couldn't see that though...
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  30. My previous link was broken, Ocean Acidification in Deep time
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  31. Thingadonta @ 25 - Your latest speculative proposition has some problems. 1. The current rapid increase in atmospheric CO2, due to fossil fuel combustion, is being mirrored in CO2 dissolved in surface sea waters (those above 800 meters) & a corresponding decline in ocean ph. 2. This relationship between atmospheric CO2 and ocean ph dates back not only 800, 000 years ( See figure 1 of intermediate version here) , but likely many millions of years. 3. Note the scale of recent change (1800 to 2000) compared to changes in ocean ph for the last 20 odd million years. It's unmatched in the record because the natural processes (weathering & carbonate deposition) can't keep up with the rate humans are injecting carbon into the atmosphere. 4. There is no evidence of an unprecedented super-ginormous increase in volcanic activity on land, why do you suppose (sidestepping issues with ocean mixing, increased stratification and time lags) there is for submarine volcanoes?
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  32. The principal response to the "ocean water is well buffered" argument is to note the contrasting time scales of the processes involved, as noted in several comments above. The pH of surface ocean water (WML) responds to rising CO2 in the atmosphere almost immediately, within a year or so. By contrast, hundreds of years are required for acidified surface water to be mixed into the deep ocean, and it takes thousands of years for reactions with calcium carbonate in the deep sea to buffer the acid. These processes and their associated time scales are incorporated into models, and that is why scientists know that buffering reactions are "too little - too late". Organisms living in the WML will feel the full impacts of acidification over the next century or so, long before the acidified water even reaches most regions of the deep ocean where buffering reactions can occur.
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  33. I wish I had seen the first figure of 31 Dappledwater before posting my previous comment. That figure illustrates the point that the chemistry of the WML responds almost immediately to rising CO2.
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  34. CO2 pollution of the oceans (acidification) is and should be regarded as a major concern because it reduces aragonite. Thus reduces the ability of calcifying animals, particularly pteropods, to form shells and hence their ability to survive. Their disappearance, predicted by 2050, would create a potentially catastrophic break in the marine food chain, resulting in massive depletion of marine life. http://www.onlineopinion.com.au/view.asp?article=8934 That outcome is made more likely by several contributing factors such as rising temperature of seawater, pollution from human waste and overfishing as fish species diminish. The latter two can be expected to increase significantly as human population grows, while warming seawater is an inevitable outcome of global warming. No one should be in doubt that the future is bleak and largely our fault.
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  35. Agnostic at 11:44 AM on 30 August, 2010 I posted this elsewhere on the "acidification" thread, so sorry to repeat, but is pertinent here. The first deep basin observations of Aragonite undersaturation in surface waters have already been observed in 2008 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 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.
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  36. actually thoughtful @ 13 So only 5% of the global population depend on fish as their only or primary source of protein. This is at odds with views expressed by James et al (2010) and the FAO which claim that over16% are dependent seafood. Peter Hogarth @ 36 Thank you (I think) for a comment which alas reinforces my view that the future is indeed bleak and unlikely to improve given our voracious fishing industry driven by the need for profitability rather than sustainability.
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