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Warning bells: what Antarctica can teach us about ocean acidification

When it comes to climate change, temperature is only part of the story. Climate gases released by human activity are dissolving into the oceans, and the increased levels of CO₂ are making the waters more…

Antarctica’s delicate marine ecosystems are under threat from climate change and ocean acidification. wikimedia/Steve Clabuesch

When it comes to climate change, temperature is only part of the story. Climate gases released by human activity are dissolving into the oceans, and the increased levels of CO₂ are making the waters more acid. This process threatens marine life from coral reefs to fragile polar ecosystems. It seems likely that the polar oceans will be the first to feel the full force of ocean acidification. These cold seas may provide an important lesson for Australia’s warmer waters.

Heading for the poles

Changes in the earth’s climate are expected to have major effects on marine biodiversity. Predicting how species will respond to shifts in the timing, magnitude and predictability of future climate patterns is one of the key issues for humanity over the next 100 years.

There are a number of ways marine species can persist in the face of these changes. They can cope within their current physiological capacity, migrate to new regions, or adapt to new conditions. Otherwise they risk becoming extinct.

The ranges of oceanic species worldwide are shifting polewards towards cooler latitudes, and as these places warm faster, marine life is moving faster too. But the effect of acidification on marine animals is expected to add to the impact of temperature.

Hard-shelled but thin-skinned

Ocean acidification makes it harder for marine animals to build their calcium carbonate skeletons, which they need for movement and protection against predators.

As oceans become more acid, seawater chemistry is altered, making calcium carbonate harder to extract and increasing the cost of producing shells. More gas dissolves in cold water and therefore animals from colder oceans are at greater risk from acidification from atmospheric increase in CO₂. Calcium carbonate saturation is already lower in polar oceans, and as oceans acidify, undersaturation is predicted to occur first in the shallow waters around Antarctica.

Ocean acidification will, therefore, result in calcium carbonate becoming a limiting resource for animals at the poles, before it becomes a limit in oceans closer to the tropics. The poles are “natural laboratories” for investigating the impact of ocean acidification, particularly when compared to lower latitudes.

A recent study has shown that the proportion of body mass given to shell production is less in colder oceans, where concentrations of available calcium (Ca2+) are reduced.

Building a skeleton requires calcium (Ca2+) ions to be pumped, from seawater, against concentration gradients. The larger the gradient - like in the polar oceans - the more energy is required. If the energy costs to the animal increase sufficiently, it may reduce the amount of energy for other functions. For example, if there is less energy for reproduction this would reduce the capacity of the species to sustain its populations.

Stress, from environmental challenge, very often reduces the immune capacity of animals, so they may become more susceptible to disease. Bacteria also multiply faster in warmer conditions.

Changing ecosystems

In the Antarctic, the warming of shallow seas could also see a return of crushing predators such as crabs, which cannot currently survive in such cold water. Shells in polar regions may be too thin to resist these new predators. This will be worse if shells are further thinned as oceans become depleted of available calcium.

This is an extreme example of how shifts in ecological balance are caused by climate change. More subtle ecological shifts in the balance of competition between species, including shifts in energy budgets and disease resistance, are likely to be seen wherever species ranges shift.

As species ranges shift across latitudes they encounter different day lengths at different times. This could drastically effect the timing (the “phenology”) of seasonal activities such as reproduction, causing mismatches with food availability if young hatch at the wrong time.

What can we learn from Antarctica?

The ability of species to cope with all these potential effects of future ocean conditions needs to be assessed. To date we have far too little information to make robust predictions.

How species ranges and abundance will change under future conditions is a vitally important area of study for biologists. We need to be able to predict the effects on both natural ecosystems and the “ecosystem services” these provide to human populations.

Understanding the underlying mechanisms of how species respond to current conditions is similarly important to understand how they will cope with future change. Comparing polar oceans and warmer zones will help interpret the effects that are being seen in the seas around Australia.

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  1. Mike Jubow

    forestry nurseryman

    These days, nothing irritates me more than the climate change deniers who try to tell us that more CO2 in the atmosphere is good because it 'fertilizes' plants and do everything to skirt around dissolved CO2 in sea water being destructive to the marine environment. To a large extent, even the 'fertilizing' effect on plants has been debunked. In a face to face discussion I had with one of these types recently, I asked this blokes opinion on whether or not the Japs should be allowed to hunt whales…

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  2. Sean Lamb

    Science Denier

    Just out of curiosity - the CO2 levels have been a lot higher in the past. For example 100 million years ago it was in excess of 1000 ppm.
    Is there data on the ocean PH, corals and shell making organisms?
    My understanding it was a time of great genetic diversity, but maybe not if you like shells.

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    1. David Arthur

      resistance gnome

      In reply to Sean Lamb

      Is there data on shell-forming organisms? Yes there is, and they were present, albeit in different numbers to present/recent past.

      It's worth noting that if the physical environment changes slowly enough, extinction rates aren't that large. It's the rapidity of the changes that mater.

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  3. Chris Owens

    Professional

    Do the CC deniers accept the science of increasing ocean acidification?

    If this was an article primarily about CC, there would be dozens of denier comments by now.

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    1. Mark Pollock

      Analyst

      In reply to Chris Owens

      No. There is a big difference between a substance becoming less basic and more acidic. The author does not appear to appreciate this.

      Also, we don't even know if the ocean is becoming less basic as a result of the minuscule (in absolute terms) increase in atmospheric CO2. It's just another scare story to compensate for the observed lack of global warming.

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    2. David Arthur

      resistance gnome

      In reply to Mark Pollock

      In aqueous systems, there is NO difference between less basic and more acidic.

      Analysts don't really understand chemistry, do they?

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    3. Mike Jubow

      forestry nurseryman

      In reply to Mark Pollock

      Mark, it seems as if you do not appreciate that the pH scale is not linear. It is an exponential scale and to move the pH by 0.1, there has been a downshift toward the acidic side. It is not minuscule as common perceptions would have it.

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    4. Mark Pollock

      Analyst

      In reply to David Arthur

      Proton transfer one way = basic. The other way, acidic.

      More to the point, is the ocean becoming less basic. Has this been measured? Shouldn't have some solid data before accepting these assumptions?

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    5. takver takvera

      Journalist and Editor at Indymedia

      In reply to Mark Pollock

      Mark, the biochemistry is fairly clear and understood based on observational data, and from my reading acidification is already affecting shell growth rates in the sub-arctic seas and the Southern Ocean around Antarctica. Hardly a scare story. Just a quick search of google scholar will find you heaps of reading material:
      http://scholar.google.com.au/scholar?q=ocean+acidification+southern+ocean&hl=en&as_sdt=0&as_vis=1&oi=scholart&sa=X&ei=p0ZcUe76NLGSiAe364GACA&ved=0CC4QgQMwAA

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    6. David Arthur

      resistance gnome

      In reply to Mark Pollock

      "Has this been measured?" Yes.

      See, for example, http://www.epa.gov/climatechange/science/indicators/oceans/acidity.html, also
      http://www.afsc.noaa.gov/Quarterly/jas2012/JAS12-Feature2.pdf, from which is this clarifying point "The increase in oceanic CO2, when incorporated into the carbonate system, has resulted in an average decrease of surface ocean pH by 0.1 units, the equiva­lent of a 30% increase in acidity".

      Analyse this: "Ocean becoming less basic is EXACTLY THE SAME AS ocean becoming more acidic."

      Think of it like this: temperature yesterday was 19 deg C, temperature today is 20 deg C. So which of the following is true?
      1) Yesterday is colder than today.
      2) Today is warmer than yesterday.

      Applying your reasoning, where ocean being less basic is not the same as ocean being more acidic, would see us having to choose between the above two statements, not accepting both.

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    7. Whyn Carnie

      Retired Engineer

      In reply to David Arthur

      Your statement "Ocean becoming less basic is EXACTLY THE SAME AS ocean becoming more acidic." is a fallacy. The analogy to warming and cooling is incorrect. Thus your final statement is irrelevant and deceptive.
      To start with the analogy, Warmness and coolnes are unquantifiable perceptions that humans can experience in qualitative manner. Acidity on the other hand is a precicely quantifiable chemical measure in no way able to be equated to alkalinity.
      The fallacy in the basic/acidic statement is…

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    8. David Arthur

      resistance gnome

      In reply to Whyn Carnie

      CO2(g) + H2O(l) <=> H2CO3(aq) <=> H+(aq) + HCO3-(aq)
      HCO3-(aq) <=> H+(aq) + {CO3}2-(aq)

      ie dissolution of CO2 in water increases acidity of that water.

      The (aq) notation identifies aquated ions, what you call H3O+, the <=> notation identifies dynamic equilibria.

      This Manichaean separation of the world of water into "acidic" and "alkaline" is incorrect. But don't despair, it's all explained for you by the friendly folk at the Oak Ridge National Laboratory's Carbon Dioxide Information Analysis Center. Read "Solution chemistry of carbon dioxide in sea water", http://cdiac.ornl.gov/ftp/cdiac74/chapter2.pdf

      That should clarify your confusion.

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  4. Mark Pollock

    Analyst

    The author raises the alarming prospect of a "return of the crushing predators"(sounds like a Japanese schlock horror movie) - and as an aside, how can the ferocious crushing predators return if they had not previously been there?

    These crushing predators also have calcium carbonate shells so shouldn't they be thinned out too? This would clearly limit their crushing ability.

    The author also tells us that increased "acidification" in the polar regions will make the little critters more susceptible to bacteriological attack as bacteria multiply faster in warmer conditions. Is there any evidence whatsoever that they polar regions are ever going to become "warm"? Warmer maybe but still very very fridge like.

    Just another scare story it seems.

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    1. David Arthur

      resistance gnome

      In reply to Mark Pollock

      If you're adapted to -10 to, say, 4 deg C, 6 deg C is way too hot for you. Analysts don't really understand ecology, do they?

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    2. Dennis Singer

      Student

      In reply to Mark Pollock

      There must be a simple description of this type of fallacy, the "I don't have the intellectual capability to make sense of it therefore it doesn't exist."

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    3. Mark Pollock

      Analyst

      In reply to David Arthur

      Yep, you lost me on that one. Did you mean -4 C? Are you saying that polar water heat is going to increase by 6 degrees? Either way, bacteriological activity is going to be similarly minimal.

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    4. Mike Jubow

      forestry nurseryman

      In reply to Mark Pollock

      Mark, read up on chitin and arthropods. You may then understand what the author was on about.

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    5. Mike Jubow

      forestry nurseryman

      In reply to David Arthur

      No, David, but they love to display their ignorance on their sleeve.

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    6. takver takvera

      Journalist and Editor at Indymedia

      In reply to Mark Pollock

      Mark, try doing some basic reading and research, Google is a good start. Your ignorance and disdain for understanding is clearly lacking. On the crushing predators: a September 2011 paper in Proceedings of the Royal Society B - 'A large population of king crabs in Palmer Deep on the west Antarctic Peninsula shelf and potential invasive impacts'. More recent article in Nature: Polar research: Trouble bares its claws. http://www.nature.com/news/polar-research-trouble-bares-its-claws-1.12015 Now those 2 references took me less than 2 minutes to find.

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    7. Michael Shand

      Software Tester

      In reply to Dennis Singer

      Argument from Personal Incredulity: Asserting that opponent’s argument must be false because you personally don’t understand it or can’t follow its technicalities. For instance, one person might assert, “I don’t understand that engineer’s argument about how airplanes can fly. Therefore, I cannot believe that airplanes are able to fly.” Au contraire, that speaker’s own mental limitations do not limit the physical world—so airplanes may very well be able to fly in spite of a person's inability to understand how they work. One person’s comprehension is not relevant to the truth of a matter

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    8. David Arthur

      resistance gnome

      In reply to Mark Pollock

      The numbers I used were intended to illustrate a concept, sorry I wasn't sufficiently specific. Try the following.

      King crabs invade Antarctica
      http://www.sciencedaily.com/releases/2011/04/110419191022.htm

      Antarctic Marine Life Under Threat From Warming Seas, New ...
      http://www.sciencedaily.com/releases/2008/02/080217200926.htm

      Fish of Antarctica threatened by climate change
      http://www.sciencedaily.com/releases/2012/02/120213154053.htm

      Global Warming Threatens Antarctic Sea Life
      http://www.sciencedaily.com/releases/2009/02/090205083301.htm

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    9. Mark Lawson

      senior journalist at Australian Financial Review

      In reply to takver takvera

      takver - I think I've pointed out to you before that the acid ocean business is a stretch at best.. go and look at your own link. It deals with changes in temperatures rather than ocean acidification.. and as you'll find if you actually read both what you cite and this article, far too little is known about the actual effects to make much of a conclusion. Sure something might be happening. What is it due to? Are we looking at a cycle or some sort of unnatural changes. If you care to do some reading yourself you will find that changes in the ocean currents are still almost an unknown field.

      the author of the article are entitled to speculate on a link between changes in currents and the increase in headline temperatures that occurred between the mid-70s and the turn of the century, and current high ocean temperatures, but bear in mind that it is largely speculation.

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  5. Whyn Carnie

    Retired Engineer

    Too many amateur chemists getting into this debate, including many from academia. Oceanic flora and fauna flourish in locally less alkaline parts of the oceans already. How do these authors explain that?
    Personally, I can't wait for the Antarctic Ice cap to melt away and allow the underlying soils to be developed as additional farmlands for those vital CO2-absorbing trees and grasses. Yaks will thrive under these conditions. There will be an added benefit of revealed minerals and orebodies, perhaps even coal and oil, which will help warm the new settlers. It will always be cold even tho' Gaia has warmed a bit elsewhere..

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    1. Felix MacNeill

      Environmental Manager

      In reply to Whyn Carnie

      Whyn, re the question concluding your first paragraph, perhaps the authors explain it by realising (as anyone awake would realise and wouldn't need to be told) that they are different species that evolved over generally quite long periods of time to local conditions. This is completely irrelevant to the point being made in the article. Nobody was saying that creatures can't exist, per se, in less alkaline waters, rather that the ones that happen to be there now will be threatened and it's improbable…

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