High levels of carbon dioxide threaten oyster survival

It has been widely reported that the build up of carbon dioxide (CO2) in the air, which is caused by human behavior, will likely lead to climate change and have major implications for life on earth. But less focus has been given to global warming’s evil twin, ocean acidification, which occurs when CO2 lowers the pH of water bodies, thus making them more acidic. This lesser known phenomenon may have catastrophic effects on all sea life.

Oysters in Peril
Inna Sokolova, associate professor of biology at the University of North Carolina at Charlotte, studies the affect of high carbon dioxide on oyster survival, growth and shell hardness. The results of her research suggest that creatures once thought to be fairly adaptable to changes in the environment, may be in serious trouble.

Sokolova’s research team includes Anna Ivanina and Ilya Kurochkin also from the University of North Carolina at Charlotte and Nicholas Lieb and Elia Beniash from the Department of Oral Biology at the University of Pittsburg. Their research findings will be reported by Sokolova at the Global Change and Global Science: Comparative Physiology in a Changing World conference from August 4-7, 2010 in Westminster, Colorado. This conference is sponsored by the American Physiological Society. Full conference program.

The research group monitored oysters that were kept in high CO2 conditions. Juvenile oysters were affected the most by high CO2 conditions. These young oysters grow at a faster rate than the adults and need to use more energy for survival. There was a higher chance that juvenile oysters would die if kept in high CO2. They also had reduced growth of their shells and their soft bodies. The young oysters’ shells were also more fragile and prone to breaking, potentially making them more susceptible to predators.

“Living in the high CO2 world may increase the cost of living which cuts into other energy expending pathways,” says Sokolova. “Everyday maintenance becomes harder making it harder to live.”

The effects on growth were less pronounced in the adult oysters since they don’t grow as fast and have slower metabolisms than the juveniles.

The fact that the early life stages are more affected by high CO2, suggests that this may serve as a bottleneck for oyster decline. Sokolova says, “Expect to see huge effects on populations in the future.”

The researchers found evidence that the oysters are sensing and trying to offset the affects of a high CO2 environment. The oyster’s soft body covering called the mantle had increased expression of carbonic anhydrase, an enzyme that regulates pH and helps make bicarbonate, which is used to make the shell. Sokolova believes that the increased levels of this enzyme show that the oysters are at least trying to compensate for the acidic conditions in response to CO2, but it doesn’t seem to be enough.

Oysters – Ecosystem Engineers of the Sea
Oysters live in estuaries – coastal water bodies that have fresh water rivers flowing into salt water – which are highly variable environments because of tides, waves and changes in salt concentration. The focus for those scientists interested in ocean acidification/climate change research generally has been on organisms in stable situations that are thought to be more affected by small changes in the environment. “People feel that oysters are tough and will tough out the changing conditions so they haven’t been a primary research focus, but oysters are vulnerable too,” says Sokolova.

Sokolova describes oysters as “ecosystem engineers,” that are responsible for preventing erosion, filtering the water, ridding the water of harmful algae, providing a habitats and nurseries for other species like crabs. In addition, they are the number one harvested mollusk, meaning their presence is important economically for the seafood industry.

“We are looking at the effects of a very real environmental stressor that oysters see even nowadays. Our research shows that even under the present conditions they may be stressed,” says Sokolova. “Monitoring these guys will help us monitor the effects on the entire ecosystem as levels of CO2 increase.”

Physiology is the study of how molecules, cells, tissues and organs function to create health or disease. The American Physiological Society has been an integral part of this discovery process since it was established in 1887.

newswise.com, 5 August 2010. Article.

5 Responses to “High levels of carbon dioxide threaten oyster survival”

  1. 1 Klaus Kaiser 10 August 2010 at 00:06

    Luckily (for the oysters), there is something called photosynthesis. That process converts CO2 to neutral and alkaline substances in the oceans. That is why the oceans have a pH of approximately 8. It is BECAUSE, not DESPITE, the atmospheric CO2 being there!

    For more details, see my book CONVENIENT MYTHS, or my blog at:
    http://www.convenientmyths.com .

  2. 2 Inna Sokolova 12 April 2011 at 19:30

    This is a rather ill-informed comment that lacks in understanding of basic biology of photosynthesis. Photosynthetic organisms such as algae and phytoplankton consume CO2 (and incorporate it into the organic matter) but this CO2 is rapidly released once the algae die or are eaten and the organics is broken down in the process of respiration. They do not convert CO2 into any kind of “alkaline” substances.

    Unfortunately (for oysters and many other organisms as well as for us), the current rate of the CO2 increase is unprecedented in the Earth history, and that’s the main problem. Many organisms are able to adapt to changing environmental conditions given sufficient time – but time is exactly what they don’t have in the present situation because the change is too rapid. Some of fastest changes in atmospheric CO2 levels known from the paleontological record occurred over the period of ~ 20,000 years (such as the Paleocene–Eocene Thermal Maximum 60 MY ago when a massive increase in atmospheric CO2 led to rapid global warming and ocean acidification) and led to mass extinctions, profound changes in ecosystems, and major perturbations in the carbon cycle. We don’t even begin to understand what would be an impact of the CO2 change of a similar magnitude that occurs 60 times faster. I am sorry but there is nothing mythological or convenient about this fact.

  3. 3 Klaus Kaiser 17 June 2011 at 03:13

    16 June, 2011
    Dear Dr. Sokolova,
    Being busy with many things, I just became aware of your reply (on 12 Apr. 2011) to my comment (on 10 Aug. 2010) to your article (of 7 Aug. 2010).
    Quite frankly, I recommend you read up on some basic ecology literature. Then you ought to realize that, contrary to your article and reply to my earlier comment, CO2 is indeed the driving force of the oceans’ (and most freshwaters’) alkaline property. While the current rate of CO2 emission to the atmosphere (a significant portion of it due to mankind’s burning of fossil fuels) is approaching nature’s “own emissions” (from volcanic vents), in an otherwise undisturbed ecosystem it will result in increasing the waters’ pH via photosynthesis. I have shown that in more detail in my article on “Ocean Acidification and the CO2-Propaganda” (http://canadafreepress.com/index.php/article/26571 ; 14 Aug. 2010).
    Therefore, I re-iterate, water is alkaline BECAUSE of CO2, not, as your writing implies, “despite of CO2”. In fact, the entire oxygen has been created from (atmospheric) CO2, and the waters’ pH is around 8 for the very same reason. If you understood some basic chemistry, you would know that plant material (on land and in water) is not acidic. If you don’t believe that, simply chew on a popsicle stick, or have fish for dinner. Neither one of them is acidic, but their entire carbon content is from atmospheric CO2.
    Cheers to science,
    Klaus K.E. Kaiser, Ph.D., etc.

  4. 4 Inna Sokolova 16 November 2011 at 23:32

    Dr. Kaiser,
    I am not sure which basic ecology and chemistry books you are referring to; perhaps you would care to provide a few references. None of the numerous basic and advanced books in ecology and ocean chemistry I have come across in the course of my professional career support any of your statements such as that water is alkaline because of CO2 or that oxygen comes from the atmospheric CO2 (if you are referring to photosynthetic oxygen, it comes from water, not CO2). I would recommend reading works by Dr. Frank Millero for a detailed scientific analysis of marine carbon cycle which takes into account all carbon inputs and outputs (including but not limited to photosynthesis and anthropogenic CO2 emission) and unequivocally demonstrates a reduction in the ocean pH with increasing atmospheric CO2. You can find more supporting works in the references cited in Millero’s work or indeed on EPOCA website.
    Sincerely, Inna Sokolova (Ph.D., not etc.)

  5. 5 Jean-Pierre Gattuso 17 November 2011 at 07:26

    I fully agree with Inna Sokolova. The statements provided by Klaus Kaiser have no scientific basis. There is no need to continue discussing on this thread which is now closed to comments. It could be re-opened when Klaus Kaiser’s findings will be published in the peer-reviewed literature.

    Jean-Pierre Gattuso
    EPOCA blog coordinator

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