Ocean Acidification Threatens Economies And Marine Life | June 24, 2013 Issue - Vol. 91 Issue 25 | Chemical & Engineering News
Volume 91 Issue 25 | p. 8 | News of The Week
Issue Date: June 24, 2013

Ocean Acidification Threatens Economies And Marine Life

Environment: Corals weaken as pH drops, UN report detail further ocean harm
Department: Science & Technology | Collection: Climate Change
News Channels: Environmental SCENE, Biological SCENE
Keywords: ocean acidification, carbonate, coral, climate change, United Nations, carbon dioxide, CO2
Researchers use the growth and density patterns revealed by these CT scans to track coral development, which is inhibited by higher-than-normal acidity.
Credit: Adina Paytan
Three panels. Left: grey striated blobs. Middle: The same shape, but with heat-map style coloration in yellows, greens, and blues. Right: An orange striated blob of a different shape.
Researchers use the growth and density patterns revealed by these CT scans to track coral development, which is inhibited by higher-than-normal acidity.
Credit: Adina Paytan

Evidence for ocean acidification abounds, but what that means for different organisms has been hard to pin down. A recent study finds that at least one coral species won’t be able to acclimatize to more acidic waters (Proc. Natl. Acad. Sci. USA 2013, DOI: 10.1073/pnas.1301589110).

Led by Elizabeth D. Crook of the University of California, Santa Cruz, researchers sampled Porites astreoides corals from waters in the Yucatan Peninsula with a natural pH gradient.

The researchers used computed tomography (CT) scans to determine annual growth rates over four years and skeletal erosion due to wear-and-tear or predation. Then they assessed how these measures vary with the water’s carbonate ion concentration, which roughly tracks pH.

Some of the corals came from waters with a pH just above 8.0, which is near the average value for oceans. Others came from an area with much less carbonate than average, where pH is 7.2–7.6. They found that corals in low-carbonate waters calcified 30% less, their skeletons were 28% less dense, and their bioerosion was nearly twice as extensive. These effects worsened in areas with even more acidic waters. The observed trends mirror those seen in short-term lab studies, suggesting they would persist over a lifetime, Crook says.

Chris Langdon of the University of Miami is concerned by the study’s findings. He notes that the oceans are becoming warmer, which also negatively affects coral. Research on how these two factors synergize is a growing field, he adds. Study coauthor Adina Paytan of UC Santa Cruz says that coral reefs serve as frameworks for diverse ecosystems and help humans by providing tourism opportunities, coastal protection, and homes for seafood.

Adding to the gloom, a new United Nations report says human activities that generate carbon emissions are acidifying the oceans and the problem could get far worse without emission cuts. By 2050, ocean pH could drop to 7.8 on average, a 150% acidity increase over preindustrial values of around 8.2. The economic impact of these changes could reach billions of dollars, the report warns.

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Larry (June 24, 2013 8:33 AM)
Despite the amount of nasty, evil atmospheric plant food, ocean pH remains basic, "suggesting this would persist over a lifetime" with lower than normal basicity.
Inna (August 29, 2013 3:43 PM)
If you carefully read this article, the negative effects on corals are seen at pH 7.2-7.6. While this pH is considered "basic" by standard chemistry conventions, this fact does not prevent corals suffering from increased erosion and reduced growth. The same was shown in many other studies where negative effects on marine organisms are seen well before pH hits 7.0 mark to which presumably you are referring. Just goes to show that nature does not care much about our conventions...
Hylke Hoogeveen (June 26, 2013 9:05 AM)
According to Gibbs's Phase Rule, ocean pH is a static 8.2. Since there is an overabundancy of buffering minerals (carbonate, silicate) in ocean water, deviations from this pH-STAT are the result of temperature (a LOWER temp speeds up the dissolution of atmosferic CO2) and the mixing velocity of oceanic layers (the availability of buffering anioncomplexes , like CO2). Conclusion: 'acidification' of the ocean should be very limited in time and space, and be confined to cold and deep regions where the uptake of CO2 outpaces mixing velocity. This confines 'acidification' to the SHALLOW layers of VERY COLD and DEEP oceanic waters. In all cases accurate meaaurements of seawater pH are extremely difficult to perform accurately. A significant margin of error should be reckoned with.

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