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Coral Reefs Unlikely To Survive In Acid Oceans

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  • mtneuman@juno.com
    Coral Reefs Unlikely To Survive In Acid Oceans Stanford CA (SPX) Dec 17, 2007 Carbon emissions from human activities are not just heating up the globe, they
    Message 1 of 1 , Dec 16, 2007
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      Coral Reefs Unlikely To Survive In Acid Oceans

      Stanford CA (SPX) Dec 17, 2007

      Carbon emissions from human activities are not just heating up the globe,
      they are changing the ocean's chemistry. This could soon be fatal to
      coral reefs, which are havens for marine biodiversity and underpin the
      economies of many coastal communities. Scientists from the Carnegie
      Institution's Department of Global Ecology have calculated that if
      current carbon dioxide emission trends continue, by mid-century 98% of
      present-day reef habitats will be bathed in water too acidic for reef

      Among the first victims will be Australia's Great Barrier Reef, the
      world's largest organic structure.

      Chemical oceanographers Ken Caldeira and Long Cao are presenting their
      results in a multi-author paper in the December 14 issue of Science* and
      at the annual meeting of American Geophysical Union in San Francisco on
      the same date. The work is based on computer simulations of ocean
      chemistry under levels of atmospheric CO2 ranging from 280 parts per
      million (pre-industrial levels) to 5000 ppm. Present levels are 380 ppm
      and rapidly rising due to accelerating emissions from human activities,
      primarily the burning of fossil fuels.

      "About a third of the carbon dioxide put into the atmosphere is absorbed
      by the oceans," says Caldeira, "which helps slow greenhouse warming, but
      is a major pollutant of the oceans." The absorbed CO2 produces carbonic
      acid, the same acid that gives soft drinks their fizz, making certain
      minerals called carbonate minerals dissolve more readily in seawater.
      This is especially true for aragonite, the mineral used by corals and
      many other marine organisms to grow their skeletons.

      "Before the industrial revolution, over 98% of warm water coral reefs
      were bathed with open ocean waters 3.5 times supersaturated with
      aragonite, meaning that corals could easily extract it to build reefs,"
      says Cao. "But if atmospheric CO2 stabilizes at 550 ppm -- and even that
      would take concerted international effort to achieve -- no existing coral
      reef will remain in such an environment." The chemical changes will
      impact some regions sooner than others. At greatest risk are the Great
      Barrier Reef and the Caribbean Sea.

      Carbon dioxide's chemical effects on the ocean are largely independent of
      its effects on climate, so measures to mitigate warming short of reducing
      emissions will be of little help in slowing acidification, the
      researchers say. In fact, impending chemical changes may require
      emissions cuts even more drastic than those for climate alone.

      "These changes come at a time when reefs are already stressed by climate
      change, overfishing, and other types of pollution," says Caldeira, "so
      unless we take action soon there is a very real possibility that coral
      reefs - and everything that depends on them -will not survive this
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