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Ocean Acidification Threatens Cold-Water Coral Ecosystems

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  • Pat Neuman
    Ocean Acidification Threatens Cold-Water Coral Ecosystems Some cold-water coral reefs are home to more than 1,300 species of animals, a diversity rivaling some
    Message 1 of 1 , Apr 5 5:02 AM
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      Ocean Acidification Threatens Cold-Water Coral Ecosystems

      Some cold-water coral reefs are home to more than 1,300 species of
      animals, a diversity rivaling some better known tropical coral
      reefs.
      by Staff Writers
      Bellevue WA (SPX) Apr 04, 2006
      Corals don't only occur in warm, sun-drenched, tropical seas; some
      species are found at depths of three miles or more in cold, dark
      waters throughout the world's oceans. Some cold-water coral reefs
      are home to more than 1,300 species of animals, a diversity rivaling
      some better known tropical coral reefs.
      Until now, scientists believed bottom trawling - a commercial
      fishing method in which vessels drag large, heavily weighted nets
      across the bottom - to be the greatest threat to cold-water corals.
      Now, however, a new study published in Frontiers in Ecology and the
      Environment suggests that human activities could be threatening cold
      water reefs in another way.

      Lead researcher John Guinotte, a marine biogeographer at Marine
      Conservation Biology Institute and colleagues say that increasing
      amounts of atmospheric carbon dioxide (CO2), driven by the burning
      of fossil fuels, are dissolving into the oceans, causing them to
      become slightly more acidic. This change in seawater chemistry could
      harm deep-sea calcifying animals like corals.

      Cold-water corals that make their skeletons from aragonite - a form
      of calcium carbonate (the main component of limestone) - are most
      vulnerable. Cold-water, reef-building corals are prevalent in the
      North Atlantic, where there is a deep layer of water supersaturated
      with aragonite. In pre-industrial times, more than 95 percent of
      cold water reefs around the world were found in waters
      supersaturated with aragonite. However, this layer of supersaturated
      water is shrinking as concentrations of CO2 increase.

      "Scientists have known for years that shallow-water tropical coral
      reefs are threatened by both warming oceans and chemical changes in
      seawater caused by the build-up of CO2 in the atmosphere. Above-
      average seawater temperatures have caused coral bleaching events
      throughout the world, and the calcification rates of corals exposed
      to more acidic conditions in laboratory experiments have shown
      worrisome declines," says Guinotte. "But now we suspect that this
      increase in CO2 will have a detrimental effect on cold-water corals
      as well. Cold-water reefs are at greater risk than shallow-water
      reefs because colder waters are naturally less hospitable for coral
      growth."

      The uptake of CO2 by oceans initiates a series of chemical reactions
      that increase acidity and decrease carbonate ion concentration in
      seawater. Corals and other marine organisms (e.g. some species of
      plankton and mollusks) use carbonate ions to build their skeletons
      or shells. Model projections indicate that by 2100, only 30 percent
      of cold-water reefs will still be in waters supersaturated with
      aragonite. With fewer carbonate ions available, there could be a
      dramatic reduction in the growth of both the corals and marine
      plankton species that make their shells from aragonite. As the
      oceans become more acidic, corals are expected to build weaker
      skeletons, a process similar to osteoporosis in humans.

      Cold-water corals provide habitat for many commercially important
      fish species and harbor several species of sponges that produce
      chemicals with anti-cancer and other medicinal uses. Unfortunately,
      says Guinotte, just as scientists are finding out how diverse and
      important cold-water corals are, they are being threatened by a one-
      two punch.

      "First, bottom trawlers smash them to bits. Then, ocean
      acidification will probably slow the skeletal growth and/or lead to
      weaker skeletons of those that remain. Ocean acidification will
      likely have serious and wide-reaching impacts, not only for coral
      ecosystems but for all life in the oceans. Many species of marine
      plankton use carbonate ions and occupy the base of most marine food
      webs, so a reduction in their numbers could lead to harmful effects
      throughout marine ecosystems."

      Only a decrease in the burning of fossil fuels is likely to slow
      this trend, say Guinotte and colleagues.

      Related Links
      Ecological Society of America
      Frontiers in Ecology and the Environment
      Marine Conservation Biology Institute

      http://www.terradaily.com/reports/Ocean_Acidification_Threatens_Cold_
      Water_Coral_Ecosystems.html
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