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NASA Study Solves Ocean Plant Mystery

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    NASA Study Solves Ocean Plant Mystery by Staff Writers Greenbelt MD (SPX) Sep 01, 2006 A NASA-sponsored study shows that by using a new technique, scientists
    Message 1 of 1 , Sep 1, 2006
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      NASA Study Solves Ocean Plant Mystery

      by Staff Writers
      Greenbelt MD (SPX) Sep 01, 2006
      A NASA-sponsored study shows that by using a new technique, scientists
      can determine what limits the growth of ocean algae, or phytoplankton,
      and how this affects Earth's climate.
      Phytoplankton is a microscopic ocean plant and an important part of
      the ocean food chain. By knowing what limits its growth scientists can
      better understand how ecosystems respond to climate change.

      The study focused on phytoplankton in the tropical Pacific Ocean. It
      is an area of the ocean that plays a particularly important role in
      regulating atmospheric carbon dioxide and the world's climate. This
      area of the ocean is the largest natural source of carbon dioxide to
      the atmosphere.

      "We concluded that nitrogen is the primary element missing for algae
      growth and photosynthesis in the northern portion of the tropical
      Pacific, while it was iron that was most lacking everywhere else,"
      said Michael J. Behrenfeld, an ocean plant ecologist from Oregon State
      University, Corvallis, Ore.

      Scientists determined when phytoplankton is stressed from lack of
      iron; it appears greener, or healthier than they really are. Normally,
      greener plants are growing faster than less green plants. When iron is
      lacking, enhanced greenness does not mean phytoplankton are growing
      better. They are actually under stress and unhealthy. These
      conclusions solved the mystery why healthy looking phytoplankton are
      actually not so healthy.

      "Because we didn't know about this effect of iron stress on the
      greenness of algae or phytoplankton before, we have always assumed
      that equally green waters were equally productive," Behrenfeld
      said. "We now know this is not the case, and that we have to treat
      areas lacking iron differently."

      For the tropical Pacific, correction for this "iron-effect" decreases
      scientists' estimates of how much carbon ocean plants photosynthesize
      for the region by roughly two billion tons. This figure represents a
      tremendous amount of carbon that remains in the atmosphere that
      scientists previously thought were being removed.

      The results about the false health of phytoplankton allow scientists
      using computer models to re-create the movement of carbon around the
      world much more accurately. Resource managers will become more
      knowledgeable about where carbon is going and the impact of
      recreational, industrial or commercial processes that use or produce
      carbon. Researchers better understand the Earth as an ecosystem, and
      can incorporate these findings in future modeling, analysis and

      While satellite data from NASA's Sea-viewing Wide Field-of-view Sensor
      played an important part in the study, the real cornerstone of the
      discovery was ship-based measurements of fluorescence.

      Fluorescence occurs when plants absorb sunlight and some of that
      energy is given back off again as red light. Scientists looked at
      approximately 140,000 measurements of fluorescence made from 1994 to
      2006 along 36,040 miles of ship tracks. They found that phytoplankton
      give off much more fluorescence when the plants do not have sufficient
      iron. It is this signal they used to fingerprint what parts of the
      ocean are iron-stressed and what parts are nitrogen-stressed.

      It is important that scientists understand how ocean plants behave
      because all plants play a critical role in maintaining a healthy
      planet. Plants annually take up billions of tons of carbon dioxide
      from the atmosphere through photosynthesis and use this carbon to
      create the food that nearly all other organisms on Earth depend on for

      Nutrients that make ocean plants thrive, such as nitrogen and
      phosphate, mostly come from the deep parts of the ocean, when water is
      mixed by the wind. Iron also can come from dust blowing in the air.

      Approximately half of the photosynthesis on Earth occurs in the
      oceans, and the remainder on land. Ocean and land plants share the
      same basic requirements for photosynthesis and growth. These
      requirements include water, light and nutrients. When these three are
      abundant, plants are abundant. When any one of them is missing, plants

      An article on this technique appears in a recent issue of Nature.
      This image grab from an animation shows where there is more or less
      plant life on our planet. It is a series of monthly images of where
      phytoplankton are from August 1997 through March 2003, as seen by NASA
      and ORBIMAGE's Sea-viewing WIde Field-of-view Sensor (SeaWiFS) on the
      SeaStar satellite. On land, the dark greens show where there is
      abundant vegetation and the tan colors show relatively sparse plant
      cover. In the ocean, red, yellow, and green areas show higher levels
      of phytoplankton, and these are regions of the ocean that are the most
      productive over time, while blue and purple areas show where there is
      very little of the microscopic marine plants called phytoplankton.
      Credit: NASA/ORBIMAGE/G. Feldman, NASA GSFC. Click here to view

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