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NASA satellites detect the "glow" of plankton

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  • David
    NASA SATELLITES DETECT GLOW OF PLANKTON IN BLACK WATERS For the first time, scientists may now detect a phytoplankton bloom in its early stages by looking at
    Message 1 of 1 , Sep 2 7:47 PM

      For the first time, scientists may now detect a phytoplankton bloom in
      its early stages by looking at its red "glow" under sunlight, due to
      the unique data from two NASA satellites. According to a study
      conducted in the Gulf of Mexico, this phenomenon can forewarn
      fishermen and swimmers about developing cases of red tides that occur
      within plumes of dark-colored runoff from river and wetlands,
      sometimes causing "black water" events.

      Dark-colored river runoff includes nitrogen and phosphorus, which are
      used as fertilizers in agriculture. These nutrients cause blooms of
      marine algae called phytoplankton. During extremely large
      phytoplankton blooms where the algae is so concentrated the water may
      appear black, some phytoplankton die, sink to the ocean bottom and are
      eaten by bacteria. The bacteria consume the algae and deplete oxygen
      from the water that leads to fish kills.

      Chuanmin Hu and Frank Muller-Karger, oceanographers at the College of
      Marine Science of University of South Florida, St. Petersburg, Fla.,
      used fluorescence data from NASA's Moderate Resolution Imaging
      Spectroradiometer (MODIS) instruments aboard both NASA's Terra and
      Aqua satellites. MODIS detects the glow or phytoplankton fluorescence,
      from the plant's chlorophyll. The human eye cannot detect the red

      The ability to detect glowing areas of water helps researchers
      identify whether phytoplankton are present in large dark water patches
      that form off the coast of Florida. Without these data, it is
      impossible to differentiate phytoplankton blooms from plumes of dark
      river runoff that contain few individual phytoplankton cells.

      Because colored dissolved organic matter that originates in rivers can
      absorb similar amounts of blue and green color signals as plants do,
      traditional satellites that simply measure ocean color cannot
      distinguish phytoplankton blooms within such patches.

      Although satellites cannot directly measure nutrients in lakes,
      rivers, wetlands and oceans, remote sensing technology measure the
      quantities of plankton. Scientists can then calculate how much
      nutrient might be needed to grow those amounts of plankton.

      Hu and others used this technique to study the nature and origin of a
      dark plume event in the fall of 2003 near Charlotte Harbor, off the
      south Florida coast. Moderate concentrations of one of Florida's red
      tide species, were found from water samples.

      "Our study traces the black water patches near the Florida Keys to
      some 200 kilometers (124 miles) away upstream," said Hu. "These
      results suggest that the delicate Florida Keys ecosystem is connected
      to what happens on land and in two remote rivers, the Peace and
      Caloosahatchee, as they drain into the ocean. Extreme climate
      conditions, such as abnormally high rainfall in spring and summer
      2003, may accelerate such connections," he added.

      These findings are based on scientific analyses of several things.
      Data used include satellite ocean color from MODIS and Sea-viewing
      Wide Field-of-view Sensor (SeaWiFS), and wind data from NASA's
      QuikSCAT satellite. U.S. Geological Survey, National Oceanic and
      Atmospheric Administration (NOAA), Florida's Fish and Wildlife
      Research Institute, and other organizations provided rain, river
      discharge, and field survey information.

      By knowing which way the winds blow and the currents flow, Hu and
      colleagues can predict where black water may move.

      Red tides occur every year off Florida and are known to cause fish
      kills, coral stress and mortality, and skin and respiratory problems
      in humans. Previous studies show that prolonged "black water" patches
      cause water quality degradation and may cause coral death. The use of
      remote sensing satellites provides effective means for monitoring and
      predicting such events.

      The link between coastal runoff and black water events is an example
      of how land and ocean ecosystems are linked together. "Coastal and
      land managers over large areas need to work together, to alleviate
      more black water events from taking place in the future," said

      This study appeared in a recent issue of the American Geophysical
      Union's Geophysical Research Letters. Coauthors of the article include
      Gabriel Vargo and Merrie Beth Neely from University of South Florida
      and Elizabeth Johns from NOAA's Atlantic Oceanographic and
      Meteorological Laboratory.

      NASA's Science Directorate works to improve the lives of all humans
      through the exploration and study of Earth's system, the solar system
      and the Universe.

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