Download USF scientists use NASA satellites to detect "glow"

USF scientists use NASA satellites to detect "glow" of natural bio-threats
TAMPA, Fla. (Aug. 31, 2004) - Oceanographers at the University of South Florida's College of
Marine Science are using remote-sensing fluorescence data gathered from NASA's Moderate
Resolution Imaging Spectroradiometer (MODIS) and other instruments aboard both NASA's
Terra Aqua satellites to differentiate between algae and plumes of dark-colored runoff from river
and wetlands, sometimes causing "blackwater." Armed with such information, researchers could
notify regional environmental managers who can obtain field samples in time to warn fisherman
and swimmers about developing cases of red tide, which occur every year off Florida, causing
fish kills, coral stress and mortality as well as skin and
respiratory problems in humans.
The USF scientists were able to detect and measure
phytoplankton bloom fluorescence - invisible to the human eye in the Gulf of Mexico when instruments captured the red glow
from the plant's chlorophyll.
"Without remote sensing data of this nature - namely looking at
Earth with a camera very sensitive to the red color where plants
fluoresce in daylight - it is impossible to differentiate plankton
blooms from plumes of dark river runoff that may contain little
phytoplankton," said Frank Muller-Karger, a professor in the
College of Marine Science.
River runoff of fertilizers containing nitrogen and phosphorus
cause blooms of marine algae, or phytoplankton. When highly
concentrated, the blooms make the water appear black. As phytoplankton die and sink to the
ocean bottom they are eaten by bacteria. The hungry bacteria also deplete oxygen in the water,
leading to fish kills. Prolonged "black water" patches cause water quality degradation and may
cause coral death.
Because dissolved organic matter originating in rivers can also absorb similar amounts of blue
light as plants, satellites measuring ocean color alone cannot be used to confirm that such dark
patches contain phytoplankton blooms. However, if the water emits red light this clearly
identifies the presence of large quantities of phytoplankton, as they glow red under sunlight.
With those measurements, scientists are able to calculate the amount of nutrients needed to grow
a given amount of plankton. The ability to detect glowing phytoplankton-rich areas of water via
remote-sensing satellite helps researchers identify where phytoplankton are plentiful and helps
predict and monitor red tide and blackwater events.
In their study, researchers used NASA satellites to study the nature and origin of a dark plume
event in the fall of 2003 near Charlotte Harbor, off the south Florida coast.
"Our study traces the black water patches near the Florida Keys to some 200 kilometers (124
miles) upstream," USF researcher Chuanmin Hu said.
"These results suggest the delicate Florida Keys ecosystem is
connected to what happens on land and in the Peace and
Caloosahatchee rivers as they drain into the Gulf. Extreme
climate conditions, such as abnormally high spring and summer
rainfall in 2003, may accelerate such connections."
To complete their study, Hu and Muller-Karger used satellite
ocean color data from MODIS and Sea-viewing Wide Field-ofview Sensor (SeaWiFS), and wind data from NASA's
QuikSCAT satellite. The U.S. Geological Survey, the National
Oceanic and Atmospheric Administration, Florida's Fish and
Wildlife Research Institute, and other organizations provided
rain, river discharge and field survey information.
"The integration of multiple data sources provides a powerful
means for monitoring the environmental health of the coastal
ocean," explained Hu.
Their study appeared in the American Geophysical Union's Geophysical Research Letters.
Gabriel Vargo and Merrie Beth Neely from University of South Florida and Elizabeth Johns
from NOAA's Atlantic Oceanographic and Meteorological Laboratory are co-authors.
For more information and images visit:
http://www.gsfc.nasa.gov/topstory/2004/0826planktonglow.html
STORY SOURCES: Frank Muller-Karger
(727) 553-3335
Chuanmin Hu
(727) 553-3987
Media Contact: Randolph Fillmore
(813) 974-8476
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