NASA Learning To Monitor Coral Reef Health From The Sky

David Steitz
Headquarters, Washington December 8, 2003
(Phone: 202/358-1730)

John Bluck
Ames Research Center, Moffett Field, Calif.
(Phone: 650/604-5026 or 650/604-9000)

RELEASE: 03-395

NASA LEARNING TO MONITOR CORAL REEF HEALTH FROM THE SKY

Coral reef health may be accurately estimated from
sensors on airplanes and satellites in the future, according
to a NASA scientist who is the principal investigator in a
collaborative project to develop a method to remotely sense
coral health.

Sometimes called the "bellwether of the seas," coral reefs can
give first indications of marine ecosystem health. "Scientists
can use coral health as a sensitive indicator of the health of
the marine environment," said Liane Guild, a scientist at NASA
Ames Research Center, Moffett Field, Calif.

"We're looking into how you could remotely detect coral reef
health using aircraft with visible light sensors," Guild said.
"First, we have to look at the coral close up, underwater, to
see what spectral reflectance the sensor picks up from
diseased, stressed and healthy coral."

One of the first steps her team took to develop aerial coral
monitoring was to take undersea light-reflectance readings of
elkhorn coral with a handheld spectroradiometer, or light
meter. A team of four scuba divers, from the Universities of
Miami, South Florida and Puerto Rico, helped Guild take the
first readings at varying depths in summer 2002 near Andros
Island, Bahamas, with assistance from the U.S. Navy Atlantic
Undersea Test and Evaluation Center. A spectroradiometer
measures the amount of ultraviolet, visible and infrared light
reflected from an object, and is similar to sensors aboard
remote-sensing airplanes and satellites.

"We moved up from the coral, little by little, to the surface
to learn how light intensity decreases in the water column,
which affects our coral reflected-light readings," Guild said.
"There also will be a layer of atmosphere between the coral,
the water and the sensor when it eventually flies aboard an
airplane to survey the reefs," she added.

"The effects of the atmosphere on light are pretty well known,
but the challenge is to correct for the effects of the layer
of water over the coral," Guild explained. "Instead of taking
the top-down approach, we are going from the bottom up to the
airplane, and later to satellite-sensing of coral health,"
Guild said.

"Ultimately, we plan to fly 'hyperspectral' instruments,
containing many detectors that collect information in the
visible light range," Guild explained. These instruments will
provide the most useful information about coral-reef community
health from above the sea, according to Guild.

The team's research emphasis is on Acropora palmata, or
elkhorn coral, a major reef-building coral. It is prevalent in
the study area, but is suffering from "white band disease."
Elkhorn coral is on the verge of becoming an endangered
species because it has severely declined in many areas of the
Caribbean, Guild noted.

The team and engineering scientists from the University of
Arizona also are developing a specialized computer model to
analyze coral reflected-light data. The computer model will
help scientists better interpret the raw data gathered by
aircraft or satellites.

Guild will discuss her group's work at the Fall Meeting of the
American Geophysical Union on December 9, at 8:45 p.m. EST, in
room 3000 of the Moscone Convention Center, San Francisco.

The research is funded by NASA's Earth Science Enterprise,
which is dedicated to understanding the Earth as an integrated
system and applying Earth System Science to improve prediction
of climate, weather and natural hazards using the unique
vantage point of space.

For information about NASA's Earth Science Enterprise on the
Internet, visit:

http://www.earth.nasa.gov

For images on the Internet, visit:

http://amesnews.arc.nasa.gov/release...ges/coral/cora
l.html

More information about the coral monitoring project is on the
Internet at:

http://geo.arc.nasa.gov/sge/coral-health

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