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NASA Helps
Researchers Diagnose Recent Coral Bleaching at Great Barrier Reef
04.05.06 An international team of
scientists are working at a rapid pace to study environmental conditions behind
the fast-acting and widespread coral bleaching currently plaguing Australia's
Great Barrier Reef. NASA's satellite data supply scientists with near-real-time
sea surface temperature and ocean color data to give them faster than ever
insight into the impact coral bleaching can have on global ecology.
This
MODIS image shows the location of coral bleaching at Heron Island within the
Capricorn Bunker Group of Great Barrier Reef. Credit: NASA
Australia's Great Barrier Reef is
a massive marine habitat system made up of 2,900 reefs spanning over 600
continental islands. Though coral reefs exist around the globe, researchers
actually consider this network of reefs to be the center of the world's marine
biodiversity, playing a critical role in human welfare, climate, and economics.
Coral reefs are a multi-million dollar recreational destinations, and the Great
Barrier Reef is an important part of Australia's economy. Scientists use ocean
temperatures and ocean "color" as indicators of what is happening with
coral. Coral is very temperature sensitive. Ocean "color," or the
concentration of chlorophyll in ocean plants, is important because it informs
scientists about changes in the ocean's biological productivity. NASA satellites
capture both temperature and color data from their space-based view of the coral
reefs.
Scientists use ocean temperatures
and ocean "color" as indicators of what is happening with coral. Coral
is very temperature sensitive. Ocean "color," or the concentration of
chlorophyll in ocean plants, is important because it informs scientists about
changes in the ocean's biological productivity. NASA satellites capture both
temperature and color data from their space-based view of the coral reefs.
The
image shows healthy coral in full color at the Great Barrier Reef. Credit:
ReefHQ
Bleaching
occurs when warmer than tolerable temperatures force corals to cast out the tiny
algae that help the coral thrive and give them their color. Without these algae,
the corals turn white and eventually die, if the condition persists for too
long. "Australia’s Great Barrier Reef is the largest and most complex
system of reefs in the world, and like so many of the coral reefs in the world’s
oceans, it's in trouble," said oceanographer Gene Carl Feldman of the Ocean
Biology Processing Group at NASA's Goddard Space Flight Center, Greenbelt, Md.
The
image is a typical example of bleached coral, shown here in January 2006 at
Keppel Reef, part of the Great Barrier Reef. Credit: Ove Hoegh-Guldberg,
University of Queensland, Australia
He
added, "Coral, which can only live within a very narrow range of
environmental conditions, are extremely sensitive to small shifts in the
environment. Like the 'canary in the coalmine,' coral can provide an early
warning of potentially dangerous things to come." In 2004, NASA scientists
developed a free, Internet-based data distribution system that enables
researchers around the globe to customize requests and receive ocean color data
and sea surface temperature data captured by the Moderate Resolution Imaging
Spectroradiometer (MODIS) instrument aboard NASA's Terra and Aqua satellites,
generally within three hours after the satellites pass over the particular
region of interest. NASA processes and distributes this data to hundreds of
scientists, educators and public officials globally on a daily basis.
Researchers,
including Scarla Weeks at the University of Queensland, Australia, are using
satellite monitoring to observe changes in sea surface temperatures and ocean
primary productivity along the Great Barrier Reef and surrounding waters. Recent
dramatic increases in sea surface temperatures are causing a rift in the
relationship between corals and the algae that live within their bodies.
"The Great Barrier Reef is an icon, and we just want to know what we can do
to save it," said Weeks. "Sea surface temperatures over the last five
months are actually higher in certain locations now than they were in 2002 when
we witnessed the worst bleaching incident to date."
Weeks
regularly downloads NASA MODIS data that shows her the extent of and where the
coral bleaching is expanding. "We're not able to do this kind of
broad-reaching work without NASA. With this satellite data delivery service,
we're able to observe what's happening in the ocean in ways we've never been
able to before," she said.
This
is an image of sea surface temperatures at the southern Great Barrier Reef
showing increased temperatures over inshore reefs, the location of the most
severe coral bleaching at present. The image was created from the Moderate
Imaging Spectroradiometer instrument onboard NASA's Terra and Aqua satellites.
The temperatures range from 25 to 30 degrees Celsius (77 to 86 degrees
Fahrenheit) as indicated on the color bar (right). . Credit: University of
Queensland
According to Weeks, not only does
the increased sea surface temperature affect life underneath the water, but it
also impacts other marine creatures like sea birds. "After the high sea
surface temperatures in 2002 caused the unprecedented bleaching incident, we saw
a devastating reproductive failure in sea birds. The adult birds ultimately
abandoned their nests resulting in a population loss in an animal vital to the
marine ecosystem.
"Rising ocean temperatures
are just one of the ever-increasing number of environmental stresses faced by
coral reefs in general and the Great Barrier Reef in particular," said
Feldman. "With this distribution service, we're sharing NASA's unique
ability to monitor our home planet from the vantage point of space and to
provide scientists with the best and most timely information to carry out their
research."
Gretchen Cook-Anderson Goddard
Space Flight Center
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