NASA - National Aeronautics and Space Administration

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 multi-million dollar recreational destinations, and the Great Barrier Reef is an important part of Australia's economy.

Image to right: This MODIS image shows the location of coral bleaching at Heron Island within the Capricorn Bunker Group of Great Barrier Reef. Click image to enlarge. Credit: NASA

Corals are much more than just a vibrantly colored backdrop to many divers' underwater adventures. Unknown to many, coral reefs are also critical to the marine ecosystem, serving as habitat and nursery grounds for fisheries, and providing coastline protection from severe storms by dampening wave action. On Australia's Great Barrier Reef, these gems of nature with their bursts of color have recently bleached, turning a stark white.

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.

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 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.

Image to left:Scuba divers document coral bleaching in January 2006 in the Keppels reef in the southern part of Great Barrier Reef. Credit: Ove Hoegh-Guldberg

"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.

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."

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 sensitive instruments on NASA's Terra and Aqua satellites, generally within three hours after the satellites pass over the particular region of interest.

Researchers including Scarla Weeks at the University of Queensland, Australia, are using these data to observe changes in sea surface temperature 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 mutually dependent relationship between corals and the algae that live within their bodies.

"The Great Barrier Reef is an icon, and we want to know what we can do to save it," said Weeks. "We would not be able to do this kind of broad-reaching work without NASA. With this satellite data delivery service we're able observe and understand what's happening in the ocean in ways we've never been able to before."

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Gretchen Cook-Anderson
Goddard Space Flight Center