NOAA 2002-019
Contact: Pat Viets
NOAA News Releases 2002
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U.S. Reefs Also Face Increasing Threats

Corals are bleaching over extensive portions of Australia's Great Barrier Reef, a sign that the reef is being seriously stressed during current record-breaking warm water conditions. Conditions have worsened since the widespread bleaching reported several weeks ago, scientists at the Commerce Department's National Oceanic and Atmospheric Administration and their colleagues in Australia reported today.

NOAA's Coral Reef Watch Program provided early warning of the bleaching conditions by using sea surface temperature data from NOAA's polar-orbiting satellites. Data from the Australian Institute of Marine Science, the Great Barrier Reef Marine Park Authority and the University of Queensland show a vast section of the Coral Sea and Great Barrier Reef where temperatures are much higher than normal due to hot, clear summer conditions.

"Reports just in from our friends at AIMS and GBRMPA tell of a worsening condition," said Al Strong, NOAA satellite oceanographer and coordinator of NOAA's Coral Reef Watch Program. "Our colleagues have compared this bleaching event to the previous record event during the 1998 El Niño, noting that the present episode began earlier in their summer and shows no signs of easing its grip. My colleagues are casting their eyes seaward for a cyclone to bring cooler waters to the surface."

"At this stage all the bleaching observed is still fairly mild, with little visible signs of significant mortality, but this is certainly just a matter of time if conditions do not improve dramatically and persistently," said Paul Marshall of GBRMPA.

AIMS and GBRMPA, having just concluded a workshop with NOAA on the Great Barrier Reef, are about to launch a structured survey program that aims to document extent and severity of bleaching over most of the Great Barrier Reef. NOAA scientists of the Coral Reef Watch Program have been assisting GBR scientists with automating several in situ monitoring sites (towers/buoys) to provide information on reef conditions as part of a sophisticated coral reef early warning system that provides real-time alerts via the Internet of possible coral bleaching events to scientists and managers worldwide.

NOAA satellite data reveal sea surface temperature anomalies and "HotSpots," or areas of the ocean with unusually warm temperatures where bleaching is likely to occur. Scientists and coral reef managers world-wide use the NOAA's Coral Reef Watch information to better forecast, track and understand coral bleaching events, and participate in CRW by providing on-the-reef observations. CRW is part of NOAA's Coral Reef Program.

NOAA reports that among domestic reefs, the northwest Hawaiian region around Midway has seen an increase in sea surface temperatures over the past two decades of nearly +0.4 deg C/decade much during the past six or seven years.

Notable sea surface temperature increases in the Caribbean are larger toward the south but approach +0.07 deg C/decade near Puerto Rico and the U.S. Virgin Islands and Bahamas. In the Northern Hemisphere tropics (Equator to 35N - globally) sea surface temperatures have been inching upwards at nearly +0.15 deg C/decade (increasing rates toward higher latitudes). In the Southern Hemisphere tropics (Equator to 35S - globally), sea surface temperatures have been more slow to rise, averaging only a third of the Northern Hemisphere increase, or +0.05 deg C/decade.

Coral reefs are important to our future because they are one of the earth's most diverse living ecosystems harboring millions of animals and plant species that play a key role in the global food web. They are full of new and undiscovered biomedical resources and serve as a buffer for coastal communities from storms, wave damage and erosion.

Coral reefs also attract hundreds of thousands of divers, snorkelers and other tourists to tropical coasts every year. This recreation and travel supports a significant tourism industry dependent on clean water and healthy coral reefs. Corals live on the upper edge of their temperature tolerance. Abnormally high water temperatures combined with low winds and still water can cause destructive bleaching of coral reefs. NOAA monitors this threat with satellite-derived sea surface temperatures, ocean surface winds, HotSpots, Degree Heating Weeks (accumulations of HotSpots) and on-site monitoring stations.

For more information, see:
For coral bleaching indices of the tropical ocean, see:
For HotSpots:
For accumulations of Thermal Stress see:
For information on NOAA's Coral Reef Program:
GBRMPA Web Site (updates bleaching information regularly)
AIMS Web site: