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Heat Stroke Bleaches World's Longest Reef TOWNSVILLE, Queensland, Australia, March 8, 2002 (ENS) - The heat wave now baking the east coast of Australia has raised fears of massive coral bleaching on the Great Barrier Reef, the world's longest reef. Scientists are worried that rising temperatures, sometimes exceeding 30 degrees Celsius (86 degrees Fahrenheit), could produce a coral bleaching episode reminiscent of the 1998 crisis. Paul Marshall of the Great Barrier Reef Marine Park Authority says, "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." The U.S. National Oceanic and Atmospheric Administration's Coral Reef Watch Program provided early warning of the bleaching conditions by using sea surface temperature data from NOAA's polar orbiting satellites. Since first reported, more of the reefs have bleached out, researchers say.
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. Bleaching occurs when stress upsets the symbiotic relationship between corals and their algae. Every coral species maintains a relationship with a microscopic algae called zooxanthallae. These algae provide their coral hosts with oxygen and part of the organic compounds they produce through photosynthesis. When stressed, many corals expel their zooxanthallae en masse. The polyps of the coral are left without pigmentation and appear nearly transparent on the animal's white skeleton. An elite international group of experts addressed their concerns about bleaching on the Great Barrier Reef in early February at a workshop on Magnetic Island, Queensland. Data from the Australian Institute of Marine Science (AIMS), the Great Barrier Reef Marine Park Authority (GBRMPA) 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, reef experts were told. Australian Institute of Marine Science researcher Dr. Terry Done and his team have surveyed five reefs in the Townsville sector of the Great Barrier Reef at distances from five to 130 kilometers (three to 80 miles) off the coast.
They reported to the workshop that slopes off Myrmidon reef, where the AIMS maintains a weather station, were healthy and normal in color. Corals living on reef tops were bleached but otherwise healthy. At Magnetic Island, examination of the reefs revealed bleached, diseased and dying corals amongst the silty shallow waters on Townsville's doorstep. Currently, a research program undertaken by AIMS, GBRMPA and NOAA is using thermal satellite imaging to identify hot spots on the reef. And NOAA scientists are learning more about the state of the corals from the Australian researchers gathering data out on the reef. "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," Strong said. "My colleagues are casting their eyes seaward for a cyclone to bring cooler waters to the surface."
Temperatures in excess of normal of one to two degrees now extend over the entire Great Barrier Reef region, and extent through the Coral Sea and toward the central Pacific Ocean, according to GBRMPA and NOAA. The World Wide Fund for Nature (WWF) Australia says, "Higher than normal sea surface temperatures are symptoms of a planet that is heating up, due to the wasteful use of fossil fuels such as coal and petroleum." The group is asking Australians to write the federal government asking that the country ratify the Kyoto Protocol to limit the emission of greenhouse gases linked with climate change. Other threats to the world's longest reef include overfishing and bottom trawling, sedimentation and run-off from rangeland beef grazing, sugar cane farming and horticulture, as well as damage from boat anchors and oil spills. The environmental group points out that only 4.5 percent of the entire Great Barrier Reef Marine Park is zoned fully protected so that fishing is prohibited. WWF is calling for a "comprehensive and representative network of fully protected areas within the Great Barrier Reef World Heritage Area." AIMS and GBRMPA are about to launch a structured survey program to document the precise extent and severity of bleaching over most of the Great Barrier Reef. NOAA scientists of the Coral Reef Watch Program have been assisting Great Barrier Reef scientists to automate monitoring towers and buoys. These devices will provide information on reef conditions to scientists and managers worldwide as part of a sophisticated coral reef early warning system that provides real-time alerts via the Internet of possible coral bleaching events. Scientists and coral reef managers use the information to better forecast, track and understand coral bleaching events, and participate in Coral Reef Watch by providing on-the-reef observations. NOAA reports that among reefs within U.S. waters, the northwest Hawaiian region around Midway has experienced an increase in sea surface temperatures over the past two decades of nearly +0.4 degrees Celsius per decade. Notable sea surface temperature increases in the Caribbean are larger toward the south and approach +0.07 degrees Celsius per decade near Puerto Rico and the U.S. Virgin Islands and Bahamas.
Coral reefs flourish mainly in the tropical latitudes, extending at most to 30 degrees north or south of the Equator in only a few cases. In the Northern Hemisphere tropics (Equator to 35 degrees north latitude globally), sea surface temperatures have been inching upwards at nearly +0.15 degrees Celsius per decade with increasing rates toward higher latitudes. In the Southern Hemisphere tropics (Equator to 35 degrees south latitude globally), sea surface temperatures have been slower to rise, averaging only a third of the Northern Hemisphere increase, or +0.05 degrees Celsius per decade. Coral bleaching events reported prior to the 1980s were attributed to localized phenomena such as major storm events, severe tidal exposures, sedimentation, rapid salinity changes, pollution, or thermal shock. The events since 1980 have not been so easily explained, but NOAA says that numerous laboratory studies have shown a direct relationship between bleaching and water temperature stress. Coral reefs are some 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 undiscovered biomedical resources and serve as a buffer for coastal communities from storms, wave damage and erosion. Coral reefs attract hundreds of thousands of divers, snorkelers and other tourists to tropical coasts every year. This recreation and travel supports a tourism industry dependent on clean water and healthy coral reefs. For information on NOAA's Coral Reef Program: http://www.coralreef.noaa.gov/ GBRMPA website, which updates bleaching information regularly: http://www.gbrmpa.gov.au/corp_site/bleaching/index.html AIMS website: http://www.aims.gov.au/index-ns.html WWF Australia: http://www.gbr.wwf.org.au/ Copyright Environment News Service (ENS) 2002. All rights reserved. |
Bleached coral (Photo courtesy 
Plate coral at Fitzroy Reef (Photo courtesy
Coral reef hotspots as of February 18,
2002 (Map courtesy 
Gorgonian and whip corals on the Great Barrier
Reef (Photo courtesy GBRMPA)