Spotting the Killer Hot Spots that Destroy Corals
Pew Institute scientist collaborates on highly effective new satellite technology to detect warm-water pools with greater precision
June 25, 2008
Killer hotspots of over-heated ocean water which destroy huge areas of coral and bring starvation to birds, fish and other sea creatures can now be pinpointed with unprecedented precision, thanks to a major advance in the use of satellite technology by researchers from the University of Queensland (UQ)in Australia and the Pew Institute for Ocean Science in Miami.
Advanced satellites and smart mathematics are enabling the scientists to detect the events which cause mass bleaching of corals at levels far beyond only large-scale events occurring under typical seasonal conditions. This is revealing the Great Barrier Reef's most threatened areas under global warming.
"The new technology gives us the power to see what is happening in the ocean around the Great Barrier Reef in much finer scale in both space and time,” said Dr. Scarla Weeks, leader of the Marine and Tropical Sciences Research Facility (MTSRF) program team, which authored the new paper in the Journal of the American Society of Limnology and Oceanography detailing their advancements. Dr. Andrew Bakun of the Pew Institute for Ocean Science collaborated on the new technology and is a co-author on the publication.
"It means we can identify those areas most at risk of being hit by hot water, enabling managers and reef visitors to take greater steps to protect them," said Dr. Weeks, who is also a rsearcher at UQ's Centre for Marine Studies (CMS) and Centre for Remote Sensing and Spatial Information Science (CRSSIS). “It also means that we can observe coral bleaching events taking place, which were missed before because the satellite data didn't have the fine scales necessary.”
A 2002 bleaching event that hit 54 percent of the Great Barrier Reef w(GBR) as clearly detected using satellite data from the U.S. National Oceanographic and Atmospheric Administration (NOAA), but the subsequent 2005-06 event, which hit the southern GBR hard, was not picked up by satellites.
One reason was the 2005/6 bleaching was an anomaly, Dr. Weeks said. It struck in November/December, whereas the usual time that warm water enters the GBR is in Australia's late summer, around February.
"The existing technology used didn't have the resolution to pick it up," Dr. Weeks said. "In fact, it couldn't observe any reefs close inshore.”
Dr. Weeks' team developed a satellite and mathematical tool that provides a dramatic improvement in the ability to read sea surface temperature anomalies from outer space. It is more accurate in time and can see much smaller areas of water.
“Using this we can identify individual reefs or groups of reefs which are most at risk of hot water and coral bleaching under climate change,” she said.
Dr. Weeks said that eddies of hot water (31 or 32 degrees Celsius) which lingered over the GBR for a number of days, could kill some corals completely, while others took years to recover.
“But hot water also affects the entire marine food chain," she said.
"We've seen devastating evidence that seabirds stop feeding their chicks when the hot water is in the vicinity – probably because the plankton and small fish they depend on also die or disappear," Dr. Weeks said.
“If hot water affects birds then it almost certainly also affects fish, as well as marine mammals like dugongs and whales, or turtles and large plankton feeders like manta rays. We are about to start research to examine this.”
Scientists consider the incidence of hot water entering the GBR from the ocean has been on the increase for several decades, and is reflected in more frequent and larger coral bleaching events. They say it is one of the most obvious manifestations of global warming.
"The corals are like the canary in the coal mine," she said.
"By bleaching they are telling us there is something amiss. The cause is these increasing thermal anomalies.
“Now we can see them happening, before our eyes, with far greater clarity and precision than before.
"We are in fact, watching global climate change unfolding in ways that will directly affect the livelihoods and prosperity of tens of thousands of Australians, given the importance of the Great Barrier Reef for tourism, fishing, recreation and the ecosystem benefits it provides.”
Dr. Weeks developed the technology with Dr. Ken Anthony and Dr. Ove Hoegh-Guldberg from UQ's Centre for Marine Studies, in collaboration with the NASA's Ocean Biology Processing Group and Professor Andrew Bakun of the Pew Institute for Ocean Science.
For Dr. Andrew Bakun: contact Pew Institute Communications Manager Kathryn Cervino at 917.612.0235
For Dr. Scarla Weeks: phone 07 3409 9058, mobile 0488 240 012
For Dr. Ken Anthony: phone 07 33659154, mobile 0427 177290
For Dr. Ove Hoegh-Guldberg: mobile 0401 106 604 or 07 3371 2135
UQ scientists can also be reached through Jan King, UQ Communications Manager, at 07 3365 1120, 0413 601 248
Media images: contact Diana Lilley tel 07 3365 2753