Scientists inspect the Great Barrier Reef, from 28,000 feet above
SYDNEY — Heron Island, a coral cay at the southern tip of Australia’s Great Barrier Reef awash in piercing sunlight and translucent seas, has been a proving ground for reef science for more than 80 years.
Because of its clear blue waters and mostly cloudless skies, Heron Island is one of a handful of sites worldwide where scientists from the United States, Bermuda and Australia have converged with a trickedout NASA Gulfstream jet to modernize the way the world looks at its fragile coral reefs, an early warning system of a changing climate.
Scientists will use a special sensor to map the conditions of large portions of the reef in fine detail, gathering data from 28,000 feet above to produce a real-time picture of how much sand, coral and algae make up big stretches of the Great Barrier Reef.
They hope the flights will prove the sensor’s worth, leading to it being placed on a satellite and ultimately unraveling some of the mysteries of how reefs adapt to man-made and natural stresses, how they calcify, and how much photosynthesis takes place on reefs and where.
Coral is made up of millions of tiny animals called polyps that form symbiotic relationships with algae, which capture sunlight and carbon dioxide to make sugars that feed the polyps. When waters warm, corals evict the algae, known as zooxanthellae, which causes the coral to turn white.
In the past, reef science has mostly involved scuba divers and intensive, small-scale, plot-based studies that can reveal much about a small slice of reef but cannot necessarily be extrapolated to gauge the health of the entire Great Barrier Reef, which covers an area roughly the size of Germany.
“This is a real step up in the way reef science is done,” said Eric Hochberg, the project’s chief investigator, from the Bermuda Institute of Ocean Sciences.
“How much coral is there on a reef ? How much is sand and algae?” Hochberg said in a telephone call from Cairns, in Australia’s far north, where the NASA flying laboratory has been based since Sept. 2. “That is something we just don’t know.”
Reefs are incubators that provide food and shelter to a quarter of the ocean’s species, protect coastal communities against the vagaries of extreme weather, and provide billions of dollars in revenue from fishing and tourism.
But the oceans also absorb most of the world’s heat and greenhouse gases, threatening the fragile reef ecosystem. Warming ocean temperatures may increase the severity of destructive weather, like hurricanes and cyclones, and speed the death of corals that are unable to sustain life after back-toback bleaching episodes.
In April, scientists reported large parts of the world’s corals, in areas such as the northern Great Barrier Reef, Guam, Indonesia and the Florida Keys in the Atlantic, had suffered extensive bleaching.
The NASA project uses a light sensor fitted into the belly of the modified jet to measure the health of the reefs. Every object has its own spectral signature and the Portable Remote Imaging Spectrometer, or Prism, picks up light that bounces off the sand, algae and coral and breaks it into hundreds of bands of color. It will provide very high quality images of the reef, said Michelle Gierach, a marine scientist from NASA’s Jet Propulsion Laboratory in Pasadena, California.
“It has the right sensitivity, resolution and uniformity to answer key questions about coral reef conditions,” Gierach said, speaking from Cairns, a reef tourism hub in the state of Queensland. It uses what is called a hyper-spectral sensor, meaning it picks up the entire color spectrum reflected back through the water and the atmosphere.
“It will bring reefs on par with how we look at the terrestrial environments,” said Stuart Phinn, a geographer and director of the University of Queensland’s remote sensing research center.
“We don’t pay attention to our reefs in the same way we do with our forests — and we should,” Phinn said. “And assuming it works, and they put a satellite up afterward, it will be a major step-change in coral reef science and management.”
Scientists hope to assemble a detailed portrait of thousands of square miles: the clear blue of shallow waters, the whitecapped dark swirls of the deep sea, and the reef, like a backbone cresting Queensland’s east coast.
And, now, they want scale, too.
Hochberg wants detail so fine that he can tell how much algae is in the bright white sand, and on the reef, and how much of any reef is coral and how much is sand.
Scientists also want to know how rising sea temperatures, water acidity, pollution, sediment and overfishing affect reefs over time.