Doing a coral health check, from 8,000m above

Experts to use special sensor to map state of Great Barrier Reef

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 tricked-out Nasa Gulfstream jet to modernise 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 8,500 metres 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 unravelling 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 tiny animals called polyps of 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.

‘A real step up’

In the past, reef science has mostly involved scuba divers and intensive, small-scale, plotbased 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 September 2.

“That is something we 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. just