Coral Experiment Shows CO2 Deadly to Reefs
April 19, 2013
ON A LARGE WOODEN deck on a coral cay island in the middle of the Great Barrier Reef, research assistant Aaron Chai removes the lid from one of 12 circular white water tanks.
“This is the ‘do nothing’ tank,” he says, peering inside at a careful arrangement of dead, slimy, algae-covered and bleached-white corals.
In July last year, this small reef ecosystem looked very different – corals of vivid purples and blues beside the bright greens of turtle weeds. Since then the levels of carbon dioxide and temperature in the bowl-shaped tank have been changed to the kind of conditions expected by the end of this century if the world ‘does nothing’ about climate change and its fossil fuel use.
“It’s the slippery slope to slime,” says the University of Queensland’s Associate Professor Sophie Dove, who is running this experiment on the university’s research station on Heron Island, about 80 kilometres off Gladstone in central Queensland.
In the ‘do nothing’ tanks all but one of the corals has died and is being slowly covered in algae. Some of the coral skeletons have actually started to dissolve in the increased acidity of the water.
“If you look at those reefs in those future tanks now, they are really not all that attractive to tourists,” says Dove. “It’s not something that people would want to go and see. It is becoming more of a mono-culture and that stuff probably isn’t that palatable to the fish. That slippery slope to slime looks to be coming true.”
As humans have pumped more carbon dioxide into the atmosphere from burning fossil fuels, oceans have absorbed about a third of this extra CO2. This makes the water slightly more acidic and in theory makes it harder for corals to maintain their skeletons.