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Coral Reef Studies

ARC Centre of Excellence for Coral Reef Studies
James Cook University Townsville
Queensland 4811 Australia

Phone: 61 7 4781 4000
Email: info@coralcoe.org.au

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Ocean breakthrough on global warming

Jul 2006

A major discovery has opened the way for researchers to measure the ability of the world’s oceans to absorb man-made CO2 – a key factor in global warming.

The discovery by Professor Malcolm McCulloch, deputy director of the Australian Research Council Centre of Excellence for Coral Reef Studies (CoECRS) and research leader at the Australian National University’s Research School of Earth Sciences, and colleagues from Italian research institutions led by Dr Paolo Montagna, will allow researchers to see far into the past to understand the biological and chemical makeup of the oceans.

This may solve one of the biggest questions facing global warming: whether or not the oceans can keep pace with human CO2 output.

Professor McCulloch’s findings are published in the latest issue of the international journal Science.  They reveal a way to calculate the amount of phosphorus, a nutrient of vital importance to all life.

“Now that we have this tool we can look more closely at the role of nutrients in the ocean and try and understand, in a lot more detail, how they operated in the past,” says Prof. McCulloch.

“We can now find out how the oceans responded to previous increases in carbon dioxide (CO2) and how quickly they can absorb it,” he says.

The tool could help answer one of the biggest questions in the global warming debate: whether the ‘biologic pump’, through which the oceans naturally absorb CO² from the atmosphere, can keep pace with the vast amounts now being produced by humans.

Plants and animals in the oceans’ surface waters drive the ‘biologic pump’ by taking up much of the CO2 from the air and storing it inside their bodies. Eventually the CO² stored in their bodies descends to the deep ocean and becomes part of the sea floor. The turbulent mixing of the oceans also helps to absorb CO2.

Scientists fear that if the ‘biologic pump’ cannot keep up with human CO2 emissions, the waters of the oceans will become more acid. This could hinder the growth of coral reefs, and may also be detrimental to other plants and animals that are critical to the operation of biological pump, which could ultimately lead to the collapse of one of the main systems that helps to remove greenhouse gases from the atmosphere.

The more plants and animals in the ocean the more productive it becomes and the more the ‘biologic pump’ can absorb greenhouse gases. The productivity of an area of ocean is indicated by the amount of phosphorus in it.

“Phosphorus is a key nutrient in the ocean that limits or controls biological productivity. Organisms use it up and because there is only so much available, there is a limit to how many organisms there can be,” explains Prof. McCulloch.

By observing the amount of phosphorus in the oceans of the past, Prof McCulloch’s newly discovered tool can visualize how hard the ‘biologic pump’ is working. By studying the productivity of past oceans we can see just how effective and fast this process is.

“We can go back in time and look at the past history of the earth and look at how it reacted,” says McCulloch, “This complements ongoing studies of our oceans,, because the dilemma is that you often don’t know whether we are in an irreversible situation till after it has happened, so we try to better understand these processes by looking at how the planet has responded in the past.”

This view into the past is made possible because of Prof. McCulloch’s discovery that the preserved skeletons of ancient deep sea corals store phosphorous in exactly the same amounts as the surrounding oceans. By using sophisticated and accurate dating methods on the corals he can piece together information on the oceans as far back as the last glacial period, nearly 20 000 years ago.

“We know that CO² has been increasing since the industrial era, but how the oceans are responding to this is uncertain,” says McCulloch.

Prof. McCulloch plans to use the newly discovered tool in future studies to provide a ‘health check-up’ of the biologic pump in order to see whether it will be able to keep up with the rate of greenhouse gas emissions from humans.

More information:
Malcolm McCulloch, Deputy Director CoECRS, +61 2 6125 9969, +61 0439 490 282
Professor Terry Hughes, Director, CoECRS, +61 7 4781 4000
Jenny Lappin, CoECRS, +61 7 4781 4222
Jane O’Dwyer, Media Manager ANU, +61 2 6125 5001

Montagna, P, McCulloch, M, Taviani, M, Mazzoli, C and Vendrell, B (2006). “Phosphorus in Cold-Water Corals as a Proxy for Seawater Nutrient Chemistry.” Science 312(5781): 1788-1791.
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Coral Reef Studies

ARC Centre of Excellence for Coral Reef Studies
James Cook University Townsville
Queensland 4811 Australia

Phone: 61 7 4781 4000
Email: info@coralcoe.org.au