Cruising the subantarctic for clues to ocean acidification

17 January 2007

The effects of ocean acidification, caused by atmospheric carbon dioxide dissolving in the ocean, will be a focus of research on a five-week marine science voyage on board the research ship, Aurora Australis, which departs Hobart for the Southern Ocean today.

The Minister for the Environment and Heritage, Senator Ian Campbell, said the Sub-Antarctic Zone Sensitivity to Environmental Change voyage will study the effects of increasing carbon dioxide on planktonic organisms – the microscopic plants and animals in the ocean - and the ability of the ocean to continue to process carbon.

"This voyage will provide critical information on the processes that govern the ocean's natural uptake of carbon dioxide, the ocean's ability to continue to process carbon dioxide, and the likely impacts of acidification on the organisms that form the base of the food web in the Southern Ocean."

The research is being coordinated through the Antarctic Climate and Ecosystems Cooperative Research Centre, and involves groups from the Australian Government Antarctic Division and the CSIRO Division of Marine and Atmospheric Research.

Chief Investigator, Dr Will Howard of the Antarctic Climate and Ecosystems Cooperative Research Centre (ACE CRC), said that the research was significant because it will combine both experimental and observational approaches to understanding the impacts of environmental changes, such as acidification, on Southern Ocean ecosystems.

The team will also look at whether the carbon dioxide taken up by phytoplankton for growth is recycled near the ocean surface or sinks and is buried in the deep ocean.

In another experiment, Dr Simon Wright and his team from the Australian Government Antarctic Division will study the effect of four different concentrations of carbon dioxide on planktonic communities collected from the sub-Antarctic region, up to 540 nautical miles south of Tasmania, and housed in 650-litre 'minicosm' tanks on board the ship.

"A battery of physical, chemical and biological measurements are planned for the minicosm communities to determine the consequences of increasing acidity caused by increasing atmospheric carbon dioxide levels," Dr Wright said.

In a third experiment Chief Scientist Dr Brian Griffiths, of CSIRO, will lead a team measuring the 'bio-optical' properties of the ocean – colour changes due to phytoplankton – and comparing these to measurements of the amount of phytoplankton and the rates that the phytoplankton take up carbon dioxide, in the surface ocean.

"Our results will be used to improve the accuracy of ocean colour satellite images, which are used to estimate the amount of phytoplankton and primary production over vast stretches of the Southern Ocean. This will help us improve our understanding of the ocean's role in the global carbon cycle," Dr Griffiths said.

These and other projects will provide a base line from which further changes in ocean properties, as a result of increasing carbon dioxide levels, global temperatures and ocean acidification, can be compared.

The 60-strong international research team includes scientists from France, Belgium, the USA, New Zealand and the Netherlands.