Early results of an experiment to test the use of ocean plankton as a sink for atmospheric carbon dioxide indicate that the process is significantly less effective than originally thought.

The Southern Ocean Iron Fertilisation Experiment aimed to investigate the effectiveness of adding iron sulphate to the ocean surface to encourage the growth of phytoplankton. These algae absorb carbon dioxide from the ocean, which in turn causes more of the gas to migrate from the atmosphere into the water.

Preliminary results suggest that although carbon can be transported 100 metres below the surface through iron fertilisation, the process is not as efficient as predicted. "I'm not certain the oceans can ever solve our carbon dioxide problem," says Kenneth Coale of Moss Landing Marine Laboratories, California, United States, who led the team of researchers.

Link to Nature news story

Reference: Nature 420, 722 (2002)