A switch in the species of phytoplankton dominating the Southern Ocean off Antarctica could accelerate global warming. During an expedition to the Ross Sea, a team led by Kevin Arrigo of the US National Aeronautics and Space Administration's (NASA) Goddard Space Flight Center near Washington DC, found that diatoms dominated wherever layers of water at different temperature were poorly mixed. Diatoms are not as good as other phytoplankton at taking up carbon dioxide, says Arrigo. Climate change models predict that waters of the Southern Ocean will become less well mixed, allowing the diatoms to spread further. Arrigo calculates that a switch to diatoms would reduce the rate at which carbon dioxide is removed from the atmosphere by as much as 36 per cent, changing the climate even further.