Airborne iron alters ocean productivity

Nicolas Cassar of Princeton University and colleagues have demonstrated that iron-containing aerosols carried by the wind increase biological production in the Southern Ocean, the body of water surrounding Antarctica (Science 2007, 317, 1067). Iron prompts algae to convert CO₂ into organic carbon matter that may sink to the deep ocean, a process that could lower atmospheric CO₂ concentrations. As shown in previous experiments, iron intentionally added to the Southern Ocean boosts organic matter sinking from surface waters. In the new work, the researchers combined prior observations, new data derived from upper ocean samples, and computer model estimates to show that the ocean's biological productivity also increases as soluble iron blows in on the wind. Cassar and colleagues point out that their results support previous speculations linking greater iron delivery to the oceans and lower CO₂ levels during ice ages and that a better understanding of dust transport patterns may help scientists predict future ocean productivity.