Rapid and early export of Phaeocystis antarctica blooms in the Ross Sea, Antarctica

The Southern Ocean is very important for the potential sequestration of car bon dioxide in the oceans(1) and is expected to be vulnerable to changes in carbon export forced by anthropogenic climate warming(2). Annual phytoplan kton blooms in seasonal ice zones are highly productive and are thought to contribute significantly to pCO(2) drawdown in the Southern Ocean. Diatoms are assumed to be the most important phytoplankton class with respect to ex port production in the Southern Ocean; however, the colonial prymnesiophyte Phaeocystis antarctica regularly forms huge blooms in seasonal ice zones a nd coastal Antarctic waters(3). There is little evidence regarding the fate of carbon produced by P. antarctica in the Southern Ocean, although remine ralization in the upper water column has been proposed to be the main pathw ay in polar waters(4,5). Here we present evidence for early and rapid carbo n export from P. antarctica blooms to deep water and sediments in the Ross Sea. Carbon sequestration from P. antarctica blooms may influence the carbo n cycle in the Southern Ocean, especially if projected climatic changes lea d to an alteration in the structure of the phytoplankton community(6,7).