Plankton are small organisms that drift with the currents in the seas and oceans. Despite their small size, they play an important planetary role due to their immense quantity. Photosynthesizing plankton, known as phytoplankton, for example, produce half of the oxygen in the atmosphere while binding huge amounts of carbon dioxide (CO2). Since the Southern Ocean around Antarctica is very rich in nutrients, phytoplankton can thrive there. It is therefore a key region for controlling atmospheric CO2 concentrations.