Adaptive capacities of Southern Ocean phytoplankton to climate change

The transfer of carbon from the atmosphere to the ocean’s interior as a consequence of phytoplankton productivity is known as the biological carbon pump, which helps regulate global climate. In the Southern Ocean, productivity also supports rich ecosystems and controls the supply of nutrients to the tropics. The Southern Ocean is unusual as productivity is limited by low iron, light, and temperature, and the phytoplankton optimized for life there has evolved critical adaptations to enhance photosynthetic rates under these joint constraints that have been found to be up to six-fold higher than in temperate species . Emerging genomic evidence further supports an unprecedented isolation of phytoplankton communities in the Southern Ocean over sufficiently long timescales for directional selection to take place . If we are to predict how such isolated populations will fare in a rapidly changing ocean, we need to first understand the unique aspects of Southern Ocean diatom physiology and how different they are with respect to diatoms living in more temperate waters. The results of PHYTOPLANKTON will help us to better understand and model the mechanisms that set the photosynthetic carbon fixation rate in the Southern Ocean and its response to ongoing global warming and climate change. The results will further help us to better predict the productivity and biodiversity of this vast ecosystem, its impact on global carbon cycles, atmospheric CO2, and global climate.