Study physiological and biochemical response of Phaeocystis antarctica to different irradiance and manganese/ iron deficiency

Iron and light are typically recognized as major limiting factors controlling phytoplankton growth in the Southern Ocean. Recent field-based evidence suggests, however, that manganese concentrations in this region can be low enough to impact phytoplankton physiology and primary productivity. Our study examined the interactive influence of combined iron and manganese deprivation on protein expression and photophysiology in Phaeocystis antarctica, a key Antarctic phytoplankter, and provide taxon-specific proteomic evidence that natural Southern Ocean Phaeocystis populations regularly experience stress due to combined low manganese and iron availability. In culture, combined low iron and manganese induced large scale changes in the Phaeocystis proteome and resulted in reorganization of key components of the photosynthetic apparatus; these differences were largely distinct from those arising from changes in irradiance. These results implicate manganese availability as an important driver of Southern Ocean productivity and demonstrate the utility of peptide mass spectrometry as a tool for mapping of manganese contributions to HNLC conditions in this region.