| The Southern Ocean is considered a zone of high nutrients and low chlorophyll (HNLC). Despite the year round availability of nutrients, phytoplankton biomass remains low. Key modes of control are now thought to be light, grazing, iron and supply of silicic acid^1^. Physiological photoprotective mechanisms used by phytoplankton to regulate photosynthesis versus rapid light fluctuations have not been considered important. In diatoms and haptophytes, which are the major component of phytoplankton biodiversity in the Southern Ocean, the one step de-epoxidation of diadinoxanthin (Dd) into diatoxanthin (Dt) of the Dd-cycle constitutes the main photoprotective mechanism^2,3^. Here we show that Southern Ocean diatoms and haptophytes have higher concentrations of... |
