Molecular physiology of Antarctic diatom natural assemblages and bloom event reveal insights into strategies contributing to their ecological success

In the Southern Ocean, phytoplankton must cope with harsh environmental conditions such as low light and growth limiting concentrations of the micronutrient iron. We collected 25 surface seawater samples from the western Antarctic Peninsula (WAP) and assessed the influence of oceanographic variables on the diversity of the phytoplankton community composition and on the metabolic strategies of diatoms by performing metatranscriptomics. We found that cross-shelf differences in oceanographic parameters such as temperature and variable nutrient concentrations account for most of the differences in phytoplankton community composition and metabolism. We opportunistically characterized the metabolic underpinnings of a large bloom of the centric diatom Actinocyclus in coastal waters of the WAP. Our results indicate that physico-chemical differences from on- to offshore are stronger than between southern and northern regions of the WAP; however, these trends could change in the future resulting in poleward shifts in functional differences in diatom communities and phytoplankton blooms. This submission includes the 25 seawater metatranscriptome samples from the WAP.