Centre Algatech

With only 1% of the total earth biomass, phytoplankton contributes to nearly 50% of the primary production. Iron is limiting for the growth of phytoplankton in vast oceanic regions (up to 30% of global oceans (Moore et al., 2002)). Iron fertilization experiments resulting in phytoplankton blooms have shown that different phytoplankton communities react differently to iron addition, leading sometimes to harmful algal blooms (Trick et al., 2010). Rising atmospheric CO2 is acidifying the surface ocean, a process that is expected to influence iron bioavailability in seawater. Understanding of the connections between iron and marine phytoplankton is critical for predicting ecosystem changes in future ocean. Yet the mechanisms of adaptation to iron limitation by marine microalgae are still poorly understood. Most of the studies are based on investigations of single species, or field samples that are problematic to interpret. Interspecific relationships in the marine ecosystem are complex and it is difficult to predict which phytoplankton species would be advantaged over others with predicted changes in the ocean chemistry. So there is a need for lab-scale experiments under standardized conditions including a spectrum of significant, well-characterized model species. Our goal is to perform such study focused on a comparative analysis of the strategies to cope with iron limitation and evaluation of interspecific competition as a function of iron content and form. Recent discoveries in the field of iron metabolism in phytoplankton (including our findings of a non-reductive siderophore uptake by diatoms, description of the role of cell surface iron binging in its uptake, involvement of ferritin in the cellular distribution of iron rather than its storage) opened new avenues to study the adaptation of phytoplankton to iron-limited environment. The proposed project will combine the knowledge of iron metabolism in microalgae (R. Sutak’s lab and his collaborators from several French labs) with the profound experience with algal physiology under nutrient limitation (O. Prášil’s lab). Our preliminary data and existing experimental know-how ensure the scientific quality of the project.