CORDIS

The biological pump refers to the mechanism by which carbon is assimilated by photosynthetic algae in the ocean photic zone and subsequently exported to depth upon death of the organisms. The largest part of this export production is generally remineralized as it travels throughout the water column where it depletes dissolved oxygen concentrations. A fraction of the export production may still reach the sea floor, where it is susceptible to be buried, thus inducing a net removal of CO2 from the ocean-atmosphere system. Therefore, the good appraisal of the response of the biological pump to changing environmental conditions is crucial to reasonably predict climate and ocean oxygenation impacts, both associated with past events and as will result from ongoing anthropogenic emissions. However, the behavior of the ecological system in the face of climatic changes and how it impacts the strength and efficiency of the biological pump remains difficult to predict. To address this, here I propose to investigate the sensitivity of the biological pump in a novel way – using a state-of-the-art ecological model including a representation of marine biogeochemical cycles. I will focus on past periods, which provide a whole evolutionary chronicle to which model outputs can be directly compared. Confrontation of model results with geological records will also allow me to develop a mechanistic understanding of the behavior of the ecological system in response to a wide range of environmental perturbations. The proposed approach constitutes an unrivaled opportunity to increase our understanding of the geological record and what it can tell us of relevance to the future. Lessons learned here, both positive and negative, have the potential to help inform the next generation of marine ecosystem models needed to make improved projections of future global change impacts on ocean ecosystems, and hence engaging a broad range of global change scientists and ultimately, policy makers.