Bio@Noon: Jérôme Pinti
Diel vertical migrations: Zooplankton, fish and carbon export
Diel Vertical Migration (DVM) is a key feature of pelagic and mesopelagic ecosystems, mainly driven by predator-prey interactions along a time-varying vertical gradient of light. The migration patterns of each organism are intrinsically linked to the patterns of its conspecifics, its prey and its predators, through feedbacks that are hard to understand—but important to consider. DVM does not only affect trophic interactions, but also the biogeochemistry of the world’s oceans. Organisms preying at the surface and actively migrating vertically transport carbon to depth, contributing to the biological carbon pump, and directly connecting surface production with the mesopelagic ecosystem.
During this talk, I will share with you the main results of my PhD focused on modeling DVM. I will start by explaining how I use game theory and trait-based modeling to model simultaneously the migration behavior of several organisms in a water column. This will be illustrated with size-based vertical migration patterns of copepods in the North Pacific. Then, I will show you how I can use this method to investigate the magnitude of the active part of the biological pump. I will present you with a model comprising of several functional groups (namely intermediate and large zooplankton, forage fish, mesopelagic fish, top predators and gelatinous organisms) that is ran on a global scale to assess the optimal DVM patterns of the considered organisms. The outputs are then used to assess the carbon export mediated by the different functional groups (through direct respiration and excretion) and coupled to an ocean inverse circulation model to assess the carbon sequestration potential of the different export pathways. Preliminary results indicate that the relative importance of fish in the biological pump is more important than previously assumed.
Centre for Ocean Life, DTU Aqua, Technical University of Denmark (Denmark).