Accueil > Actualités > Séminaires > Séminaire d'Olivier Aumont


Titre : Role of the diurnal vertical migrations of zooplankton and micronekton in the global carbon cycle
Nom du conférencier : Olivier Aumont
Son affiliation : LOCEAN
Laboratoire organisateur : LOCEAN
Date et heure : 27-11-2014 11h00
Lieu : salle de réunion LOCEAN, tour 45/55, 4eme étage
Résumé :

Diurnal vertical migration (DVM) of zooplankton and micronekton is a very common phenomenon in the marine systems. Classically, migrating organisms feed at night in the upper ocean and sink at dawn down to several hundreds of meters, presumably to escape visual predation during daytime. These migrations may have an important impact on the biogeochemical fluxes of nutrients, carbon, and oxygen by generating an active vertical transport of organic matter, which differ greatly from the sedimentation of particles. Local studies, either based on observations or models, have estimated the contribution of DVM to 10-30% of the total export of carbon. However, large-scale analyses are still to be done. During the French national project ANR-CEPS MACROES, the biogeochemical model PISCES and the ecosystem model APECOSM have been fully coupled (2-way coupling) in a global configuration. In APECOSM, the marine ecosystem is represented by three generic communities of which one corresponds to the organisms performing DVM. This modeling system is thus appropriate to study the impacts of DVM on the marine biogeochemistry at the global scale. First, the model behavior is evaluated against available data, in particular acoustic data. This validation shows that the model is able to capture the spatial and temporal patterns of the migrating biomass and of its migration depth. Then, by performing sensitivity studies, the impact of the DVM on the biogeochemical cycles of carbon, nutrients and oxygen is estimated. Results suggest that DVM plays a significant role, especially in the tropical regions.