Influence of oceanic conditions in the energy transfer efficiency estimation of a micronekton model

Micronekton – small marine pelagic organisms mostly in the size range 1–10 cm – is a key component of the ocean ecosystem, as it constitutes the main source of forage for all larger predators. Moreover, the mesopelagic component of micronekton that undergoes Diel Vertical Migration (DVM) likely plays a key role in the transfer and storage of CO2 in the deep ocean: the so-called ‘biological pump’ mechanism. SEAPODYM-MTL is a spatially explicit dynamical model of micronekton. It simulates six functional groups of migrant and non-migrant micronekton, in the epipelagic and mesopelagic layers. Coefficients of energy transfer efficiency between primary production and each group are unknown. But they are essential as they control the predicted biomass. Since these coefficients are not directly measurable, a data assimilation method is used to estimate them. In this study, Observing System Simulation Experiments (OSSE) in the framework of twin experiments are used to test various observation networks at a global scale regarding energy transfer coefficients estimation. Observational networks show a variety of performances. It appears that environmental conditions are crucial to determine network efficiency. According to our study, ideal sampling areas are warm, non-dynamic and productive waters like the eastern side of tropical Oceans. These regions are found to reduce the error of estimated coefficients by 20 % compared to cold and dynamic sampling regions. The results are discussed in term of interactions between physical and biological processes.