Relevance of various formulations of phytoplankton chlorophyll a:carbon ratio in a 3D marine ecosystem model

Abstract

Numerous experimental studies showed that the phytoplankton Chl a -to-Carbon ratio ( Chl a :C) is highly variable, whereas most of the marine ecosystem models use a constant ratio. In this work, we tested three different formulations for computing the modelled Chl a in a 3D coupled hydrodynamical–biogeochemical model of the Southwest lagoon of New Caledonia. The first formulation considers a constant Chl a :C ratio. In the second one, Chl a is a diagnostic variable related to the variable phytoplankton nitrogen-to-carbon ratio. In the last formulation, Chl a is a state variable of the model, which is dynamically simulated. Results showed important differences between the formulations, the first leading to overestimate the Chl a concentration in low nutrients conditions. Thus, this study strengthens the importance of the Chl a modelling in a coupled model in order to better estimate a crucial variable for validation of ecosystem models. To cite this article: V. Faure et al., C. R. Biologies 329 (2006).