This research addresses global change issues and aims to study the effect of anthropogenic and climate changes on the diversity of phytoplankton in the coastal ocean and analyse their impact on ecosystem goods (or damages) and services (atmospheric CO2 uptake). The methodology includes the further development of the existing MIRO-CO2 biogeochemical model for constructing a generic model able to describe the dynamics of different phytoplankton functional types (PFTs) and to identify the environmental factors governing their spatio-temporal distribution. This model will be iteratively developed and validated in different areas (Bay of Biscay, Bay of Seine, English Channel and Southern Bight of the North Sea), which represent from the Southwest to the Northeast a successive dominance of different PFTs: calcifying organisms (Coccolithophoridae) in the Bay of Biscay, toxic algae (Dinophysis, dinoflagellates and diatoms like Pseudo-nitzschia) in the Bay of Seine and Phaeocystis colonies in the Channel and Southern Bight of the North Sea. A module corresponding to each of these PFTs will be developed/improved based on a review of the literature and tested on each site. Once validated, the model will be used to identify the environmental factors determining the spatio-temporal distribution of PFTs and their specific effect on the absorption of atmospheric CO2 or damage on the ecosystem. We also plan to use the validated model to predict possible changes of PFTs in response to expected anthropogenic or climate changes (acidification, surface water warming, reverted-eutrophication). The model construction and first achievements are presented here.