On the benefits of using cell quotas in addition to intracellular elemental ratios in flexible-stoichiometry Plankton functional type models. Application to the Mediterranean Sea
2021
Baklouti, Melika | Pagès, Rémi | Alekseenko, Elena | Guyennon, Arnaud | Grégori, Gérald
In the last decades, among the marine biogeochemical models, there have been an increasing number of marine Plankton Functional Type (PFT) models. Since the precursor NPZD models, the general trend has been towards the development of models that are more and more complex, either by the number of variables they include and/or by the level of detail they consider. In this respect, flexible-stoichiometry models have been an important step in the history of this class of models. Since then, additional developments have been described in the literature, and the present paper focuses on one of them, namely the introduction of abundance in addition to biomass to describe PFTs. This new feature offers an opportunity for model assessment with the increasing number of studies and datasets obtained by flow cytometry, and it provides the means to derive cell quotas (here expressed as an amount of a given biogenic element per unit cell) for each PFT of the model. Cell quotas are used, along with intracellular ratios, for the regulation of the kinetics of the different biogeochemical processes embedded in the model, and it is suggested here that their role may be decisive for the successful representation of some processes, such as, for example, mineralization by heterotrophic bacteria. Several other benefits provided by cell quotas are presented in this paper, among them the in-depth knowledge they provide on the functioning of the trophic web and on the nutritional status of organisms. Finally, the seasonal variations of the cell quotas in the PFT representing large phytoplankton can be used to explain the occurrence of the NW Mediterranean spring bloom from the internal status point of view.
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