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Post Doc Position, FRANCE

Post-doctoral position on biogeochemical modelling
Title: Developing a mechanistic model of phytoplankton and zooplankton growth based on a global
ocean biogeochemical model (PISCES)

Principal Investigator:
· Dr Olivier AUMONT, IRD/LOCEAN, Centre IRD de Bretagne, BP 70, 29280 Plouzané,
France, Olivier.Aumont@ird.fr, Ph.: +33 2 98 22 45 06, Fax: +33 2 98 22 45 14

Collaborators:
· Pr Jean-Christophe POGGIALE, UdM/LMGEM, Centre d'Océanologie de Marseille, Case
901 – Campus de Luminy, 13288 Marseille, France, Jean-Christophe.Poggiale@univmed.fr,
Ph: +33 4 91 82 91 19

Duration:
18 months

General goals
Currently, the biogeochemical model PISCES follows the classical but too simplistic Monod
formalism. In other words, phytoplankton (and zooplankton) growth directly depends on the
availability of necessary nutrients with basic colimitation rules. A major consequence of this “ad-hoc”
approach is the constant stoichiometry of the living organisms which is highly unrealistic and the lack
of mechanistic roots of the different processes. The objective of this task is to abandon this approach
to adopt a more mechanistic formalism. Several mechanistic descriptions of phytoplankton physiology
have been published so far (e.g., Geider et al., 1998; Flynn et al., 2001; Pahlow et al., 2009). Rather
than using these specific descriptions, we will develop a rather new model based on the dynamic
energy budget theory proposed by Kooijman (2000). This choice is dictated by the following reasons:
i. This theory is general and can be applied to all living organisms. As such, both phytoplankton
and zooplankton can be modelled using the same theoretical background. However, for
phytoplankton, an extension or an adaptation of the available theoretical formalism will be
necessary.
ii. This position is funded by a French national project called MACROES. One of the objectives
of MACROES is to couple the biogeochemical model PISCES with the pelagic ecosystems
model APECOSM (Maury et al., 2007a,b). As APECOSM is based on the DEB formalism,
the achievement of the work proposed here will allow to model the whole marine ecosystem
(PISCES coupled with APECOSM) using the same theoretical formalism resulting in a
maximum consistency between the two different models.

Activities
1) The first task of the post-doc will be the development of a DEB-based model of phytoplankton .
In a first step, a generic DEB model of phytoplankton will be constructed including the main
physiological aspects. Six limiting factors will be considered (Light, Carbon, Nitrogen, Phosphorus,
Iron and Silicon) and explicitly represented in cells reserves and structures. This model will be tested
against laboratory experiments, in a manner similar to what has been done with previously published
mechanistic models. In a second step, this model will be embedded within PISCES, without changing
the ecosystem structure of the model (two phytoplankton species). The model will then be run at 1-D
stations where data are available (for instance, NABE, BATS, HOT, ...) and then, at the global scale.
2) The second planned activity is to extend the model to zooplankton.

Localisation:
The engineer will be based in Brest (France) under the supervision of Olivier AUMONT. Strong
collaborations will be established with J.-C. Poggiale in Marseille and Bas Kooijman from the
Netherlands.

Eligibility:
Strong knowledge in biological oceanography and ecosystem modelling is required. Knowledge in
physical oceanography will be considered as a plus. Furthermore, the model is developed in fortran 90.
As a consequence, strong knowledge in this programming language is requested.

Salary:
23 000 € per year before taxes.

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