Etude du modèle APECOSM en 0D Calibration des paramètres, des classes de taille O. Aumont, T. Gorgues Réunion MACROES, Mai 2011

APECOSM: Several problems The biomass was increasing with weight In other words, the slope of the biomass spectrum was < 1, for high food levels F = 0.2 F = 0.7 Biomass Weight Weight The spectrum was strongly unstable Biomass spectrum F = 0.2 F = 0.7 Weight (kg) Years Weight (kg) Years

Impact of the number of size classes : advection schemes 100, tvd Slope : 20, upstream : -1.06 20, tvd : -1.13 100, upstream : -1.13 100, tvd : -1.136 100, upstream 20, tvd 20, upstream Biomass spectrum Weight Use of a higher order advection scheme reduces the number of necessary size classes

Predation function Sigmoidal function similar to a gate function 𝑓 ρ = 1 1+exp α 1 ρ 1 −ρ × 1− 1 1+exp α 2 ρ 2 −ρ  where r is the predator/prey size ratio Gaussian function 𝑓 ρ =exp  − log ρ 3 −𝑚 2 2× σ 2   − log ρ 3 −𝑚 2 2× σ 2  sigma Gauss (3,2) Gauss (3,1)

Impact of the predation function Gaussian (m=3,s=2) Sigma (r1=3, r2=100) Biomass spectrum Weight (kg) year m=3, s=2 m=3, s=1 m=2, s=2 m=2, s=1 Sigmoidal tends to be unstable which has been previously shown for similar predation selectivity Decreasing the predator/prey ratio steepens the spectrum Changing the width improves stability and changes the slope, especially for the small size classes Slope : -1.13, -1.15, -1.15, -1.16 Biomass spectrum

Introduction of some level of biodiversity For one species : 𝑑𝑔𝑁 𝑑𝑚 =−μ𝑁 with 𝑔=α×ℎ× 𝑚 𝑛 −𝑘𝑚 If we assume that the community spectrum is as : 𝑁 𝑐 = κ 𝑐 𝑚 −λ 𝑁=κ 𝑚 𝑖𝑛𝑓 𝑚 −𝑛− α 𝑝 αℎ 𝑓 𝑚 Then, we have : μ= α 𝑝 𝑚 1+𝑛−λ For an infinity of species : κ 𝑚 𝑖𝑛𝑓 = κ 𝑐 𝑚 𝑖𝑛𝑓 𝑛−3+ α 𝑝 αℎ It can be shown that : (Andersen and Beyer, 2006)

Impact of the power of the ingestion function 2/3 2/3 Biodiversité Biodiversité 0.766 0.766 0.866 0.86 Slopes : [-1.4, -0.88] [-0.97, -1.5] [-1.07, -1.5] [-1.08, -1.5] 2/3 2/3 Biodiversité Biodiversité Biomass 0.766 0.766 0.8666 0.866 Biomass spectrum Weight (kg) Weight (kg) The slope of the size spectrum is extremely sensitive to the power of the ingestion function A realistic size spectrum should have at equilibrium a slope everywhere below -1 The slope is also sensitive to the mortality function especially for high biomass

Impact of the mortality Quad, 10-18 Quad, 10-19 Linear biodiversité Biomass 0.66 Weight (kg) Weight (kg) Biomass spectrum For standard monospecific DEB, the shape is sensitive to the mortality function For biodiversified DEB, the slope is only weakly altered. The mean biomass is changed. The choice of the mortality function is often arbitrary and difficult. Quadratic functions are considered as a good choice, especially for stability reasons.

Impact of temperature, food abundance Weight (kg) Weight (kg) Years Impact of food abundance Biomass spectrum f=0.04 f=0.08 f=0.2 f=0.3 f=0.5 f=0.7 Biomass spectrum

PISCES en DEB Gros retard, essentiellement lié à un retard sur le recrutement du post-doc Le post-doc, Thomas Gorgues a été recruté au 1 mars 2011, soit près d'un an de retard Avancement actuel : Passage du zooplancton (micro, meso) en DEB réalisé Tous les paramètres ont été choisis pour être très proches d'avant Fonctions de prédation, Taux d'ingestion, maintenance, etc ... Priorité des 6 prochains mois : Passage du phytoplancton en DEB : Difficile car n'existe pas réellement dans la littérature