Blanchard, G. G. Laboratoire de biologie et biochimie marines, gblancha@ifremer.fr

Cloern, J. J. United States Geological Survey, jecloern@usgs.gov

Gros, P. Ph. IFREMER - Centre de Brest, phgros@ifremer.fr

SHORT-TERM DYNAMICS OF INTERTIDAL MICROPHYTOBENTHIC BIOMASS: MATHEMATICAL MODELLING

We formulate a deterministic mathematical model to describe the dynamics of the microphytobenthos of intertidal mudflats. It is « minimal » because it only takes into account the essential processes governing the functioning of the system : the autotrophic production, the active upward and downward migrations of epipelic microalgae, the saturation of the mud surface by a biofilm of diatoms, and the global net loss rates of biomass. According to the photic environment of the benthic diatoms inhabiting intertidal mudflats, and to their migration rhythm, the model is composed by two sub-systems of ordinary differential equations ; they describe the simultaneous evolution of the biomass « S » concentrated in the mud surface biofilm - the photic layer - and of the biomass « F » diluted in the first topmost centimeter of the mud -the aphotic layer. Qualitatively, the model solutions agree fairly with the in situ observed dynamics of the S + F biomass. The study of the mathematical properties of the model, under some simplifying assumptions, shows the convergence of solutions to a stable cyclic equilibrium, whatever the frequencies of the physical synchronizers of the production. The sensitivity analysis reveals the necessity of a better knowledge of the processes of biomass losses, which are so far uncertain, and may further vary in space and time.

Day: Friday, Feb. 5

Time: 09:45 - 10:00am

Location: Eldorado Hotel

Code: SS46FR0945E