Modelling trophic interactions between benthic primary producers and the common cockle (Cerastoderma edule) in estuarine ecosystems (Normandy)

Benthic ecosystems are characterised by complex interactions between their constituting compartments. In this study, the trophic and non-trophic interactions between cockle (Cerastoderma edule) and microphytobenthos (MPB) were analysed using modelling approaches. The cockle growth pattern was analysed with an ecophysiological model. Trophic signal reconstruction reinforced the need to integrate food diversity in the diet of cockle whose main components were seen to be phytoplankton and MPB. A model of MPB resuspension in the water column under the bioturbation by cockle was also set up. Results showed that the biomass of cockle significantly determines the amount of suspended material. Moreover, a positive correlation between the intensity of resuspension and the body size of cockles was found. Finally, a model of MPB primary production integrating migration processes and EPS production (Extracellular Polymeric Substances) was applied. Results validated the control of the migration by internal cellular C:N ratio of MPB. Moreover, nutrients could be a limiting factor for MPB growth, and the biodiffusion of nutrients by sediment fauna sustained the microphytobenthic primary production levels.

Keywords: Microphytobenthos, Cerastoderma edule, bioturbation, modelisation, trophic diversity, resuspension