CARBON FLOWS IN A SUBTIDAL FINE SAND COMMUNITY FROM THE WESTERN ENGLISH-CHANNEL - A SIMULATION ANALYSIS

Organic carbon flows through the Pierre Noire fine sand community (Bay of Morlaix, France) are described with a trophodynamic point model, Data collected during several annual cycles are used to calibrate the seasonal variations of each benthic compartment. Mean annual values of state variables are correctly simulated. In a first approach, the seasonal variations were simulated using 2 forcing functions: input of energy and temperature influence. In a second run, spawning and recruitment effects were introduced as regulating factors for the macrobenthic compartments. The resulting annual carbon budget synthesizes the information we have on this common type of ecosystem. Phytoplankton production represents the major food supply to the benthic system and the importance of pelagic-benthic coupling in this area is confirmed. A large proportion of the carbon input is consumed by bacteria which is the main trophic source for meiofauna. Meiofauna is an important link between the bacteria + detritus and the carnivore level, and cannot be considered as an independent food web. The significance of regulation factors such as spawning and recruitment processes in the dynamics of the macrofauna is explored,