Particulate matter and organic carbon budgets for the Gulf of Lions (NW Mediterranean)

An analysis of sedimentological, sediment trap and hydrological data was performed to investigate the transport and fate of particulate matter in the Gulf of Lions. The sedimentological properties outline the major sedimentary units of the shelf (Rhone prodelta, mid-shelf mud belt, outer shelf) and slope. The geometry of these sedimentary units and the southwestwards increase of particulate fluxes on the slope highlight the influence of the general cyclonic circulation on the dispersion of land-derived particulate matter. Considering the known input and output terms, budgets of particulate matter and organic carbon in the Gulf of Lions are proposed. Inputs were river supply, atmospheric deposition and primary production; outputs were sediment burial and advective export on the slope. Degradation of particulate organic carbon in the water column and at the sediment-water interface was also estimated. Mass and POC budgets were balanced within uncertainties. Nevertheless, these results illustrate the difficulty in establishing budgets based on elements estimated at different time scales, for which the system is not necessarily in a steady state.