VERTICAL PARTICLE FLUXES IN THE LIGURIAN SEA

Since 1987, we have monitored the vertical flux of particles regularly at two time-series stations in the Ligurian Sea. Automated sediment traps were used to collect samples at several depths, particularly at 80-100 m, 200 m and 1000 m. Vertical particle fluxes are relatively low in this open ocean region. In the upper 200 m, the annual mass flux was 30 to 34 g m-2 y-1, and total carbon flux ranged from 5.1 to 7.6 g m-2 y-1. The export production (i.e. POC flux at 200 m) was 4.0 g m-2 y-1. Fluxes varied substantially over time, their patterns being related to both the seasonality of the physical environment (water column mixing in winter) and biological activity (spring phytoplankton bloom). Important quantitative and qualitative changes with depth were observed. The organic C:N atom ratio increased with depth (from 7.5 to 9.4), which indicates a rapid degradation of biogenic material.