VERTICAL PARTICLE-FLUX IN OUTER SHELF WATERS OF THE SOUTHERN BAY-OF-BISCAY IN SUMMER 1993

Export of particulate matter out of the euphotic zone was measured in the southern Bay of Biscay in summer 1993 using shallow (50 m) sedimen t traps deployed for a short period in outer shelf waters. The sedimen ted material consisted of intact and degraded faecal pellets, diatom f rustules, coccolithophorid cells, detached coccoliths and zooplankton remains. Measured vertical fluxes were 173-236 mg C m(-2) day(-1), 18- 20 mg N m(-2) day(-1) and 3.8-4.5 mg C m(-2) day(-1), respectively for particulate organic carbon (POC), particulate organic nitrogen (PON) and particulate inorganic carbon (PIC). The downward flux of POC repre sented 24-37% of the estimated primary production. Export of PIC accou nted for only 2% of the total carbon flux. A large proportion (50-70%) of the material retained in the traps originated from phytoplankton. The contribution of 'living' phytoplankton to organic carbon fluxing o ut of the fertile zone was, however, less than 10%.