Biogeosciences www.biogeosciences.net 1726-4170 1726-4189 5 5 2008 10.5194/bg-5-1361-2008 http://www.biogeosciences.net/5/1361/2008/ http://www.biogeosciences.net/5/1361/2008/bg-5-1361-2008.html http://www.biogeosciences.net/5/1361/2008/bg-5-1361-2008.pdf 1361 1372 2008-09-29 Distribution and fluxes of aggregates >100 μm in the upper kilometer of the South-Eastern Pacific L. Guidi G. Gorsky gorsky@obs-vlfr.fr H. Claustre J. C. Miquel M. Picheral L. Stemmann Université Pierre et Marie Curie-Paris 6, Laboratoire d'Océanographie de Villefranche; CNRS, Laboratoire d'Océanographie de Villefranche, Villefranche-sur-Mer, France Department of Oceanography, Texas A and M University, College Station, Texas, TX, USA IAEA Marine Environment Laboratory, Monaco, Monaco Large sinking particles transport organic and inorganic matter into the deeper layers of the oceans. Between 70 and 90% of the aggregates exported from the surface mixed layer are disaggregated within the upper 1000 m. This decrease with depth indicates that fragmentation and remineralization processes are intense during sedimentation. Generally, the estimates of vertical flux rely on sediment trap data but difficulties inherent in their design limit the reliability of this information. During the BIOSOPE study in the south-eastern Pacific, 76 vertical casts using the Underwater Video Profiler (UVP) and deployments of drifting sediment traps provided an opportunity to fit the UVP data to sediment trap flux measurements. We applied the calculated UVP flux in the upper 1000 m to the whole 8000 km BIOSOPE transect. Comparison between the large particulate material (LPM) abundance and the estimated fluxes from both UVP and sediment traps showed different patterns in different regions. On the western end of the BIOSOPE section the standing stock of particles in the surface layer was high but the export between 150 and 250 m was low. Below this layer the flux values increased. 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