| Summary: | International audience The effects of iron on the fate of carbon exported to deep layers and on its main transfer pathways are investigated using Underwater Vision Profiler data obtained northeast and southeast of Kerguelen Island during KEOPS 2 (Oct.-Nov. 2011). The temporal increase of the particle volume in the mixed layer, from pre-bloom to spring bloom condition, was maximal at the southeastern site. However, particle volume was lower than already measured in this area at later stage of the bloom (KEOPS1, Jouandet et al., 2011). The spatio-temporal variability was associated to particle size distribution (PSD) changes. Southern site was characterized by a higher abundance of large particles (> 500 µm) compared to the Northeastern site. Comparison with KEOPS 1 data highlights an increase of the large particle production from pre bloom to the end of the bloom. Finally, changes in PSD led to a 10-fold lower carbon export flux at the early stage of the bloom than at its maximum. Mechanisms leading to the observed variation will be discussed through the use of a multiple particle analysis approach.
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