The KEOPS 2 cruise around the Kerguelen island plateau put emphasis on determining the affinities of phytoplankton for different new or regenerated nutrients, on elemental uptake ratios and whether processes such as nitrification and ammonium regeneration in surface waters are of importance in sustaining phytoplankton primary production in distinct iron-fertilized systems. The processes that determine carbon export to depth were a central issue of KEOPS 2.

Niskin and phytonet samples were collected at various stations during the spring diatom bloom. Samples were either fixed with lugol for observation in light microscopy or stained with PDMPO, a fluorescent probe marking new Si deposition over a 24h incubation, for epifluorescence microscopy analyses.