Bio-optical and phytoplankton pigment measurements were carried out at several transatlantic ship cruises (Table 1) to validate satellite derived biogeochemical properties in open ocean waters. The remote sensing reflectances were determined from hyperspectral above and below water radiometric measurements using TriOS-RAMSES radiometers in open ocean waters and used to validate MERIS and MODIS remote sensing reflectance data. From water samples pigment composition and particulateabsorption were determined by HPLC (Hoffmann et al. 2006) and filter pad method (Tassan and Ferrari 1995), respectively. The phytoplankton pigment and bio-optical data from stations of the cruise ANT-XXV/1 (2008) were analyzed using a cluster-based approach proposed in Torrecilla et al., 2010 with the aim ofidentifying different phytoplankton assemblages and biooptical provinces in open ocean waters.