The timing and duration of coccolithophore blooms along the Patagonian shelf break, as well as insights on the mechanisms that drive and maintain these blooms, were analyzed using time series of chlorophyll chl a, calcite, and sea-surface temperature (SST) derived from remote sensing data (SeaWiFS and AVHRR) and historic hydrographic data. The seasonal variability and succession of phytoplankton groups respond to light intensity and nutrient supply within the mixed layer due to seasonal changes in stratification. The early spring bloom is diatom-dominated and starts in September under nutrient-rich Malvinas waters when the mixed layer begins to shallow (<80 m), and peaks around November with mixed layer depths (MLD) less than 40 m. After nutrient depletion from the spring bloom, a coccolithophore bloom begins in November when the MLD is less than 40 m, and peaks in January when the MLD reaches its minimum (18 m) and PAR reaches its maximum intensity.