Upwelling systems are thought to be characterized by the dominance of chain-forming diatoms, and the large fisheries typical of coastal upwelling systems are considered to be based on the classical food chain of “diatoms - copepods - fish” (Cushing, 1989). Little consideration has been given to the contribution of coccolithophorids to the phytoplankton communities in upwelling systems. The coccolithophorids belong to the Prymnesiophyceae and are able to synthesize external calcium carbonate platelets, or coccoliths, which cover the outer surface of the cell. Coccolithophorids are globally cosmopolitan (Brown and Yoder, 1994) and known to form near mono-specific blooms that can extend over large areas of the ocean surface (Holligan et al., 1983, 1993). Such blooms provide a milky turquoise colour to the ocean, owing to the scattering properties of the coccoliths (Balch et al., 1996a). These small inorganic platelets are extremely effective scatterers, particularly when detached from the host cells. It is largely the influence of high concentrations of these detached coccoliths that cause coccolithophorid blooms to differ optically from other blooms of noncalcifying marine phytoplankton (Ackleson et al., 1994; Balch et al., 1996a) due to their high effective refractive index and typically small size (Voss et al., 1998).