Temporal and spatial variability of CZCS-derived phytoplankton pigment concentrations off the western Iberian Peninsula

A total of 722 Coastal Zone Color Scanner (CZCS) images obtained during 197 9-1985 were used to investigate the variability of surface phytoplankton in the Portugal Current System off western Iberia. Seasonal fluctuations of p igment biomass are clearly identified with amplitudes and phases varying fr om the shelf offshore and also with latitude. Interannual fluctuations are also present. The spatial distribution of phytoplankton varies strongly wit h topographic constraints and dynamical factors, such as the topography of the shelf and upper slope, pronounced coastline features, stratification du e to the heating-cooling seasonal cycle and to river runoff, fronts, coasta l upwelling, mesoscale filaments and jet-like structures, and surface curre nts. Surface pigment biomass is generally higher in the north, mainly in re lation to the Galicia Front, and on the shelf, especially in winter (due to stratification and nutrient enrichment induced by river outflow) and in su mmer (as a result of coastal upwelling). Wavenumber analysis reveals a stro ng influence of mesoscale and submesoscale processes on phytoplankton growt h and aggregation. The relevance of this study for the global carbon cycle and for fisheries is briefly described.