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We estimated phytoplankton primary productivity (PP) in the euphotic zone of the California Current System using chlorophyll concentration (Chl) from CZCS imagery. The area was divided into two regions, Southern California (SC) and Baja California (BC), with inshore and offshore subregions, and into two seasons, cool and warm. The Chl and PP values were in general higher and more variable inshore than offshore. The cool season had higher PP values, except in the offshore subregion of BC. The effect of El Niño (ENSO) 1982–1983 was more evident inshore, leading to lower PP values during the warm season of 1983 and the cool season of 1984. Mesotrophic and eutrophic waters dominated in the inshore subregions, whereas the major contribution in the offshore subregions was from oligotrophic waters. The total PP estimated was on average 23.78% below the corresponding in situ CalCOFI PP data, 51.82% inshore and 5.93% offshore, which is within the expected agreement between in situ and modeling methods. The average daily PP for SC inshore and offshore was 0.80 and 0.61 g C m–2, respectively, and for BC inshore and offshore it was 1.03 and 0.18 g C m–2, respectively. The total PP in the euphotic zone of the study area (January 1979 to June 1986) was 2.39 Gt C. We calculated an annual average PP for the whole study area of 0.32 Gt C.

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