An estimate of global net primary production in the ocean has been computed from the monthly mean near-surface chlorophyll fields for 1979–1986 obtained by the Nimbus 7 CZCS radiometer. Our model required information about the subsurface distribution of chlorophyll, the parameters of the photosynthesis-light relationship, the sun angle and cloudiness. The computations were partitioned among 57 biogeochemical provinces that were specified from regional oceanography and by examination of the chlorophyll fields. Making different assumptions about the overestimation of chlorophyll by the CZCS in turbid coastal areas, the global net primary production from phytoplankton is given as 45–50 Gt C year−1. This may be compared with current published estimates for land plants of 45–68 Gt C year−1 and for coastal vegetation of 1.9 Gt C year−1.

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