Conversion of energy sources, such as photons, into biomass.

Primary productivity takes place within primary producers, a.k.a., autotrophs, a.k.a., .

The most familiar of that contribute to primary productivity is photosynthesis. Nonetheless, there are numerous organisms, chemoautotrophs, that use energy sources other than from to drive carbon fixing.

Primary productivity serves as the of all ecosystems except for those which are "fed" by upstream organic material, e.g., falling to depths.