(image Uwe Kils)
Primary production is the production of organic molecules from inorganic materials through photosynthesis. It is the creation of biomass by certain living systems (notably plants) that is the basis of the food chain.
Primary production in oceanography and limnology refers to the production of biomass by phytoplankton in aquatic environments utilizing energy from sunlight. The small algal cells are then consumed by — and provide organic building blocks and energy for — small animals such as ciliates, copepods, and krill. Primary production is the basis for all life in the open oceans.