ABSTRACT
Primary production is the synthesis of organic carbon compounds from the inorganic carbon source represented by carbon dioxide, which is performed by organisms known as autotrophs or primary producers. In general, ecologically important autotrophs are photoautotrophs, which can fix inorganic carbon using the sunlight’s energy in the process of photosynthesis (see Chapter 13), however, primary producers also include chemoautotrophs, that is, organisms capable of fixing CO2 based on the energy of chemical reactions, such as bacteria living near hydrothermal vents on the bottom of the oceans. Algae (microalgae, macroalgae, sea grasses, etc.), plants, and some particular bacteria (photosynthetic cyanobacteria, also known as blue-green algae) are the common examples of primary producers in aquatic and terrestrial ecosystems. The term phytoplankton indicates the fraction of plankton (organisms in the water column that float or, anyway, cannot swim against currents) made up of primary producers, such as microalgae and cyanobacteria, which yield most oceanic primary production.
