In ecology, primary production is the synthesis of organic compounds from atmospheric or aqueous carbon dioxide. It principally occurs through the process of photosynthesis, which uses light as its source of energy, but it also occurs through chemosynthesis, which uses the oxidation or reduction of inorganic chemical compounds as its source of energy. Almost all life on Earth relies directly or indirectly on primary production. The organisms responsible for primary production are known as primary producers or autotrophs, and form the base of the food chain. In terrestrial ecoregions, these are mainly plants, while in aquatic ecoregions algae predominate in this role. Ecologists distinguish primary production as either net or gross, the former accounting for losses to processes such as cellular respiration, the latter not.
About 1 % of the solar radiation reaching the earth is converted into biomass[ Primary production represents the basis for the organic carbon cycle.
Plants capture and store solar energy through photosynthesis. During photosynthesis, living plants convert carbon dioxide in the air into sugar molecules they use for food. In the process of making their own food, plants also provide the oxygen we need to breathe. Thus, plants provide the energy and air required by most life forms on Earth. Plant productivity also plays a major role in the global carbon cycle by absorbing some of the carbon dioxide released when people burn coal, oil, and other fossil fuels. The carbon plants absorb becomes part of leaves, roots, stalks or tree trunks, and ultimately, the soil.
In oceanology and limnology, primary production is the production of phytoplankton in the ocean and fresh water, which obtain their energy through photosynthesis, using nutrients. These small green cells are in turn consumed by first-order heterotrophic consumers, small animals such as ciliates, copepods and krill. Primary production is the basis of all life in the pelagic, i.e. far-off land area of the oceans.
On the ocean floor, the marine benthal, for example the Black Smokers on the mid-ocean ridge, an ecosystem of its own exists. Its basis is not photosynthesis, but chemosynthesis, i.e. the production of energy by decomposing inorganic compounds such as hydrogen sulphide. There, geothermal energy ultimately represents the source of all life processes, whereas in the photosynthesis process this is the energy of the sun.
In terrestrial ecosystems, primary production takes place through photosynthesis by plants, for example the trees of the forest. Primary production by chemosynthesis (chemotrophy) plays no role here.
Productivity is measured in grams dry weight per square meter and year. The highest primary production takes place in the Wadden Sea and in the tropical rainforests.
Primary production is largely converted back into inorganic substances by consumers and destructors. The surplus forms peat and water sludge, from which coal and crude oil are produced in geological periods.
Net Primary Productivity (1 month – Terra/MODIS):
Net Primary Productivity 2000 -2016
The maps above show one way to monitor the carbon “metabolism” of Earth’s vegetation. They show net primary productivity, which is how much carbon dioxide vegetation takes in during photosynthesis minus how much carbon dioxide the plants release during respiration (metabolizing sugars and starches for energy). The data come from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite. Values range from near 0 grams of carbon per square meter per day (tan) to 6.5 grams per square meter per day (dark green). A negative value means decomposition or respiration overpowered carbon absorption; more carbon was released to the atmosphere than the plants took in.