ACER Blog Explores “Primary Production”

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A four level trophic pyramid sitting on a layer of soil and its community of decomposers. Source: By Thompsma (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons

When scientists consider ecosystems, you will more often hear the term primary production. What is the link between these terms? Are they the same thing? Why do scientists measure it?

Photosynthesis is the process by which light energy is used to power chemical reactions that convert carbon dioxide (CO2) to carbohydrates. Here, light energy is used to split a water molecule into 2 hydrogen and 1 oxygen. The energy from that action is then used to create a carbohydrate, in this case, the sugar glucose from carbon dioxide (what you breathe out when you exhale). Scientists also refer to this process as carbon fixation as an inorganic form of carbon has been converted to (fixed into) an organic molecule that contains carbon.

Photosynthesis is the process forming the base of the food chain. Photosynthetic organisms are the only organisms capable of taking an inorganic form of carbon and, using an energy source, making food. Other organisms are dependent on this ‘manufactured’ food, so the amount of photosynthesis determines the amount of food that is available to all other organisms in the food chain or web. The amount of food made over time is called primary production. Put another way, primary production is the amount of carbon fixed over a period of time measured for a specific area. It is primary as it is the base of the food chain and it is production as organic matter is produced from inorganic matter.

Primary production is typically reported as grams of carbon per some unit of time, such as g carbon per day per square meter. If we talk about the organisms that eat, that is consume, this primary production, we can use the term secondary production. This is the amount of new flesh (biomass in scientific lingo) created, either by organisms growing larger or heavier, or from making new organisms by reproducing. The higher the consumer is in the food chain, the higher the level of production (for example: tertiary (3rd), 4th or 5th levels).

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