Difference Between Gross Primary Productivity and Net Primary Productivity

Gross Primary Productivity vs Net Primary Productivity
 

Have you ever wondered how would food come into our hands? Animals and other consumer organisms cannot eat or consume solar energy, but photosynthetic plants and algae are greatly capable of doing so. It sounds sensible that the production of food takes place in plants by using solar energy via photosynthesis, which is the primary production. Therefore, primary production must take place to start the production of food or in other words to store energy that is consumable for the living beings. When the two adjectives Gross and Net are put before the term primary productivity, the meanings become different from each other.

What is Primary Productivity?

Primary productivity is the production of organic compounds, often called food, using carbon dioxide as raw materials and sunlight as the energy source. However, the chemosynthesis also takes place and contributes to the primary productivity. Primary production takes place in almost everywhere on the Earth through photosynthesis and chemosynthesis. As the word Primary means, it is the first time that the production of food takes place. Importantly, it could take place in anywhere and anytime if the energy is available. The highest proportion of primary production is resulted from the photosynthesis during daytime in open places, while chemosynthetic organisms transform chemical energy of compounds into consumable food in any place at any time. Both terrestrial and aquatic ecosystems contribute to the primary production. Simple carbohydrates are the first produced molecules in the primary production, but later those are modified into complex, long chain carbohydrates, proteins, lipids, and nucleic acids. Primary productivity is the main driving force that sustains life.

What is Gross Primary Productivity?

Gross Primary Productivity is often abbreviated as GPP, and it is simply the full amount of food generated. It should be noticed that this is the rate at which the autotrophs or the primary producers of an ecosystem produces food in a defined period. The GPP is expressed in mass of food in a given area (terrestrial) or volume (aquatic) for a defined time (e.g. grams per square metre per year).

What is Net Primary Productivity?

It is interesting to notice that the generated food is used to produce energy in the form of Adenosine Triphosphate (ATP) for all the living beings including plants through respiration. That means the primary producers themselves use a considerable amount of food for respiration. Therefore, the available amount of food for consumers in an ecosystem differs from the GPP. The net primary productivity (NPP) is defined as that remaining amount of food. In other words, NPP is the difference between GPP and the amount of food used for respiration by producers in a defined time and area. That means, NPP is the basic driving force of life, in terms of food.