Phosphorus Cycle

Phosphorus Cycle

Phosphorus cycle is a type of biogeochemical cycle that represents the flow of this mineral element in the ecosystem. It involves transferring of phosphorus within soil, water and biotic system. As compared to other nutrient cycles, this cycle operates in a very slow manner.
Phosphorus is a mineral element, crucial for normal functioning of the living organisms. It is an essential plant nutrient, required in large amount for proper growth and development of any plant. Hence, it is included in the primary nutrients for plants, along with nitrogen and potassium. When it comes to its presence in humans (and animals), it is a component of energy (ATP), cell membrane, bones, and nucleic acids (RNA and DNA). After getting converted into phosphate, it is responsible for carrying out a number of vital processes in the body.

Similar to other biologically active chemical elements, detailed studies have been done regarding phosphorus cycle. As the name signifies, this cycle indicates the movement of this mineral in the ecosystem. It operates in a closed system, wherein this mineral occurs in different forms and gets recycled again. However, in case of light energy, it functions in an open system and gets lost within the ecosystem, instead of recycling.

The Element

Phosphorus was discovered for the first time by Hennig Brand, a German alchemist in 1669. In chemistry, it is represented by the symbol 'P', has an atomic number 15, and atomic mass 30.973762. There are two main types of elemental allotropes, red and white phosphorus. Insoluble in water, pure white phosphorus melts at a temperature of about 44.15° C, while its boiling point is recorded to be 280.5° C. In nature, it is very reactive and found in different mineral forms or as phosphates in inorganic rocks.

Cycle: Steps Explained

In the prevailing temperature and pressure ranges, phosphorus occurs in liquid or solid mineral forms. Considering this, it is naturally found in water, rocks, sediments, and soil. Recycling of this element occurs within hydrosphere, lithosphere, and biosphere. To be more precise, the atmospheric compartment of the ecosystem is less profound in regulating the cycle, which is not so in other biogeochemical cycles, such as carbon cycle and nitrogen cycle.

Speaking about phosphorus cycle summary, the aquatic plants absorb inorganic form of this element from water and bottom layer of the water body (in case of rooted plants). Land plants derive this element from the soil and fertilizers that are applied externally. While absorption by plants, the inorganic form is converted into organic forms. Both aquatic and terrestrial plants are eaten by herbivorous fish, birds, and animals, thus transferring organic form of this element to the consumers in the next level.

The carnivores receive phosphorus by consuming herbivores. When plants, fish, birds, and other animals die, they get deposited in water bodies and soil. Under favorable environmental conditions, the dead organisms are decomposed by bacteria and other microbes, during which, the organic form of this element is again converted into inorganic form. The inorganic form is then recycled to the water and soil. This is taken up by the plants again. Thus, the same steps of the cycle are repeated.

No doubt, phosphorus remains in a particular ecosystem compartment for a longer period, but it recycles back to the environment. Thus, its percentage composition remains at a near constant value. Scientific studies have claimed that this cycle is the slowest of all the biogeochemical cycles.