Phosphorus Cycle plays a vital and indispensable role in living organisms. Phosphorus in the form of phosphates are necessary for the growth and maintenance of animal bones and teeth.
It is one of the most important element required by plants for their growth. It is a constituent of nucleic acids, phospholipids, ATP, and ADP. The main reservoirs of phosphorus are rocks and other deposits.
From these, phosphorus is made available to the living organisms via a slow process of weathering of the rocks.
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Phosphorus is absorbed by the plants through their root system, in its oxidized form, as phosphate, where it gets incorporated into different phosphorus, containing compounds. From plants, phosphorus finds its way to other living organisms.
The decay of dead organisms and plants release the phosphorus content back to the soil, which is again recycled.
Some phosphorus finds its way to .the water bodies (rivers and oceans). In oceans, the phosphorus is consumed by fish and sea birds and any excess phosphorus in deposited into the sediments.
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The flow chart of phosphorus cycle is represented in Fig. Below.
In fresh water, the floating algae (phytoplankton) absorb soluble inorganic phosphate and convert them into organophosphates.
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The algae are eaten by zooplankton, which in turn are eaten by other aquatic animals like fish. The aquatic animals after their death and decay by microorganisms settle to the bottom of water.
Finally the microorganisms release phosphates into the water bodies and the cycle continuous Fig. Below.
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A major problem associated with the presence of excess of phosphate fertilizers (and also other fertilizers) is eutrophication of lakes. The increase in the nutrients (by agricultural run offs) in the water bodies is called eutrophication.
These nutrients, particularly phosphorus cause population explosion of photosynthetic bacteria and blue-green algae.
With the passage of time, the whole of the lake or pond is covered by a thick layer of algae resulting in depletion of the availability of oxygen. This results in the death of algae, bacteria and fish.