




		Phosphorus : Background Information

How Is Phosphorus Cycled Through Ecosystems?

There are two main processes occurring in all ecosystems - energy flow and material cycling. Phosphorus is cycled between living organisms and the earth's crust as energy flows through a food web.

Phosphorus in Living Organisms
Phosphorus in the Earth's Crust
The Phosphorus Cycle

Phosphorus in Living Organisms

Phosphorus cycles through plants and animals

In aquatic ecosystems, the short-term cycling of phosphorus is through the food web of living organisms.

Plants absorb inorganic phosphates through their roots and convert them into organic phosphates.
Animals obtain their phosphorus by eating plants or other animals. Animals excrete inorganic phosphorus in urine.
Bacteria decompose dead plants and animals and then release inorganic phosphorus back into the environment to continue the cycle.

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Phosphorus in the Earth's Crust

Phosphorus is released by water erosion

During the long-term cycling of phosphorus in the Earth's crust, phosphorus leaches out of soil and weathers out of rock. This inorganic phosphorus flows downstream and eventually accumulates at the bottom of rivers, lakes and oceans.

If left undisturbed for millions of years, bottom sediments transform into phosphorus-containing rock.

"Stored" phosphorus may return again to the surface during the uplifting of mountains, during the mining of potash or when bottom sediments are disturbed.

The phosphorus cycle starts again as water erodes the uplifted phosphorus rock.

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The Phosphorus Cycle

Phosphorus moves between plants, animals, bacteria, rock, soil and water. This is called a biogeochemical cycle. Three natural processes contribute to this cycling of phosphorus - food webs, decomposition and the rock cycle.

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