The Phosphorus Cycle
- The main reservoir of phosphorus is rock and soil. As water rushes over these rocks, erosion occurs and phosphorus is dissolved. The phosphorus becomes a phosphate in this process and is washed into rivers and streams.
- Plant roots absorb these phosphates that are dissolved in water in the soil and use them to synthesize organic molecules. The phosphates then become concentrated in plant tissues.
- When the plants are consumed, the animals that consumed them obtain the phosphates they need.
- The phosphates in plants and animals are returned to the water when the plants and animals die and decompose.
- Also, large amounts of phosphorus in the form of phosphates are carried by rivers and streams as runoff to the ocean. While much of these phosphates then concentrate in marine sediment, some of it is incorporated into the bodies of marine animals.
- When sea birds consume these fish, the phosphorus returns to the ocean in the form of excrement.
- Lastly, geologic upthrust is involved in the phosphorus cycle. Geologic upthrust is when once-submerged sedimentary rocks rich in phosphorus are exposed due to the movement of the Earth's plates. When these rocks weather, phosphorus returns to water and the soil.
Summary:
Reservoirs: Rock and soil are the biggest reservoirs of phosphorus. The ocean, rivers and streams are also a large reservoir of phosphorus.
Sinks and Sources: Since the phosphorus cycle doesn't involve the atmosphere, there are no sinks and sources.
Pathways of Movement: River/stream erosion of rock and run-off, absorption by plant roots, animal consumption of plants, and geological upthrust are methods by which phosphorus is moved.