1.6 The Phosphorus Cycle

Phosphorus Sources

- Weathering of rocks that contain P
- Mining P for synthetic fertilizers, detergents, and cleaners

Assimilation

- P is absorbed by plant roots and assimilates into tissues; animals assimilate P by eating plants or other animals

Decomposition

- Animal waste, plant matter, and other biomass is broken down by bacteria/soil decomposers that return phosphate to the soil

Sedimentation

- P does not dissolve well in water
- Falls to the bottom of the ocean as sediment
- Sediment compressed by water pressure

Geological Uplift

- Tectonic plates collide, forcing up rock layers that form mountains
- P cycle restarts

Eutrophication

- Caused by excess P or N
- Major algae bloom -> kills plants below surface -> algae die and bacteria use up O2 to break it down -> low O2 levels kill aquatic animals -> bacteria uses even more O2 to decomp. dead animals

Major reservoirs of P

- Rocks & Sediments