The Phosphorus Cycle

Phosphorus normally occurs in nature as part of a phosphate ionAn atom, molecule or compound that carries either a positive (cation) or negative (anion) electrical charge., consisting of a phosphorus atom and some number of oxygen atoms, the most abundant form (called orthophosphate) having four oxygen: PO₄^3-. Most phosphatesA salt or ester of a phosphoric acid,
an organic compound of phosphoric acid in which the acid group is bound to nitrogen or a carboxyl group in a way that permits useful energy to be released (as in metabolism),
a nutrient used in fertilizers. are found as salts in ocean sedimentsSolid material that has been or is being eroded, transported, and deposited. Transport can be due to fluvial, marine, glacial or aeolian agents. or in rocks. Over time, geologic processes can bring ocean sediments to land, and weathering will carry terrestrial phosphatesA salt or ester of a phosphoric acid,
an organic compound of phosphoric acid in which the acid group is bound to nitrogen or a carboxyl group in a way that permits useful energy to be released (as in metabolism),
a nutrient used in fertilizers. back to the ocean. Plants absorb phosphates from the soil. The plants may then be consumed by herbivores who in turn may be consumed by carnivoresAn organism that eats only the meat of other organisms.. After death, the animal or plant decays, and the phosphates are returned to the soil. RunoffThe topographic flow of water from precipitation to stream channels located at lower elevations. Occurs when the infiltration capacity of an area's soil has been exceeded. It also refers to the water leaving an area of drainage. Also called overland flow. may carry them back to the ocean or they may be reincorporated into rock.

The primary biological importance of phosphates is as a component of nucleotidesChemical compounds that consists of a heterocyclic base, a sugar, and one or more phosphate groups. The monomers of nucleic acids, with three or more bonding together in order to form a nucleic acid.
Nucleotides are the structural units of RNA, DNA, which serve as energy storage within cells (ATP) or when linked together, form the nucleic acidsIs an organic compound composed primarily of different combinations of carbon, hydrogen, nitrogen, oxygen, and phosphorus. They are very complex compounds being created by the atomic linking of thousands of individual atoms. DNA or deoxyribonucleic acid, the genetic blueprint of life, is an example of a nucleic acid. DNA and RNA. Phosphorus is also found in bones, whose strength is derived from calcium phosphate, and in phospholipids (found in all biological membranes). Recent science indicates that phosphorous is the limiting nutrient for cyanobacteriaBacteria that have the ability to photosynthesize. algae and dynoflagelattes affecting such phenomena as Red Tide.

Phosphates move quickly through plants and animals; however, the processes that move them through the soil or ocean are very slow, making the phosphorus cycle overall one of the slowest biogeochemical cycles.

The Phosphorus Cycle
Source: Norman Hopkins 2006 (image 800x640)

Useful Links:

Phosphorus Cycle

U.S. Environmental Protection Agency, The Phosphorus Cycle