Biological importance: Phosphorus is a component of nucleic acids, phospholipids, as well as bones and teeth.

Forms available to life: Inorganic phosphate (PO₄^3-) is absorbed by plants.

Reservoirs: The largest reservoirs are in sedimentary rocks.

Key processes: Weathering of rocks adds phosphorus to soil; some leaches into groundwater and soil and find its way to sea.

Phosphate taken up by producers cycle through the food web via consumers.