The Phosphorus Cycle: From Rock to Life and Back

0:00Every living thing needs phosphorus. Where does it come from?

0:04Most phosphorus is stored in rock as phosphate, phosphorus joined to oxygen.

0:11Rain slowly breaks down the rock. This is weathering, and it releases phosphate into the soil.

0:18Plants absorb phosphate through their roots, and animals get it by eating plants or other animals.

0:25All living things use it for DNA and cell membranes, and many animals for bones and teeth.

0:32Decomposers, like bacteria and fungi, break down wastes and dead remains, returning phosphate to the soil.

0:41Some phosphate washes into lakes and oceans.

0:44It settles to the bottom as sediment, and over millions of years the layers are pressed into new rock.

0:51Slow movements of Earth's crust, called uplift, raise this rock to the surface again.

0:58Unlike carbon, phosphorus has no common gas form, so the air plays almost no part in its cycle.

1:06So it moves through rock, soil, water and living things, and the full cycle is very slow.

1:14People mine phosphate rock to make fertilizer for crops.

1:18Rainwater flowing off the land, called runoff, carries extra phosphate into lakes.

1:24The extra phosphate makes algae grow very fast. This is an algae bloom.

1:31When the algae die, decomposers use up the oxygen in the water, so fish can die.

1:38So phosphorus cycles slowly from rock to living things and back to rock.