Fosforitsükkel

The phosphorus cycle, or fosforitsükkel in Estonian, describes the biogeochemical cycle that moves phosphorus through the lithosphere, hydrosphere, and biosphere. Phosphorus is an essential nutrient for all living organisms, playing a crucial role in DNA, RNA, and ATP. Unlike carbon or nitrogen cycles, the phosphorus cycle does not have a significant atmospheric component.

The primary reservoir of phosphorus is rocks, particularly sedimentary rocks that contain phosphate minerals. Weathering of these rocks, a slow process driven by rain and erosion, releases phosphate into the soil and water. Plants absorb dissolved phosphate from the soil through their roots. Animals obtain phosphorus by consuming plants or other animals.

When organisms die, decomposers like bacteria and fungi break down their organic matter, returning phosphorus to the soil and water. This organic phosphorus can then be taken up by plants again, continuing the cycle. In aquatic ecosystems, phosphate can settle to the bottom sediments, where it may become locked away for long periods, eventually forming new sedimentary rocks.

Human activities significantly impact the phosphorus cycle. The mining of phosphate rock for fertilizers and detergents leads to the increased release of phosphorus into the environment. This can cause eutrophication in lakes and rivers, where excessive nutrient enrichment leads to algal blooms that deplete oxygen and harm aquatic life. Agricultural runoff carrying fertilizers is a major source of this pollution.