1.6, The Phosphorus Cycle

Phosphorus cycle

movement of P atoms and molecules b/w sources /reservoirs

Major reservoirs

rocks + sediment containing p minerals

What makes the phosphorus cycle different from others?

P cycle is very slow compared to C/H₂O/N cycles

What is the result of the phosphorus cycle being so slow?

Because it cycles slowly, it is a limiting nutrient meaning plant growth in the ecosystem is often limited by P availability

What is phosphorus used for?

P is needed by all organisms for DNA, ATP (energy ), bone, and tooth enamel in some animals

What is a major natural phosphorus source?

major natural source of P is weatherins of rock that contain P mineral

How does phosphate get into water and soil?

Wind and rain break down rock and phospates(PO₄^-3 ) which is then released and dissolved into water, rain water carries phosphates into nearby soils and bodies of water

Weathering is so slow that...

P is often a limiting nutrient in aquatic and terrestrial ecosystems

Synthetic (human) sources of phosphorus

Mining phosphate minerals and adding to products like synthetic fertilizers and detergents/ cleaners

Home sources of phosphorus

phosphates from detergents and cleaners that enter bodies of water via wastewater from homes

Assimilation

Just like N, P is absorbed by plant roots and assimilated into tissues; animals assimilate P by eating plants or other animals

What do bacteria and soil decomposers do for the phosphorus cycle?

animal waste, plant matter and other biomass is broken down by bacteria/soil decomposers that return phosphates to soil

Sedimentation

Phosphates don’t dissolve very well into water; much of it forms solid bits of phosphates that fall to the bottom as sediments

Sedimentary rocks

P sediments can be compressed into sediment rocks over long time periods by overlying water

Geological uplift

tectonic plate collision forcing up rock layers that form mountains; P cycle can start over again with weathering and release of phosphate from rock

Eutrophication

because they’re limiting nutrients in aq. ecosystems, extra input of N and P leads to eutrophication (excess nutrients) which fuels algae growth

What does eurotrophication cause?

Algae blooms

Algae bloom

algae bloom covers the surface of water, blocking sunlight and killing plants below surface