1.6 -Phosphorous Cycle

Phosphate (PO₄³⁻)

Biologically usable form of phosphorus released through weathering of rocks

Main phosphorus reservoirs

Rocks and phosphorus-containing sediments

Weathering

Physical breakdown of rocks by wind and rain that releases phosphate into soil and water

Why phosphorus cycle is slow

Phosphorus has no gas phase and must move via solid phosphate and water transport

Limiting nutrient (phosphorus)

Nutrient that restricts plant growth because it is released very slowly from rocks

Biological role of phosphorus

Essential for ATP, DNA, bones, and tooth enamel

Natural phosphorus source

Weathering of phosphate-containing rocks

Synthetic phosphorus source

Mining phosphate rock for fertilizers, detergents, and cleaners

Phosphorus assimilation

Plant roots absorb phosphate from soil; animals obtain phosphorus by eating plants or other animals

Decomposition (phosphorus cycle)

Decomposers return phosphorus from dead organisms and waste back into the soil

Sedimentation

Process where phosphate precipitates out of water and settles as solid sediments

Geological uplift

Tectonic processes that expose buried phosphate rocks to weathering

Runoff (phosphorus)

Movement of phosphates from soil into nearby water bodies due to rain or irrigation

Eutrophication

Excess nitrogen and phosphorus in water causing algal blooms and oxygen depletion

Algal bloom

Rapid growth of algae due to excess nutrients that blocks sunlight

Dead zone

Area of water with extremely low oxygen where most aquatic life cannot survive

Positive feedback loop (eutrophication)

Oxygen loss causes organism death, increasing decomposition and further oxygen depletion