🔬 APES Topic 1.6: The Phosphorus Cycle

Phosphorus (as phosphate)

A vital macronutrient essential for forming DNA, RNA, ATP, phospholipids, and bones.

Limiting Nutrient

A nutrient that is scarce and limits plant growth, especially phosphorus in soils and freshwater.

Major Reservoirs of Phosphorus

Rocks and sediments, which contain phosphorus-bearing minerals that weather over time.

Uptake by Plants

The process by which plants absorb dissolved phosphate from the soil.

Decomposition / Mineralization

The process where decomposers break down organic phosphorus from dead organisms, returning it to inorganic form.

Runoff / Leaching

The process by which unused soil phosphate washes into water bodies.

Eutrophication

Nutrient enrichment of water bodies leading to algal blooms and oxygen depletion.

Why Phosphorus is Often Limiting

Due to its low bioavailability, lack of an atmospheric phase, and high biological demand.

Weathering / Erosion

Processes through which rocks break down, releasing phosphate into soil and water.

Sedimentation & Burial

Phosphate settling in aquatic sediments and becoming buried over time.