Why is phosphorus often the nutrient that limits plant growth in aquatic ecosystems?

Phosphorus is frequently the limiting nutrient for plant growth in aquatic ecosystems primarily because it lacks a volatile gaseous state, unlike other essential nutrients such as carbon, nitrogen, and sulfur. Because it does not cycle through the atmosphere, phosphorus moves unidirectionally from land through aquatic environments into ocean sediments, where it becomes trapped in deep reservoirs.12

This scarcity is compounded by the fact that phosphorus is essential for life, playing a critical role in energy transfer and the structure of DNA. While phosphorus is released into ecosystems through the weathering of bedrock, much of it is steadily lost to the ocean depths, making it the scarcest and most limiting element in many ecological systems.21

When human activities—such as the use of fertilizers and detergents—introduce excess phosphorus into these systems, it can trigger eutrophication, leading to explosive, harmful growth of algae and microorganisms that degrade water quality.13