Question

How could phosphorus act as a limiting factor?

Answer 1

The (algal) cell, `C106H263O110N16P`, and eutrophication

Explanation:

Using a simple stoichiometric analysis and recollecting the atomic mass of nitrogen (14) and phosphorus (31), the ratio of the mass of nitrogen to phosphorus in algae is `=(16*14)/31=7.2`

As a rough guideline value, when the concentration of nitrogen in water is at least 10 times the concentration of phosphorus, the water body will most probably be phosphorus limited. When the same ratio is less than 10, it will probably be nitrogen limited (for freshwater environments only).

Vollenweider (1975) underlines that phosphorus is acceptable in freshwater bodies if it is between 0.01 mg/L and 0.02 mg/L. More than 0.02 mg/L is excessive ( Vollenweider 1975).

Reference:
Vollenweider, R. A. (1975) Input-output models with special reference to the phosphorus loading concept in limnology. Schweiz. Z. Hydrol. 37: 53-83.