What is C:N:P?

Almost all elements of living organisms are made up of carbon (C), nitrogen (N) and phosphorus (P). Carbon is the basis of biomass (e.g. sugars, starches, cellulose), but it is also predominantly available in animal fat tissues. Nitrogen is the basic element of proteins, of muscles (besides carbon), phosphorus can be found in great quantities within bones and scales.

The ratio of these elements is characteristic for groups of living organisms and ecosystems, and the changes in the ratio can indicate various processes. In oceans the C:N:P ratio is relatively stable 106:16:1 both in the water and the animals, plants and algae “feeding” in the water. The nitrogen-phosphorus rate in a lake is usually defined by phosphorus being available in suboptimal amounts for plants and algae to grow to their greatest potential. This is actually favourable from a human but also from an ecological perspective, since an unlimited algae growth is not beneficial both to us or to the inhabitants of the lake.

Within the bodies of plants or algae and the animals feeding on them this ratio is not constant. Thus, in order to collect the nutrients that are available in lesser amounts, they have to consume more food and thus ingest surplus amounts of the nutrients that are easily available. The amount of phosphorus is also subject to change during individual development. The older the creature, the greater amount of phosphorus is bound into their structural elements such as bones and cartilage. After death during decomposition, the phosphorus is released into the water column of the sediment and is available to the algae again.