Redfield ratio or Redfield stoichiometry is the molecular ratio of carbon, nitrogen and phosphorus in phytoplankton. The stoichiometric ratio is C:N:P = 106:16:1. The term is named after the American oceanographer Alfred C. Redfield, who first described the ratio in an article in 1934 (Redfield 1934).

Explanation

Redfield described the remarkable congruence between the chemistry of the deep ocean and the chemistry of living things in the surface ocean. Both have N:P ratios of about 16 (atoms to atoms). When nutrients are not limiting, the molar element ratio C:N:P in most phytoplankton is 106:16:1. Redfield thought it wasn't purely coincidental that the vast oceans would have a chemistry perfectly suited to the requirements of living organisms. He considered how the cycles of not just N and P but also C and O could interact to result in this match.

Although the Redfield ratio is remarkably stable in the deep ocean, phytoplankton may have large variations in the C:N:P composition, and their life strategy play a role in the C:N:P ratio, which has made some researches speculate that the Redfield ratio perhaps is a general average rather than specific requirement for phytoplankton growth (e.g., Arrigo 2005).

Diatoms need in addition to other nutrients silicate for their frustules (cell walls) and the proposed Redfield nutrient ratio for diatoms is C:Si:N:P = 106:15:16:1.

See also

• ecological stoichiometry

References

• Arrigo, K.R., Marine microorganisms and global nutrient cycles , Nature, Vol 437, pp. 349-355, 2005
• Redfield A.C., On the proportions of organic derivations in sea water and their relation to the composition of plankton. In James Johnstone Memorial Volume. (ed. R.J. Daniel). University Press of Liverpool, pp. 177-192, 1934.
• Redfield, A.C., The biological control of chemical factors in the environment, American Scientist, 1958