Redfield Ratio
The Redfield ratio is the consistent proportion of carbon, nitrogen and phosphorus in marine plankton and in the deep ocean, about 106 carbon : 16 nitrogen : 1 phosphorus by atoms. It was described by the oceanographer Alfred Redfield in 1934.
The Redfield ratio is the consistent proportion of carbon, nitrogen and phosphorus in marine plankton and in the deep ocean, about 106 carbon : 16 nitrogen : 1 phosphorus by atoms. It was described by the oceanographer Alfred Redfield in 1934.
Discovery: What Did Redfield Notice?
Redfield found that the nitrate and phosphate dissolved in deep ocean water occur in a ratio of about 16 to 1, matching the ratio of nitrogen to phosphorus in the cells of phytoplankton. He concluded that the life of the surface ocean shapes the chemistry of the deep: organisms take up nutrients in fixed proportions, sink, and release them again as they decay.
Use: What Does the Ratio Explain?
The ratio is a simple guide to which nutrient limits growth: where nitrate is scarce relative to phosphate, nitrogen is limiting. It links the biological pump, which exports carbon, to the supply of nutrients, and it is built into models of biogeochemical cycles. Processes such as nitrogen fixation and denitrification can shift the balance.
Limits: Is It Really Constant?
The ratio is an average, and individual species and regions deviate widely. Warm, nutrient-poor waters tend to have more carbon per phosphorus than cold, nutrient-rich ones, and measured ratios differ between lineages. Changes in the ocean, such as eutrophication from fertilizer runoff and rising temperature, may alter the stoichiometry of marine life. See phosphorus and biogeochemistry.
Redfield Ratio at a Glance
| Property | Value |
|---|---|
| Ratio | C:N:P about 106:16:1 |
| Described by | Alfred Redfield, 1934 |
| Applies to | Marine plankton and deep-ocean nutrients |