Redfield Ratio - Deviations From The Canonical Redfield Ratio

Deviations From The Canonical Redfield Ratio

The Redfield ratio was initially derived empirically from measurements of the elemental composition of plankton in addition to the nitrate and phosphate content of seawater collected from a few stations in the Atlantic Ocean. This was later supported by hundreds of independent measurements. However, looking at the composition of individual species of phytoplankton grown under nitrogen or phosphorus limitation shows that this nitrogen to phosphorus ratio can vary anywhere from 6:1 to 60:1. While understanding this problem, Redfield never attempted to explain it with the exception of noting that the N:P ratio of inorganic nutrients in the ocean interior was an average with small scale variability to be expected.

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 researchers speculate that the Redfield ratio perhaps is a general average rather than specific requirement for phytoplankton growth (e.g., Arrigo 2005). However, the Redfield ratio was recently found to be related to a homeostatic protein-to-rRNA ratio fundamentally present in both prokaryotes and eukaryotes (Loladze and Elser 2011). Furthermore, the Redfield ratio has been shown to vary at different spatial scales as well as average slightly higher (166:20:1) than Redfield's original estimate (Sterner et al. 2008).

Despite reports that the elemental composition of organisms such as marine phytoplankton in an oceanic region do not conform to the canonical Redfield ratio, the fundamental concept of this ratio continues to remain valid and useful.