ENV-34

Redfield C:N:P ratio

C:N:P = 106:16:1 (molar) in marine phytoplankton. Nutrient demand follows.

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BiokineticsRedfield 1934

Governing equation

n_N=\dfrac{16}{106}n_C,\quad n_P=\dfrac{1}{106}n_C

where

n_C: Organic carbon (µmol/L)
n_N: Nitrogen demand (µmol/L)
n_P: Phosphorus demand (µmol/L)

Lecture brief

Historical brief

Streeter–Phelps (1925) oxygen sag, settling theory and Guldberg–Waage kinetics made water and air quality a rate problem. The lab computes sag, overflow and a snapshot of reactor mass balance. This sheet (ENV-34 — Redfield C:N:P ratio) is the form associated with Redfield 1934. Working symbols: $n_C$ $\rightarrow$ $n_N$ , $n_P$ . Redfield observed a nearly constant elemental ratio in plankton and deep water, tying biology to ocean chemistry.

Purpose

Purpose: compute

n_N

n_P

from

n_C

in Environmental via

n_N=\dfrac{16}{106}n_C,\quad n_P=\dfrac{1}{106}n_C

C:N:P = 106:16:1 (molar) in marine phytoplankton. Nutrient demand follows. Use it when a real environmental question must be answered in SI before a code check.

Live realistic example

In symbols

Live case. Given

n_C = 106.000\,\mathrm{\mu mol/L}

, the governing relation

n_N=\dfrac{16}{106}n_C,\quad n_P=\dfrac{1}{106}n_C

yields

n_N = 16.00\,\mathrm{\mu mol/L}

n_P = 1.000\,\mathrm{\mu mol/L}

. Three elemental bars in 106:16:1. Move a slider: the numbers are this situation, not a canned story.

Calculator

Inputs

Organic carbon n_C106 µmol/L

Outputs

Nitrogen demand n_N16.00 µmol/L
Phosphorus demand n_P1.000 µmol/L

Reading speed

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Narration of this film

Three elemental bars in 106:16:1.

Redfield observed a nearly constant elemental ratio in plankton and deep water, tying biology to ocean chemistry.

Reading speed

Watch on YouTube