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very living organism—
from tiny ocean algae
to a mighty redwood—is
made up of chemical elements
in varying ratios. Ecological
stoichiometry considers the
balance of these elements, and
how the ratios change during
chemical reactions. Studying
such ratios throws light on the
way the living world operates,
revealing how organisms obtain
the nutrients and other chemicals
they require for life from the
resources in their environment.The field of ecological stoichiometry
was comprehensively described
for the first time by American
biologists Robert Sterner and James
Elser; in Ecological Stoichiometry
(2002), they used mathematical
models to demonstrate the
application at every level, from
molecules and cells to individual
plants and animals, populations,
communities, and ecosystems.Key chemicals
In ecological research, the three
main elements examined are
carbon (C), nitrogen (N), and
phosphorus (P), because each
plays a vital role. Carbon is a basic
building block of all life and an
important part of many chemical
processes. Nitrogen is a major
constituent of all proteins, while
phosphorus is crucial for cell
development and storing energy.
An organism’s C:N:P ratio is not
necessarily consistent. Plants have
a variable ratio: they can adjust the
balance of their elements according
to their environment. For instance,
the proportion of carbon in their
chemical makeup can rise on a
particularly sunny day because
more photosynthesis occurs—the
process by which they take carbonALL LIFE IS
CHEMICAL
ECOLOGICAL STOICHIOMETRY
IN CONTEXT
KEY FIGURES
Robert Sterner (1958–),
James Elser (1959 –)BEFORE
1840 German biologist and
chemist Justus von Liebig
asserts that the limitations
on agriculture productivity are
primarily chemical.1934 US oceanographer Alfred
Redfield measures the atomic
ratio of carbon, nitrogen, and
phosphorus (C:N:P) in plankton
and seawater, and finds it to be
relatively consistent in all
oceans. The Redfield Ratio soon
becomes a benchmark for such
research in all habitats.AFTER
2015 In “Ocean stoichiometry,
global carbon, and climate,”
Robert Sterner highlights
inconsistencies in C:N:P ratios
in phytoplankton, which absorb
more atmospheric carbon in
low-nutrient, low-latitude ocean
surface waters and adjust their
ratios accordingly.Individual organisms also
show differences in
stoichiometry during their life
cycles. Young organisms may
have different compositions
from older ones ...
Robert Sterner and
James J. ElserUS_074-075_Ecology_Stoichiometry.indd 74 12/11/18 6:24 PM