Root, R. B., 1967. The niche exploitation pattern of the blue-gray
gnatcatcher. Ecological Monographs, 37, 317–350.
Townsend, C. R., Begon M., and Harper J. L., 2008. Physical conditions and the availability of resources. In Essentials of Ecology.
Oxford: Wiley-Blackwell Publishing, pp. 70–109.
Whittaker, R. H., and Levin, S. A., 1975. Niche: Theory and Application. Stroudsburg, PA: Dowden, Hutchinson and Ross.
448 pp.
ECOLOGICAL STOICHIOMETRY
Patricia M. Glibert
Horn Point Laboratory, University of Maryland Center for
Environmental Science, Cambridge, MD, USA
Synonyms
Biological stoichiometry
Definition
The study of the interaction of chemical resources
(elements) in organisms and the environment; the study
of the balance of energy and materials in an ecosystem.
Introduction
Ecological stoichiometry is a rapidly expanding research
area focusing on how the balance of chemical elements
are related to community structure through differences in
the apportionment of these elements in organisms and
the rates by which these elements are recycled and mineralized in food webs (Sterner and Elser, 2002).
A new concept with historical roots
Ecological stoichiometry is a relatively recent conceptual
framework for understanding the interactions of organisms in relation to energy and elemental flow. It builds
on classical concepts of Liebig’s Law of the Minimum
relating to nutrient limitation (Leibig, 1855), Lotka’s
(1925) understanding of the dynamics of predators and
prey, Lindeman’s understanding of trophic dynamics
(Lindeman, 1942), and Redfield’s (1934) concept of balanced proportions of elements in the ocean. Ecological
stoichiometry brings these concepts together by recognizing that different organisms both within and between trophic groups have fundamentally different elemental
requirements, that food web structure is a function of not
only food quantity but food quality, and that these interactions result in a complex suite of feedbacks that shape
community composition. These relationships are linked
via elemental composition of the interacting organisms.
The stoichiometric framework recognizes that changes in
the proportions of dissolved nutrients in the environment
have profound effects on food webs even when the availability of these elements are not in limiting proportions,
with the potential of transforming ecosystems to new stable states. In short, the concept of ecological stoichiometry
suggests that, while the total nutrient load of a system may
set the amount of biomass that can be supported, the composition, both in form of nutrients and the proportion of
different nutrient elements, affects the composition of the
community, from autotrophs to heterotrophs.
A focus on the major nutrient elements
Of the naturally occurring elements, ecological stoichiometry is largely concerned with the major nutrients, carbon,
(C) nitrogen (N), and phosphorus (P), although the fundamental principles can be applied to other elements such as
silica (Si), iron (Fe), calcium (Ca), and other minor elements required for life as well. These elements comprise
the major biochemical and organic molecules of which
organisms are composed including nucleic acids, lipids,
amino acids, proteins, pigments, carbohydrates, and skeletal components of larger organisms. Organisms diverge
in their chemical needs for these elements. How they regulate their chemical composition affects their ability to
survive and grow, and it also affects the organisms around
them by the alteration of food quality for the next trophic
level and by the recycling of the elements via regeneration
and excretion.
Stoichiometry and primary producers
Primary producers, including algae, are considered to be
comparatively flexible (within limits) in their stoichiometry; they often follow the “you are what you eat” model
(Sterner and Elser, 2002; Figure 1a). It has been well
established that many algae have the ability to take up
nutrients in the proportion they are available, including
an ability to take up nutrients in excess of their growth
demands for certain periods of time, or as functions of
varying temperatures, growth rates, and light conditions
(e.g., Rhee, 1978; Glibert and Goldman, 1981; Finkel
et al., 2010). This leads to a fairly wide range of variation
in C:N:P ratios in algae (Klausmeier et al., 2004). Thus,
although the Redfield ratio is often used to infer elemental
composition in phytoplankton, the actual elemental composition of microalgae in culture and phytoplankton in
nature is highly variable (Geider and LaRoche, 2002;
Finkel et al., 2010).
Stoichiometry and consumers
In contrast to microbial primary producers, many heterotrophs exhibit much more “rigid” or “homeostasis” in the
stoichiometry of their biomass (Figure 1b). They are
comparatively more constrained in their C:N:P ratio.
(Note that many microheterotrophs such as heterotrophic
flagellates are excluded from this generalization.) Heterotrophs typically maintain a stricter stoichiometry
because of the fixed stoichiometry in body tissue, especially muscle, bone, and other organs (Sterner and Elser,
2002), although they too may also be subject to some
degree of variability, especially with regard to C versus
nutrient elements (e.g., Malzahn et al., 2010). Grazers
are able to stabilize their biomass stoichiometry more
than phototrophs because they have excretion and release
228
ECOLOGICAL STOICHIOMETRY
gnatcatcher. Ecological Monographs, 37, 317–350.
Townsend, C. R., Begon M., and Harper J. L., 2008. Physical conditions and the availability of resources. In Essentials of Ecology.
Oxford: Wiley-Blackwell Publishing, pp. 70–109.
Whittaker, R. H., and Levin, S. A., 1975. Niche: Theory and Application. Stroudsburg, PA: Dowden, Hutchinson and Ross.
448 pp.
ECOLOGICAL STOICHIOMETRY
Patricia M. Glibert
Horn Point Laboratory, University of Maryland Center for
Environmental Science, Cambridge, MD, USA
Synonyms
Biological stoichiometry
Definition
The study of the interaction of chemical resources
(elements) in organisms and the environment; the study
of the balance of energy and materials in an ecosystem.
Introduction
Ecological stoichiometry is a rapidly expanding research
area focusing on how the balance of chemical elements
are related to community structure through differences in
the apportionment of these elements in organisms and
the rates by which these elements are recycled and mineralized in food webs (Sterner and Elser, 2002).
A new concept with historical roots
Ecological stoichiometry is a relatively recent conceptual
framework for understanding the interactions of organisms in relation to energy and elemental flow. It builds
on classical concepts of Liebig’s Law of the Minimum
relating to nutrient limitation (Leibig, 1855), Lotka’s
(1925) understanding of the dynamics of predators and
prey, Lindeman’s understanding of trophic dynamics
(Lindeman, 1942), and Redfield’s (1934) concept of balanced proportions of elements in the ocean. Ecological
stoichiometry brings these concepts together by recognizing that different organisms both within and between trophic groups have fundamentally different elemental
requirements, that food web structure is a function of not
only food quantity but food quality, and that these interactions result in a complex suite of feedbacks that shape
community composition. These relationships are linked
via elemental composition of the interacting organisms.
The stoichiometric framework recognizes that changes in
the proportions of dissolved nutrients in the environment
have profound effects on food webs even when the availability of these elements are not in limiting proportions,
with the potential of transforming ecosystems to new stable states. In short, the concept of ecological stoichiometry
suggests that, while the total nutrient load of a system may
set the amount of biomass that can be supported, the composition, both in form of nutrients and the proportion of
different nutrient elements, affects the composition of the
community, from autotrophs to heterotrophs.
A focus on the major nutrient elements
Of the naturally occurring elements, ecological stoichiometry is largely concerned with the major nutrients, carbon,
(C) nitrogen (N), and phosphorus (P), although the fundamental principles can be applied to other elements such as
silica (Si), iron (Fe), calcium (Ca), and other minor elements required for life as well. These elements comprise
the major biochemical and organic molecules of which
organisms are composed including nucleic acids, lipids,
amino acids, proteins, pigments, carbohydrates, and skeletal components of larger organisms. Organisms diverge
in their chemical needs for these elements. How they regulate their chemical composition affects their ability to
survive and grow, and it also affects the organisms around
them by the alteration of food quality for the next trophic
level and by the recycling of the elements via regeneration
and excretion.
Stoichiometry and primary producers
Primary producers, including algae, are considered to be
comparatively flexible (within limits) in their stoichiometry; they often follow the “you are what you eat” model
(Sterner and Elser, 2002; Figure 1a). It has been well
established that many algae have the ability to take up
nutrients in the proportion they are available, including
an ability to take up nutrients in excess of their growth
demands for certain periods of time, or as functions of
varying temperatures, growth rates, and light conditions
(e.g., Rhee, 1978; Glibert and Goldman, 1981; Finkel
et al., 2010). This leads to a fairly wide range of variation
in C:N:P ratios in algae (Klausmeier et al., 2004). Thus,
although the Redfield ratio is often used to infer elemental
composition in phytoplankton, the actual elemental composition of microalgae in culture and phytoplankton in
nature is highly variable (Geider and LaRoche, 2002;
Finkel et al., 2010).
Stoichiometry and consumers
In contrast to microbial primary producers, many heterotrophs exhibit much more “rigid” or “homeostasis” in the
stoichiometry of their biomass (Figure 1b). They are
comparatively more constrained in their C:N:P ratio.
(Note that many microheterotrophs such as heterotrophic
flagellates are excluded from this generalization.) Heterotrophs typically maintain a stricter stoichiometry
because of the fixed stoichiometry in body tissue, especially muscle, bone, and other organs (Sterner and Elser,
2002), although they too may also be subject to some
degree of variability, especially with regard to C versus
nutrient elements (e.g., Malzahn et al., 2010). Grazers
are able to stabilize their biomass stoichiometry more
than phototrophs because they have excretion and release
228
ECOLOGICAL STOICHIOMETRY