Nature 408, 578 - 580 (2000) © Macmillan Publishers Ltd.  

Nutritional constraints in terrestrial and freshwater food webs

JAMES J. ELSER, WILLIAM F. FAGAN, ROBERT F. DENNO, DEAN R. DOBBERFUHL, AYOOLA 
FOLARIN, ANDREA HUBERTY, SEBASTIAN INTERLANDI, SUSAN S. KILHAM, EDWARD 
MCCAULEY, KIMBERLY L. SCHULZ, EVAN H. SIEMANN & ROBERT W. STERNER


Biological and environmental contrasts between aquatic and terrestrial 
systems have hindered analyses of community and ecosystem structure across 
Earth's diverse habitats. Ecological stoichiometry provides an integrative 
approach for such analyses, as all organisms are composed of the same major 
elements (C, N, P) whose balance affects production, nutrient cycling, and 
food-web dynamics. Here we show both similarities and differences in the 
C:N:P ratios of primary producers (autotrophs) and invertebrate primary 
consumers (herbivores) across habitats. Terrestrial food webs are built on an 
extremely nutrient-poor autotroph base with C:P and C:N ratios higher than in 
lake particulate matter, although the N:P ratios are nearly identical. 
Terrestrial herbivores (insects) and their freshwater counterparts 
(zooplankton) are nutrient-rich and indistinguishable in C:N:P stoichiometry. 
In both lakes and terrestrial systems, herbivores should have low growth 
efficiencies (10–30%) when consuming autotrophs with typical 
carbon-to-nutrient ratios. These stoichiometric constraints on herbivore 
growth appear to be qualitatively similar and widespread in both environments.